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Sample records for k1-x lixta1-y nbyo3

  1. Piezoelectric and ferroelectric properties of lead-free (1-x)(Na{sub 1y}K{sub y})(Nb{sub 1−z}Sb{sub z})O{sub 3}-xBaTiO{sub 3} solid solution

    Energy Technology Data Exchange (ETDEWEB)

    Sasikumar, S., E-mail: sasikuhan@gmail.com [Research Centre and Post Graduate Department of Physics, The Madura College, Madurai 625 011, Tamil Nadu (India); Saravanan, R. [Research Centre and Post Graduate Department of Physics, The Madura College, Madurai 625 011, Tamil Nadu (India); Aravinth, K. [SSN Research Center, SSN College of Engineering, Kalavakkam 603 110, Tamil Nadu (India)

    2017-05-01

    The solid solutions of lead-free (1-x)(Na{sub 1-y}K{sub y})(Nb{sub 1-z}Sb{sub z})O{sub 3}-xBaTiO{sub 3} (with x=0.1, 0.2; y=0.03, 0.05; z=0.05, 0.1) (abbreviated as (1-x)NKNS-xBT) ceramics have been synthesized using conventional solid-state reaction method. The results of X-ray diffraction analysis show that all the grown specimens of NKNS display typical perovskite structure. With BaTiO{sub 3} (BT) addition, a structural phase transition from tetragonal to cubic structure has been observed. The structural parameters of (1-x)NKNS-xBT powders were determined by profile refinements based on the analysis of X-ray powder diffraction. The charge density distributions of the prepared samples have been investigated by observed structure factors to understand the chemical bonding nature of (1-x)NKNS-xBT powders. The optical absorption of the ceramics has been investigated using UV–visible spectrophotometer. Scanning electron microscopic (SEM) measurements were performed to study the surface morphology of the prepared solid solutions. The elemental compositions of the (1-x)NKNS-xBT samples were analyzed by energy-dispersive X-ray (EDS) spectrometer. The dielectric constant versus temperature plots of the solid solutions exhibit ferroelectric to paraelectric phase transition, which is dependent on the BaTiO{sub 3} content. The ferroelectric nature of the samples has been determined through polarization and electric field hysteresis measurements.

  2. Structural evolution and dielectric properties of (Ba{sub 1x}Nd{sub x})(Ti{sub 1y}Fe{sub y})O{sub 3} ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Han, D.-D. [Research Center for Materials Science and Engineering, Jilin Institute of Chemical Technology, Jilin 132022 (China); College of Chemistry, Northeast Normal University, Changchun 130024 (China); Lu, D.-Y., E-mail: cninjp11232000@yahoo.com [Research Center for Materials Science and Engineering, Jilin Institute of Chemical Technology, Jilin 132022 (China); Sun, X.-Y. [Research Center for Materials Science and Engineering, Jilin Institute of Chemical Technology, Jilin 132022 (China)

    2013-11-05

    Highlights: •Structural evolution and dielectric properties of (Ba{sub 1x}Nd{sub x})(Ti{sub 1y}Fe{sub y})O{sub 3} were studied. •A cubic ceramic with x = y = 0.05 exhibits a high-k Y5V behavior (ε{sub RT}{sup ′} = 6790). •The T{sub m} in BNTF with x = 0.05 decreased linearly at a rate of −5 °C/mol% Fe ions. •Evolution in the 840 cm{sup −1} Raman band gives evidence for Nd{sup 3+}–Fe{sup 3+} complex formation. •Defect chemistry associated with structure evolution is discussed. -- Abstract: The influence of donor and acceptor co-doping on structure and dielectric properties of (Ba{sub 1x}Nd{sub x})(Ti{sub 1y}Fe{sub y})O{sub 3} (BNTF) (x = 0.05, y = 0.01–0.07; and x = 0–0.08, y = 0.05) ceramics was investigated with X-ray diffraction (XRD), scanning electron microscopy (SEM), electron paramagnetic resonance (EPR), Raman spectroscopy, and dielectric measurements. When x < y, two types of Nd{sup 3+}–Fe{sup 3+} and Fe{sup 3+}–V{sub O}–Fe{sup 3+} defect complexes formed and could not coexist, leading to the mixed phases of cubic and hexagonal. A single-phase ceramic with a cubic or tetragonal structure formed for xy and the dielectric-peak temperature (T{sub m}) in BNTF with x = 0.05 decreased linearly with increasing y at a rate of −5 °C/mol% Fe ions. A high-k Y5V behavior can be realized at x = y = 0.05 (i.e., C-N5F5). The same concentrations of Nd{sup 3+} and Fe{sup 3+} formed Nd{sup 3+}–Fe{sup 3+} complexes, which could effectively suppress the dielectric loss and silence the 840 cm{sup −1} band called “Raman charge effect” associated with Nd{sup 3+} donors. C-N5F5 exhibited a cubic structure, medium-sized grains (3.3 μm), low dielectric loss (<0.06), and high-k Y5V behavior (ε{sub RT}{sup ′} = 6790). Defect chemistry associated with structure evolution is discussed.

  3. Production and electrical parameters of La /SUB 1-x/ Ca /SUB x/ Cr /SUB 1-y/ Ni /SUB y/ O3 (x ranging from 0-0.3; y ranging from 0-1)

    International Nuclear Information System (INIS)

    Kononyuk, I.F.; Surmach, N.G.; Tolochko, S.P.

    1986-01-01

    This paper deals with the conditions for the formation of LaCr /SUB 1-y/ Ni /SUB y/ O 3 , La /SUB 1-x/ Ca /SUB x/ CrO 3 , and La /SUB 1-x/ Ca /SUB x/ Cr /SUB 1-y/ Ni /SUB y/ O 3 solid solutions and the electrical parameters of these. The initial materials were lanthanum, calcium, nickel, and chromium nitrates of pure or analytical grade. It is shown that partial replacement of lanthanum by calcium does not have any substantial effect on the electrical parameters of La /SUB 1-x/ Ca /SUB x/ Cr /SUB 1-y/ Ni /SUB y/ O 3 solid solutions for y = 0.2-0.6, but it increases the conductivity of La /SUB 1-x/ Ca /SUB x/ CrO 3 by three orders of magnitude as x varies from 0 to 0.3. The electrical parameters are virtually the same for lanthanum chromites containing calcium and strontium. The solubility of calcium in lanthanum chromite is reduced in the presence of nickel

  4. Internal friction and elastic modulus of NdxY1-xBa2Cu3Oy (x 0.0-1.0) at 200 kHz near the orthorhombic-to-tetragonal phase transition

    International Nuclear Information System (INIS)

    Inagaki, M.

    2000-01-01

    The internal friction and Young's modulus of a series of superconductors Nd x Y 1-x Ba 2 Cu 3 O y (x = 0.0-1.0) were measured over the temperature range from 300 to 1050 K using a 200 kHz LiNbO3 piezoelectric composite oscillator. Anelastic relaxation peaks due to oxygen migration were observed at about 850 K. The minimum Young's modulus, which is related to the orthorhombic-to-tetragonal phase transition, was also observed near this temperature. The temperature at the minimum Young's modulus decreased with an increase in the neodymium composition. In contrast, the internal friction peak temperature showed an unsystematic shift with an increase in x, while changes of the average cell structure exhibited a linear relationship when plotted versus the average ionic radius for trivalent rare-earth ions with the coordination number eight. (author)

  5. Spin reorientation and magnetic anisotropy in Y2Co17-xCr x (x 1.17-3.0) compounds

    International Nuclear Information System (INIS)

    Fuquan, B.; Tegus, O.; Dagula, W.; Brueck, E.; Boer, F.R. de; Buschow, K.H.J.

    2005-01-01

    Spin reorientation transitions and magnetic anisotropy in Y 2 Co 17-x Cr x (x = 1.17-3.0) compounds have been investigated by means of X-ray diffraction and magnetization measurements. The powder X-ray diffraction patterns show that most samples crystallize as a single phase with the rhombohedral Th 2 Zn 17 -type structure. However, in the compound Y 2 Co 14 Cr 3 the Th 2 Zn 17 phase coexist with the hexagonal Th 2 Ni 17 -type phase. The lattice parameters a and c hardly change and the unit cell volume V increases slightly with increasing Cr content. The X-ray diffraction patterns of the aligned powder of the samples have confirmed that at room temperature the compound with x = 1.17 has planar anisotropy, but the compounds with x = 1.76, 2.34 and 3.00 have uniaxial anisotropy. Spin reorientation phenomena occur in all of the compounds. With increasing Cr content, the Curie temperature, the spin reorientation temperature, the spontaneous magnetization, and the anisotropy constant K 2 of the Y 2 Co 17-x Cr x (x = 1.17-3.0) compounds decrease strongly while the anisotropy constant K 1 increases in the range of x from 1.17 to 2.34 and then decreases in the range of x from 2.34 to 3.00

  6. Synthesis and characterization of perovskite-type Sr{sub x}Y{sub 1x}FeO{sub 3−δ} (0.63≤x<1.0) and Sr{sub 0.75}Y{sub 0.25}Fe{sub 1y}M{sub y}O{sub 3−δ} (M=Cr, Mn, Ni), (y=0.2, 0.33, 0.5)

    Energy Technology Data Exchange (ETDEWEB)

    Biendicho, J.J. [Department of Materials and Environmental Chemistry, Stockholm University, S-106 91 Stockholm (Sweden); The ISIS Facility, STFC Rutherford Appleton Laboratory, Didcot, OX11 0QX Oxfordshire (United Kingdom); Shafeie, S. [Department of Materials and Environmental Chemistry, Stockholm University, S-106 91 Stockholm (Sweden); Frenck, L. [Department of Materials and Environmental Chemistry, Stockholm University, S-106 91 Stockholm (Sweden); Université Pierre et Marie Curie, 75005 Paris (France); Gavrilova, D. [M.V. Lomonosov Moscow State University, 119991 Moscow (Russian Federation); Böhme, S. [Department of Materials and Environmental Chemistry, Stockholm University, S-106 91 Stockholm (Sweden); Technische Universität Chemnitz, Institut für Chemie, Straße der Nationen 62, D-09111 Chemnitz (Germany); Bettanini, A.M. [Department of Materials and Environmental Chemistry, Stockholm University, S-106 91 Stockholm (Sweden); Department of Molecular Sciences and Nanosystems, University Ca’ Foscari of Venice, 30123 Venice (Italy); Svedlindh, P. [Department of Engineering Sciences, Uppsala University, Box 534, SE-751 21 Uppsala (Sweden); Hull, S. [The ISIS Facility, STFC Rutherford Appleton Laboratory, Didcot, OX11 0QX Oxfordshire (United Kingdom); Zhao, Z. [School of Industrial Engineering and Management, Royal Institute of Technology, SE-100 44 Stockholm (Sweden); Istomin, S.Ya., E-mail: istomin@icr.chem.msu.ru [Department of Materials and Environmental Chemistry, Stockholm University, S-106 91 Stockholm (Sweden); M.V. Lomonosov Moscow State University, 119991 Moscow (Russian Federation); Grins, J.; Svensson, G. [Department of Materials and Environmental Chemistry, Stockholm University, S-106 91 Stockholm (Sweden)

    2013-04-15

    Oxygen-deficient ferrates with the cubic perovskite structure Sr{sub x}Y{sub 1x}FeO{sub 3−δ} were prepared in air (0.71≤x≤0.91) as well as in N{sub 2} (x=0.75 and 0.79) at 1573 K. The oxygen content of the compounds prepared in air increases with increasing strontium content from 3−δ=2.79(2) for x=0.75 to 3−δ=2.83(2) for x=0.91. Refinement of the crystal structure of Sr{sub 0.75}Y{sub 0.25}FeO{sub 2.79} using TOF neutron powder diffraction (NPD) data shows high anisotropic atomic displacement parameter (ADP) for the oxygen atom resulting from a substantial cation and anion disorder. Electron diffraction (ED) and high-resolution electron microscopy (HREM) studies of Sr{sub 0.75}Y{sub 0.25}FeO{sub 2.79} reveal a modulation along 〈1 0 0〉{sub p} with G± ∼0.4〈1 0 0〉{sub p} indicating a local ordering of oxygen vacancies. Magnetic susceptibility measurements at 5–390 K show spin-glass behaviour with dominating antiferromagnetic coupling between the magnetic moments of Fe cations. Among the studied compositions, Sr{sub 0.75}Y{sub 0.25}FeO{sub 2.79} shows the lowest thermal expansion coefficient (TEC) of 10.5 ppm/K in air at 298–673 K. At 773–1173 K TEC increases up to 17.2 ppm/K due to substantial reduction of oxygen content. The latter also results in a dramatic decrease of the electrical conductivity in air above 673 K. Partial substitution of Fe by Cr, Mn and Ni according to the formula Sr{sub 0.75}Y{sub 0.25}Fe{sub 1y}M{sub y}O{sub 3−δ} (y=0.2, 0.33, 0.5) leads to cubic perovskites for all substituents with y=0.2. Their TECs are higher in comparison with un-doped Sr{sub 0.75}Y{sub 0.25}FeO{sub 2.79}. Only M=Ni has increased electrical conductivity compared to un-doped Sr{sub 0.75}Y{sub 0.25}FeO{sub 2.79}. - Graphical abstract: Oxygen-deficient ferrates with the cubic perovskite structure Sr{sub x}Y{sub 1x}FeO{sub 3−δ} were prepared both in air (0.71≤x≤0.91) and N{sub 2} (x=0.75 and 0.79) at 1573 K. Refinement of the

  7. Specific heat measurements of CePt{sub 3}Si and Ce{sub 1+x}Pt{sub 3+y}Si{sub 1+z}

    Energy Technology Data Exchange (ETDEWEB)

    Motoyama, G. [Graduate School of Material Science, University of Hyogo, Kamigori-cho, Ako-gun, Hyogo 678-1297 (Japan)]. E-mail: motoyama@sci.u-hyogo.ac.jp; Watanabe, M. [Graduate School of Material Science, University of Hyogo, Kamigori-cho, Ako-gun, Hyogo 678-1297 (Japan); Maeda, K. [Graduate School of Material Science, University of Hyogo, Kamigori-cho, Ako-gun, Hyogo 678-1297 (Japan); Oda, Y. [Graduate School of Material Science, University of Hyogo, Kamigori-cho, Ako-gun, Hyogo 678-1297 (Japan); Ueda, K. [Graduate School of Material Science, University of Hyogo, Kamigori-cho, Ako-gun, Hyogo 678-1297 (Japan); Kohara, T. [Graduate School of Material Science, University of Hyogo, Kamigori-cho, Ako-gun, Hyogo 678-1297 (Japan)

    2007-03-15

    We have measured the specific heat of a series of polycrystalline CePt{sub 3}Si and Ce{sub 1+x}Pt{sub 3+y}Si{sub 1+z} samples whose compositions vary slightly from the stoichiometric composition. We observed two peaks derived from magnetic anomalies on the specific heat measurements of the Ce{sub 1+x}Pt{sub 3+y}Si{sub 1+z} samples. One of the peaks relates to the antiferromagnetic phase transition at T{sub N}=2.2K. The other is a large peak at 2.7K observed for the sample that showed a ferromagnetic anomaly at 3.0K on the temperature dependence of the magnetization. Heat treatment had different effects between these anomalies.

  8. Enhanced energy storage and pyroelectric properties of highly (100)-oriented (Pb1-x-yLaxCay)Ti1-x/4O3 thin films derived at low temperature

    Science.gov (United States)

    Zhu, Hanfei; Ma, Hongfang; Zhao, Yuyao

    2018-05-01

    Highly (100)-oriented (Pb1-x-yLaxCay)Ti1-x/4O3 (x = 0.15, y = 0.05; x = 0.1, y = 0.1; x = 0.05, y = 0.15) thin films were deposited on Pt/Ti/SiO2/Si substrates at a low temperature of 450 °C via a sol-gel route. It was found that all the (Pb1-x-yLaxCay)Ti1-x/4O3 thin films could be completely crystallized and the content of La/Ca showed a significant effect on the electrical properties of films. Among the three films, the (Pb1-x-yLaxCay)Ti1-x/4O3 (x = 0.1, y = 0.1) thin film exhibited the enhanced overall electrical properties, such as a low dielectric loss (tan ⁡ δ energy density (Wre ∼ 15 J/cm3), as well as a large pyroelectric coefficient (p ∼ 190 μC/m2K) and figure of merit (Fd‧∼ 77 μC /m2K). The findings suggest that the fabricated thin films with a good (100) orientation can be an attractive candidate for applications in Si-based energy storage and pyroelectric devices.

  9. Superconducting transition temperature in the Y(1-x)M(x)Ba2Cu3O(y) system

    Science.gov (United States)

    Suzuki, Takeyuki; Yamazaki, Tsutomu; Sekine, Ryuuta; Koukitsu, Akinori; Seki, Hisashi

    1989-04-01

    Experimental results are presented for the inclusion of compositional additives, M, to the sintered high-temperature superconductor Y(1-x)M(x)Ba2Cu3O(y); M can be the oxides of Mg, Ce, Gd, Yb, Ti, Zr, V, Nb, Ta, Cr, Mo, W, Mn, Fe, Co, Ni, Zn, B, Al, Ga, In, Si, Ge, Sn, Pb, Sb, Bi, and Te, as well as Li, Na, K, Ca, Sr, and La carbonates. Temperature dependence of the electrical resistance was measured down to about 80 K. Attention is given to the influence of ionic radius and the valence of the M species.

  10. Tunable thermodynamic activity of La x Sr1-x Mn y Al1-y O3-δ (0 ≤ x1, 0 ≤ y1) perovskites for solar thermochemical fuel synthesis.

    Science.gov (United States)

    Ezbiri, M; Takacs, M; Theiler, D; Michalsky, R; Steinfeld, A

    2017-02-28

    Nonstoichiometric metal oxides with variable valence are attractive redox materials for thermochemical and electrochemical fuel processing. To guide the design of advanced redox materials for solar-driven splitting of CO 2 and/or H 2 O to produce CO and/or H 2 (syngas), we investigate the equilibrium thermodynamics of the La x Sr 1- x Mn y Al 1- y O 3- δ perovskite family (0 ≤ x1, 0 ≤ y1) and La 0.6 Ca 0.4 Mn 0.8 Al 0.2 O 3- δ , and compare them to those of CeO 2 as the baseline. Oxygen nonstoichiometry measurements from 1573 to 1773 K and from 0.206 to 180 mbar O 2 show a tunable reduction extent, increasing with increasing Sr content. Maximal nonstoichiometry of 0.32 is established with La 0.2 Sr 0.8 Mn 0.8 Al 0.2 O 3- δ at 1773 K and 2.37 mbar O 2 . As a trend, we find that oxygen capacities are most sensitive to the A-cation composition. Partial molar enthalpy, entropy and Gibbs free energy changes for oxide reduction are extracted from the experimental data using defect models for Mn 4+ /Mn 3+ and Mn 3+ /Mn 2+ redox couples. We find that perovskites exhibit typically decreasing enthalpy changes with increasing nonstoichiometries. This desirable characteristic is most pronounced by La 0.6 Sr 0.4 Mn 0.4 Al 0.6 O 3- δ , rendering it attractive for CO 2 and H 2 O splitting. Generally, perovskites show lower enthalpy and entropy changes than ceria, resulting in more favorable reduction but less favorable oxidation equilibria. The energy penalties due to larger temperature swings and excess oxidants are discussed in particular. Using electronic structure theory, we conclude with a practical methodology estimating thermodynamic activity to rationally design perovskites with variable stoichiometry and valence.

  11. Magnetic behavior of the alloys (Ce{sub 1-x}Y{sub x}){sub 2}PdSi{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Mallik, R [Tata Inst. of Fundamental Res., Colaba, Mumbai (India); Sampathkumaran, E V [Tata Inst. of Fundamental Res., Colaba, Mumbai (India)

    1996-11-01

    The results of X-ray diffraction (Cu K{sub {alpha}}), electrical resistivity ({rho}), heat capacity (C) and magnetic susceptibility ({chi}) measurements are reported for a new pseudoternary solid solution, (Ce{sub 1-x}Y{sub x}){sub 2}PdSi{sub 3} (x=0.0, 0.2, 0.5, 0.8, 1.0). The X-ray diffraction patterns indicate that single phase alloys can be formed in a derived version of the AlB{sub 2}-type hexagonal structure for x{>=}0.2, while for x=0.0, apparently there is an additional weak phase. In the case of the alloy Ce{sub 2}PdSi{sub 3}, the majority of Ce ions do not exhibit magnetic ordering down to 1.4 K, though magnetic ordering at 7 K from one of the two crystallographically inequivalent sites cannot be ruled out. For other compositions, no magnetic ordering is observed above 1.4 K. The Kondo effect is operative in all these alloys, with the strength of the Kondo effect increasing with the compression of the lattice by the gradual replacement of Ce by Y. The C/T exhibits a low temperature enhancement in all Ce containing alloys. (orig.).

  12. Transport and thermoelectric properties of n-type Ruddlesden-Popper phase (Sr1-xGdx)3(Ti1-yTay)2O7 oxides

    International Nuclear Information System (INIS)

    Sun, R R; Qin, X Y; Li, L L; Li, D; Zhang, J; Wang, Q Q

    2012-01-01

    The transport and thermoelectric properties of (Sr 1-x Gd x ) 3 (Ti 1-y Ta y ) 2 O 7 (x = 0.05, y = 0.05-0.15; x = 0.1, y = 0.05-0.1) compounds with Ruddlesden-Popper (RP) phase, prepared by a conventional solid-state reaction method plus spark plasma sintering (SPS), were investigated in the temperature range from 300 to 1000 K. The results indicate that the electrical resistivity ρ for all compounds increases with temperature, and has a relation ρ ∝ T M (i.e. the mobility μ ∝ T -M ) with M = 1.58-1.92 at T ≳ 650 K, indicating that the phonon scattering is predominant. Basically, the absolute value of the Seebeck coefficient |S| increases almost linearly with temperature above ∼400 K, showing degenerated semiconducting behaviour. Moreover, both ρ and |S| decrease with the increase in both Ta and Gd content, which can be attributed to an increase in the carrier concentration. The lattice thermal conductivity κ L of the compounds decreases monotonically with an increase in both Ta and Gd content due to mass-defect phonon scattering, and the lowest κ L (κ L = 3.3 W K -1 m -1 at room temperature and 2.0 W K -1 m -1 at 1000 K) is achieved in (Sr 0.9 Gd 0.1 ) 3 (Ti 0.9 Ta 0.1 ) 2 O 7 . Among all the compounds investigated here, the largest dimensionless figure of merit ZT = 0.08 (at 1000 K) is obtained in the compound (Sr 0.9 Gd 0.1 ) 3 (Ti 0.95 Ta 0.05 ) 2 O 7 .

  13. XYO{sub 3} (X = K, Na; Y = Nb, Ta) based superlattices for photocatalysis

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Guang-Zhao; Chen, Xiao-Rui; Yuan, Hong-Kuan; Kuang, An-Long [School of Physical Science and Technology, Southwest University, Chongqing 400715 (China); Chen, Hong [School of Physical Science and Technology, Southwest University, Chongqing 400715 (China); Key Laboratory of Luminescent and Real-Time Analytical Chemistry, Ministry of Education, College of Chemistry and Chemical Engineering, Southwest University, Chongqing 400715 (China)

    2017-05-15

    The photocatalytic activities of XYO{sub 3} (X = K, Na; Y = Ta, Nb) and XYO{sub 3}/X1Y1O{sub 3} (X, X1 = K, Na; Y, Y1 = Ta, Nb) systems are investigated by using hybrid density functional. All the XYO{sub 3} and XYO{sub 3}/X1Y1O{sub 3} systems are indirect band gap semiconductors, and the band gap of KNbO{sub 3}/KTaO{sub 3} is smaller than those of KNbO{sub 3} and KTaO{sub 3}, while the band gaps of KNbO{sub 3}/NaNbO{sub 3}, KNbO{sub 3}/NaTaO{sub 3}, KTaO{sub 3}/NaNbO{sub 3}, KTaO{sub 3}/NaTaO{sub 3}, and NaNbO{sub 3}/NaTaO{sub 3} are respectively between the band gaps of these two crystals which make up these superlattices. The electronic structure of KNbO{sub 3}/NaTaO{sub 3} is the same as that of KTaO{sub 3}/NaNbO{sub 3} since both have the same component and similar crystal structure. The band edges of all the considered superlattices are thermodynamically allowed for the water reduction and oxidation processes, and therefore, they could be used for photocatalytic water splitting. Band structures for (i) KNbO{sub 3}/KTaO{sub 3}, (ii) KNbO{sub 3}/NaNbO{sub 3}, (iii) KNbO{sub 3}/NaTaO{sub 3}, (iv) KTaO{sub 3}/NaNbO{sub 3}, (v) KTaO{sub 3}/NaTaO{sub 3}, and (vi) NaNbO{sub 3}/NaTaO{sub 3} superlattices. The horizontal dashed lines represent the Fermi levels. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  14. New view on In{sub x}Ga{sub 1-x}N{sub y}As{sub 1-y}alloys

    Energy Technology Data Exchange (ETDEWEB)

    Elyukhin, Vyacheslav A. [Departamento de Ingenieria Electrica, Centro de Investigacion y de Estudios Avanzados del Instituto Politecnico Nacional, Avenida Instituto Politecnico Nacional 2508, 07360, Mexico (Mexico)

    2015-12-15

    Semiconductors with isoelectronic centers are actively studied to fabricate arrays of identical single photon emitters. Self-assembling of 4N10In and 1N4In clusters in GaAs-rich In{sub x}Ga{sub 1-x}N{sub y}As{sub 1-y} is represented. All or almost all In atoms are in 4N10In clusters from 0 to 800 C in In{sub x}Ga{sub 1-x}N{sub y}As{sub 1-y} with x = 1 x 10{sup -4}, y = 1 x 10{sup -4} and x = 1 x 10{sup -5}, y = 1 x 10{sup -5}. All or almost all nitrogen atoms are in 1N4In clusters if x = 0.01, y = 1 x 10{sup -4} and x = 1 x 10{sup -3}, y = 1 x 10{sup -6}. There are both types of clusters in alloys with x = 5 x 10{sup -5}, y = 5 x 10{sup -7}; x = 2 x 10{sup -4}, y = 2 x 10{sup -6}; x = 1 x 10{sup -4}, y = 1 x 10{sup -5} and x = 2 x 10{sup -3}, y = 2 x 10{sup -4} and portions of nitrogen atoms in clusters depend on the composition and temperature. Thus, In{sub x}Ga{sub 1-x}N{sub y}As{sub 1-y} are promising semiconductors to obtain arrays of identical isoelectronic clusters with the desirable density. (copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  15. NMR study of (Y1-xLax) Mn2X2 (X = Ge, Si) compounds

    International Nuclear Information System (INIS)

    Ichinose, K.; Nagai, H.; Tsujimura, A.; Oyasato, M.

    1988-01-01

    Nuclear magnetic resonances of 55 Mn and 139 La nuclei in (Y 1-x La x ) Mn 2 X 2 (X = Ge, Si) have been observed at 4.2 K in their ferromagnetic state for 0.3x1. The hyperfine fields at these nuclei are independent of La concentration. This result shows that Mn moment is almost constant when replacing Y with La

  16. Polymorphic phase transition and morphotropic phase boundary in Ba{sub 1-x}Ca{sub x}Ti{sub 1-y}Zr{sub y}O{sub 3} ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Abdessalem, M. Ben; Aydi, S.; Aydi, A.; Abdelmoula, N.; Khemakhem, H. [Universite de Sfax, Faculte des Sciences de Sfax (FSS), Laboratoire des Materiaux Multifonctionnels et Applications (LaMMA) LR16ES18, B.P.1171, Sfax (Tunisia); Sassi, Z. [Laboratoire de Genie Electrique et Ferroelectricite (LGEF) de L' INSA de Lyon, Lyon (France)

    2017-09-15

    This paper deals with Ca and Zr co-doped BaTiO{sub 3} (BCTZ{sub (x,} {sub y)}) (x = 0.1, 0.13, 0.2 and y = 0.05, 0.1, 0.15). These ceramics were prepared using the conventional solid state method. The symmetry, dielectric properties, Raman spectroscopy, ferroelectric behavior and piezoelectric effect were examined. X-ray diffraction (XRD) results display that morphotropic boundary occurs from tetragonal to orthorhombic region of BCZT{sub (x=0.1,} {sub 0.2,} {sub y=0.05,} {sub 0.1)} and polymorphic phase transitions from tetragonal to orthorhombic, orthorhombic to rhombohedral regions of BCZT{sub (x=0.13,} {sub y=0.1)}. The evolution of the Raman spectra was investigated as a function of compositions at room temperature, in correlation with XRD analysis and dielectric measurements. We note that the substitution of Ca in Ba site and Zr ions in Ti site slightly decreased the cubic-tetragonal temperature transition (T{sub C}) and increased the orthorhombic-tetragonal (T{sub 1}) and rhombohedral-orthorhombic (T{sub 2}) temperatures transitions. The ferroelectric properties were examined by a P-E hysteresis loop. The two parameters ΔT{sub 1} and ΔT{sub 2} are defined as ΔT{sub 1} = T{sub C} - T{sub 1} and ΔT{sub 2} = T{sub C} - T{sub 2}, they come close to T{sub C} for x = 0.13, y = 0.1, which reveals that this composition is around the polymorphic phase. The excellent piezoelectric coefficient of d{sub 33} = 288 pC N{sup -1}, the electromechanical coupling factor k{sub p} = 40%, high constant dielectric 9105, coercive field E{sub c} = 0.32 (KV mm{sup -1}) and remanent polarization P{sub r} = 0.1 (μc mm{sup -2}) were obtained for composition x = 0.13, y = 0.1. (orig.)

  17. Neutron structural studies of La3.5-x-y(Y)yBa3.5-xCa2xCu7Oz (x = y = 0.0 and 0.5) system

    International Nuclear Information System (INIS)

    Subbarao, M.V.; Kulkarni, R.G.; Rajagopal, H.; Sequeira, A.S.

    1997-01-01

    By mixing equal amounts of La 4-x Ca x Ba 3 Cu 7 O z and La 3 Ba 4-x Ca x Cu 7 O z in the proportion of 1 : 1, a series of superconductors part of La replaced by Y with the nominal composition of La 3.5-x-y )(Y) y Ba 3.-5-x Ca 2x Cu 7 O z (LYCP) have been prepared. Two samples with x = y = 0.0 (A) and x = y = 0.5 (B) characterized by x-ray diffraction display tetragonal triple perovskite structure. In order to investigate the effect of substituents (Ca/Y) on structure of this system, neutron diffraction measurements have been carried out at 300 K and λ n =1.216A at Dhruva reactor

  18. Phase transformations in multiferroic Bi{sub 1x}La{sub x}Fe{sub 1y}Ti{sub y}O{sub 3} ceramics probed by temperature dependent Raman scattering

    Energy Technology Data Exchange (ETDEWEB)

    Xu, L. P.; Zhang, X. L.; Zhang, J. Z.; Hu, Z. G., E-mail: zghu@ee.ecnu.edu.cn; Chu, J. H. [Key Laboratory of Polar Materials and Devices, Ministry of Education, Department of Electronic Engineering, East China Normal University, Shanghai 200241 (China); Zhang, L. L.; Yu, J. [Functional Material Research Laboratory, Tongji University, Shanghai 200092 (China)

    2014-10-28

    Optical phonons and phase transitions of Bi{sub 1x}La{sub x}Fe{sub 1y}Ti{sub y}O{sub 3} (BLFTO, 0.02 ≤ x ≤ 0.12, 0.01 ≤ y ≤ 0.08) ceramics have been investigated by Raman scattering in the temperature range from 80 to 680 K. Four phase transitions around 140, 205, 570, and 640 K can be observed. The Raman modes are sensitive to the spin reorientation around 140 and 205 K, owing to the strong magnon-phonon coupling. The transformation around 570 K is a structural transition from rhombohedral to orthorhombic phase due to an external pressure induced by the chemical substitution. The anomalies of the phonon frequencies near Néel temperature T{sub N} have been discussed in the light of the multiferroicity. Moreover, it was found that the structural transition temperature and T{sub N} of BLFTO ceramics decrease towards room temperature with increasing doping composition as a result of size mismatch between substitution and host cations.

  19. Thermoelectric properties of Ca1-xYxMnO3 and Ca0.9Y0.1-yFeyMnO3 perovskite compounds

    DEFF Research Database (Denmark)

    Thuy, Nguyen Thi; Minh, Dang Le; Van Nong, Ngo

    2012-01-01

    Polycrystalline Ca1-xYxMnO3 (x = 0.0; 0.1; 0.3; 0.5; 0.7) and Ca0.9Y0.1-yFeyMnO3 (y = 0.00; 0.01; 0.03; 0.05) compounds were prepared by solid-state reaction. X-ray diffraction (XRD) analysis revealed all XRD peaks of all the samples as identical to the orthorhombic structure. The thermoelectric ...

  20. Crystal structure investigations of ZrAsxSey (x>y, x+y≤2) by single crystal neutron diffraction at 300 K, 25 K and 2.3 K

    International Nuclear Information System (INIS)

    Niewa, Rainer; Czulucki, Andreas; Schmidt, Marcus; Auffermann, Gudrun; Cichorek, Tomasz; Meven, Martin; Pedersen, Bjoern; Steglich, Frank; Kniep, Ruediger

    2010-01-01

    Large single crystals of ZrAs x Se y (x>y, x+y≤2, PbFCl type of structure, space group P4/nmm) were grown by Chemical Transport. Structural details were studied by single crystal neutron diffraction techniques at various temperatures. One single crystal specimen with chemical composition ZrAs 1.595(3) Se 0.393(1) was studied at ambient temperature (R1=5.10 %, wR2=13.18 %), and a second crystal with composition ZrAs 1.420(3) Se 0.560(1) was investigated at 25 K (R1=2.70%, wR2=5.70 %) and 2.3 K (R1=2.30 %, wR2=4.70 %), respectively. The chemical compositions of the crystals under investigation were determined by wavelength dispersive X-ray spectroscopy. The quantification of trace elements was carried out by Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry. According to the crystal structure refinements the crystallographic 2a site is occupied by As, together with a significant amount of vacancies. One of the 2c sites is fully occupied by As and Se (random distribution). With respect to the fractional coordinates of the atoms, the crystal structure determinations based on the data obtained at 25.0 K and 2.3 K did not show significant deviations from ambient temperature results. The temperature dependence of the displacement parameters indicates a static displacement of As on the 2a sites (located on the (0 0 1) planes) for all temperatures. No indications for any occupation of interstitial sites or the presence of vacancies on the Zr (2a) site were found. - Graphical abstract: Large single crystals of ZrAs x Se y grown by Chemical Transport to study structural details as the As-Se order scheme by single crystal neutron diffraction.

  1. Strong piezoelectricity in (1 - x)(K0.4Na0.6)(Nb0.96Sb0.04)O3-xBi0.5K0.5Zr1-ySnyO3 lead-free binary system: identification and role of multiphase coexistence.

    Science.gov (United States)

    Zheng, Ting; Wu, Jiagang; Xiao, Dingquan; Zhu, Jianguo; Wang, Xiangjian; Xin, Lipeng; Lou, Xiaojie

    2015-03-18

    Here we report a strong piezoelectric activity in (1 - x)(K0.4Na0.6)(Nb0.96Sb0.04)O3-xBi0.5K0.5Zr1-ySnyO3 lead-free ceramics by designing different phase boundaries. The phase boundaries concerning rhombohedral-orthorhombic-tetragonal (R-O-T) and rhombohedral-tetragonal (R-T) multiphase coexistence were attained by changing BKZS and Sn contents and then were identified by the X-ray diffraction patterns as well as temperature-dependent permittivity and ν1 Raman modes associated with BO6 perovskite octahedron. A high strain (strain = 0.21-0.28% and d33* = 707-880 pm/V) and a strong piezoelectric coefficient (d33 = 415-460 pC/N) were shown in the ceramics located at the multiphase coexistence region. The reported results of this work are superior to that (d33* ∼ 570 pm/V and d33 ∼ 416 pC/N) of the textured (K,Na,Li)(Nb,Ta,Sb)O3 ceramics [Nature 2004, 432, 84]. We believe that the material system of this work will become one of the most promising candidates for piezoelectric actuators.

  2. Fe site occupancy and superconductivity in Y1-zCazBaz(Cu1-xFex)3O6+y

    International Nuclear Information System (INIS)

    Smith, M.G.; Taylor, R.D.; Oesterreicher, H.

    1990-01-01

    X-ray diffraction and 57 Fe Moessbauer spectroscopy studies show that partial substitution of Ca for Y in Y 1-z Ca z Ba 2 (Cu 1-x Fe x ) 3 O 6+y (0.05 ≤ z ≤ 0.15,0.003 ≤ x ≤ 0.20) result in increased Fe solubility and a larger percentage of Fe occupancy of the Cu(2) plane site (prepared conventionally). Materials with z > 0.00 have a slightly depressed superconducting transition onset temperature T c relative to the z = 0.00 compounds. It is also shown that Fe occupancy of the Cu(2) site in Y 1-z Ca z Ba 2 (Cu 1-x Fe x ) 3 O 6+y can be substantially increased when these materials are treated at high temperatures in inert atmospheres followed by oxygenation at low temperatures. T c decreases more rapidly in these latter materials compared to the conventionally prepared ones. Implications concerning ordered Fe cluster formation and superconducting pair breaking in the Cu(2) site are drawn. 7 refs., 4 tabs

  3. Oxygen transport in La1-xSrxFe1-yMnyO3-δ perovskites

    DEFF Research Database (Denmark)

    Mikkelsen, L.; Andersen, I.G.K.; Skou, E.M.

    2002-01-01

    The oxygen transport in La1-xSrxFe1-yMnyO3-delta (LSFM) with 0 less than or equal to x less than or equal to 0.5 and y = 0.2 and 03 has been examined with a thermogravimetric method. As long as x less than or equal to y, the oxygen transport was found to be very slow while the oxygen transport in...

  4. Influence of the sintering temperature on the Sr content in a Ca_(_1_−_x_−_y_)Ce_xSr_yAl_zTi_(_1_−_z_)O_3 perovskite (x = 0.04–0.16) co-doped with Ce

    International Nuclear Information System (INIS)

    Kamel, Nour-el-hayet; Mouheb, Yasmina; Kamel, Ziane; Moudir, Dalila; Aouchiche, Fairouz; Arabi, Azeddine

    2016-01-01

    A Sr-Ce co-doped perovskite, with the chemical formula: Ca_(_1_−_x_−_y_)Ce_xSr_yAl_zTi_(_1_−_z_)O_3 (y = 0.04, 0.08, 0.12 and 0.16, x = 0.05) is synthesized by sol–gel process. The influence of the sintering temperature, Ts, on the rate of inserted Sr was investigated at 1223, 1373 and 1473 K. The Sr amount sequestered in the perovskite reaches 85% (y = 0.16, 9.50 wt%) for Ts = 1373 K, giving sintering densities between 3.520 and 4.400. XRD analysis reveals an orthorhombic CaTiO_3 structure. The lattice parameters obey to Vegard’s law for Ts = 1373 and 1473 K. SEM analysis shows orthorhombic grains of 0.514 μm × 1 μm mean dimensions. MCC1 and MCC2 tests, performed on minerals sintered at 1373 K, indicate that the most durable one is that containing 9.50 wt% Sr. MCC1 test gave 6.998·10"−"6 g/cm"2 d of Sr, and MCC2 2.143·10"−"4 g/cm"2 d of Ce. The temperature favors the Sr dissolution to the detriment of Ce. The Ca dissolution rate reaches 1.002·10"−"6 to 2.005·10"−"6 g/cm"2 d. - Highlights: • Ca_(_1_−_x_−_y_)Ce_xSr_yAl_zTi_(_1_−_z_)O_3 perovskite is synthesized by sol–gel. • The influence of the sintering temperature, Ts, on the rate of inserted Sr was investigated at 1223, 1373 and 1473 K. • 85% of total Sr was sequestered in the perovskite for Ts = 1373 K. • MCC1 and MCC2 leach tests indicate that the most durable mineral is that containing 9.50 wt.% Sr. • MCC1 test gave 8.10 10"−"1"0 kg/m"2.d Sr. The lower is the leaching temperature the higher is the mineral durability.

  5. Magnetic properties of CexY1-xPt compared to CexLa1-xPt ones

    Science.gov (United States)

    Očko, M.; Zadro, K.; Drobac, Đ.; Aviani, I.; Salamon, K.; Mixon, D.; Bauer, E. D.; Sarrao, J. L.

    2018-04-01

    We have investigated the magnetic properties of the CexY1-xPt Kondo ferromagnetic alloy system in the temperature range from 1.8 K to 320 K. The results of these investigations can be summarized as follows: dc-susceptibility can be described by the Curie-Weiss law at higher temperatures down to about 100 K, but also at low temperatures above the ferromagnetic phase transition. At higher temperatures, the extracted Curie-Weiss parameter, θp, is negative and at low temperature θC is positive. The extracted effective magnetic moment above 100 K increases with the Ce content up to almost the theoretical value of the isolated Ce3+ ion, μ = 2.54 μB, for CePt. This suggests an increase of the hybridization with decreasing Ce content, or said equivalently, it means that the increase of the Kondo interaction diminishes effective magnetic moment. These observations confirm the main conclusions inferred from an earlier transport properties investigation of this alloy system. The corresponding θC differs within 1 K from the Curie temperature, TC, which is determined by the resistivity measurements. The most intriguing result of the investigation of CexY1-xPt is the linear concentration dependence of TC vs. x and, moreover, it is the same as in CexLa1-xPt although in the former system the hybridization diminishes considerably the effective magnetic moment per Ce ion, while in the latter system, hybridization is minor and independent of x. We offer the explanations of these intriguing experimental results.

  6. Mn-substituted perovskites RECoxMn1-xO3: a comparison between magnetic properties of LaCoxMn1-xO3 and GdCoxMn1-xO3

    Directory of Open Access Journals (Sweden)

    Barahona, P.

    2008-08-01

    Full Text Available Cooperative phenomena constitute important mechanisms to explain the magnetic properties of the perovskite manganites REMnO3, in which the rare-earth and/or Mn is partially replaced by divalent elements. In this way, the manganese ion changes its valence state (Mn3+ Mn4+, triggering strong magnetic interactions. In this work we describe the case of GdCoxMn1-xO3 (0.0 ≤ x1.0 for which the antiferromagnetic interaction between the Gd sublattice and the Mn/Co network leads to a reversal of the magnetic moment at low temperature. No inversion is observed for the LaCoxMn1-xO3 series, in which the ordering temperature may attain a maximum of 235 K for LaCo0.50Mn0.50O3, while it is only 120 K for similar Co/Mn ratio in the case of GdCo0.50Mn0.50O3. Magnetic properties are described in terms of two regimes: one, for x 3 manganite and another one, for x > 0.5, when Mn substitutes Co in the GdCoO3 cobaltite, while the magnetic interactions are maximized at x(Co = 0.50. This hypothesis is discussed in terms of the respective oxidation states of both manganese (Mn3+ / Mn4+ and cobalt (Co2+ / Co3+.El fenómeno cooperativo constituye un importante mecanismo para explicar las propiedades magnéticas de las perovskitas manganitas TRMnO3, en las que el catión de tierra rara, TR, y/o el catión Mn3+ son parcialmente reemplazados por cationes divalentes. Por esta vía el ión de manganeso cambia de estado de valencia (Mn3+ Mn4+, generando fuertes interacciones magnéticas. En el presente trabajo se describe el caso de las soluciones sólidas GdCoxMn1-xO3 (0.0 ≤ x1.0 para las que la interacción antiferromagnética entre la subred del Gd3+ y la red Mn/Co lleva a una inversión del momento magnético a baja temperatura. No se ha observado inversión para la serie LaCoxMn1-xO3, en que la temperatura de orden puede alcanzar un máximo de 235K para LaCo0.50Mn0.50O3, mientras que en el caso de GdCo0.50Mn0.50O3, en que sí se observa inversión, la

  7. Search for negative U in the Ba1-xKxBi1-yPbyO3 system using constrained density-functional theory

    International Nuclear Information System (INIS)

    Vielsack, G.; Weber, W.

    1996-01-01

    Calculations using constrained density-functional theory have been carried out for the Ba 1-x K x Bi 1-y Pb y O 3 system, using a full-potential linearized-augmented-plane-wave method and employing fcc supercell geometries with two formula units. The results have been mapped onto Hubbard-type models in order to extract values of interaction parameters U at the Bi sites. Two different mapping procedures have been utilized. The first one is the standard method, based on the comparison of total-energy curvatures. The second method, proposed in the present work, relies on the analysis of single particle energies and yields much smaller numerical errors. For BaBiO 3 interaction parameters are obtained for the following models: (i) s and p orbitals at Bi and p orbitals at O sites. Here, U s =3.1±0.4 eV, U sp =1.4±0.2 eV, U p =2.2±0.4 eV are found, (ii) s(Bi) and p(O) orbitals, yielding U s =1.9±0.7 eV, and (iii) an effective one-band model, leading to U s =0.6±0.4 eV. Further studies have been performed for breathing distorted BaBiO 3 and for various Ba 1-x K x Bi 1-y Pb y O 3 alloys using virtual crystal approximations. The resulting U values are somewhat larger than for pure BaBiO 3 . Thus, in all cases, the values of Bi U parameters are found to be positive. There is no indication of a negative U of electronic origin. copyright 1996 The American Physical Society

  8. NMR study of Y2(Co1-xFex)14B compounds

    International Nuclear Information System (INIS)

    Maruyama, F.; Ichinose, K.; Nagai, H.; Adachi, K.; Misawa, M.; Tsujimura, A.

    1992-01-01

    59 Co and 89 Y NMR of Y 2 (Co 1-x Fe x ) 14 B compounds has been measured at 4.2 K. The line positions shift rapidly to higher frequency for x≤0.3 and are almost constant for 0.3 1 and 8j 2 sites give a large contribution to the anisotropy of the 3d sublattice. (orig.)

  9. Thermoelectric properties of p-type Ag{sub 1x}(Pb{sub 1y}Sn{sub y}){sub m}Sb{sub 1−z}Te{sub m+2}

    Energy Technology Data Exchange (ETDEWEB)

    Ahn, Kyunghan [Department of Chemistry, Northwestern University, Evanston, IL 60208 (United States); Center for Nanoparticle Research, Institute for Basic Science, (IBS), Seoul 151-742 (Korea, Republic of); Kong, Huijun; Uher, Ctirad [Department of Physics, University of Michigan, Ann Arbor, MI 48109 (United States); Kanatzidis, Mercouri G., E-mail: m-kanatzidis@northwestern.edu [Department of Chemistry, Northwestern University, Evanston, IL 60208 (United States)

    2016-10-15

    The thermoelectric properties of Ag{sub 1x}(Pb{sub 1y}Sn{sub y}){sub m}Sb{sub 1−z}Te{sub m+2} (4≤m≤16, −0.1≤x≤0.3, 1/3≤y≤2/3, 0.2≤z≤0.4; Lead Antimony Silver Tellurium Tin, LASTT-m) compositions were investigated in the temperature range of 300 to ~670 K. All samples crystallize in the average NaCl-type structure without any noticeable second phase and exhibit very narrow bandgaps of <0.1 eV. We studied a range of m values, silver concentrations (x), Pb/Sn ratios (y), and antimony concentrations (z) to determine their effects on the thermoelectric properties. The samples were investigated as melt grown polycrystalline ingots. Varying the Ag contents, the Pb/Sn ratios, and the Sb contents off-stoichiometry allowed us to control the electrical conductivity, the Seebeck coefficient, and the thermal conductivity. The electrical conductivity tends to decrease with decreasing m values. The highest ZT of ~1.1 was achieved at ~660 K for Ag{sub 0.9}Pb{sub 5}Sn{sub 5}Sb{sub 0.8}Te{sub 12} mainly due to the very low lattice thermal conductivity of ~0.4 W/(m K) around 660 K. Also, samples with charge-balanced stoichiometries, Ag(Pb{sub 1y}Sn{sub y}){sub m}SbTe{sub m+2}, were studied and found to exhibit a lower power factor and higher lattice thermal conductivity than the Ag{sub 1x}(Pb{sub 1y}Sn{sub y}){sub m}Sb{sub 1−z}Te{sub m+2} compositions. - Graphical abstract: The Ag{sub 1x}(Pb{sub 1y}Sn{sub y}){sub m}Sb{sub 1−z}Te{sub m+2} system defines a complex and flexible class of tunable thermoelectric class of materials with high performance.

  10. Characterization and carbon monoxide oxidation activity of La1-ySryCr1-xRuxO3 perovskites

    Directory of Open Access Journals (Sweden)

    C. MARINOVA

    2000-01-01

    Full Text Available The oxidation of CO over La1-ySryCr1-xRuxO3 perovskite type oxides with y=0.3 and 0 £ x £ 0.100 have been studied. X-ray fluorescence analysis confirmed that content of elements in the bulk corresponds to the established nominal perovskite stoichiometry, indicating that no significant oxidation of ruthenium into volatile polyvalent oxides with their consequented escape from the sample occurred in air up to the temperature of 1000°C. According to X-ray diffraction analysis, all sampls achieved the perovskite hexagonal with the presence of some SrCrO4. X-ray photoelectron spectroscopy analysis of ruthenium samples shows higher Ru and Sr surface concentraitions than in the bulk. The binding energy for Ru3p is virtually the same in all samples and consistent with that of Ru4+ (463.6-464.3eV. Kinetic studies were performed in a differential recycle reactor with a recycling ratio 80. The results show that substitution of Ru4+ for Cr3+ in La1-ySryCrO3 leads to a significant increase in both the activity and the activation energy. The global CO oxidation rate, referred on the BET surface area, correlates with the surface Ru4+ atomic concentraiton. Hence, the activity reflect the surface enrichment in ruthenium. Moreover, an identical apparent activation energy E = 93 kJ/mol and the same specific rate per ruthenium surface ion were obtained for samples with a Ru content x ³ 0.05 suggest that exposed Ru4+ ions mainly participate in the reaction.

  11. On Positive Solutions for the Rational Difference Equation Systems x n+1 = A/x n y n (2), and y n+1 = By n /x n-1 y n-1.

    Science.gov (United States)

    Ma, Hui-Li; Feng, Hui

    2014-01-01

    Our aim in this paper is to investigate the behavior of positive solutions for the following systems of rational difference equations: x n+1 = A/x n y n (2), and y n+1 = By n /x n-1 y n-1, n = 0,1,…, where x -1, x 0, y -1, and y 0 are positive real numbers and A and B are positive constants.

  12. Transesterification of palm oil on K{sub y}Mg{sub 1} {sub -} {sub x}Zn{sub 1} {sub +} {sub x}O{sub 3} catalyst: Effect of Mg-Zn interaction

    Energy Technology Data Exchange (ETDEWEB)

    Olutoye, M.A.; Hameed, B.H. [School of Chemical Engineering, Engineering Campus, Universiti Sains Malaysia, 14300 Nibong Tebal, Penang (Malaysia)

    2010-06-15

    The Mg-Zn interaction effect of K{sub y}Mg{sub 1} {sub -} {sub x}Zn{sub 1} {sub +} {sub x}O{sub 3} heterogeneous type catalyst and its performance on transesterification of palm oil have been studied using the response surface methodology and the factorial design of experiments. The catalyst was synthesized using the co-precipitation method and the activity was assessed by transesterification of palm oil into fatty acid methyl esters. The ratio of the Mg/Zn metal interaction, temperature and time of calcination were found to have positive influence on the conversion of palm oil to fatty acid methyl ester (FAME) with the effect of metal to metal ratio and temperature of calcination being more significant. The catalytic activity was found to decrease at higher calcination temperature and the catalyst type K{sub 2}Mg{sub 0.34}Zn{sub 1.66}O{sub 3} with Mg/Zn ratio of 4.81 gave FAME content of 73% at a catalyst loading of 1.404 wt.% of oil with molar ratio of methanol to oil being 6:1 at temperature of 150 C in 6 h. A regression model was obtained to predict conversions to methyl esters as a function of metal interaction ratio, temperature of calcination and time. The observed activity of the synthesized catalyst was due to its synergetic structure and composition. (author)

  13. Neutron structural studies of La{sub 3.5-x-y}(Y){sub y}Ba{sub 3.5-x}Ca{sub 2x}Cu{sub 7}O{sub z} (x = y = 0.0 and 0.5) system

    Energy Technology Data Exchange (ETDEWEB)

    Subbarao, M V; Kulkarni, R G [Department of Physics, Saurashtra University, Rajkot (India); Rajagopal, H; Sequeira, A S [Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai (India)

    1997-07-01

    By mixing equal amounts of La{sub 4-x}Ca{sub x}Ba{sub 3}Cu{sub 7}O{sub z} and La{sub 3}Ba{sub 4-x} Ca{sub x}Cu{sub 7}O{sub z} in the proportion of 1 : 1, a series of superconductors part of La replaced by Y with the nominal composition of La{sub 3.5-x-y}(Y){sub y} Ba{sub 3.-5-x}Ca{sub 2x}Cu{sub 7}O{sub z} (LYCP) have been prepared. Two samples with x = y = 0.0 (A) and x = y = 0.5 (B) characterized by x-ray diffraction display tetragonal triple perovskite structure. In order to investigate the effect of substituents (Ca/Y) on structure of this system, neutron diffraction measurements have been carried out at 300 K and {lambda}{sub n}=1.216A at Dhruva reactor.

  14. Microstructure and properties of hot extruded Mg-3Zn-Y-xCu (x = 0, 1, 3, 5) alloys

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Bao-sheng; Kuang, Ya-fei; Fang, Da-qing; Chai, Yue-sheng [Taiyuan Univ. of Science and Technology (China). College of Materials Science and Engineering; Taiyuan Univ. of Science and Technology (China). Engineering Research Center for Magnesium Alloys of Shanxi Province; Zhang, Yue-zhong [Taiyuan Univ. of Science and Technology (China). Engineering Research Center for Magnesium Alloys of Shanxi Province; Taiyuan Univ. of Science and Technology (China). College of Chemical and Biological Engineering

    2017-04-15

    In petroleum drilling engineering, materials with high strength and rapid degradation are required for degradable fracturing ball applications. In this work, the microstructure, mechanical properties, and corrosion behavior of extruded Mg-3Zn-Y-xCu (x = 0, 1, 3, 5 weight percent) alloys are investigated using optical microscopy, scanning electronic microscopy equipped with energy dispersive X-ray spectroscopy, X-ray diffraction, transmission electronic microscopy, compression tests, electrochemical measurements, and hydrogen evolution tests, to explore their potential as excellent candidate alloys for degradable fracturing ball applications. It is found that the Mg-3Zn-Y alloy is mainly composed of α-Mg, Mg{sub 3}Zn{sub 3}Y{sub 2}, and Mg{sub 3}Zn{sub 6}Y phases. After Cu addition, a new MgZnCu phase is formed, while the Mg{sub 3}Zn{sub 3}Y{sub 2} phase disappears. The Mg-3Zn-Y-3Cu alloy shows the highest compressive strength (473 MPa) and yield strength (402 MPa), mainly attributed to the combined effect of the fine-grain and dispersed precipitation of Mg{sub 3}Zn{sub 6}Y and MgZnCu. The corrosion rate of Mg-3Zn-Y-3Cu reaches 0.41 mm day{sup -1} in 3.5 wt.% KCl solution. Consequently, Mg-3Zn-Y-3Cu alloy is a suitable degradable fracturing ball-seat material.

  15. On the system of rational difference equations xn+1 = f(xn,yn-k), yn+1 = f(yn, xn-k)

    OpenAIRE

    Xi Hongjian; Sun Taixiang; Hong Liang

    2006-01-01

    We study the global asymptotic behavior of the positive solutions of the system of rational difference equations xn+1 = f(xn,yn-k), yn+1 = f(yn, xn-k), n = 0,1,2,..., under appropriate assumptions, where k ∈ {1,2,...} and the initial values x-k, x-k+1,...,x0, y-k, y-k+1, ..., y0 ∈ (0,+∞). We give sufficient conditions under which every positive solution of this equation converges to a positive equilibrium. The main theorem in [1] is included in our result.

  16. Galvanomagnetic effects in n-Hg1-x-yCdxMnyTe and n-Hg1-yMnyTe crystals with εg>0

    International Nuclear Information System (INIS)

    Gluzman, N.G.; Lerinman, N.K.; Sabirzyanova, L.D.; Bodnaruk, O.A.; Gorbatyuk, I.N.; Rarenko, I.M.

    1989-01-01

    Longitudinal ρ zz and transverse ρ xx magnetoresistances and R hall coefficient in H magnetic fields up to 100 kE at 1.2≤T≤300 K are measured at n-Hg 1-x-y Cd x Mn y Te and n-Hg 1-y Mn y Te crystals (100≤ε g ≤260 meV) with N D -N A ≅10 15 cm -3 . Shubnikov-de-Gaas (SG) oscillations were observed at all specimens. Maxima positions of SG oscillations depend on T. For Hg 1-y Mn y Te crystals the position of zero maximum is shifted to large H direction, it is caused by abrupt (as compared to zone one) reduction of summary g-factor. Magnetophonon oscillations are determined at longitudinal magnetoresistance. Transition from metal conductivity to activation one occuring in magnetic field is studied; activation energy in nonmetallic range is determined. Some peculiarities of galvanomagnetic phenomena in n-Hg 1-y Mn y Te specimens, which indicate presence of p-type inclusions in n-type crystals, are determined

  17. The influence of excess K2O on the electrical properties of (K,Na)1/2Bi1/2TiO3 ceramics

    Science.gov (United States)

    Li, Linhao; Li, Ming; Sinclair, Derek C.

    2018-04-01

    The solid solution (KxNa0.50-x)Bi0.50TiO3 (KNBT) between Na1/2Bi1/2TiO3 and K1/2Bi1/2TiO3 (KBT) has been extensively researched as a candidate lead-free piezoelectric material because of its relatively high Curie temperature and good piezoelectric properties, especially near the morphotropic phase boundary (MPB) at x ˜ 0.10 (20 mol. % KBT). Here, we show that low levels of excess K2O in the starting compositions, i.e., (Ky+0.03Na0.50-y)Bi0.50TiO3.015 (y-series), can significantly change the conduction mechanism and electrical properties compared to a nominally stoichiometric KNBT series (KxNa0.50-x)Bi0.50TiO3 (x-series). Impedance spectroscopy measurements reveal significantly higher bulk conductivity (σb) values for y ≥ 0.10 samples [activation energy (Ea) ≤ 0.95 eV] compared to the corresponding x-series samples which possess bandgap type electronic conduction (Ea ˜ 1.26-1.85 eV). The largest difference in electrical properties occurs close to the MPB composition (20 mol. % KBT) where y = 0.10 ceramics possess σb (at 300 °C) that is 4 orders of magnitude higher than that of x = 0.10 and the oxide-ion transport number in the former is ˜0.70-0.75 compared to processing. This demonstrates the electrical properties of KNBT to be sensitive to low levels of A-site nonstoichiometry and indicates that excess K2O in KNBT starting compositions to compensate for volatilisation can lead to undesirable high dielectric loss and leakage currents at elevated temperatures.

  18. Nonlinear acoustic properties of the ternary (La sub 2 O sub 3) sub x (Sm sub 2 O sub 3) sub y (P sub 2 O sub 5) sub (1-x-y) phosphate glasses

    International Nuclear Information System (INIS)

    Senin, H.B.; Sidek, H.A.A.; Saunders, G.A.

    1994-01-01

    From measurements of changes in transit time of 10 MHz of ultrasonic wave as a function of temperature and hydrostatic pressure, the linear and non-linear acoustic properties of the ternary (La sub 2 O sub 3) sub x (Sm sub 2 O sub 3) sub y (P sub 2 O sub 5) sub (1-x-y) glasses with compositions near to that corresponding to the metaphosphate have been determined. For each glass the second order elastic stiffness tensor components C sub ijs (SOEC) continue to increase down to 10K in a manner consistent with phonons interactions with two level systems. Measurements of the effects of hydrostatic pressure on the ultrasonic wave velocities have been used to determine the hydrostatic pressure derivatives (dC sub ij/dP) sub T,P=0 of the SOEC and (dB0 sup s)/dP) sub T,P=0 of the bulk modulus B0 sup s at room temperature (293K). For the ternary (La sub 2 O sub 3) sub x (Sm sub 2 O sub 3) sub y (P sub 2 O sub 5) sub (1-x-y) glasses, (dC sub 11/dP), (dC sub 44/dP), and (dBo/dP), are small but positives; these glasses stiffen under pressure. The elastic behaviour of these ternary glasses lies intermediate between those of (Sm sub 2 O sub 3)(P sub 2 O sub 5) sub (1-x) and (La sub 2 O sub 3) sub y (P sub 2 O sub 5) sub (1-x-y) glasses. Replacement of the Sm sup 3+ by La sup 3+ in the ternary phosphate glasses negates the acoustic mode softening. Possible sources of the different effects of La sub 3+ and Sm sub 3+ modifiers on the nonlinear acoustic properties of metaphosphate glasses are discussed

  19. Resolution and evolution of the duck-billed platypus karyotype with an X1Y1X2Y2X3Y3X4Y4X5Y5 male sex chromosome constitution.

    Science.gov (United States)

    Rens, Willem; Grützner, Frank; O'brien, Patricia C M; Fairclough, Helen; Graves, Jennifer A M; Ferguson-Smith, Malcolm A

    2004-11-16

    The platypus (2n = 52) has a complex karyotype that has been controversial over the last three decades. The presence of unpaired chromosomes and an unknown sex-determining system especially has defied attempts at conventional analysis. This article reports on the preparation of chromosome-specific probes from flow-sorted chromosomes and their application in the identification and classification of all platypus chromosomes. This work reveals that the male karyotype has 21 pairs of chromosomes and 10 unpaired chromosomes (E1-E10), which are linked by short regions of homology to form a multivalent chain in meiosis. The female karyotype differs in that five of these unpaired elements (E1, E3, E5, E7, and E9) are each present in duplicate, whereas the remaining five unpaired elements (E2, E4, E6, E8, and E10) are absent. This finding indicates that sex is determined by the alternate segregation of the chain of 10 during spermatogenesis so that equal numbers of sperm bear either one of the two groups of five elements, i.e., five X and five Y chromosomes. Chromosome painting reveals that these X and Y chromosomes contain pairing (XY shared) and differential (X- or Y-specific) segments. Y differential regions must contain male-determining genes, and X differential regions should be dosage-compensated in the female. Two models for the evolution of the sex-determining system are presented. The resolution of the longstanding debate over the platypus karyotype is an important step toward the understanding of mechanisms of sex determination, dosage compensation, and karyotype evolution.

  20. Structural and thermodynamic characterization of the perovskite-related BA{sub 1+y}UO{sub 3+x} and (BA,SR){sub 1+y}UO{sub 3+x} phases

    Energy Technology Data Exchange (ETDEWEB)

    Cordfunke, E.H.P. [Netherlands Energy Research Foundation (ECN), Petten (Netherlands); Booij, A.S. [Netherlands Energy Research Foundation (ECN), Petten (Netherlands); Smit-Groen, V. [Netherlands Energy Research Foundation (ECN), Petten (Netherlands); Vlaanderen, P. van [Netherlands Energy Research Foundation (ECN), Petten (Netherlands); IJdo, D.J.W. [Rijksuniversiteit Leiden (Netherlands). Gorlaeus Labs.

    1996-11-01

    The perovskite-type BaUO{sub 3} structure has been investigated by X-ray and neutron diffraction. The Ba/U ratio, the (Ba, Sr)/U ratio, and the oxygen stoichiometry in Ba{sub 1+y}UO{sub 3+x} were varied, and the integral enthalpies of formation determined by solution calorimetry. In addition, equilibrium oxygen partial pressures were measured using a reversible EMF cell. The chemical defect mechanism is discussed, and it is shown that a continuous series BaUO{sub 3}-Ba{sub 1+y}UO{sub 3+x}-Ba{sub 3}UO{sub 6} exist in which uranium vacancies are gradually filled up with barium ions, whereas uranium is oxidized via the pentavalent to the hexavalent state in Ba{sub 3}UO{sub 6}(=Ba{sub 2}(Ba, U)O{sub 6}). (orig.).

  1. Piezoelectricity in K1xNaxNbO3: First-principles calculation

    International Nuclear Information System (INIS)

    Li Qiang; Zhang Rui; Lv Tian-Quan; Zheng Li-Mei

    2015-01-01

    The piezoelectric properties of K 1x Na x NbO 3 are studied by using first-principles calculations within virtual crystal approximation. To understand the critical factors for the high piezoelectric response in K 1x Na x NbO 3 , the total energy, piezoelectric coefficient, elastic property, density of state, Born effective charge, and energy barrier on polarization rotation paths are systematically investigated. The morphotropic phase boundary in K 1x Na x NbO 3 is predicted to occur at x = 0.521, which is in good agreement with the available experimental data. At the morphotropic phase boundary, the longitudinal piezoelectric coefficient d 33 of orthorhombic K 0.5 Na 0.5 NbO 3 reaches a maximum value. The rotated maximum of is found to be along the 50° direction away from the spontaneous polarization (close to the [001] direction). The moderate bulk and shear modulus are conducive to improving the piezoelectric response. By analyzing the energy barrier on polarization rotation paths, it is found that the polarization rotation of orthorhombic K 0.5 Na 0.5 NbO 3 becomes easier compared with orthorhombic KNbO 3 , which proves that the high piezoelectric response is attributed to the flattening of the free energy at compositions close to the morphotropic phase boundary. (paper)

  2. Nanocrystalline La1-xSrxCo1-yFe yO3 perovskites fabricated by the micro-emulsion route for high frequency response devices fabrications

    KAUST Repository

    Azhar Khan, Muhammad

    2014-09-01

    Nanocrystalline La1-xSrxCo1-yFe yO3 (x=0.00-0.60) perovskites were fabricated by a cheap economic route (i.e. micro-emulsion method) and characterized by thermogravimetric analysis (TGA), X-ray diffraction (XRD), fourier transform infrared (FTIR) spectroscopy, and scanning electron microscopy (SEM). TGA analysis showed ~35% weight loss. The crystallite size determined by XRD and SEM ranged from 30 to 80 nm and ~30 to 50 nm, respectively. The dielectric behavior was evaluated in the range of 1.0×106 Hz to 3.0×10 9 Hz at 298 K, the dielectric parameters resulting appreciably enhanced by co-doping with Sr and Fe. The maximum dielectric parameters (ε′=103.35, ε″=58.92 and tan δ=0.57) were observed for La0.4Sr0.6Co0.4Fe0.6O 3 at 15×106 Hz. Results suggest the potential use of these nanocrystalline perovskites in GHz-operated microwave devices. © 2014 Elsevier Ltd and Techna Group S.r.l.

  3. Synthesis, crystal structure investigation and magnetism of the complex metal-rich boride series Cr{sub x}(Rh{sub 1-y}Ru{sub y}){sub 7-x}B{sub 3} (x=0.88-1; y=0-1) with Th{sub 7}Fe{sub 3}-type structure

    Energy Technology Data Exchange (ETDEWEB)

    Misse, Patrick R.N.; Mbarki, Mohammed [Institute of Inorganic Chemistry, RWTH Aachen University, 52066 Aachen (Germany); Fokwa, Boniface P.T., E-mail: boniface.fokwa@ac.rwth-aachen.de [Institute of Inorganic Chemistry, RWTH Aachen University, 52066 Aachen (Germany)

    2012-08-15

    Powder samples and single crystals of the new complex boride series Cr{sub x}(Rh{sub 1-y}Ru{sub y}){sub 7-x}B{sub 3} (x=0.88-1; y=0-1) have been synthesized by arc-melting the elements under purified argon atmosphere on a water-cooled copper crucible. The products, which have metallic luster, were structurally characterized by single-crystal and powder X-ray diffraction as well as EDX measurements. Within the whole solid solution range the hexagonal Th{sub 7}Fe{sub 3} structure type (space group P6{sub 3}mc, no. 186, Z=2) was identified. Single-crystal structure refinement results indicate the presence of chromium at two sites (6c and 2b) of the available three metal Wyckoff sites, with a pronounced preference for the 6c site. An unexpected Rh/Ru site preference was found in the Ru-rich region only, leading to two different magnetic behaviors in the solid solution: The Rh-rich region shows a temperature-independent (Pauli) paramagnetism whereas an additional temperature-dependent paramagnetic component is found in the Ru-rich region. - Graphical abstract: The new complex boride series Cr{sub x}(Rh{sub 1-y}Ru{sub y}){sub 7-x}B{sub 3} (x=0.88-1; y=0-1) has been synthesized by arc melting the elements under purified argon atmosphere. Beside the 3d/4d site preference within the whole solid solution, an unexpected Rh/Ru site preference was found in the Ru-rich region only, leading to two different magnetic behaviors: The Rh-rich region shows a temperature-independent (Pauli) paramagnetism whereas an additional temperature-dependent paramagnetic component is found in the Ru-rich region. Highlights: Black-Right-Pointing-Pointer Synthesis of a new boride series fulfilling Vegard Acute-Accent s rule. Black-Right-Pointing-Pointer 3d/4d site preference. Black-Right-Pointing-Pointer Unexpected Ru/Rh site preference. Black-Right-Pointing-Pointer Rh-rich region is Pauli paramagnetic. Black-Right-Pointing-Pointer Ru-rich region is Pauli and temperature-dependent paramagnetic.

  4. Optical characterization in Pb(Zr{sub 1-x} Ti{sub x}){sub 1-y} Nb{sub y} O{sub 3} ferroelectric ceramic system

    Energy Technology Data Exchange (ETDEWEB)

    Durruthy-Rodriguez, M.D. [Instituto de Cibernetica, Matematica y Fisica, CITMA, Departamento de Fisica Aplicada, La Habana (Cuba); CINVESTAV-Unidad Queretaro, IPN, Santiago de Queretaro, Queretaro (Mexico); Costa-Marrero, J.; Hernandez-Garcia, M. [Instituto de Cibernetica, Matematica y Fisica, CITMA, Departamento de Fisica Aplicada, La Habana (Cuba); Calderon-Pinar, F. [Universidad de La Habana, Laboratorio de Magnetismo, Instituto de Ciencia y Tecnologia de Materiales, La Habana (Cuba); Malfatti, Celia [Universidade Federal do Rio Grande do Sul, Departamento de Metalurgia, Escola de Engenharia, Porto Alegre, RS (Brazil); Yanez-Limon, J.M. [CINVESTAV-Unidad Queretaro, IPN, Santiago de Queretaro, Queretaro (Mexico)

    2011-05-15

    In this work, visible photoluminescence was observed at room temperature in a sintered Pb(Zr{sub 1-x}Ti{sub x}){sub 1-y}Nb{sub y}O{sub 3} perovskite-type structure system, doped with Nb using the next excitation bands 325, 373 and 457 nm. The intensity and energy of such emissions have been studied by changing the Nb concentration (0<y<0.01) and the Ti content (x), with x=0.20,0.40,0.53,0.60 and 0.80, on both sides of the morphotropic phase boundary (MPB) zone. The principal bands become visible at energies of 1.73, 2.56 and 3.35 eV. The results reveal the role of the Nb{sup 5+} ion substitutions by Zr{sup 4+} or Ti{sup 4+} ions and the symmetry presented in the rhombohedral or tetragonal side of the MPB. Raman spectra which are similar for compositions: 20/80, 40/60 and 53/47 (tetragonal phases) show nine bands, centered around 137, 194, 269, 331, 434, 550, 612, 712 and 750 cm{sup -1}. The spectra for samples 60/40 and 80/20, rhombohedral phase, show significant differences, only six bands appear, centered around 124, 209, 234, 330, 549 and 682 cm{sup -1}. In addition, optical absorption spectroscopy, structural and micro-structural measurements were carried out by using Uv-vis spectroscopy, X-ray diffraction and scanning electron microscopy techniques, respectively. The experimental results of band gap energy, e.g., in our samples are in accordance with the findings by J. Baedi et al. in the calculations of band structure, energy gap and density of states for different phases of Pb(Zr{sub 1-x} Ti{sub x})O{sub 3} using density functional theory (DFT). (orig.)

  5. Structural properties and superconductivity of SrFe2As2-xPx (0.0 ≤ x1.0) and CaFe2As2-yPy (0.0 ≤ y ≤ 0.3)

    International Nuclear Information System (INIS)

    Shi, H L; Yang, H X; Tian, H F; Lu, J B; Wang, Z W; Qin, Y B; Song, Y J; Li, J Q

    2010-01-01

    The SrFe 2 As 2-x P x (0.0 ≤ x1.0) and CaFe 2 As 2-y P y (0.0 ≤ y ≤ 0.3) materials were prepared by a solid-state reaction method. X-ray diffraction measurements indicate that the single-phase samples can be successfully obtained for SrFe 2 As 2-x P x (0.0 ≤ x ≤ 0.8) and CaFe 2 As 2-y P y (0.0 ≤ y ≤ 0.3). Visible contraction of the lattice parameters is determined due to the relatively smaller radius of P ions in comparison with that of As. The spin-density-wave (SDW) instability associated with the tetragonal to orthorhombic phase transition is suppressed noticeably in both systems following the increase in P content. The highest superconducting transitions are observed at about 27 K in SrFe 2 As 1.3 P 0.7 and at about 13 K in CaFe 2 As 1.925 P 0.075 , respectively. Structural analysis suggests that lattice contraction could notably affect the superconductivity in these materials.

  6. Electrical resistivity and thermopower of Y1-xPrxCo2 Compounds

    International Nuclear Information System (INIS)

    Uchima, K; Takaesu, Y; Teruya, A; Akamine, H; Kakihana, M; Tomori, K; Uejo, T; Nakamura, A; Hedo, M; Nakama, T; Yagasaki, K; Burkov, A T

    2015-01-01

    Electrical resistivity ρ and thermopower S of the pseudo-binary compounds of Y 1-x Pr x Co 2 have been measured in the temperature range between 2 and 300 K under magnetic fields up to 10 T, together with the pressure measurements of ρ and S in Y 0.4 Pr 0.6 Co 2 . The Curie temperature decreases with decreasing x, and vanishes at the critical composition x c ≈ 0.4, where the residual resistivity attains a maximum value. The Curie temperature and the residual resistivity of Y 0.4 Pr 0.6 Co 2 show the same pressure dependence as those of the heavy-rare-earth based compounds. These behaviors of ρ and S indicate the inhomogeneous distribution of the Co 3d magnetization. The magnetoresistance of the light-rare earth Y 1-x Pr x Co 2 system is negative in the whole range of x, except for x = 0 and 1, which is a characteristic behavior related with magnetic state and magnitude of the effective field acting on the Co 3d subsystem

  7. Behavior of the irreversibility line in the new superconductor La1.5+xBa1.5+x-yCayCu3Oz

    International Nuclear Information System (INIS)

    Parra Vargas, C.A.; Pimentel, J.L.; Pureur, P.; Landínez Téllez, D.A.; Roa-Rojas, J.

    2012-01-01

    The irreversibility properties of high-T c superconductors are of major importance for technological applications. For example, a high irreversibility magnetic field is a more desirable quality for a superconductor . The irreversibility line in the H-T plane is constituted by experimental points, which divides the irreversible and reversible behavior of the magnetization. The irreversibility lines for series of La 1.5+x Ba 1.5+x-y Ca y Cu 3 O z polycrystalline samples with different doping were investigated. The samples were synthesized using the usual solid estate reaction method. Rietveld-type refinement of x-ray diffraction patterns permitted to determine the crystallization of material in a tetragonal structure. Curves of magnetization ZFC-FC for the system La 1.5+x Ba 1.5+x-y Ca y Cu 3 O z , were measured in magnetic fields of the 10-20,000 Oe, and allowed to obtain the values for the irreversibility and critical temperatures. The data of irreversibility temperature allowed demarcating the irreversibility line, T irr (H). Two main lines are used for the interpretation of the irreversibility line: one of those which suppose that the vortexes are activated thermally and the other proposes that associated to T irr a phase transition occurs. The irreversibility line is described by a power law. The obtained results allow concluding that in the system La 1.5+x Ba 1.5+x-y Ca y Cu 3 O z a characteristic bend of the Almeida-Thouless (AT) tendency is dominant for low fields and a bend Gabay-Toulouse (GT) behavior for high magnetic fields. This feature of the irreversibility line has been reported as a characteristic of granular superconductors and it corroborates the topological effects of vortexes mentioned by several authors .

  8. Combinatorial search for green and blue phosphors of high thermal stabilities under UV excitation based on the K(Sr1-x-y)PO4:Tb3+ xEu2+y system.

    Science.gov (United States)

    Chan, Ting-Shan; Liu, Yao-Min; Liu, Ru-Shi

    2008-01-01

    The present investigation aims at the synthesis of KSr 1-x-y PO 4:Tb(3+) x Eu(2+) y phosphors using the combinatorial chemistry method. We have developed square-type arrays consisting of 121 compositions to investigate the optimum composition and luminescence properties of KSrPO 4 host matrix under 365 nm ultraviolet (UV) light. The optimized compositions of phosphors were found to be KSr 0.93PO 4:Tb(3+) 0.07 (green) and KSr 0.995PO 4:Eu(2+) 0.005 (blue). These phosphors showed good thermal luminescence stability better than commercially available YAG:Ce at temperature above 200 degrees C. The result indicates that the KSr 1-x-y PO 4:Tb(3+) x Eu (2+)y can be potentially useful as a UV radiation-converting phosphor for light-emitting diodes.

  9. Scaling Laws of Nitrogen Soft X-Ray Yields from 1 to 200 kJ Plasma Focus

    International Nuclear Information System (INIS)

    Akel, M.; Lee, S.

    2013-01-01

    Numerical experiments are carried out systematically to determine the nitrogen soft x-ray yield for optimized nitrogen plasma focus with storage energy E 0 from 1 kJ to 200 kJ. Scaling laws on nitrogen soft x-ray yield, in terms of storage energies E 0 , peak discharge current I p eak and focus pinch current I p inch were found. It was found that the nitrogen x-ray yields scales on average with y s xr, N= 1.93xE o 1 .21 J (E 0 in kJ) with the scaling showing gradual deterioration as E 0 rises over the range. A more robust scaling is y s xr = 8x10 - 8I 0 3.38 p inch . The optimum nitrogen soft x-ray yield emitted from plasma focus is found to be about 1 kJ for storage energy of 200 kJ. This indicates that nitrogen plasma focus is a good water-window soft x-ray source when properly designed. (author)

  10. Structure, magnetism and electronic properties in 3d-5d based double perovskite ({Sr_{1-x}} Y x )2FeIrO6

    Science.gov (United States)

    Kharkwal, K. C.; Pramanik, A. K.

    2017-12-01

    The 3d-5d based double perovskites are of current interest as they provide model systems to study the interplay between electronic correlation (U) and spin-orbit coupling (SOC). Here, we report detailed structural, magnetic and transport properties of doped double perovskite material (Sr1-x Y x )2FeIrO6 with x ≤slant 0.2 . With substitution of Y, the system retains its original crystal structure but structural parameters change with x in nonmonotonic fashion. The magnetization data for Sr2FeIrO6 show antiferromagnetic type magnetic transition around 45 K however, a close inspection of the data indicates a weak magnetic phase transition around 120 K. No change of structural symmetry has been observed down to low temperature, although the lattice parameters show sudden changes around the magnetic transitions. Sr2FeIrO6 shows an insulating behavior over the whole temperature range, which nevertheless does not change with Y substitution. The nature of charge conduction is found to follow thermally activated Mott’s variable range hopping and power law behavior for parent and doped samples, respectively. Interestingly, evolution of structural, magnetic and transport behavior in (Sr1-x Y x )2FeIrO6 is observed to reverse with x > 0.1 , which is believed to arise due to a change in the transition metal ionic state.

  11. Role of phonon scattering by elastic strain field in thermoelectric Sr1xYxTiO3−δ

    KAUST Repository

    Bhattacharya, S.

    2014-06-12

    Perovskite-type SrTiO3-δ ceramics are multifunctional materials with significant potential as n-type thermoelectric (TE) materials. The electronic and thermal transport properties of spark plasma sintered polycrystalline Sr1-xYxTiO3-δ (x=0.05, 0.075, 0.1) ceramics are systematically investigated from (15-800) K. The Sr0.9Y0.1TiO3-δ simultaneously exhibits a large Seebeck coefficient, α>-80μV/K and moderately high electrical resistivity, ρ∼0.8mΩ-cm at a carrier concentration of ∼1021cm-3 at 300K resulting in a high TE power factor defined herein as (α2σT)∼0.84W/m-K at 760K. Despite the similar atomic masses of Sr (87.6g/mol) and Y (88.9g/mol), the lattice thermal conductivity (κL) of Sr1-xY xTiO3-δ is significantly reduced with increased Y-doping, owing to the smaller ionic radii of Y3+ (∼1.23Å, coordination number 12) compared to Sr2+ (∼1.44Å, coordination number 12) ions. In order to understand the thermal conductivity reduction mechanism, the κL in the Sr1-xY xTiO3-δ series are phenomenologically modeled with a modified Callaway\\'s equation from 30-600K. Phonon scattering by elastic strain field due to ionic radii mismatch is found to be the prominent scattering mechanism in reducing κL of these materials. In addition, the effect of Y-doping on the elastic moduli of Sr1-xY xTiO3-δ (x=0, 0.1) is investigated using resonant ultrasound spectroscopy, which exhibits an anomaly in x=0.1 in the temperature range 300-600K. As a result, the phonon mean free path is found to be further reduced in the Sr0.9Y0.1TiO3-δ compared to that of SrTiO3-δ, resulting in a considerably low thermal conductivity κ∼2.7W/m-K at 760K. Finally, we report a thermoelectric figure of merit (ZT)∼0.3 at 760K in the Sr0.9Y 0.1TiO3-δ, the highest ZT value reported in the Y-doped SrTiO3 ceramics thus far. © 2014 AIP Publishing LLC.

  12. Role of phonon scattering by elastic strain field in thermoelectric Sr1xYxTiO3−δ

    KAUST Repository

    Bhattacharya, S.; Mehdizadeh Dehkordi, A.; Tennakoon, S.; Adebisi, R.; Gladden, J. R.; Darroudi, T.; Alshareef, Husam N.; Tritt, T. M.

    2014-01-01

    Perovskite-type SrTiO3-δ ceramics are multifunctional materials with significant potential as n-type thermoelectric (TE) materials. The electronic and thermal transport properties of spark plasma sintered polycrystalline Sr1-xYxTiO3-δ (x=0.05, 0.075, 0.1) ceramics are systematically investigated from (15-800) K. The Sr0.9Y0.1TiO3-δ simultaneously exhibits a large Seebeck coefficient, α>-80μV/K and moderately high electrical resistivity, ρ∼0.8mΩ-cm at a carrier concentration of ∼1021cm-3 at 300K resulting in a high TE power factor defined herein as (α2σT)∼0.84W/m-K at 760K. Despite the similar atomic masses of Sr (87.6g/mol) and Y (88.9g/mol), the lattice thermal conductivity (κL) of Sr1-xY xTiO3-δ is significantly reduced with increased Y-doping, owing to the smaller ionic radii of Y3+ (∼1.23Å, coordination number 12) compared to Sr2+ (∼1.44Å, coordination number 12) ions. In order to understand the thermal conductivity reduction mechanism, the κL in the Sr1-xY xTiO3-δ series are phenomenologically modeled with a modified Callaway's equation from 30-600K. Phonon scattering by elastic strain field due to ionic radii mismatch is found to be the prominent scattering mechanism in reducing κL of these materials. In addition, the effect of Y-doping on the elastic moduli of Sr1-xY xTiO3-δ (x=0, 0.1) is investigated using resonant ultrasound spectroscopy, which exhibits an anomaly in x=0.1 in the temperature range 300-600K. As a result, the phonon mean free path is found to be further reduced in the Sr0.9Y0.1TiO3-δ compared to that of SrTiO3-δ, resulting in a considerably low thermal conductivity κ∼2.7W/m-K at 760K. Finally, we report a thermoelectric figure of merit (ZT)∼0.3 at 760K in the Sr0.9Y 0.1TiO3-δ, the highest ZT value reported in the Y-doped SrTiO3 ceramics thus far. © 2014 AIP Publishing LLC.

  13. Luminescence properties of In/sub 1-x/PGa/sub x/ layers (0,6 (<=) x (<=) 0. 7) produced by liquid epitaxy on GaAs/sub 1-y/P/sub y/ substrates

    Energy Technology Data Exchange (ETDEWEB)

    Ermakov, O N; Ignatkina, R S; Sushkov, V P; Chukichev, M V

    1977-06-01

    Photoluminescence (PL) and cathodoluminescence (CL) of Insub(1-x)Gasub(x)P (0.6 <=) x (<=) 0.7) layers grown by the method of liquid epitaxy on GaAssub(1-y)Psub(y) (0.2 (<=) y (<=) 0.4) substrates oriented in the (111)-B plane have been investigated. Spectral distribution of PL and CL of the n- and p-type Insub(1-x)Gasub(x)P layers has been studied over the temperature range from 300 to 65 K and at different excitation levels. Radiative ''band-band'' recombination has been shown to participate in formation of the A line. The B line in the luminescence spectra of specially nondoped Insub(1-x)Gasub(x)P is related to recombination through an uncontrolled acceptor centre. The arising of the C band in the CL spectra of Insub(1-x)Gasub(x)P doped with zinc and tellurium is ascribed to donor-acceptor recombination. The external yield of CL of the Insub(0.33)Gasub(0.67)P n-type (specially nondoped) and p-type (doped with Zn adn Te) layers has been determined at 300 K.

  14. Magnetic hyperfine fields in Dy/sub 1-x/Y/sub x/Al2

    International Nuclear Information System (INIS)

    Hessel, A.; Kalvius, G.M.; Shenoy, G.K.; Zinn, W.; Wiedemann, W.

    1982-01-01

    161 Dy Moessbauer spectroscopy was carried out at 4.2 K on Dy/sub 1-x/Y/sub x/Al 2 for 0 less than or equal to x less than or equal to 0.6. For x=0 we find B=580 T and f/sub Q/=2810 MHz, close to free-ion values. For x > 0 both B and f/sub Q/ decrease weakly. We obtain (δB)/sub n/ = -14 T, (δf/sub Q/)/sub n/ = -110 MHz and (δB)/sub nn/ = + 1.6 T, (δf/sub Q/)/sub nn/ = +4 MHz per replaced nearest and next-nearest Dy 3 + neighbor, respectively

  15. Síntese e caracterização de La1-X SrX MnO3±δ e La1-X SrX Co1-Y FeY O3-δ utilizados como catodo em células a combustível de óxido sólido Synthesis and characterization of La1-X SrX MnO3± δ and La1-X SrX Co1-Y FeY O3- δ used as cathode in solid oxide fuel cells

    Directory of Open Access Journals (Sweden)

    R. A. Vargas

    2008-09-01

    Full Text Available Na síntese de materiais, muitos desafios estão relacionados com propriedades requeridas, levando pesquisadores a buscarem materiais alternativos que possuam características adequadas para funcionarem como componentes nas células a combustível de óxido sólido. Atualmente, os materiais mais estudados como catodos são os óxidos mistos La1-X SrX MnO3±δ e La1-X SrX Co1-Y FeY O3-δ. Neste trabalho utilizaram-se como precursores os nitratos dos respectivos elementos químicos. O objetivo é apresentar algumas características físicas, químicas e microestruturais desses materiais, obtidos pela técnica dos citratos. As principais análises utilizadas para caracterização foram: análise termogravimétrica, calorimetria diferencial de varredura, picnometria por gás hélio, fluorescência de raios X, cromatografia de absorção gasosa, distribuição granulométrica por espalhamento laser, adsorção gasosa, difração de raios X e microscopia eletrônica de varredura. Os resultados mostram que as composições estudadas contem partículas homogêneas com presença de carbono residual, áreas de superfícies específicas adequadas e tamanho médio de partículas inferiores a 1 mm. As propriedades estudadas estão compatíveis com dados da literatura. Conclui-se que os compostos sintetizados possibilitam o estudo e preparação de suspensões cerâmicas para fabricação de filmes finos.In the synthesis of ceramic materials, new challenges are related with the intrinsic properties. Consequently, researchers look for alternative materials with adjusted characteristics for components in solid oxide fuel cells. Currently, the most studied materials as cathode are oxides: La1-X SrX MnO3±δ and La1-X SrX Co1-Y FeY O3-δ. In this work, the nitrates of the respective chemical elements were used as raw materials. The objective of this work is to present the physical, chemical and microstructural characteristics of these materials, prepared by the

  16. A study of the reactions $\\pi^{-}p\\rightarrow K^{*}X, K^{*}\\Sigma$ and $K^{*}Y1^{*}$ (1385) at 3.93 GeV/c

    CERN Document Server

    Yaffe, D; Chaloupka, V; Ferrando, A; Korkea-Aho, M K; Losty, Michael J; Montanet, Lucien; Paul, E; Zatz, J; Zieminski, Z; Abramovich, M no 1; Chaloupka, V no 1; Ferrando, A no 1; Korkea-Aho, M no 1; Losty, M J no 1; Montanet, L no 1; Paul, E no 1; Zatz, J no 1; Zieminski, Z no 1; Yaffe, D no 1

    1974-01-01

    The authors have investigated the final states K*/sup 0/(890) Lambda , K*/sup 0/(890) Sigma /sup 0/ and K*/sup 0/(890) Y/sub 1/*/sup 0/(1385) produced in pi /sup -/p interactions at 3.93 GeV/c. They present the differential cross sections and spin density matrix elements for the resonances as functions of momentum transfer, as well as the Lambda and Sigma /sup 0/ polarizations. The Sigma /sup 0/ polarization is found to be positive and maximal. An amplitude analysis is performed for the K* Lambda and K* Sigma /sup 0/ reactions, and it is found that one natural parity transversity amplitude is dominant for the latter. (15 refs).

  17. Control of Co content and SOFC cathode performance in Y1-ySr2+yCu3-xCoxO7+δ

    Science.gov (United States)

    Šimo, F.; Payne, J. L.; Demont, A.; Sayers, R.; Li, Ming; Collins, C. M.; Pitcher, M. J.; Claridge, J. B.; Rosseinsky, M. J.

    2014-11-01

    The electrochemical performance of the layered perovskite YSr2Cu3-xCoxO7+δ, a potential solid oxide fuel cell (SOFC) cathode, is improved by increasing the Co content from x = 1.00 to a maximum of x = 1.30. Single phase samples with x > 1.00 are obtained by tuning the Y/Sr ratio, yielding the composition Y1-ySr2+yCu3-xCoxO7+δ (where y ≤ 0.05). The high temperature structure of Y0.95Sr2.05Cu1.7Co1.3O7+δ at 740 °C is characterised by powder neutron diffraction and the potential of this Co-enriched material as a SOFC cathode is investigated by combining AC impedance spectroscopy, four-probe DC conductivity and powder XRD measurements to determine its electrochemical properties along with its thermal stability and compatibility with a range of commercially available electrolytes. The material is shown to be compatible with doped ceria electrolytes at 900 °C.

  18. Defect structure, electronic conductivity and expansion of properties of (La1xSrx)sCo1yNiyO3−δ

    DEFF Research Database (Denmark)

    Hjalmarsson, Per; Søgaard, Martin; Mogensen, Mogens Bjerg

    2010-01-01

    This study reports on oxygen nonstoichiometry, electronic conductivity and lattice expansion of three compositions as function of T and PO2 in the (La1xSrx)sCo1yNiyO3−δ (x=0.1, y=0.4; x=0.1, y=0.3; x=0.2, y=0.2) materials system. The nonstoichiometry data were successfully fitted using the itin......This study reports on oxygen nonstoichiometry, electronic conductivity and lattice expansion of three compositions as function of T and PO2 in the (La1xSrx)sCo1yNiyO3−δ (x=0.1, y=0.4; x=0.1, y=0.3; x=0.2, y=0.2) materials system. The nonstoichiometry data were successfully fitted using...... the itinerant electron model which indicates the existence of delocalized electronic states. This was also reflected in the high electronic conductivities, above 1000 S cm−1, measured for all three compositions. The electronic conductivity was shown to decrease linearly with the oxygen nonstoichiometry...... parameter, δ, supporting that the conductivity is dependent on p-type charge carriers. Comparing calculated p-type mobilities with data reported in literature on La1xSrxCoO3 indicated that Ni-substitution into (La1xSrx)sCoO3−δ increases the p-type mobility. The electronic conductivity was also found...

  19. Structure and magnetic properties of GdxY1xFeO3 obtained by mechanosynthesis

    International Nuclear Information System (INIS)

    Bolarín-Miró, A.M.; Sánchez-De Jesús, F.; Cortés-Escobedo, C.A.; Valenzuela, R.; Ammar, S.

    2014-01-01

    Highlights: • Orthohombic GDxY1-xFeO3 was obtained by mechanosynthesis after 5 h of milling. • Mechanosynthesized GdxY1-xFeO3 show weak ferromagnetic behavior. • Mechanosynthesis promotes unexpected magnetic properties in GdxY1-xFeO3. • The maximum magnetization that was reached 7.7 emu/g for Gdo.75Y0.25FeO3. • For Gd0.5Y0.5FeO3, the magnetization decreases down to 2.1 emu/g. -- Abstract: Solid solutions of yttrium–gadolinium orthoferrites Gd x Y 1x FeO 3 (0 ⩽ x1) were prepared by high-energy ball milling. The aim of this work was to study the influence of the synthesis parameters on the crystal structure and the magnetic behavior of these solid solutions. The precursors, Fe 2 O 3 , Y 2 O 3 and Gd 2 O 3 , mixed in a stoichiometric ratio to obtain these orthoferrites, were milled for different times (up to 5 h). X-ray diffraction and Rietveld refinement were used to elucidate the phase transformation as a function of the milling time. Results showed the complete formation of orthoferrite with an orthorhombic structure (S.G. Pbnm) without any annealing after 5 h of milling for all of the compositions. The effect of the synthesis process and the x value on the crystal structure and the magnetic properties were also studied. All of the synthesized powders demonstrated weak ferromagnetic behavior. In particular, an increase in the maximum magnetization for all the compositions was found, with a maximum that reached 7.7 emu/g for Gd 0.75 Y 0.25 FeO 3 . For Gd 0.5 Y 0.5 FeO 3 , the magnetization decreases down to 2.1 emu/g. A small contamination of metallic Fe was confirmed through electron spin resonance experiments

  20. Microstrain engineered magnetic properties in Bi1-x Ca x Fe1-y Ti y O3-δ nanoparticles: deviation from Néel’s 1/d size-dependent magnetization behaviour

    Science.gov (United States)

    Mocherla, Pavana S. V.; Sahana, M. B.; Gopalan, R.; Ramachandra Rao, M. S.; Nanda, B. R. K.; Sudakar, C.

    2017-10-01

    Magnetization of antiferromagnetic nanoparticles is known to generally scale up inversely to their diameter (d) according to Néel’s model. Here we report a deviation from this conventional linear 1/d dependence, altered significantly by the microstrain, in Ca and Ti substituted BiFeO3 nanoparticles. Magnetic properties of microstrain-controlled Bi1-x Ca x Fe1-y Ti y O3-δ (y  =  0 and x  =  y) nanoparticles are analyzed as a function of their size ranging from 18 nm to 200 nm. A complex interdependence of doping concentration (x or y), annealing temperature (T), microstrain (ɛ) and particle size (d) is established. X-ray diffraction studies reveal a linear variation of microstrain with inverse particle size, 1/d nm-1 (i.e. ɛ · d  =  16.5 nm·%). A rapid increase in the saturation magnetization below a critical size d c ~ 35 nm, exhibiting a (1/d) α (α  ≈  2.6) dependence, is attributed to the influence of microstrain. We propose an empirical formula M \\propto (1/d)ɛ β (β  ≈  1.6) to highlight the contributions from both the size and microstrain towards the total magnetization in the doped systems. The magnetization observed in nanoparticles is thus, a result of the competing magnetic contribution from the terminated spin cycloid on the surface and counteracting microstrain present at a given size.

  1. Structure and magnetic properties of Gd{sub x}Y{sub 1x}FeO{sub 3} obtained by mechanosynthesis

    Energy Technology Data Exchange (ETDEWEB)

    Bolarín-Miró, A.M. [Área Académica de Ciencias de la Tierra y Materiales, Universidad Autónoma del Estado de Hidalgo Mineral de la Reforma, Hidalgo 42184 (Mexico); Sánchez-De Jesús, F., E-mail: fsanchez@uaeh.edu.mx [Área Académica de Ciencias de la Tierra y Materiales, Universidad Autónoma del Estado de Hidalgo Mineral de la Reforma, Hidalgo 42184 (Mexico); Cortés-Escobedo, C.A. [Centro de Investigación e Innovación Tecnológica del IPN, Distrito Federal 02250 (Mexico); Valenzuela, R. [Depto. de Materiales Metálicos y Cerámicos, Instituto de Investigaciones en Materiales, Universidad Nacional Autónoma de México, México D.F. 04510 (Mexico); Ammar, S. [ITODYS, UMR 7086, Université de Paris-Diderot, 75250 Paris Cedex (France)

    2014-02-15

    Highlights: • Orthohombic GDxY1-xFeO3 was obtained by mechanosynthesis after 5 h of milling. • Mechanosynthesized GdxY1-xFeO3 show weak ferromagnetic behavior. • Mechanosynthesis promotes unexpected magnetic properties in GdxY1-xFeO3. • The maximum magnetization that was reached 7.7 emu/g for Gdo.75Y0.25FeO3. • For Gd0.5Y0.5FeO3, the magnetization decreases down to 2.1 emu/g. -- Abstract: Solid solutions of yttrium–gadolinium orthoferrites Gd{sub x}Y{sub 1x}FeO{sub 3} (0 ⩽ x1) were prepared by high-energy ball milling. The aim of this work was to study the influence of the synthesis parameters on the crystal structure and the magnetic behavior of these solid solutions. The precursors, Fe{sub 2}O{sub 3}, Y{sub 2}O{sub 3} and Gd{sub 2}O{sub 3}, mixed in a stoichiometric ratio to obtain these orthoferrites, were milled for different times (up to 5 h). X-ray diffraction and Rietveld refinement were used to elucidate the phase transformation as a function of the milling time. Results showed the complete formation of orthoferrite with an orthorhombic structure (S.G. Pbnm) without any annealing after 5 h of milling for all of the compositions. The effect of the synthesis process and the x value on the crystal structure and the magnetic properties were also studied. All of the synthesized powders demonstrated weak ferromagnetic behavior. In particular, an increase in the maximum magnetization for all the compositions was found, with a maximum that reached 7.7 emu/g for Gd{sub 0.75}Y{sub 0.25}FeO{sub 3}. For Gd{sub 0.5}Y{sub 0.5}FeO{sub 3}, the magnetization decreases down to 2.1 emu/g. A small contamination of metallic Fe was confirmed through electron spin resonance experiments.

  2. Study of Y{sub 1x}Er{sub x}FeO{sub 3} (0≤x≤1) powder synthesized by sol–gel method and their magnetic properties

    Energy Technology Data Exchange (ETDEWEB)

    Cheng, Man; Jiang, Guojian, E-mail: guojianjiang@sit.edu.cn; Yang, Wenqian; Duan, Li; Peng, Wei; Chen, Jiang; Wang, Xiaojian

    2016-11-01

    A series of single phase Y{sub 1x}Er{sub x}FeO{sub 3} (0≤x≤1) orthoferrite samples were synthesized by sol-gel method and their magnetic properties were studied in detail. The prepared samples were characterized by X-ray diffraction (XRD), vibrating sample magnetometer (VSM) and differential scanning calorimetry (DSC). The obviously weak ferromagnetic property, which caused by Dzialoshinski Moriya (DM) antisymmetric exchange mechanism, was observed in YFeO{sub 3} for the magnetization jump at H=0 Oe. The magnetization of YFeO{sub 3} was evidently changed by doping Er{sup 3+}. The increase of the Er{sup 3+} content in Y{sub 1x}Er{sub x}FeO{sub 3} greatly enhanced the paramagnetic component and gradually decreased the ferromagnetic component. - Highlights: • We synthesized a series of single phase Y{sub 1x}Er{sub x}FeO{sub 3} orthoferrite powder by sol–gel method. • We studied magnetic properties of Y{sub 1x}Er{sub x}FeO{sub 3} (0≤x≤1) in detail. • The magnetization of YFeO{sub 3} was evidently changed by doping Er{sup 3+}.

  3. Nanocrystalline La1-xSrxCo1-yFe yO3 perovskites fabricated by the micro-emulsion route for high frequency response devices fabrications

    KAUST Repository

    Azhar Khan, Muhammad; Khan, Kamran; Mahmood, Azhar; Murtaza, Gulam; Akhtar, Majid Niaz; Ali, Irshad M.; Shahid, Muhammad; Shakir, Imran; Farooq Warsi, Muhammad

    2014-01-01

    Nanocrystalline La1-xSrxCo1-yFe yO3 (x=0.00-0.60) perovskites were fabricated by a cheap economic route (i.e. micro-emulsion method) and characterized by thermogravimetric analysis (TGA), X-ray diffraction (XRD), fourier transform infrared (FTIR

  4. Influence of Mn site doping on electrical resistivity of polycrystalline La1-yAyMn1-xBxO3 (A=Ba, Sr; B=Cu, Cr, Co Manganites

    Directory of Open Access Journals (Sweden)

    Paunović N.

    2008-01-01

    Full Text Available We have the measured electrical resistivity of La1-yBayMn1-xCuxO3 (0.17≤y≤0.30; 0.04≤x≤0.10, La1-ySryMn1-xCrxO3 and La1-ySryMn1-xCoxO3 (0.270≤y≤0.294; 0.02≤x≤0.10 polycrystalline samples in the 25-325 K temperature range. The increase of Mn site doping concentration leads to an increase of the electrical resistivity of the samples and the appearance of a “double-peak” structure in the electrical resistivity versus temperature graphs. The first peak represents the insulator-metal transition in vicinity of the paramagnetic-ferromagnetic transition (TC. We have found that the intensity of the second peak increases with an increase of concentration of Mn substituents, due to the hole scattering by the random potential of the Mn site impurities.

  5. On the electronic phase diagram of Ba{sub 1-x}K{sub x}(Fe{sub 1-y}Co{sub y}){sub 2}As{sub 2} and EuFe{sub 2}(As{sub 1-x}P{sub x}){sub 2} superconductors. A local probe study using Moessbauer spectroscopy and muon spin relaxation

    Energy Technology Data Exchange (ETDEWEB)

    Goltz, Til

    2015-10-28

    In this thesis, I study the electronic and structural phase diagrams of the superconducting 122 iron pnictides systems Ba{sub 1-x}K{sub x}(Fe{sub 1-y}Co{sub y}){sub 2}As{sub 2} and EuFe{sub 2}(As{sub 1-x}P{sub x}){sub 2} by means of the local probe techniques {sup 57}Fe Moessbauer spectroscopy (MS) and muon spin relaxation (μSR). For both isovalent substitution strategies - Co/K for Fe/Ba and P for As, respectively - the antiferromagnetic Fe ordering and orthorhombic distortion of the parent compounds BaFe{sub 2}As{sub 2} and EuFe{sub 2}As{sub 2} are subsequently suppressed with increasing chemical substitution and superconductivity arises, once long-range and coherent Fe magnetic order is sufficiently but not entirely suppressed. For Ba{sub 1-x}K{sub x}(Fe{sub 1-y}Co{sub y}){sub 2}As{sub 2} in the charge compensated state (x/2 ∼ y), a remarkably similar suppression of both, the orthorhombic distortion and Fe magnetic ordering, as a function of increasing substitution is observed and a linear relationship between the structural and the magnetic order parameter is found. Superconductivity is evidenced at intermediate substitution with a maximum T{sub SC} of 15 K coexisting with static magnetic order on a microscopic length scale. The appearance of superconductivity within the antiferromagnetic state can by explained by the introduction of disorder due to nonmagnetic impurities to a system with a constant charge carrier density. Within this model, the experimental findings are compatible with the predicted s{sup ±} pairing symmetry. For EuFe{sub 2}(As{sub 1-x}P{sub x}){sub 2}, the results from {sup 57}Fe MS and ZF-μSR reveal an intriguing interplay of the local Eu{sup 2+} magnetic moments and the itinerant magnetic Fe moments due to the competing structures of the iron and europium magnetic subsystems. For the investigated single crystals with x = 0.19 and 0.28, {sup 57}Fe MS evidences the interplay of Fe and Eu magnetism by the observation of a transferred

  6. Enhanced piezoelectricity in (1 -x)Bi1.05Fe1-yAyO3-xBaTiO3 lead-free ceramics: site engineering and wide phase boundary region.

    Science.gov (United States)

    Zheng, Ting; Jiang, Zhenggen; Wu, Jiagang

    2016-07-28

    Site engineering has been employed to modulate the piezoelectric activity of high temperature (1 -x)Bi1.05Fe1-yScyO3-xBaTiO3 lead-free ceramics fabricated by a conventional solid-state method together with a quenching technique. The effects of x and y content on the phase structure, microstructure, and electrical properties have been investigated in detail. A wide rhombohedral (R) to pseudo-cubic (C) phase boundary was formed in the ceramics with x = 0.30 and 0 ≤y≤ 0.07, thus leading to enhanced piezoelectricity (d33 = 120-180 pC N(-1)), ferroelectricity (Pr = 19-22 μC cm(-2)) and a high Curie temperature (TC = 478-520 °C). In addition, the influence of different element substitutions for Fe(3+) on phase structure and electrical behavior was also investigated. Improved piezoelectricity (d33 = 160-180 pC N(-1)) and saturated P-E loops can be simultaneously achieved in the ceramics with A = Sc, Ga, and Al due to the R-C phase boundary. As a result, site engineering may be an efficient way to modulate the piezoelectricity of BiFeO3-BaTiO3 lead-free ceramics.

  7. Charge transfer luminescence of Yb3+ ions in LiY1-xYbxP4O12 phosphates

    International Nuclear Information System (INIS)

    Stryganyuk, G; Zazubovich, S; Voloshinovskii, A; Pidzyrailo, M; Zimmerer, G; Peters, R; Petermann, K

    2007-01-01

    Spectral-kinetic studies have been performed for LiY 1-x Yb x P 4 O 12 (x = 0; 0.1; 0.9) phosphates at T = 8-320 K using synchrotron radiation for excitation within the 5-17 eV energy range. Mechanisms for the excitation of Yb 3+ charge transfer and f-f luminescence are discussed. The quasimolecular character of Yb 3+ charge transfer luminescence (CTL) is pointed out. The central Yb 2+ ion and hole delocalized over the surrounding ligands are proposed for consideration as a 'charge transfer cluster' (Yb 2+ CT cluster). Possible mechanisms of Yb 3+ CTL quenching are presumed

  8. Behavior of the irreversibility line in the new superconductor La{sub 1.5+x}Ba{sub 1.5+x-y}Ca{sub y}Cu{sub 3}O{sub z}

    Energy Technology Data Exchange (ETDEWEB)

    Parra Vargas, C.A. [Grupo de Fisica de Materiales, Escuela de Fisica, Universidad Pedagogica y Tecnologica de Colombia, Tunja (Colombia); Pimentel, J.L.; Pureur, P. [Instituto de Fisica, Universidade Federal do Rio Grande do Sul, 91501-970 Porto Alegre, RS (Brazil); Landinez Tellez, D.A. [Grupo de Fisica de Nuevos Materiales, Departamento de Fisica, Universidad Nacional de Colombia, AA 5997, Bogota DC (Colombia); Roa-Rojas, J., E-mail: carlos.parra@uptc.edu.co [Grupo de Fisica de Nuevos Materiales, Departamento de Fisica, Universidad Nacional de Colombia, AA 5997, Bogota DC (Colombia)

    2012-08-15

    The irreversibility properties of high-T{sub c} superconductors are of major importance for technological applications. For example, a high irreversibility magnetic field is a more desirable quality for a superconductor . The irreversibility line in the H-T plane is constituted by experimental points, which divides the irreversible and reversible behavior of the magnetization. The irreversibility lines for series of La{sub 1.5+x}Ba{sub 1.5+x-y}Ca{sub y}Cu{sub 3}O{sub z} polycrystalline samples with different doping were investigated. The samples were synthesized using the usual solid estate reaction method. Rietveld-type refinement of x-ray diffraction patterns permitted to determine the crystallization of material in a tetragonal structure. Curves of magnetization ZFC-FC for the system La{sub 1.5+x}Ba{sub 1.5+x-y}Ca{sub y}Cu{sub 3}O{sub z}, were measured in magnetic fields of the 10-20,000 Oe, and allowed to obtain the values for the irreversibility and critical temperatures. The data of irreversibility temperature allowed demarcating the irreversibility line, T{sub irr}(H). Two main lines are used for the interpretation of the irreversibility line: one of those which suppose that the vortexes are activated thermally and the other proposes that associated to T{sub irr} a phase transition occurs. The irreversibility line is described by a power law. The obtained results allow concluding that in the system La{sub 1.5+x}Ba{sub 1.5+x-y}Ca{sub y}Cu{sub 3}O{sub z} a characteristic bend of the Almeida-Thouless (AT) tendency is dominant for low fields and a bend Gabay-Toulouse (GT) behavior for high magnetic fields. This feature of the irreversibility line has been reported as a characteristic of granular superconductors and it corroborates the topological effects of vortexes mentioned by several authors .

  9. X1X1X2X2/X1X2Y sex chromosome systems in the Neotropical Gymnotiformes electric fish of the genus Brachyhypopomus

    Directory of Open Access Journals (Sweden)

    Adauto Lima Cardoso

    2015-06-01

    Full Text Available Several types of sex chromosome systems have been recorded among Gymnotiformes, including male and female heterogamety, simple and multiple sex chromosomes, and different mechanisms of origin and evolution. The X1X1X2X2/X1X2Y systems identified in three species of this order are considered homoplasic for the group. In the genus Brachyhypopomus, only B. gauderio presented this type of system. Herein we describe the karyotypes of Brachyhypopomus pinnicaudatus and B. n. sp. FLAV, which have an X1X1X2X2/X1X2Y sex chromosome system that evolved via fusion between an autosome and the Y chromosome. The morphology of the chromosomes and the meiotic pairing suggest that the sex chromosomes of B. gauderio and B. pinnicaudatus have a common origin, whereas in B . n. sp. FLAV the sex chromosome system evolved independently. However, we cannot discard the possibility of common origin followed by distinct processes of differentiation. The identification of two new karyotypes with an X1X1X2X2/X1X2Y sex chromosome system in Gymnotiformes makes it the most common among the karyotyped species of the group. Comparisons of these karyotypes and the evolutionary history of the taxa indicate independent origins for their sex chromosomes systems. The recurrent emergence of the X1X1X2X2/X1X2Y system may represent sex chromosomes turnover events in Gymnotiformes.

  10. Ferromagnetism in Fe{sub 3-x-y}Ni{sub x}GeTe{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Stahl, Juliane; Johrendt, Dirk [Muenchen Univ. (Germany). Dept. Chemie; Pomjakushin, Vladimir [Paul Scherrer Institute, Villigen (Switzerland). Lab. for Neutron Scattering

    2016-07-01

    Polycrystalline samples of Fe{sub 3-y}GeTe{sub 2} (0.08 ≤ y ≤ 0.29) and the solid solutions Fe{sub 3-x-y}Ni{sub x}GeTe{sub 2} (0.24 ≤ x1.32; 0.14 ≤ y ≤ 0.41) were synthesized at 898-973 K in a resistance furnace and characterized by X-ray and neutron powder diffraction with Rietveld analysis (Fe{sub 3}GeTe{sub 2} type, P6{sub 3}/mmc, a = 402.665(3), c = 1632.820(14) pm for x = 0, y = 0.08). Fe{sub 3}Ge layers with planar FeGe hexagons and additional iron atoms above and below the rings are separated by double layers of tellurium atoms. Fe{sub 3}GeTe{sub 2} is ferromagnetic below T{sub C} = 230 K with magnetic moments aligned along the c axis. T{sub C} depends on the iron content and decreases with increasing iron vacancies continuously to 153 K in Fe{sub 2.71}GeTe{sub 2}. Further reduction of T{sub C} is possible by nickel substitution until magnetic ordering is nearly absent in Fe{sub 1.33}Ni{sub 1.32}GeTe{sub 2}. The suppression of the magnetic ordering is caused by random dilution of the magnetic iron atoms either by vacancies or by non-magnetic nickel atoms.

  11. Growth and characterization of NixCu1-x alloy films, NixCu1-x/NiyCu1-y multilayers, and nanowires

    International Nuclear Information System (INIS)

    Kazeminezhad, I.

    2001-12-01

    It was found that it is possible to grow Ni x Cu 1-x alloy systems of arbitrary composition by electrodepositing well-defined sub-monolayer quantities of Ni and Cu in alternation using a new method based on that used previously to prepare potentiostatically deposited magnetic multilayers from a single sulphamate-based electrolyte. Following growth, the chemical composition of Ni x Cu 1-x alloy films was obtained by ZAF-corrected energy dispersive X-Ray (EDX) analysis and less than a 4% difference between the nominal and actual composition was observed. The structure of the films was investigated by high-angle X-ray diffractometry (HAXRD) and transmission electron microscopy (TEM). The films grown on polycrystalline Cu substrates had (100) texture, while those grown on Au-coated glass had (111) texture. Some evidence of Ni clustering was obtained by vibrating sample magnetometry (VSM). Self-organisation of the deposited metal was suggested for Ni potentials more positive than ∼-1.4V. The transition from a Ni/Cu multilayer to a Ni x Cu 1-x alloy was also studied and an interesting aspect, namely a plateau region in a plot of magnetisation as a function of Ni layer thickness was observed, suggesting a preferred Ni cluster size in these alloy films. Anisotropic magnetoresistance (AMR) of the films decreased with increasing Cu content at 300K and 77K. SQUID measurements for Ni 0.52 Cu 0.48 and Ni 0.62 CU 0.38 films showed that they become much more strongly ferromagnetic at low temperatures. Evidence for blocked -superparamagnetic behaviour above a blocking temperature (T B ) of the films was obtained from zero-field-cooled (ZFC) and field-cooled (FC) magnetic susceptibility measurements. Ni x Cu 1-x /Ni y Cu 1-y alloy/alloy multilayer films with short repeat distance were successfully fabricated using this method. Up to third order satellite peaks observed in HAXRD showed that the interface is sharp. Room temperature longitudinal magnetoresistance measurements showed

  12. Scintillation properties of polycrystalline LaxY1-xO3 ceramic

    Science.gov (United States)

    Sahi, Sunil; Chen, Wei; Kenarangui, Rasool

    2015-03-01

    Scintillators are the material that absorbs the high-energy photons and emits visible photons. Scintillators are commonly used in radiation detector for security, medical imaging, industrial applications and high energy physics research. Two main types of scintillators are inorganic single crystals and organic (plastic or liquid) scintillators. Inorganic single crystals are expensive and difficult to grow in desire shape and size. Also, some efficient inorganic scintillator such as NaI and CsI are not environmental friendly. But on the other hand, organic scintillators have low density and hence poor energy resolution which limits their use in gamma spectroscopy. Polycrystalline ceramic can be a cost effective alternative to expensive inorganic single crystal scintillators. Here we have fabricated La0.2Y1.8O3 ceramic scintillator and studied their luminescence and scintillation properties. Ceramic scintillators were fabricated by vacuum sintering of La0.2Y1.8O3 nanoparticles at temperature below the melting point. La0.2Y1.8O3 ceramic were characterized structurally using XRD and TEM. Photoluminescence and radioluminescence studies were done using UV and X-ray as an excitation source. We have used gamma isotopes with different energy to studies the scintillation properties of La0.2Y1.8O3 scintillator. Preliminary studies of La0.2Y1.8O3 scintillator shows promising result with energy resolution comparable to that of NaI and CsI.

  13. Mild hydrothermal synthesis, crystal structure, spectroscopic and magnetic properties of the [MxIIM2.5-xIII(H2O)2(HPIIIO3)y(PVO4)2-yF] [M=Fe, x=2.08, y=1.58; M=Co, Ni, x=2.5, y=2] compounds

    International Nuclear Information System (INIS)

    Orive, Joseba; Mesa, Jose L.; Legarra, Estibaliz; Plazaola, Fernando; Arriortua, Maria I.; Rojo, Teofilo

    2009-01-01

    The [M x II M 2.5-x III (H 2 O) 2 (HP III O 3 ) y (P V O 4 ) 2-y F] [M=Fe (1), x=2.08, y=1.58; M=Co (2), x=2.5, y=2; Ni (3), x=2.5, y=2] compounds have been synthesized using mild hydrothermal conditions at 170 deg. C during five days. Single-crystals of (1) and (2), and polycrystalline sample of (3) were obtained. These isostructural compounds crystallize in the orthorhombic system, space group Aba2, with a=9.9598(2), b=18.8149(4) and c=8.5751(2) A for (1), a=9.9142(7), b=18.570(1) and c=8.4920(5) A for (2) and a=9.8038(2), b=18.2453(2) and c=8.4106(1) A for (3), with Z=8 in the three phases. An X-ray diffraction study reveals that the crystal structure is composed of a three-dimensional skeleton formed by [MO 5 F] and [MO 4 F 2 ] (M=Fe, Co and Ni) octahedra and [HPO 3 ] tetrahedra, partially substituted by [PO 4 ] tetrahedra in phase (1). The IR spectra show the vibrational modes of the water molecules and those of the (HPO 3 ) 2- tetrahedral oxoanions. The thermal study indicates that the limit of thermal stability of these phases is 195 deg. C for (1) and 315 deg. C for (2) and (3). The electronic absorption spectroscopy shows the characteristic bands of the Fe(II), Co(II) and Ni(II) high-spin cations in slightly distorted octahedral geometry. Magnetic measurements indicate the existence of global antiferromagnetic interactions between the metallic centers with a ferromagnetic transition in the three compounds at 28, 14 and 21 K for (1), (2) and (3), respectively. Compound (1) exhibits a hysteresis loop with remnant magnetization and coercive field values of 0.72 emu/mol and 880 Oe, respectively. - Abstract: Polyhedral view of the crystal structure of the [M x II M 2.5-x III (H 2 O) 2 (HP III O 3 ) y (P IV O 4 ) 2-y F] [M=Fe, x=2.08, y=1.58; M=Co, Ni, x=2.5, y=2] compounds showing the sheets along the [001] direction.

  14. NMR study of 59Co in Gdsub(1-x)Ysub(x)(Fesub(0.7)Cosub(0.3))2 and Gdsub(1-x)Ysub(x)(Fesub(0.5)Cosub(0.5))2

    International Nuclear Information System (INIS)

    Ichinose, Kazuyoshi; Yoshie, Hiroshi; Nagai, Hiroyuki; Tsujimura, Akira; Fujiwara, Katsuyuki.

    1982-01-01

    Nuclear magnetic resonance of 59 Co nuclei in Gdsub(1-x)Ysub(x)(Fesub(.7)Cosub(.3)) 2 and Gdsub(1-x)Ysub(x)(Fesub(.5)Cosub(.5)) 2 has been observed at 77 K as a function of Y concentration. The contribution of 4f electrons of Gd atoms to the hyperfine fields is estimated as at most 10 kOe in these two systems. This value is interpreted as the sum of the change in three kinds of contributions caused by Y substitution; the core polarization in the central Co atom, the conduction electron polarization arising from nearest neighbor Fe and Co atoms and the transferred typerfine field from neighboring Gd atoms. The temperature dependence of resonance frequencies in Gd(Fesub(.7)Cosub(.3)) 2 and Gd(Fesub(.5)Cosub(.5)) 2 has also been measured. (author)

  15. Nanocrystalline Ce 1- xY xO 2- x/2 (0≤ x≤0.35) Oxides via Carbonate Precipitation: Synthesis and Characterization

    Science.gov (United States)

    Li, Ji-Guang; Ikegami, Takayasu; Wang, Yarong; Mori, Toshiyuki

    2002-10-01

    A novel carbonate (co)precipitation method, employing nitrates as the starting salts and ammonium carbonate as the precipitant, has been used to synthesize nanocrystalline CeO 2 and Ce 1- xY xO 2- x/2 ( x≤0.35) solid-solutions. The resultant powders are characterized by elemental analysis, differential thermal analysis/thermogravimetry (DTA/TG), X-ray diffractometry (XRD), Brunauer-Emmett-Teller (BET) analysis, and high-resolution scanning electron microscopy (HRSEM). Due to the direct formation of carbonate solid-solutions during precipitation, Ce 1- xY xO 2- x/2 solid-solution oxides are formed directly during calcination at a very low temperature of ˜300°C for 2 h. The thus-produced oxide nanopowders are essentially non-agglomerated, as revealed by BET in conjunction with XRD analysis. The solubility of YO 1.5 in CeO 2 is determined via XRD to be somewhere in the range from 27 to 35 mol%, from which a Y 2O 3-related type-C phase appears in the final product. Y 3+-doping promotes the formation of spherical nanoparticles, retards thermal decomposition of the precursors, and suppresses significantly crystallite coarsening of the oxides during calcination. The activation energy for crystallite coarsening increases gradually from 68.7 kJ mol -1 for pure CeO 2 to 138.6 kJ mol -1 for CeO 2 doped with 35 mol% YO 1.5. The dopant effects on crystallite coarsening is elaborated from the view point of solid-state chemistry.

  16. Preparation and properties of Y{sub 1-x}Ho{sub x}Ba{sub 2}Cu{sub 3}O{sub 7-{delta}} thin films by TFA-MOD method

    Energy Technology Data Exchange (ETDEWEB)

    Jian Hongbin [Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031 (China); Li Qi; Shi Dongqi [Institute for Superconducting and Electronic Materials, University of Wollongong, Wollongong 2522 (Australia); Zhang Li [Department of Mathematic and Physics, Anhui University of Architecture, Hefei 230022 (China); Yang Zhaorong [Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031 (China); Dou Shixue [Institute for Superconducting and Electronic Materials, University of Wollongong, Wollongong 2522 (Australia); Zhu Xuebin, E-mail: xbzhu@issp.ac.cn [Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031 (China); Sun Yuping [Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031 (China)

    2011-12-15

    Y{sub 1-x}Ho{sub x}BCO thin films were prepared by TFA-MOD. The best performances were obtained for the Y{sub 0.6}Ho{sub 0.4}BCO thin film. The pinning mechanism was {delta}l-type for all derived thin films. Y{sub 1-x}Ho{sub x}Ba{sub 2}Cu{sub 3}O{sub 7-{delta}} (x = 0, 0.1, 0.2, 0.3, 0.4, 0.5) thin films were prepared on LaAlO{sub 3} (0 0 1) substrates by trifluoroacetate metal organic deposition (TFA-MOD) without change of the processing parameters. The highest J{sub c} was attributed to the sample of Y{sub 0.6}Ho{sub 0.4}Ba{sub 2}Cu{sub 3}O{sub 7-{delta}} thin film, whose critical current density is about 1.6 times as compared to that of YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} thin film at 77 K and self field. The flux pinning type was not varied with Ho substitution and can be attributed to {delta}l pinning model, which is attributed to the close ionic radius between the Y{sup 3+} and Ho{sup 3+} ions. The improvement of J{sub c} by Ho substitution without change of the processing parameters will provide an effective route to enhance the J{sub c} of YBCO-based thin films using TFA-MOD method.

  17. Electrical properties of the LaLi y Co1 - y O3 - δ (0 ≤ y ≤ 0.10) oxides

    Science.gov (United States)

    Vecherskii, S. I.; Konopel'ko, M. A.; Batalov, N. N.; Antonov, B. D.; Reznitskikh, O. G.; Yaroslavtseva, T. V.

    2017-08-01

    The effect of the Li ion concentration on the phase composition, the electrical conductivity, and the thermoelectric power of the LaLi y Co1- y O3-δ (0 ≤ y ≤ 0.1) oxides synthesized by cocrystallization has been studied. It is found that the region of the perovskite-like solid solution LaLi y Co1- y O3-δ is no higher than y = 0.037. In the temperature range 300-1020 K, lithium alloying leads to an increase in the electrical conductivity and a decrease in the positive thermoelectric power of the single-phase samples compared to LaCoO3-δ. The results are discussed using the density of states model proposed by Senarus Rodriguez and Goodenough for LaCoO3-δ and La1- x Sr x CoO3-δ and using the Mott theory of noncrystalline substances.

  18. Synthesis of Y{sub 1-x}Al{sub x}Ba{sub 2}Cu{sub 3}O{sub 7-δ} via combustion route: Effects of Al{sub 2}O{sub 3} nanoparticles on superconducting properties

    Energy Technology Data Exchange (ETDEWEB)

    Mohd Suan, Mohd Shahadan, E-mail: mohdshahadan@utem.edu.my [Department of Engineering Materials, Faculty of Manufacturing Engineering, Universiti Teknikal Malaysia Melaka, 76100 Durian Tunggal, Melaka (Malaysia); Johan, Mohd Rafie [Nanomaterial Engineering Research Group, Advanced Materials Research Laboratory, Department of Mechanical Engineering, University of Malaya, 50603 Kuala Lumpur (Malaysia)

    2017-02-01

    Combustion reaction was used to synthesis Al{sub 2}O{sub 3} nanoparticles embedded Y{sub 1-x}Al{sub x}Ba{sub 2}Cu{sub 3}O{sub 7-δ} simultaneously. The effects of Al{sub 2}O{sub 3} nanoparticles with nominal molar mass (x{sub mol}) of 0.02, 0.04, 0.06, 0.08 and 0.10 towards the critical current density J{sub C} of Y{sub 1-x}Al{sub x}Ba{sub 2}Cu{sub 3}O{sub 7-δ} were verified by magnetic measurement. Resulted XRD patterns revealed that the calcined samples consist of pure Al{sub 2}O{sub 3} and Y{sub 1-x}Al{sub x}Ba{sub 2}Cu{sub 3}O{sub 7-δ} phases which had been confirmed by EDX results. The SEM images showed that Al{sub 2}O{sub 3} nanoparticles (~10 nm) were distributed in polycrystalline YBa{sub 2}Cu{sub 3}O{sub 7-δ} grains and grain boundaries. The presence of higher concentration of Al{sub 2}O{sub 3} nanoparticles has developed Al{sup 3+} rich spots which diffused within the YBa{sub 2}Cu{sub 3}O{sub 7-δ} superconducting matrix to form Y{sub 1-x}Al{sub x}Ba{sub 2}Cu{sub 3}O{sub 7-δ} and was confirmed by EDX analysis. The samples were electrically superconducting at temperature above 85 K as measured by using standard four-probe technique. The magnetic field (H) dependent magnetization (M), M-H hysteresis loops measured at 77 K for x{sub mol}≤0.06 samples are significantly improved attributed to the increase of trapped fluxes in the samples. Remarkable increase of magnetic J{sub C} (H) in Al{sub 2}O{sub 3} nanoparticles added samples compared to the as prepared polycrystalline YBa{sub 2}Cu{sub 3}O{sub 7-δ} sample indicating strong pinning effect. It is suggested that well-distributed Al{sub 2}O{sub 3} nanoparticles in the polycrystalline YBa{sub 2}Cu{sub 3}O{sub 7-δ} matrix achieved via auto-combustion reaction has efficiently pin the magnetic vortex. The magnetic J{sub C} was optimized to ~6 kAcm{sup -2} in x{sub mol}=0.06 sample. On the other hand, insignificant magnetic J{sub C} improvement in x{sub mol}≥0.08 samples is probably resulted from the

  19. Structural instability of Y1-xPrxBa2Cu3O7-δ superconductors studied by positron annihilation lifetime

    International Nuclear Information System (INIS)

    Gou Zhenhui; Chen Feng; Zheng Shengnan; Zhao Zhongxian; Zhu Shengyun

    1995-01-01

    The temperature dependence of the positron annihilation lifetime in high-quality, single-phase Y 1-x Pr x Ba 2 Cu 3 O 7-δ has been measured from 78 to 300K for a better understanding of the origin of the normal state anomaly observed in high T c superconductivity studies. The normal state anomaly has been detected around 30 to 40K above T c for the samples with x=0.0 and 0.1, but, it was not found for the sample with x=0.2 where T c is lower than 80K. The experimental results show that the phase transition-like behavior caused by the structural instability results in the normal state anomaly which acts as a the precursor of high T c superconductivity. (orig.)

  20. Ranked solutions of the matric equation A1X1=A2X2

    Directory of Open Access Journals (Sweden)

    A. Duane Porter

    1980-01-01

    Full Text Available Let GF(pz denote the finite field of pz elements. Let A1 be s×m of rank r1 and A2 be s×n of rank r2 with elements from GF(pz. In this paper, formulas are given for finding the number of X1,X2 over GF(pz which satisfy the matric equation A1X1=A2X2, where X1 is m×t of rank k1, and X2 is n×t of rank k2. These results are then used to find the number of solutions X1,…,Xn, Y1,…,Ym, m,n>1, of the matric equation A1X1…Xn=A2Y1…Ym.

  1. Ba{sub y}Sr{sub 1y}TiO{sub 3} buffer layers for strain tuning of infinite-layer Sr{sub 1x}La{sub x}CuO{sub 2} thin films

    Energy Technology Data Exchange (ETDEWEB)

    Sakuma, Keita, E-mail: sakuma.keita@d.mbox.nagoya-u.ac.jp; Ito, Masataka; He, Yilun; Hajiri, Tetsuya; Ueda, Kenji; Asano, Hidefumi

    2016-08-01

    We report on the precise tuning of lattice strain in an infinite-layer electron-doped high temperature superconductor Sr{sub 1x}La{sub x}CuO{sub 2} (SLCO; a{sub SLCO} = 0.3949 nm for x = 0.1), which is a perovskite-related oxide, using perovskite BaTiO{sub 3}–SrTiO{sub 3} (BSTO; Ba{sub y}Sr{sub 1y}TiO{sub 3}) buffer layers. The BSTO buffer layers formed on (001) (La{sub 0.18}Sr{sub 0.82})(Al{sub 0.59}Ta{sub 0.41})O{sub 3} substrates by magnetron sputtering were fully relaxed with high crystalline quality due to high oxygen partial pressure deposition and post annealing at 950 °C. The lattice constants of the BSTO buffer layers could be controlled in the range of 0.3926–0.3973 nm by changing the Ba content (y = 0.2–0.7). These BSTO buffer layers allow coherent growth of SLCO thin films, and a clear dependence of the superconducting transition temperature on the lattice strain was observed. The fabrication of these BSTO/superconductor heterostructures may provide novel devices composed of functional perovskite thin films, in addition to a general approach for the precise control of lattice strain in functional perovskite thin films. - Highlights: • Ba{sub y}Sr{sub 1y}TiO{sub 3} buffer layers were developed for the strain tuning of perovskite-related oxides. • Strain effect in Sr{sub 1x}La{sub x}CuO{sub 2} was investigated by using Ba{sub y}Sr{sub 1y}TiO{sub 3} buffer layers. • Ba{sub y}Sr{sub 1y}TiO{sub 3} buffer layers can be used to tune the strain in other perovskite oxides.

  2. Bellman-Krein formula for an integral equation with kernel of the type k(x,y)=k(x - y) x- y sup(-α)

    International Nuclear Information System (INIS)

    Youssef, M.Y.A.; El Walik, S.A.

    1976-08-01

    With the aid of the Bellman-Krein formula for the resolvent, it is shown how to solve the integral equation with kernel of the type k(x,y)=k(x - y) x - ysup(-α), 0<α< n, i.e. the kernel with weak singularity

  3. Synthesis and X-ray diffraction studies of dysprosium-calcium ferrites Dy1-xCaxFeO3-y (0≤x≤2/3)

    International Nuclear Information System (INIS)

    Li, J.; Song, D.; Su, Z.; Wang, T.M.

    1997-01-01

    Samples of dysprosium-calcium ferrites Dy 1-x Ca x FeO 3-y with x ranging from 0 to 2/3 were novelly prepared in air by solid state reaction and characterized by X-ray powder diffraction. These samples are single-phased orthorhombic perovskite-type compounds belonging to the space group D 2h 16 -Pbnm. The lattice constants of the Dy 1-x Ca x FeO 3-y samples have been refined by Cohen's least-squares method. The initial substitution of Ca for Dy leads to a decrease of the lattice constants. Further substitution of Ca for Dy has hardly any influence on the lattice dimensions. (orig.)

  4. Non-Fermi liquid and spin-glass behavior of the Sc1-xUxPd3 system

    International Nuclear Information System (INIS)

    Gajewski, D.A.; Allenspach, P.; Seaman, C.L.; Maple, M.B.

    1994-01-01

    Previous electrical resistivity ρ(T), magnetic susceptibility χ(T), and specific heat C(T) measurements on the Y 1-x U x Pd 3 system have revealed Kondo behavior for 0 K , where T K is the Kondo temperature: ρ(T)/ρ(0)∼1-T/(aT K ) and C(T)/T∼-(1/T K )ln T with evidence for a finite T=0 residual entropy S(0)=(R/2)ln(2). We report measurements of ρ(T), χ(T), and C(T) on the Sc 1-x U x Pd 3 system which reveal similar Kondo, non-Fermi liquid, and spin-glass behaviors. ((orig.))

  5. Structural Transition and Electrical Properties of (1 - x)(Na0.4K0.1Bi0.5)TiO3- xSrTiO3 Lead-Free Piezoceramics

    Science.gov (United States)

    Liu, Xing; Zhai, Jiwei; Shen, Bo; Li, Feng; Li, Peng

    2017-10-01

    (1 - x)(Na0.4K0.1Bi0.5)TiO3- xSrTiO3 (NKBT- xST) ceramics with x = 0 mol.%, 3 mol.%, and 5 mol.% (0ST, 3ST, and 5ST) have been prepared by a conventional solid-state reaction method and their ferroelectric, electrostrictive, and pyroelectric properties investigated. Addition of ST considerably disrupted the long-range ferroelectric order of NKBT- xST ceramics, and the 5ST ceramic exhibited ergodic relaxor phase structure. T FR shifted to near or below room temperature for 5ST ceramic, accompanied by a significant decline of ferroelectricity and enhanced strain. As the temperature approached T FR, the NKBT- xST ceramics exhibited predominantly electrostrictive effect, and the 5ST ceramic presented relatively high electrostrictive coefficient Q 33 of 0.0193 m4/C2. High pyroelectric response was observed for 0ST, 3ST, and 5ST ceramics in the vicinity of T FR due to the large polarization release during the ferroelectric-relaxor structural transition. The 5ST ceramic exhibited high and frequency-insensitive (100 Hz to 10 kHz) room-temperature pyroelectric properties with pyroelectric coefficient p of 656 μC m-2 K-1 and figures of merit F i, F v, and F d reaching 233 pm/V, 0.013 m2/C, and 7.61 μPa-1/2, respectively, indicating that 5ST ceramic is a promising candidate to replace PZT-based ceramics.

  6. Magnetic instabilities in Er1-xYxCo3 studied by NMR

    International Nuclear Information System (INIS)

    Niki, H.; Fukumura, T.; Kinjou, H.; Kinjou, T.; Pieper, M.W.; Gratz, E.; Paul-Boncour, V.; Markosyan, A.S.

    2006-01-01

    The field dependence of 59 Co NMR in ferrimagnetic Er 1-x Y x Co 3 was measured up to 8T at 4.2K. For pure ErCo 3 in fields perpendicular to the c axis the resonance frequencies change discontinuously between 2 and 3T due to a field induced metamagnetic transition. The transition is characterized by rotations of Er and Co magnetic moments away from the easy c-axis. The angles between the Co moments and the c axis at x=0.1 are obtained. The easy axis is found to be along the c axis for x=0 and 0.1, and inclined from the c axis for x=0.3 and 0.5

  7. Effect of γ- Ray Irradiation on the Solid Ionic Conductor of (Cul)x(Na3PO4)1-X Materials (x= 0.1 and x= 0.3)

    International Nuclear Information System (INIS)

    Purwanto, P.

    2008-01-01

    Study on the effect of γ- ray irradiation on solid state conductor (Cul) x (Na 3 PO 4 ) 1-X have been done. The solid ionic conductor of (Cul) x (Na 3 PO 4 ) 1-X (x= 0.1 and x= 0.3) had been made by mixing Cul with Na 3 PO 4 by formula of (Cul) x (Na 3 PO 4 ) 1-X where x= 0.1 and x= 0.3 then pressed with 48.26 x 10 6 N/m 2 into pellete in diametre 1.5 x 10 - 2 m. The solid ionic conductor was then γ- ray irradiated with dose of 5 to 30 kGy. The result showed that the structure of (Cul) x (Na 3 PO 4 ) 1-X was Cul and Na 3 PO 4 . Crystall lattice strain of (Cul) x (Na 3 PO 4 ) 1-X were measured stable against the influence of radiation. The conductivity measurement of (Cul) x (Na 3 PO 4 ) 1-X was carried out by LCR at the frequence of 0.1 Hz to 100 kHz. The result showed that the conductivities of (Cul) x (Na 3 PO 4 ) 1-X after irradiation were increasing with radiation dose. (author)

  8. Anomalous Interface and Surface Strontium Segregation in (La 1y Sr y ) 2 CoO 4±δ /La 1x Sr x CoO 3−δ Heterostructured Thin Films

    KAUST Repository

    Feng, Zhenxing

    2014-03-20

    Heterostructured oxides have shown unusual electrochemical properties including enhanced catalytic activity, ion transport, and stability. In particular, it has been shown recently that the activity of oxygen electrocatalysis on the Ruddlesden-Popper/perovskite (La1-ySr y)2CoO4±δ/La1-xSr xCoO3-δ heterostructure is remarkably enhanced relative to the Ruddlesden-Popper and perovskite constituents. Here we report the first atomic-scale structure and composition of (La1-ySr y)2CoO4±δ/La1-xSr xCoO3-δ grown on SrTiO3. We observe anomalous strontium segregation from the perovskite to the interface and the Ruddlesden-Popper phase using direct X-ray methods as well as with ab initio calculations. Such Sr segregation occurred during the film growth, and no significant changes were found upon subsequent annealing in O2. Our findings provide insights into the design of highly active catalysts for oxygen electrocatalysis. © 2014 American Chemical Society.

  9. Anomalous Interface and Surface Strontium Segregation in (La 1y Sr y ) 2 CoO 4±δ /La 1x Sr x CoO 3−δ Heterostructured Thin Films

    KAUST Repository

    Feng, Zhenxing; Yacoby, Yizhak; Gadre, Milind J.; Lee, Yueh-Lin; Hong, Wesley T.; Zhou, Hua; Biegalski, Michael D.; Christen, Hans M.; Adler, Stuart B.; Morgan, Dane; Shao-Horn, Yang

    2014-01-01

    Heterostructured oxides have shown unusual electrochemical properties including enhanced catalytic activity, ion transport, and stability. In particular, it has been shown recently that the activity of oxygen electrocatalysis on the Ruddlesden-Popper/perovskite (La1-ySr y)2CoO4±δ/La1-xSr xCoO3-δ heterostructure is remarkably enhanced relative to the Ruddlesden-Popper and perovskite constituents. Here we report the first atomic-scale structure and composition of (La1-ySr y)2CoO4±δ/La1-xSr xCoO3-δ grown on SrTiO3. We observe anomalous strontium segregation from the perovskite to the interface and the Ruddlesden-Popper phase using direct X-ray methods as well as with ab initio calculations. Such Sr segregation occurred during the film growth, and no significant changes were found upon subsequent annealing in O2. Our findings provide insights into the design of highly active catalysts for oxygen electrocatalysis. © 2014 American Chemical Society.

  10. Influence of the sintering temperature on the Sr content in a Ca{sub (1−x−y)}Ce{sub x}Sr{sub y}Al{sub z}Ti{sub (1−z)}O{sub 3} perovskite (x = 0.04–0.16) co-doped with Ce

    Energy Technology Data Exchange (ETDEWEB)

    Kamel, Nour-el-hayet; Mouheb, Yasmina, E-mail: mouhebyascrna@hotmail.com; Kamel, Ziane; Moudir, Dalila; Aouchiche, Fairouz; Arabi, Azeddine

    2016-08-15

    A Sr-Ce co-doped perovskite, with the chemical formula: Ca{sub (1−x−y)}Ce{sub x}Sr{sub y}Al{sub z}Ti{sub (1−z)}O{sub 3} (y = 0.04, 0.08, 0.12 and 0.16, x = 0.05) is synthesized by sol–gel process. The influence of the sintering temperature, Ts, on the rate of inserted Sr was investigated at 1223, 1373 and 1473 K. The Sr amount sequestered in the perovskite reaches 85% (y = 0.16, 9.50 wt%) for Ts = 1373 K, giving sintering densities between 3.520 and 4.400. XRD analysis reveals an orthorhombic CaTiO{sub 3} structure. The lattice parameters obey to Vegard’s law for Ts = 1373 and 1473 K. SEM analysis shows orthorhombic grains of 0.514 μm × 1 μm mean dimensions. MCC1 and MCC2 tests, performed on minerals sintered at 1373 K, indicate that the most durable one is that containing 9.50 wt% Sr. MCC1 test gave 6.998·10{sup −6} g/cm{sup 2} d of Sr, and MCC2 2.143·10{sup −4} g/cm{sup 2} d of Ce. The temperature favors the Sr dissolution to the detriment of Ce. The Ca dissolution rate reaches 1.002·10{sup −6} to 2.005·10{sup −6} g/cm{sup 2} d. - Highlights: • Ca{sub (1−x−y)}Ce{sub x}Sr{sub y}Al{sub z}Ti{sub (1−z)}O{sub 3} perovskite is synthesized by sol–gel. • The influence of the sintering temperature, Ts, on the rate of inserted Sr was investigated at 1223, 1373 and 1473 K. • 85% of total Sr was sequestered in the perovskite for Ts = 1373 K. • MCC1 and MCC2 leach tests indicate that the most durable mineral is that containing 9.50 wt.% Sr. • MCC1 test gave 8.10 10{sup −10} kg/m{sup 2}.d Sr. The lower is the leaching temperature the higher is the mineral durability.

  11. The complex metal-rich boride Ti1+xRh2-x+yIr3-yB3 (x=0.68, y=1.06) with a new structure type containing B4 zigzag fragments: Synthesis, crystal chemistry and theoretical calculations

    Science.gov (United States)

    Goerens, Christian; Fokwa, Boniface P. T.

    2012-08-01

    Polycrystalline samples and single crystals of the new complex boride Ti1+xRh2-x+yIr3-yB3 (x=0.68; y=1.06) were synthesized by arc-melting the elements in a water-cooled copper crucible under an argon atmosphere and characterized by X-Ray diffraction as well as EDX measurements. The crystal structure was refined on the basis of single crystal data. The new phase, which represents a new structure type containing trans zigzag B4 fragments as well as isolated boron atoms crystallizes in the orthorhombic space group Pbam (Nr. 55) with the lattice parameters a=8.620(1) Å, b=14.995(2) Å and c=3.234(1) Å. First-principles density functional theory calculations using the Vienna ab-initio simulation package (VASP) were performed on an appropriate structural model (using a supercell approach) and the experimental crystallographic data could be reproduced accurately. Based on this model, the density of states and crystal orbital Hamilton population (for bonding analysis) were calculated, using the linear muffin-tin orbital atomic sphere approximation (LMTO-ASA) method. According to these calculations, this metal-rich compound should be metallic, as expected. Furthermore, very strong boron-boron interactions are observed in the trans zigzag B4 fragment, which induce a clear differentiation of two types of metal-boron contacts with different strength. The observed three-dimensional metal-metal interaction is in good agreement with the predicted metallic behavior.

  12. IGF-1 protects SH-SY5Y cells against MPP+-induced apoptosis via PI3K/PDK-1/Akt pathway.

    Science.gov (United States)

    Kim, Chanyang; Park, Seungjoon

    2018-03-01

    Insulin-like growth factor (IGF)-1 is a well-known anti-apoptotic pro-survival factor and phosphatidylinositol-3-kinase (PI3K)/Akt pathway is linked to cell survival induced by IGF-1. It is also reported that Akt signaling is modulated by 3-phosphoinositide-dependent kinase-1 (PDK1). In the current study, we investigated whether the anti-apoptotic effect of IGF-1 in SH-SY5Y cells exposed to 1-methyl-4-phenylpyridinium (MPP + ) is associated with the activity of PI3K/PDK1/Akt pathway. Treatment of cells with IGF-1 inhibited MPP + -induced apoptotic cell death. IGF-1-induced activation of Akt and the protective effect of IGF-1 on MPP + -induced apoptosis were abolished by chemical inhibition of PDK1 (GSK2334470) or PI3K (LY294002). The phosphorylated levels of Akt and PDK1 were significantly suppressed after MPP + exposure, while IGF-1 treatment completely restored MPP+-induced reductions in phosphorylation. IGF-1 protected cells from MPP + insult by suppressing intracellular reactive oxygen species (ROS) production and malondialdehyde levels and increasing superoxide dismutase activity. Mitochondrial ROS levels were also increased during MPP + exposure, which were attenuated by IGF-1 treatment. In addition, IGF-1-treated cells showed increased activities of succinate dehydrogenase and citrate synthase, stabilization of mitochondrial transmembrane potential, increased ratio of Bcl-2 to Bax, prevention of cytochrome c release and inhibition of caspase-3 activation with PARP cleavage. Furthermore, the protective effects of IGF-1 on oxidative stress and mitochondrial dysfunction were attenuated when cells were preincubated with GSK2334470 or LY294002. Our data suggest that IGF-1 protects SH-SY5Y cells against MPP + -associated oxidative stress by preserving mitochondrial integrity and inhibiting mitochondrial apoptotic cascades via the activation of PI3K/PDK1/Akt pathway. © 2018 The authors.

  13. First-principles calculations of the electronic structure and optical properties of K1xNaxTaO3 (x=0, 0.25, 0.5, 0.75, 1)

    International Nuclear Information System (INIS)

    Zhao, Na; Wang, Yue-Hua; Wang, Qing-Xi; Hu, Wen-Jing

    2012-01-01

    The first-principles calculations are performed to investigate the cubic phase composite K 1x Na x TaO 3 (x=0, 0.25, 0.5, 0.75, 1), by using density functional theory (DFT) with the full potential linearized augmented plane wave (FP-LAPW) method. The energy band structures, density of states (DOS), electron density and optical properties are obtained. The results show that Na ion plays an important role in K 1x Na x TaO 3 . With the content of Na ion increasing, the changes of lattice parameters, energy gaps, bond lengths and optical properties of K 1x Na x TaO 3 are regular. Moreover, the dependence of ferroelectric photocatalysis on both optical properties and internal electronic structure are analyzed in detail. It is proposed that the doped materials are promising photocatalytic materials. - Graphical abstract: The density of states (DOS) of K 1x Na x TaO 3 (x=0.5). Highlights: ► The first-principles calculations are performed, by using DFT with FP-LAPW method. ► The changes of internal electronic structure and optical property of doped materials are regular. ► The dependence of ferroelectric photocatalysis on optical properties is analyzed. ► The dependence of ferroelectric photocatalysis on internal electronic structure is analyzed. ► The doped materials are promising photocatalytic materials.

  14. Analytical representation of the thermal conductivity and electrical resistivity of UC/sub 1 +- x/, PuC/sub 1-x/, and (U/sub y/Pu/sub 1-y/)C/sub 1 +- x/

    International Nuclear Information System (INIS)

    Storms, E.K.

    1982-12-01

    This report uses selected measurements from the literature to construct analytical expressions that describe the electrical and thermal conductivity of pure, high-density UC/sub 1 +- x/, PuC/sub 1-x/, and (U/sub y/Pu/sub 1-y/C/sub 1 +- x/ as a function of x,y, and temperature. The approach shows that many of the differences between the reported measurements can be resolved if the carbon cntent of the single-phase material is taken into account. Analytical expressions are also given that describe the temperature variation of the phase boundaries for these phases. 16 figures

  15. Synthesis and photocatalytic activity of hydrated layered perovskite K2-xLa2Ti3-xNb xO10 (0 ≤ x1) and protonated derivatives

    International Nuclear Information System (INIS)

    Huang Yunfang; Wu Jihuai; Wei Yuelin; Hao Sancun; Huang Miaoliang; Lin Jianming

    2007-01-01

    A series of photocatalytic intercalated materials K 2-x La 2 Ti 3-x Nb x O 10 (0 ≤ x1) and a series of its protonated derivatives H 2-x La 2 Ti 3-x Nb x O 10 were prepared by solid-state reaction and ion-exchange reaction. The photocatalytic activities of samples were evaluated using methanol as electron donor under UV irradiation. All H 2-x La 2 Ti 3-x Nb x O 10 samples possessed approximately twofold higher photocatalytic activity than the corresponding K 2-x La 2 Ti 3-x Nb x O 10 . This difference was most pronounced for the photocatalyst H 1.9 La 2 Ti 2.9 Nb 0.1 O 10 which showed the highest activity: 22 μmol H 2 /catalyst (g) for 5 h, more than three times the activity of K 1.9 La 2 Ti 2.9 Nb 0.1 O 10

  16. Control of Ge1-x-ySixSny layer lattice constant for energy band alignment in Ge1-xSnx/Ge1-x-ySixSny heterostructures

    Science.gov (United States)

    Fukuda, Masahiro; Watanabe, Kazuhiro; Sakashita, Mitsuo; Kurosawa, Masashi; Nakatsuka, Osamu; Zaima, Shigeaki

    2017-10-01

    The energy band alignment of Ge1-xSnx/Ge1-x-ySixSny heterostructures was investigated, and control of the valence band offset at the Ge1-xSnx/Ge1-x-ySixSny heterointerface was achieved by controlling the Si and Sn contents in the Ge1-x-ySixSny layer. The valence band offset in the Ge0.902Sn0.098/Ge0.41Si0.50Sn0.09 heterostructure was evaluated to be as high as 330 meV, and its conduction band offset was estimated to be 150 meV by considering the energy bandgap calculated from the theoretical prediction. In addition, the formation of the strain-relaxed Ge1-x-ySixSny layer was examined and the crystalline structure was characterized. The epitaxial growth of a strain-relaxed Ge0.64Si0.21Sn0.15 layer with the degree of strain relaxation of 55% was examined using a virtual Ge substrate. Moreover, enhancement of the strain relaxation was demonstrated by post-deposition annealing, where a degree of strain relaxation of 70% was achieved after annealing at 400 °C. These results indicate the possibility for enhancing the indirect-direct crossover with a strained and high-Sn-content Ge1-xSnx layer on a strain-relaxed Ge1-x-ySixSny layer, realizing preferable carrier confinement by type-I energy band alignment with high conduction and valence band offsets.

  17. Studies on the Ln/sub 2/O/sub 3/ (Ln: rare-earth elements)-SrO-V/sub 2/O/sub 3/ system, 2. Some physical properties for Ln sub(1-x)Sr sub(x)VO sub(3-0. 1x) and SrO. Ln sub(1-x)Sr sub(x)VO sub(3-0. 1x) (Ln: Nd or Eu)

    Energy Technology Data Exchange (ETDEWEB)

    Shin-ike, T [Osaka Dental Coll., Hirakata (Japan); Adachi, G; Shiokawa, J

    1981-01-01

    Electrical and magnetic properties of the perovskite type solid solutions, Ln sub(1-x)Sr sub(x)VO sub(3-0.1x) (Ln: Nd or Eu), and the K/sub 2/NiF/sub 4/ type solid solutions, SrO.Ln sub(1-x)Sr sub(x)VO sub(3-0.1x) (Ln: Nd or Eu), were studied in the temperature range 77 - 300 K. The electrical conductivity increased with x for the perovskite type solid solutions and the reverse behavior was observed for the K/sub 2/NiF/sub 4/ type compounds. All the solid solutions examined exhibited a metal-insulator transition at some values of x. Both Nd sub(1-x)Sr sub(x)VO sub(3-0.1x) and Eu sub(1-x)Sr sub(x)VO sub(3-0.1x) were antiferromagnets having a weak ferromagnetism at a low value of x at a low temperature. The K/sub 2/NiF/sub 4/ type solid solutions revealed a weak ferromagnetism at a high value of x at a low temperature.

  18. Doping effect on ferromagnetism, ferroelectricity and dielectric constant in sol-gel derived Bi1-xNdxFe1-yCoyO3 nanoceramics

    Science.gov (United States)

    Das, Sananda; Sahoo, R. C.; Bera, K. P.; Nath, T. K.

    2018-04-01

    Doping at the post-transition metal site by trivalent rare-earth ions and 3d transition metal site by transition metal ions in perovskite lattice has observed a variety of magnetic and electronic orders with spatially correlated charge, spin and orbital degrees of freedom. Here, we report large ferromagnetism and enhanced dielectric constant (at ∼100 Hz) in chemically synthesized single phase multiferroic Bi1-xNdxFe1-yCoyO3 (x = 0, 0.10; y = 0, 0.10) nanoparticles (average particles size ∼45 nm). We have also examined the ferroelectric nature of our chemically synthesized samples. The Rietveld refinement of the XRD data reveals the structural symmetry breaking from distorted rhombohedral R3c structure of BiFeO3 to the triclinic P1 structure in Bi0.9Nd0.1Fe0.9Co0.1O3 (BNFCO) without having any iron rich impurity phase. The magnetization in these nanoceramics most likely originates from the coexistence of mixed valence states of Fe ion (Fe2+ and Fe3+). A high room temperature dielectric constant (∼1050) has been observed at 100 Hz of BNFCO sample. The frequency dependent anomalies near Neel temperature of antiferromagnet in temperature variation of dielectric study have been observed for all the doped and co-doped samples exhibiting typical characteristic of relaxor ferroelectrics. A spectacular enhancement of remanent magnetization MR (∼7.2 emu/gm) and noticeably large coercivity HC (∼17.4 kOe) at 5 K have been observed in this BNFCO sample. Such emergence of ferromagnetic ordering indicates the canting of the surface spins at the surface boundaries because of the reduction of particle size in nanodimension. We have also observed P-E hysteresis loops with a remanent polarization of 26 μC/cm2 and coercive field of 5.6 kV/cm of this sample at room temperature. From impedance spectroscopy study the estimated activation energy of 0.41 eV suggests the semiconducting nature of our nanoceramic BNCFO sample.

  19. Phase analysis of the system La1-xBaxFeO3-y (0≤x≤0.70) by means of X-ray diffraction and Moessbauer spectroscopy

    International Nuclear Information System (INIS)

    Li, J.; Jing, J.

    1992-01-01

    X-ray diffraction and Moessbauer measurements were performed on novelly synthesized La 1-x Ba x FeO 3-y (0≤x≤0.70). Two phases were found in the system. La 1-x Ba x FeO 3-y for 0≤x≤0.10 is an orthorhombic perovskite. La 1-x Ba x FeO 3-y for 0.54≤x≤0.70 is a cubic perovskite. La 1-x Ba x FeO 3-y for 0.10≤x≤0.54 consists of these two phases. (orig.)

  20. Synthesis, crystal structure investigation and magnetism of the complex metal-rich boride series Crx(Rh1-yRuy)7-xB3 (x=0.88-1; y=0-1) with Th7Fe3-type structure

    Science.gov (United States)

    Misse, Patrick R. N.; Mbarki, Mohammed; Fokwa, Boniface P. T.

    2012-08-01

    Powder samples and single crystals of the new complex boride series Crx(Rh1-yRuy)7-xB3 (x=0.88-1; y=0-1) have been synthesized by arc-melting the elements under purified argon atmosphere on a water-cooled copper crucible. The products, which have metallic luster, were structurally characterized by single-crystal and powder X-ray diffraction as well as EDX measurements. Within the whole solid solution range the hexagonal Th7Fe3 structure type (space group P63mc, no. 186, Z=2) was identified. Single-crystal structure refinement results indicate the presence of chromium at two sites (6c and 2b) of the available three metal Wyckoff sites, with a pronounced preference for the 6c site. An unexpected Rh/Ru site preference was found in the Ru-rich region only, leading to two different magnetic behaviors in the solid solution: The Rh-rich region shows a temperature-independent (Pauli) paramagnetism whereas an additional temperature-dependent paramagnetic component is found in the Ru-rich region.

  1. Transport properties of Na doped La sub 1 sub - sub x Ca sub x sub - sub y Na sub y MnO sub 3 measured in a pulsed magnetic field

    CERN Document Server

    Bhattacharya, S; Pal, S; Chatterjee, P; Mukherjee, R K; Chaudhuri, B K

    2002-01-01

    Temperature-dependent magnetization and magnetoresistance of the Na doped La sub 1 sub - sub x Ca sub x sub sub - sub y Na sub y MnO sub 3 type samples with x=0.3 and 0 T sub p up to 320 K) conductivity data satisfy the variable range hopping (VRH) model. For T > 320 the small polaron hopping model is more appropriate than the VRH model. Even with a very small change of y, the density of states at the Fermi level N(E sub F) changes considerably. The resistivity of these materials measured under pulsed and continuous DC magnetic fields behaves in an identical fashion. The relaxation time (decay time of the magnetic pulse within the sample) varies with field strength, which indicates that, with a change of magnetic field, the ordering of spin in the ferromagnetic regime changes.

  2. Magnetorefractive effect in the La{sub 1x}K{sub x}MnO{sub 3} thin films grown by MOCVD

    Energy Technology Data Exchange (ETDEWEB)

    Sukhorukov, Yu.P., E-mail: suhorukov@imp.uran.ru [Institute of Metal Physics, Ural Division of RAS, 620990 Ekaterinburg (Russian Federation); Telegin, A.V. [Institute of Metal Physics, Ural Division of RAS, 620990 Ekaterinburg (Russian Federation); Bessonov, V.D. [Institute of Metal Physics, Ural Division of RAS, 620990 Ekaterinburg (Russian Federation); University of Bialystok, 15-424 Bialystok (Poland); Gan’shina, E.A.; Kaul’, A.R.; Korsakov, I.E.; Perov, N.S.; Fetisov, L.Yu. [Faculty of Physics, Moscow State University, Moscow 119991 (Russian Federation); Yurasov, A.N. [Moscow State Technical University of Radioengineering, Electronics and Automation, 119454 Moscow (Russian Federation)

    2014-10-01

    Thin epitaxial La{sub 1x}K{sub x}MnO{sub 3} films were grown using two-stage procedure. Influence of substitution of La{sup 3+} ions with K{sup +} ions on the optical and electrical properties of La{sub 1x}K{sub x}MnO{sub 3} films (x=0.05, 0.10, 0.15 i 0.18) has been studied in detail. A noticeable magnetorefractive effect in the films under study was detected in the infrared range. Magnetorefractive effect as well as transverse magneto-optical Kerr effect and magnetoresistance have the maximum in optimally doped sample with x=0.18 corresponding to the highest Curie temperature. The experimental data for compositions close to optimally doped films are in good agreement with the data calculated in the framework of a theory developed for manganites. The resonance-like contribution to magnetoreflection spectra of manganite films has been observed in the vicinity of the phonon bands. It is shown that magnetic and charge inhomogeneities strongly influence on the magneto-optical effects in films. Thin films of La{sub 1x}K{sub x}MnO{sub 3} with the large values of Kerr and magnetorefractive effect are promising magneto-optical material in the infrared range. - Highlights: • Giant magnetorefractive effect was obtained in La{sub 1x}K{sub x}MnO{sub 3} films in the infrared. • Inhomogeneity as well as doping level strongly influences the value of magnetorefractive effect. • Resonance-like bands have been observed in the magnetoreflection spectra of the films. • The obtained experimental data can be explained in the framework of the MRE theory.

  3. Transverse- and zero-field μSR [muon-spin-rotation] investigation of magnetism and superconductivity in (Y1-xPrx)Ba2Cu3O7

    International Nuclear Information System (INIS)

    Cooke, D.W.; Jahan, M.S.; Kwok, R.S.; Lichti, R.L.; Adams, T.R.; Boekema, C.; Dawson, W.K.; Kebede, A.; Schwegler, J.; Crow, J.E.; Mihalsin, T.

    1990-01-01

    Zero-field muon-spin-rotation (μSR) measurements on (Y 1-x Pr x )Ba 2 Cu 3 O 7 [x = 1.0, 0.8, 0.6, and 0.54] show evidence for antiferromagnetic ordering of the Cu moments within the Cu--O planes, with Neel temperatures 285,220, 35, 30, and 20 K respectively. For x = 1.0 the local muon magnetic field is ∼16 mT, but decreases to ∼12 mT at 17 K, due to additional magnetic ordering. The zero-field data, in conjunction with transport data, allow construction of a complete diagram for this system. Transverse-field (1 kOe) μSR data for x = 0.2 (T c = 75 K) show that the muon depolarization is determined primarily by the Cu nuclear moments for T>T c . Fitting the superconducting-state data to a BCS model yields an extrapolated zero-temperature magnetic penetration depth of 2170 angstrom. 9 refs., 3 figs

  4. Real-Space Bonding Indicator Analysis of the Donor-Acceptor Complexes X3BNY3, X3AlNY3, X3BPY3, and X3AlPY3 (X, Y = H, Me, Cl).

    Science.gov (United States)

    Mebs, Stefan; Beckmann, Jens

    2017-10-12

    Calculations of real-space bonding indicators (RSBI) derived from Atoms-In-Molecules (AIM), Electron Localizability Indicator (ELI-D), Non-Covalent Interactions index (NCI), and Density Overlap Regions Indicator (DORI) toolkits for a set of 36 donor-acceptor complexes X 3 BNY 3 (1, 1a-1h), X 3 AlNY 3 (2, 2a-2h), X 3 BPY 3 (3, 3a-3h), and X 3 AlPY 3 (4, 4a-4h) reveal that the donor-acceptor bonds comprise covalent and ionic interactions in varying extents (X = Y = H for 1-4; X = H, Y = Me for 1a-4a; X = H, Y = Cl for 1b-4b; X = Me, Y = H for 1c-4c; X, Y = Me for 1d-4d; X = Me, Y = Cl for 1e-4e; X = Cl, Y = H for 1f-4f; X = Cl, Y = Me for 1g-4g; X, Y = Cl for 1h-4h). The phosphinoboranes X 3 BPY 3 (3, 3a-3h) in general and Cl 3 BPMe 3 (3f) in particular show the largest covalent contributions and the least ionic contributions. The aminoalanes X 3 AlNY 3 (2, 2a-2h) in general and Me 3 AlNCl 3 (2e) in particular show the least covalent contributions and the largest ionic contributions. The aminoboranes X 3 BNY 3 (1, 1a-1h) and the phosphinoalanes X 3 AlPY 3 (4, 4a-4h) are midway between phosphinoboranes and aminoalanes. The degree of covalency and ionicity correlates with the electronegativity difference BP (ΔEN = 0.15) < AlP (ΔEN = 0.58) < BN (ΔEN = 1.00) < AlN (ΔEN = 1.43) and a previously published energy decomposition analysis (EDA). To illustrate the importance of both contributions in Lewis formula representations, two resonance formulas should be given for all compounds, namely, the canonical form with formal charges denoting covalency and the arrow notation pointing from the donor to the acceptor atom to emphasis ionicity. If the Lewis formula mainly serves to show the atomic connectivity, the most significant should be shown. Thus, it is legitimate to present aminoalanes using arrows; however, for phosphinoboranes the canonical form with formal charges is more appropriate.

  5. The new mixed cluster trielide K{sub 3}Ga{sub 11-x}In{sub x} (x = 1.16-1.36). Synthesis, crystal chemistry, and chemical bonding

    Energy Technology Data Exchange (ETDEWEB)

    Falk, Martha; Meyer, Carolin; Roehr, Caroline [Institut fuer Anorganische und Analytische Chemie, Universitaet Freiburg (Germany)

    2017-12-13

    The new cluster compound K{sub 3}Ga{sub 11-x}In{sub x}, which exhibits a very small In/Ga phase width of x = 1.16 to 1.36 only, was obtained in the course of a systematic synthetic, crystallographic and bond theoretical investigation of mixed potassium trielides of the ternary system K-In-Ga. The compound, which was synthesized from nearly stoichiometric amounts of the elements at a maximum temperature of 500 C, crystallizes in a new orthorhombic crystal structure type [space group Cmmm, a = 1577.9(5), b = 3355.1(8), c = 655.2(2) pm, Z = 10, R{sub 1} = 0.0471]. In the complex polyanion, the triels form two crystallographically different [Ga{sub 12}] icosahedra, which are present in a 1:2 ratio, and a previously unknown [M{sub 13}] ''double-cluster'' consisting of two vertex-sharing [M{sub 7}] pentagonal bipyramids. All clusters are connected among each other and via a four-bonded pure In and Ga atom [In(1), Ga(1)]. The polyanion of the compound with the overall formula K{sub 15}M{sub 55} can thus be split up according to [Ga(1X){sub 12}][Ga(2X){sub 12}]{sub 2}[M(3X){sub 13}]In(1){sub 4}Ga(1){sub 2}. Herein, the all-exo bonded closo icosahedra carry a charge of -2, the six four-bonded In/Ga contribute with a charge of -6 and the new [M{sub 13}] ''double-cluster'' thus carries a charge of -3. Under the reasonable assumption of an ''intermediate'' interaction between the two cluster fragments, this charge, i.e. the presence of 15 skeleton electron pairs, is in accordance with the mno electron counting rules. FP-LAPW DFT band structure calculations of two ordered model compounds support this interpretation: The tDOS exhibits a small bandgap and the electron density map suggests a limited additional interaction between the Ga{sub 5} bases of the two bipyramidal cluster fragments. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  6. K2-EDTA and K3-EDTA Greiner Tubes for HbA1c Measurement.

    Science.gov (United States)

    Vrtaric, Alen; Filipi, Petra; Hemar, Marina; Nikolac, Nora; Simundic, Ana-Maria

    2016-02-01

    To determine whether K2-ethylenediaminetetraacetic acid (EDTA) and K3-EDTA Greiner tubes could be used interchangeably for glycosylated hemoglobin, type A1C (HbA1c) measurement via the Abbott Laboratories ARCHITECT chemiluminescent microparticle HbA1c assay on the ARCHITECT i2000SR immunoanalyzer at our university hospital. We drew blood from a total of 45 outpatients into plastic Greiner Vacuette tubes, some of which were lined with K2-EDTA and others with K3-EDTA anticoagulant. Data are presented as median and interquartile range values. We used the Wilcoxon test and Passing-Bablok regression for tube comparison. For K2-EDTA tubes median HbA1c concentration was 54 mmol/mol (41 to 71 mmol/mol) and for K3-EDTA tubes 56 mmol/mol (43 to 69 mmol/mol). There was no statistically significant difference between K2-EDTA and K3-EDTA (bias= -1.29 mmol/mol; P = 0.24). Passing-Bablok regression showed that there is no constant and proportional error: y = -0.23 (95% CI[-3.52 to 0.69]) + 1.00( 95% CI[0.98 to 1.06]) x. In this study, we provide evidence for the lack of any clinically and statistically significant bias between K2-EDTA and K3-EDTA HbA1c measurements. Thus, Greiner tubes lined with K2-EDTA and those lined with K3-EDTA can safely be used interchangeably to measure HbA1c via the Abbott Laboratories ARCHITECT assay. © American Society for Clinical Pathology, 2015. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  7. Characterization of Mixed xWO3(1-xY2O3 Nanoparticle Thick Film for Gas Sensing Application

    Directory of Open Access Journals (Sweden)

    M. H. Shahrokh Abadi

    2010-05-01

    Full Text Available Microstructural, topology, inner morphology, and gas-sensitivity of mixed xWO3(1-xY2O3 nanoparticles (x = 1, 0.95, 0.9, 0.85, 0.8 thick-film semiconductor gas sensors were studied. The surface topography and inner morphological properties of the mixed powder and sensing film were characterized with X-ray diffraction (XRD, atomic force microscopy (AFM, transmission electron microscopy (TEM, and scanning electron microscopy (SEM. Also, gas sensitivity properties of the printed films were evaluated in the presence of methane (CH4 and butane (C4H10 at up to 500 °C operating temperature of the sensor. The results show that the doping agent can modify some structural properties and gas sensitivity of the mixed powder.

  8. (1x)[(K$_{0.5}$Na$_{0.5}$)NbO$_3$–LiSbO$_3

    Indian Academy of Sciences (India)

    Lead-free piezoelectric ceramics ( 1x ) [0.95(K 0.5 Na 0.5 )NbO 3 –0.05LiSbO 3 ]– x BiFe 0.8 Co 0.2 O 3 (KNN–LS– x BFC) were prepared by a conventional sintering technique. The effect of BFC content on the structure, piezoelectricand electrical properties of KNN–LS ceramics was investigated. The results reveal that ...

  9. Atmospheric chemistry of n-CxF2x+1CHO (x = 1, 2, 3, 4)

    DEFF Research Database (Denmark)

    Hurley, M. D.; Ball, J. C.; Wallington, T. J.

    2006-01-01

    Smog chamber/FTIR techniques were used to study the atmospheric fate of n-C(x)F(2)(x)(+1)C(O) (x = 1, 2, 3, 4) radicals in 700 Torr O(2)/N(2) diluent at 298 +/- 3 K. A competition is observed between reaction with O(2) to form n-C(x)()F(2)(x)()(+1)C(O)O(2) radicals and decomposition to form n-C(x...... to the atmospheric chemistry of n-C(x)F(2)(x)(+1)C(O) radicals and their possible role in contributing to the formation of perfluorocarboxylic acids in the environment....

  10. Study of electrical transport properties of (U 1- xY x)RuP 2Si 2

    Science.gov (United States)

    Radha, S.; Park, J.-G.; Roy, S. B.; Coles, B. R.; Nigam, A. K.; McEwen, K. A.

    1996-02-01

    Electrical resistivity and magnetoresistance ( {δϱ}/{ϱ}) measurements on a series of (U 1- xY x)Ru 2Si 2 (0 ⩽ x ⩽ 0.9) compounds in the temperature range 4.2-300 K and in magnetic fields up to 45 kOe are reported. The resistivity measurements do not show any signature of antiferromagnetism for x > 0.5. The compound URu 2Si 2 exhibits a large, positive ( {δϱ}/{ϱ}) presumably due to destruction of Kondo coherence as well as due to antiferromagnetism. The presence of even 5% Y at U-site weakens the Kondo coherence and reduces the magnetoresistance considerably.

  11. Growth of Ba1-zSrzBiO3-y single crystals and the prospects for its application for liquid phase epitaxy of Ba1-xKxBiO3-δ superconductor

    International Nuclear Information System (INIS)

    Soldatov, A.G.; Barilo, S.N.; Shiryaev, S.V.; Finskaya, V.M.

    2002-01-01

    In order to get a substrate for liquid phase epitaxy of the Ba 1-x K x BiO 3-δ (BKBO) superconducting films a possibility to grow single crystals of the Ba 1-z Sr z BiO 3-y (BSBO) solid solution series was investigated. The BSBO crystals with z = 0; 0.2; 0.29; 0.45; 0.49; 0.50; 0.54; 0.58 were obtained by crystallization from melt. The temperature versus composition phase diagram of the BaO · 1/2Bi 2 O 3 -SrO · 1/2Bi 2 O 3 system was constructed. A comparative analysis of the effect of cation composition and oxygen nonstoichiometry on the BSBO lattice parameters was carried out. The growth features of superconducting BKBO films onto BSBO substrates are discussed [ru

  12. Luminescence properties of LiSr2Y1-xLnxO4 (Ln=Eu,Tb,Tm) (0≤x≤1)

    International Nuclear Information System (INIS)

    Kubota, S.; Suzuyama, Y.; Yamane, H.; Shimada, M.

    1998-01-01

    Investigations of the luminescence properties of LiSr 2 Y 1-x Eu x O 4 , LiSr 2 Y 1-x Tb x O 4 and LiSr 2 Y 1-x Tm x O 4 (0≤x≤1) at room temperature are reported. These samples were synthesized by a solid state reaction. The excitation spectra of Tb 3+ emission in LiSr 2 Y 1-x Tb x O 4 (0≤x≤1) consist of broad bands corresponding to a transition between the 4f 8 and 4f 7 5d 1 states of Tb 3+ . The maximum intensity is situated at about 318 nm. This is at a much longer wavelength than those of other Tb 3+ doped phosphors. This is explained by a large offset of the adiabatic potential curve of the 4f 7 5d 1 state. (orig.)

  13. Synthesis and characterization of perovskite-type La1-yCayMn1-xB″xO3±δ nanomaterials (B″ = Ni, Fe; x = 0.2, 0.5; y = 0.4, 0.25)

    Science.gov (United States)

    Franke, Daniela; Trots, Dmytro; Vasylechko, Leonid; Vashook, Vladimir; Guth, Ulrich

    2018-02-01

    Perovskite-type nanomaterials of the compositions La1-yCayMn1-xB″xO3±δ with B'' = Ni, Fe; x = 0.2, 0.5 and y = 0.4, 0.25 were prepared using two different preparation routes (synthesis by precipitation and the PVA/sucrose method) at 500 °C-700 °C. The calcined products of the syntheses were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX) and physisorption measurements. The materials from the PVA/sucrose method contain particles with diameters from 33 nm to 48 nm, generate specific surface areas up to 33 m2/g and form pure compared to 45 nm-93 nm and up to 18 m2/g from precipitation method which contain a significant amount of sodium ions. The agglomeration process was analyzed for one nanomaterial (B'' = Fe, x = 0.2, y = 0.4) from the PVA/sucrose method using temperature dependent XRD showing only a slight growth (4.3%) of nanoparticles at 600 °C. The materials from the PVA/sucrose method turned out to be more suitable as electrode materials in electrochemical applications (SOFC, sensors) because of smaller particle sizes, higher specific surface areas and purity.

  14. Crystal structures and electronic properties of UTixNb3-xO10 (x=0,1/3,1) and of the intercalation compound Li0.9UTiNb2O10

    International Nuclear Information System (INIS)

    Dickens, P.G.; Flynn, G.J.; Patat, S.; Stuttart, G.P.

    1997-01-01

    Complete crystal structures of the related phases UTi x Nb 3-x O 10 (x=0,1/3,1) and of the intercalation compound Li 0.9 UTiNb 2 O 10 have been determined by Rietveld analysis of room-temperature powder neutron diffraction data. The new structural data combined with magnetic susceptibility measurements made in the range 5 y 1 U V 1+y-x U VI x-y Ti IV x Nb V 3-x O 10 (y≤ x1) with U V (f 1 ) being the only paramagnetic species present. (Author)

  15. Magnetic-entropy change in Mn1.1Fe0.9P0.7As0.3-xGe x

    International Nuclear Information System (INIS)

    Tegus, O.; Fuquan, B.; Dagula, W.; Zhang, L.; Brueck, E.; Si, P.Z.; Boer, F.R. de; Buschow, K.H.J.

    2005-01-01

    We have studied the magnetic properties and magnetic-entropy changes of Mn 1.1 Fe 0.9 P 0.7 As 0.3-x Ge x compounds with x = 0, 0.05, 0.1, 0.15 and 0.3. X-ray diffraction (XRD) study shows all the compounds crystallize in the Fe 2 P-type structure. Magnetic measurements show that the Curie temperature increases from 150 K for Mn 1.1 Fe 0.9 P 0.7 As 0.3 to 380 K for Mn 1.1 Fe 0.9 P 0.7 Ge 0.3 . A field-induced first-order magnetic phase transition is observed above the Curie temperature for the compounds with x up to 0.15. There exists an optimal composition in which the first-order phase transition is the sharpest. The optimal composition for this system is x = 0.1. The maximal magnetic-entropy change derived from the magnetization data is about 40 J/(kg K) for a field change from 0 to 3 T

  16. Silica-supported tungsten carbynes (≡SiO)xW(≡CH)(Me)y (x = 1, y = 2; X = 2, y = 1): New efficient catalysts for alkyne cyclotrimerization

    KAUST Repository

    Riache, Nassima

    2015-02-23

    The activity of silica-supported tungsten carbyne complexes (≡SiO)xW(≡CH)(Me)y (x = 1, y = 2; x = 2, y = 1) toward alkynes is reported. We found that they are efficient precatalysts for terminal alkyne cyclotrimerization with high TONs. We also demonstrate that this catalyst species is active for alkyne cyclotrimerization without the formation of significant alkyne metathesis products. Additional DFT calculations highlight the importance of the W coordination sphere in supporting this experimental behavior.

  17. Semidirect product gauge group [SU(3)cxSU(2)L]xU(1)Y and quantization of hypercharge

    International Nuclear Information System (INIS)

    Hattori, Chuichiro; Matsunaga, Mamoru; Matsuoka, Takeo

    2011-01-01

    In the standard model the hypercharges of quarks and leptons are not determined by the gauge group SU(3) c xSU(2) L xU(1) Y alone. We show that, if we choose the semidirect product group [SU(3) c xSU(2) L ]xU(1) Y as its gauge group, the hyperchages are settled to be n/6 mod Z(n=0,1,3,4). In addition, the conditions for gauge-anomaly cancellation give strong constraints. As a result, the ratios of the hypercharges are uniquely determined and the gravitational anomaly is automatically canceled. The standard charge assignment to quarks and leptons can be properly reproduced. For exotic matter fields their hypercharges are also discussed.

  18. Stability of Cd_1_–_xZn_xO_yS_1_–_y Quaternary Alloys Assessed with First-Principles Calculations

    International Nuclear Information System (INIS)

    Varley, Joel B.; He, Xiaoqing; Rockett, Angus; Lordi, Vincenzo

    2017-01-01

    One route to decreasing the absorption in CdS buffer layers in Cu(In,Ga)Se_2 and Cu_2ZnSn(S,Se)_4 thin-film photovoltaics is by alloying. Here we use first-principles calculations based on hybrid functionals to assess the energetics and stability of quaternary Cd, Zn, O, and S (Cd_1_–_xZn_xO_yS_1_–_y) alloys within a regular solution model. Our results identify that full miscibility of most Cd_1_–_xZn_xO_yS_1_–_y compositions and even binaries like Zn(O,S) is outside typical photovoltaic processing conditions. Finally, the results suggest that the tendency for phase separation of the oxysulfides may drive the nucleation of other phases such as sulfates that have been increasingly observed in oxygenated CdS and ZnS.

  19. Nuclear magnetic resonance study of (Y[sub 1-x]R[sub x])[sub 2]Co[sub 14]B compounds (R=Gd, Tb)

    Energy Technology Data Exchange (ETDEWEB)

    Myojin, T. (Takamatsu National Coll. of Technology, Takamatsu (Japan)); Hayashi, M. (Takamatsu Coll. (Japan)); Ohno, T. (Faculty of Engineering, Tokushima Univ. (Japan)); Imaeda, Y. (Faculty of Engineering, Tokushima Bunri Univ., Shido (Japan)); Ushida, T. (Faculty of Engineering, Tokushima Bunri Univ., Shido (Japan)); Tsujimura, A. (Faculty of Engineering, Tokushima Bunri Univ., Shido (Japan)); Hihara, T. (Faculty of Integrated Arts and Sciences, Hiroshima Univ. (Japan))

    1993-03-15

    Influence of the Gd spin on the Co hyperfine field has been studied by [sup 59] Co nuclear magnetic resonance (NMR) in (Y[sub 1-x]Gd[sub x])[sub 2]Co[sub 14]B compounds. It is shown that the hyperfine coupling constants from the Gd spin for 8j[sub 1] and 8j[sub 2] sites are negative while those for 16k[sub 1] and 16k[sub 2] sites are positive. The dependence of the spin orientation temperature on the non-magnetic Y concentration in (Y[sub 1-x]Tb[sub x])[sub 2]Co[sub 14]B is also investigated by magnetization and [sup 59]Co NMR measurements. A spin phase diagram for this compound is proposed. (orig.)

  20. Impedance and magnetoelectric characteristics of (1 - x)BaTiO3- xLa0.7Sr0.3MnO3 ( x = 0.1 and 0.3) nano-composites

    Science.gov (United States)

    Nayek, C.; Murugavel, P.; Dinesh Kumar, S.; Subramanian, V.

    2015-08-01

    We have synthesized the phase-pure (1 - x)BaTiO3- xLa0.7Sr0.3MnO3 ( x = 0.1 and 0.3) magnetoelectric composites without interdiffusion among the existing phases. The magnetic measurements revealed an anomaly at the ferroelectric Curie temperature (393 K) of BaTiO3, and the dielectric data revealed an anomaly at the ferromagnetic transition temperature (360 K) of La0.7Sr0.3MnO3 ascertaining the magnetoelectric coupling in the composite. Impedance analysis indicated dipolar polarization contributions to the dielectric spectrum with two non-Debye-type relaxations. Both the grain and grain boundary contributions were present in the system with dominant grain boundary effect in all the composites. The composites show semiconducting behavior with the barrier hopping-type conducting mechanism. To avoid the free charge carrier and the space charge contributions, the magnetoelectric response was measured at high frequency range. The maximum values of magnetoelectric voltage coefficient measured at 100 kHz were 221 and 219 mV/Oe-cm for x = 0.1 and 0.3 samples, respectively.

  1. Nanopowders Y{sub 1y}Nd{sub y}V{sub 1x}Cr{sub x}O{sub 4} with y=0 and 1; x=0, 0.1, 0.2 and 0.5 synthesized by a sol–gel process. Relationship between morphological characteristics and optical properties

    Energy Technology Data Exchange (ETDEWEB)

    Alcaraz, L. [Departamento de Química Inorgánica I, Facultad de Ciencias Químicas, Universidad Complutense de Madrid, Ciudad Universitaria s/n, 28040 Madrid (Spain); Isasi, J., E-mail: isasi@quim.ucm.es [Departamento de Química Inorgánica I, Facultad de Ciencias Químicas, Universidad Complutense de Madrid, Ciudad Universitaria s/n, 28040 Madrid (Spain); Caballero, A.C. [Departamento de Electrocerámica, Instituto de Cerámica y Vidrio (CSIC), Kelsen, 5, 28049 Madrid (Spain); Izquierdo, J.G.; Bañares, L. [Departamento de Química Física I and Centro de Láseres Ultrarrápidos, Facultad de Ciencias Químicas, Universidad Complutense de Madrid, Ciudad Universitaria s/n, 28040 Madrid (Spain)

    2015-05-15

    Y{sub 1y}Nd{sub y}V{sub 1x}Cr{sub x}O{sub 4} nanopowders with y=0 and 0.1; x=0, 0.1, 0.2 and 0.5, have been synthetized by a sol–gel process followed by heating in an oxygen flow. This second treatment was done only in the case of samples containing chromium. The samples have been characterized by X-ray diffraction (XRD), Fourier Transform Infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The structural analysis revealed that when chromium was inserted at vanadium-sites in Y{sub 0.9}Nd{sub 0.1}VO{sub 4}, the host retained the tetragonal symmetry corresponding to a zircon-type structure, attributed to the space group I4{sub 1}/amd. In addition, a loss of crystallinity was observed when chromium substitutes vanadium into the Y{sub 0.9}Nd{sub 0.1}VO{sub 4} host. The morphological studies revealed agglomerates of spherical particles whose size is increased with the Cr content and confirmed the composition of all synthetized samples. FTIR spectra of these samples exhibit a broadening and a slight shift of the bands around 830 cm{sup −1} towards higher values of frequency when the chromium content increases. The effect of vanadium substitution by chromium on the optical properties was also evaluated by UV–vis absorption and photoluminescence (PL) spectroscopies. The broad UV band absorption is due to the presence of Cr{sup 5+}. A decrease of PL emission is found when chromium substitutes vanadium in the YVO{sub 4} host. - Highlights: • Nanophosphors Y{sub 1y}Nd{sub y}V{sub 1x}Cr{sub x}O{sub 4} with y=0, 0.1 and x=0, 0.1, 0.2 and 0.5 have been synthesized. • Structural analysis reveals structural distortions associated to chromium insertion. • Morphological studies confirm the nanocristalline size and the stoichiometry of synthesized samples. • Chromium insertion causes a decrease of the PL emission intensity.

  2. Transport properties of Y1-xRxCo2 (R=Er, Ho) in magnetic field

    International Nuclear Information System (INIS)

    Uchima, Kiyoharu; Nakama, Takao; Takaesu, Yoshinao; Misashi, Masataka; Yagasaki, Katsuma; Hedo, Masato; Uwatoko, Yoshiya; Burkov, Alexander T.

    2006-01-01

    Thermopower S and resistivity ρ of Y 1-x R x Co 2 (R=Er, Ho) compounds have been measured in the temperature range from 1.5 to 300-bar K under magnetic fields up to 15-bar T. Strong enhancement of resistivity and fundamental changes in temperature variation of thermopower are observed at low temperatures in the compounds within the composition range where uniform Co 3d magnetization collapses. The magnetic state of Co 3d electrons has a dominant effect on the characteristic behavior of S and ρ in these compounds

  3. Effects of calcium doping on the superconducting properties of top-seeded melt growth processed Y1.5Ba2-xCaxCu3Oy superconductors

    International Nuclear Information System (INIS)

    Park, S.D.; Kim, H.J.; Park, B.J.; Han, Y.H.; Jun, B.-H.; Lee, J.S.; Kim, C.-J.

    2011-01-01

    We study effects of calcium doping in melt processed Y123 superconductors. We examine a superconducting transition temperature and current density. A transition temperature and current density decreases by calcium doping. Calcium doping leads to coarseing of Y211 particles. Y211 refining effect by CeO 2 is disappreared by calcium doping. The effect of calcium doping on the superconducting properties of top seeded melt growth (TSMG) processed Y 1.5 Ba 2-x Ca x Cu 3 O y superconductors was studied in terms of calcium content (X ca ). YBa 2-x Ca x Cu 3 O 7-δ (X ca = 0, 0.005, 0.01, 0.02, 0.04, 0.1, 0.3) powders were synthesized by the powder calcination method. YBa 2-x Ca x Cu 3 O 7-δ powders were mixed with 0.25 mole Y 2 O 3 powder and 1 wt.% CeO 2 as Y 2 BaCuO 5 (Y211) refiner, and finally made into Y 1 . 5 Ba 2-x Ca x Cu 3 O y (Y1.5) + 1 wt.% CeO 2 composition. The single Y123 growth on the top surface was observed up to X ca = 0.1, while the multiple Y123 growth was observed at X ca ≥ 0.1. The superconducting transition temperature (T c ) and critical current density (J c ) of TSMG processed Y1.5 samples were inversely proportional to X ca . The Y211 size increased with increasing X ca due to the enhancement of Y211 coarsening by calcium doping. No Y211 refining effect by CeO 2 was observed in the calcium doped samples. The T c and J c decrease by calcium doping are likely to be due to the calcium incorporation with the Y123 lattice and formation of coarse Y211 particles.

  4. X-ray absorption investigation of the valence state and electronic structure of La1xCaxCoO3−δ in comparison with La1xSrxCoO3−δ and La1xSrxFeO3−δ

    International Nuclear Information System (INIS)

    Haas, O.; Ludwig, Chr.; Bergmann, U.; Singh, R.N.; Braun, A.; Graule, T.

    2011-01-01

    3d metal K-shell X-ray absorption spectra of perovskites with the composition La 1x Ca x CoO 3−δ (x=0, 0.2, 0.4, 0.5, 0.6, 0.8), La 1x Sr x CoO 3−δ (x=0, 0.1, 0.2, 0.3, 0.4, 0.5) and La 1x Sr x FeO 3−δ (x=0, 0.2, 0.4, 0.5, 0.6, 0.8) are compared on the basis of pre-edges, white line features and extended fine structures. The measurements were performed at 300 K and for La 1x Ca x CoO 3−δ also at temperatures as low as 10–20 K. Going to low-temperature the measurements indicate an increase in t 2g ⁎ and a decrease in e g ⁎ orbital occupancy, which is most accentuated in the LaCoO 3 sample. Virtually no Co K-edge shift was observed for the La 1x Ca x CoO 3−δ and La 1x Sr x CoO 3−δ compounds and the Co–O distances are also not significantly reduced when La 3+ is partially substituted by Ca 2+ or Sr 2+ . From the pre-edge features of these perovskites we are tended to conclude that the t 2g ⁎ orbitals are less, and the e g ⁎ orbitals are more occupied with increasing x in the Ca and Sr substituted compounds, whereas the total d-electron density is not changing. These results indicate that cobalt prefers a valence state of 3 + in these Co perovskites. This could also be confirmed with iodometric titrations. The Fe perovskites behave differently. In contrast to the Co perovskites, for La 1x Sr x FeO 3−δ perovskites the Fe K-edge is shifted, the pre-edge features intensity is increasing and the Fe–O bond length is decreasing with increasing x. The valence states of the iron in the La 1x Sr x FeO 3−δ perovskites in fact increase as much as x increases. - Graphical abstract: Co K and Fe K pre-edge of La 1x Ca x CoO 3−δ and La 1x Sr x FeO 3−δ perovskites one of the evidences in favor of δ=x/2 for the Co-perovskites and δ=0 for the Fe-perovskites. Highlights: ► XAS a valuable tool to evaluate the valence states of Co and Fe perovskites. ► For La 1x Ca x CoO 3−δ and La 1x Sr x CoO 3

  5. Some observations on the synthesis and electrolytic properties of (Ba1-xCax (M0.9Y0.1O3, M = Ce, Zr-based samples modified with calcium

    Directory of Open Access Journals (Sweden)

    Dudek Magdalena

    2016-03-01

    Full Text Available In this paper, the impact of partial substitution of calcium for barium in (Ba1-xCax (M0.9Y0.1 O3, M = Ce, Zr on physicochemical properties of the powders and sintered samples was investigated. The powders, with various contents of calcium (x = 0, 0.02, 0.05, 0.1, were prepared by means of thermal decomposition of organometallic precursors containing EDTA. All of the BaCeO3-based powders synthesised at 1100 °C were monophasic with a rhombohedral structure, however, completely cubic BaZrO3-based solid solutions were obtained at 1200 °C. A study of the sinterability of BaZr0.9Y0.1O3 and BaCe0.9Y0.1O3-based pellets was performed under non-isothermal conditions within a temperature range of 25 to 1200 °C. The partial substitution of barium for calcium in the (Ba1-xCax (M0.9Y0.1 O3, M = Ce, Zr solid solution improved the sinterability of the samples in comparison to the initial BaCe0.9Y0.1O3 or BaZr0.9Y0.1O3. The relative density of calcium-modified BaCe0.9Y0.1O3-based samples reached approximately 95 to 97 % after sintering at 1500 °C for 2 h in air. The same level of relative density was achieved after sintering calcium-modified BaZr0.9Y0.1O3 at 1600 °C for 2 h. Analysis of the electrical conductivity from both series of investigated materials showed that the highest ionic conductivity, in air and wet 5 % H2 in Ar, was attained for the compositions of x = 0.02 to 0.05 (Ba1-xCax(M0.9Y0.1O3, M = Zr, Ce. The oxygen reduction reaction on the interface Pt│BaM0.9Y0.1O3, M = Ce, Zr was investigated using Pt microelectrodes. Selected samples of (Ba1-xCax (M0.9Y0.1O3, M = Zr, Ce were tested as ceramic electrolytes in hydrogen-oxygen solid oxide fuel cells operating at temperatures of 700 to 850 °C.

  6. Dielectric studies of Co3-xMnxO4 (x=0.1-1.0) cubic spinel multiferroic

    Science.gov (United States)

    Meena, P. L.; Kumar, Ravi; Prajapat, C. L.; Sreenivas, K.; Gupta, Vinay

    2009-07-01

    A series of Co3-xMnxO4 (x =0.1-1.0) multiferroic cubic spinel ceramics were prepared to study the effect of Mn substitution at Co site on the crystal structures and dielectric properties. No significant change in the structural symmetry was observed with increasing x up to 1.0. A linear increase in lattice parameter with x is attributed to the substitution of Co3+ by Mn3+ (large ionic radii) at the octahedral sites. An antiferromagnetic-type ordering of Co3O4 changes to ferrimagnetic-type order after incorporation of Mn. The effect of Mn substitution on the dielectric constant and loss tangent was studied over a wide range of frequency (75 kHz-5 MHz) and temperature of 150-450 K. The measured value of room temperature ac conductivity at 1.0 MHz was found to increase from 2.0×10-6 to 4.4×10-4 Ω-1 cm-1 and follows power law (σac=Aωs) behavior. The dielectric constant ɛ'(ω) shows a weak frequency dispersion and small temperature dependence below 250 K for all ceramic samples. However, a strong temperature and frequency dependence on ɛ'(ω) was observed at higher temperature (>250 K). The temperature dependent ɛ'(ω) data show the existence of room temperature ferroelectricity in all prepared samples.

  7. Tolerance factor rules for Sr1-x-yCaxBayMnO3 perovskites

    International Nuclear Information System (INIS)

    Dabrowski, B.; Chmaissem, O.; Mais, J.; Kolesnik, S.; Jorgensen, J.D.; Short, S.

    2003-01-01

    Synthesis of new perovskite Sr 1-x-y Ca x Ba y MnO 3-δ compounds is described in detail and dependence of their phase stability and structural distortions on the tolerance factor is discussed. Oxygen contents have been measured over extended temperature and composition ranges. Neutron powder diffraction was used to precisely measure the A-O and Mn-O bond lengths and derive accurate interatomic distances [Ca-O], [Sr-O], [Ba-O], and [Mn-O]. By using these parameters instead of tabulated ionic radii we have derived the functional dependence of the tolerance factor t=t(x,y,T,δ) on composition, temperature, and oxygen content. At a fixed oxygen content, the tolerance factor is an increasing function of temperature as a result of greater thermal expansion of the average bond relative to the bond. We find that the stability of the perovskite phase at high temperature is governed, as expected, by the magnitude of tolerance factor (t≤1) which can be adjusted by controlling the oxygen content 3-δ. This dependence of the tolerance factor on oxygen content and temperature can be utilized to design synthesis conditions for the controlled formation of the new, kinetically stable, perovskite phases

  8. Phase and morphology evolution of (Na1-xKxNbO3 powders related to calcinations and K2CO3 content

    Directory of Open Access Journals (Sweden)

    Steven J. Milne

    2007-03-01

    Full Text Available Sodium-potassium niobate ((Na1-xKxNbO3 powders with x = 0.2, 0.4, 0.6 and 0.8 were prepared following the conventional mixed oxide method and characterized by TG-DTA, XRD and SEM techniques.The effects of calcination temperature, dwell time and K2CO3 content on phase formation behavior and morphology of the powders were investigated. The calcination temperature and dwell time were found tohave a pronounced effect on the phase formation of the calcined sodium-potassium niobate powders. It was found that the crystallized phase depended on calcination conditions. The high calcination temperature andlong dwell time clearly favored particle growth and the formation of large and hard agglomerates. All the (Na1-xKxNbO3 powders showed a similar orthorhombic phase structure. The K2CO3 content significantlyaffected the calcination temperature and particle size and shape. Large particle size, cubic shape and a lower calcined condition were observed in (Na1-xKxNbO3 powder with low K2CO3 content (x = 0.2.

  9. The effect of substrate temperature upon the compositions of Mg and Se in Zn{sub 1-x}Mg{sub x}Se{sub y}Te{sub 1-y} layer grown by MOVPE

    Energy Technology Data Exchange (ETDEWEB)

    Nishio, M.; Ito, R.; Tanaka, K.; Urata, K.; Nakamura, Y.; Tanaka, T. [Department of Electrical and Electronic Engineering, Graduate School of Science and Engineering, Saga University, 1 Honjo, Saga 840-8502 (Japan); Saito, K.; Guo, Q.X. [Synchrotron Light Application Center, Saga University, 1 Honjo, Saga 840-8502 (Japan)

    2014-07-15

    The growth of Zn{sub 1-x}Mg{sub x}Se{sub y}Te{sub 1-y} layers was performed on (100) ZnTe substrate by metalorganic vapour phase epitaxy using dimethylzinc, bis-methylcyclopentadienyl-magnesium, diethyltelluride and diethylselenide. The effects of substrate temperature upon the compositions of Mg and Se have been investigated. The Mg composition in Zn{sub 1-x}Mg{sub x}Se{sub y}Te{sub 1-y} layer is significantly enhanced at low substrate temperature. Although the Se composition decreases with decreasing the substrate temperature, Zn{sub 1-x}Mg{sub x}Se{sub y}Te{sub 1-y} layer with a relatively high Se composition of 0.3 is obtainable at a low substrate temperature as low as 380 C. For all the layers, a two-mode behaviour with ZnTe- and MgTe-like longitudinal optical phonon modes is confirmed by Raman scattering. (copyright 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  10. Magnetic field effect on the electrical resistivity of Y1-xNixBa2Cu3O7-δ superconductor

    Science.gov (United States)

    Hadi-Sichani, Behnaz; Shakeripour, Hamideh; Salamati, Hadi

    2018-06-01

    The Ni- substituted Y1-xNixBa2Cu3O7-δ high temperature superconducting samples with 0 ≤ x zero to 1 Tesla, applied perpendicular to the current direction. To study of magnetoresistance is one of the most important ways to investigate the intergranular nature of superconducting materials. The resistive transition is made of two parts. The first- unaffected to applied magnetic field part which is near the onset of superconductivity. This region is due to superconductivity in grains. The second- broaden tail part which is due to the connectivity of the grains. At temperatures close to Tc 0, (ρ = 0), under applied magnetic fields, weak links are affected and the vortices are penetrated and move inside the intergranular and then the tail part is broaden. This broadening part observed in the electrical resistivity, ρ(T), and in the derivative of the electrical resistivity, dρ/dT, becomes too small or even absent in Ni doped samples. For pure sample, Tc 0 was around 90 K; by applying a magnetic field H = 0.3 T it shifted to 40 K. This broadening is 91.4 K to 80 K for x = 0.002 and 91.7 K to 85 K for x = 0.004 samples. We found an optimal value of Ni doping concentration which improves the coupling of the grains. Then, vortices get strongly pinned. These observations suggest that the Ni substitution can reduce the weak links and increase the Jc values of these superconductors.

  11. Phase stability, crystal structure and magnetism in (U1-xNbx)2 Ni21B6 and (UyNb1-y)3Ni20B6

    Science.gov (United States)

    Provino, Alessia; Bhattacharya, Amitava; Dhar, Sudesh K.; Pani, Marcella; Gatti, Flavio; Paudyal, Durga; Manfrinetti, Pietro

    Ternary phases with composition T2M21X6 and T3M20X6 (T = transition metal; M = 3 d metal; X = B, C, P) are reported to crystallize with the W2Cr21C6-type and Mg3Ni20B6-type, respectively (ternary ordered derivatives of the cubic Cr23C6-type, cF116). They attract interest due to their refractory, mechanical, and peculiar magnetic properties. Literature data on these compounds only concern apparently stoichiometric 2:21:6 and 3:20:6 phases. Often only nominal composition has been reported, with few structural refinements and no measurements of physical properties. Lack of detailed stoichiometry and crystallographic data does not allow sufficient understanding of the crystal chemistry and properties of these compounds. We studied stability, crystal structure and magnetism of (U1-xNbx)2 Ni21B6 and (UyNb1-y)3Ni20B6; stable phases are U2Ni21B6 and Nb3Ni20B6, as also confirmed by theoretical calculations. The two pristine compounds solubilize Nb and U, respectively, up to a given extent. The substitution of U by Nb leads to a structural change from the W2Cr21C6- to the Mg3Ni20B6-type. While U2Ni21B6 is a Pauli paramagnet (itinerant non-magnetic state of U-5 f electrons), in agreement with literature, magnetization data for (UyNb1-y)3 Ni20B6 show itinerant ferromagnetism with TC >300 K.

  12. Optical properties of lattice matched In{sub x}Ga{sub 1-x}P{sub 1-y}N{sub y} heteroepitaxial layers on GaP

    Energy Technology Data Exchange (ETDEWEB)

    Imanishi, T.; Wakahara, A.; Kim, S.M.; Yonezu, H.; Furukawa, Y. [Department of Electrical and Electron Engineering, Toyohashi University of Technology, 1-1 Hibarigaoka, Tempaku-cho, Toyohashi, Aichi 411-8580 (Japan)

    2005-04-01

    Optical constants and band structure of In{sub x}Ga{sub 1-x}P{sub 1-y}N{sub y} lattice matched to GaP (100) substrate are investigated. Nitrogen concentration in the film estimated by X-ray diffraction and X-ray photoelectron spectroscopy, was 1.4%, 1.8% and 3.5%. Refractive index and transition critical points E{sub 0} ({gamma}{sub v} to {gamma}{sub c}), E{sub 1} (L{sub v} to L{sub c}) and E{sub 2} (X{sub v} to X{sub c}) are evaluated by spectroscopic ellipsometry. When N composition increases from 1.4% to 3.5%, both photoluminescence (PL) peak energy, E{sub PL}, and E{sub 0} shift to lower energy, and the energy difference {delta}E=E{sub 0}-E{sub PL} decrease from 380 meV to 110 meV. The large red-sift of E{sub PL} from the E{sub 0} suggest that the luminescence is of defect-related luminescence, and crossover point of indirect band structure estimated by the extrapolation of N-composition dependence of {delta}E is estimated to be around in In{sub 0.1}Ga{sub 0.9}P{sub 0.96}N{sub 0.04}. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  13. Pressure effect on electrical resistivity of Y1-xGdxCo2

    International Nuclear Information System (INIS)

    Nakama, T.; Takaesu, Y.; Yagasaki, K.; Sakai, E.; Kurita, N.; Hedo, M.; Uwatoko, Y.; Burkov, A.T.

    2006-01-01

    Electrical resistivity of Y 1-x Gd x Co 2 alloy system has been measured at temperatures from 2 to 300K in magnetic field up to 15T and under pressure up to 10GPa. The compounds with the composition near to phase boundary between paramagnetic and ferromagnetic ground state (x c ∼0.12) show strong enhancement of electrical resistivity at low temperatures. Large positive magnetoresistance was observed in ferromagnetic alloys in composition range 0.15 1-x Gd x Co 2 at low temperatures is in agreement with the variation of magnetoresistance with the composition

  14. Piezoelectric properties and thermal stability of (Na0.53K0.47-xAgx)Nb1-xSbxO3 ceramics

    International Nuclear Information System (INIS)

    Zheng, Limei; Wang, Jinfeng; Wang, Chunming; Gai, Zhigang; Wu, Qingzao; Zhang, Rui

    2011-01-01

    Many (K 1-x Na x )NbO 3 (KNN)-based ceramics with high piezoelectric performance exhibit undesirable strong temperature dependence due to the orthorhombic-tetragonal polymorphic phase transition near room temperature. In order to improve the temperature stability of the ceramics, many additives have been added into the KNN-based ceramics to shift T O-T down to below room temperature. Contrary to the previous approach (Na 0.53 K 0.47-x Ag x )Nb 1-x Sb x O 3 (NKANS) ceramics with T O-T well above room temperature have been prepared by a conventional solid-state reaction method. The density and the electrical properties are effectively improved by the addition of AgSbO 3 , and optimum piezoelectric properties are found in the ceramics with 0.05 ≤ x ≤ 0.07, with maximum k p ∝ 0.46 for NKANS5 and maximum d 33 ∝ 199 pC/N for NKANS7. More importantly, k p remains virtually almost unchanged up to the T O-T temperature (≥100 C), indicating that the NKANS ceramics exhibit a much improved piezoelectric thermal stability. The analyses suggest that both the high T O-T value and diffuse orthorhombic-tetragonal phase transition should be responsible for the good temperature stability. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  15. Modulation-free bismuth-lead cuprate superconductors: BiPbSr1+xL1-xCuO6 and BiPbSr2Y1-xCaxCu2O8

    International Nuclear Information System (INIS)

    Manivannan, V.; Gopalakrishnan, J.; Rao, C.N.R.

    1991-01-01

    Modulation-free BiPbSrLCuO 6 (L=La, Pr, Nd) and BiPbSr 2 YCu 2 O 8 , which are isotypic with the n=1 and 2 members of the Bi 2 Sr 2 Ca n-1 Cu n O 2n+4 family, have been prepared and characterized. These parent compounds are nonsuperconducting, but when doped with holes by substitution chemistry give modulation-free superconducting cuprates of the general formulas BiPbSr 1+xL1-x CuO 6 and BiPbSr 2 Y 1-x Ca x Cu 2 O 8 , exhibiting maximum T c 's of 24 and 85 K, respectively. Significantly, the hole concentration at the maximum T c is 0.12 in the cuprate family with a single Cu-O layer and 0.22 in that with two Cu-O layers

  16. Oxygen diffusion in Y sub 1 sub - sub x Pr sub x Ba sub 2 Cu sub 3 O sub 7 sub - subdelta observed by resistivity measurements

    CERN Document Server

    Diosa, J E; Mellander, B E

    1997-01-01

    In situ resistivity measurements have been used to monitor the oxygen uptake and removal for the ceramic system Y sub 1 sub - sub x Pr sub x Ba sub 2 Cu sub 3 O sub 7 sub - subdelta (YPBCO) in the temperature range 300 - 1000 K. The study of the out-diffusion of oxygen was performed by annealing the oxygenated samples in ambient air at constant heating rates. We found that, independently of x, the oxygen concentration O sub 7 sub - subdelta is preserved up to 600 K, and that oxygen diffuses out of the oxides at temperatures higher than 600 K. However, the rate of oxygen removal from PrBa sub 2 Cu sub 3 O sub 7 sub - subdelta (PBCO) is greatly reduced as compared to the rate for pure YBa sub 2 Cu sub 3 O sub 7 sub - subdelta (YBCO), and decreases with increasing x in YPBCO. The study of the in-diffusion of oxygen was performed by annealing the deoxygenated samples in ambient air at constant heating rates. We found that, independently of x, the oxygen uptake takes place in the temperature range 550 - 750 K, whe...

  17. NMR studies on magnetic properties of intermetallic compounds Er1-xYxCo3

    International Nuclear Information System (INIS)

    Niki, H.; Kinjo, T.; Yogi, M.; Pieper, M.W.; Gratz, E.; Markosyan, A.S.

    2007-01-01

    Field dependence of 59 Co NMR in ferrimagnetic Er 1-x Y x Co 3 was measured up to 8T at 4.2K using aligned powdered samples. For pure ErCo 3 in fields perpendicular to the c axis the resonance frequencies change discontinuously between 2 and 3T due to a field induced metamagnetic transition. The easy axis is found to be along the c axis for x=0 and 0.1. An average angle for the Co moments of 45+/-5 o from the c axis is obtained from field dependence of 59 Co NMR at x=0.3. Directions of Co moments are also found to be inclined from the c axis for x=0.5

  18. Emission characteristics of Y1Ba2Cu3O7-δ cathode

    International Nuclear Information System (INIS)

    Korenev, S.A.

    1988-01-01

    The results are presented of experimental investigation of the electron beam in diode with cathode on the base of Y 1 Ba 2 Cu 3 O 7-δ . After corresponding cathode training, the cathode made from Y 1 Ba 2 Cu 3 O 7-δ material may be practicable of stable current electron beam yeild. It is shown experimentally that the voltage of diode of about 100-300 kV there exists an evident possibility of forming the electron beams with the current density of 70 A-380 A/cm 2 . The motion velicity of cathode plasma in the direction of anode for this material of a cathode amounts to (1-3)x 10 6 cm/s

  19. Growth and scintillation properties of Ce{sup 3+}-doped (Y{sub 1-x}Gd{sub x})AlO{sub 3} crystals

    Energy Technology Data Exchange (ETDEWEB)

    Fujimoto, Yutaka; Wakahara, Shingo; Suzuki, Shotaro; Kurosawa, Shunsuke [Institute of Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577 (Japan); Yanagida, Takayuki [New Industry Creation Hatchery Center, Tohoku University, 6-6-10 Aramaki, Aoba-ku, Sendai 980-8579 (Japan); Yoshikawa, Akira [Institute of Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577 (Japan); New Industry Creation Hatchery Center, Tohoku University, 6-6-10 Aramaki, Aoba-ku, Sendai 980-8579 (Japan)

    2012-12-15

    The optical and scintillation properties of 0.5% fixed Ce-doped (Y{sub 1-x}Gd{sub x})AlO{sub 3} single crystals have been investigated at three different levels of Gd doping: x = 0.2, 0.4 and 0.6. Single crystal of the Ce{sup 3+}-doped (Y{sub 0.8}Gd{sub 0.2})AlO{sub 3}, (Y{sub 0.6}Gd{sub 0.4})AlO{sub 3} and (Y{sub 0.4}Gd{sub 0.6})AlO{sub 3} were successfully grown by {mu}-PD technique in nitrogen atmosphere. From X-ray diffraction analysis, no impurity phase was detected for the grown Ce-doped crystals. Ce-doped (Y{sub 0.6}Gd{sub 0.4})AlO{sub 3} crystal demonstrated highest fluorescence quantum efficiency ({proportional_to} 25%) with improvement of excitation efficiency due to the Gd-doping. When irradiated by the alpha-rays from a {sup 241}Am source, all the Ce-doped crystals showed luminescence band that corresponding to 5d (t{sub 2g})-4f transition of Ce{sup 3+}. The scintillation decay time was characterized by two components; the fast component (5-15 ns) is ascribed to 5d-4f transition of Ce{sup 3+}, while the slow one (100-200 ns) may be related to energy transfer between Ce{sup 3+} and Gd{sup 3+} ion. According to the result of {sup 137}Cs gamma-ray irradiated pulse height spectra compared with BGO scintillator, the relative scintillation light output was found to be about 12200 {+-} 1220 (Gd 20%) and 16000 {+-} 1600 (Gd 40%) ph/MeV. (copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  20. Electron spin resonance of Gd3+ in the intermetallic Gd1-xYxNi3Ga9 (0 ≤ x ≤ 0.90) compounds

    Science.gov (United States)

    Mendonça, E. C.; Silva, L. S.; Mercena, S. G.; Meneses, C. T.; Jesus, C. B. R.; Duque, J. G. S.; Souza, J. C.; Pagliuso, P. G.; Lora-Serrano, R.; Teixeira-Neto, A. A.

    2017-10-01

    In this work, experiments of X-ray diffraction, magnetic susceptibility, heat capacitance, and Electron Spin Resonance (ESR) carried out in the Gd1-xYxNi3Ga9 (0 ≤ x ≤ 0.90) compounds grown through a Ga self flux method are reported. The X-ray diffraction data indicate that these compounds crystallize in a trigonal crystal structure with a space group R32. This crystal structure is unaffected by Y-substitution, which produces a monotonic decrease of the lattice parameters. For the x = 0 compound, an antiferromagnetic phase transition is observed at TN = 19.2 K, which is continuously suppressed as a function of the Y-doping and extrapolates to zero at x ≈ 0.85. The ESR data, taken in the temperature range 15 ≤ T ≤ 300 K, show a single Dysonian Gd3+ line with nearly temperature independent g-values. The linewidth follows a Korringa-like behavior as a function of temperature for all samples. The Korringa rates (b = ΔH /ΔT ) are Y-concentration-dependent indicating a "bottleneck" regime. For the most diluted sample (x = 0.90), when it is believed that the "bottleneck" effect is minimized, we have calculated the q-dependent effective exchange interactions between Gd3+ local moments and the c-e of 〈Jf-ce 2(q ) 〉 1 /2 = 18(2) meV and Jf -c e(q =0 ) = 90(10) meV.

  1. Coexistence of 3d-ferromagnetism and superconductivity in (Li{sub 1-x}Fe{sub x}OH)(Fe{sub 1-y}Li{sub y}Se)

    Energy Technology Data Exchange (ETDEWEB)

    Brueckner, Felix; Sarkar, Rajib; Kamusella, Sirko; Klauss, Hans-Henning [Institut fuer Festkoerperphysik, Technische Universitaet Dresden (Germany); Luetkens, Hubertus [Paul-Scherrer-Institut, Villigen (Switzerland); Pachmayr, Ursula; Nitsche, Fabian; Johrendt, Dirk [Department Chemie, Ludwig-Maximilians-Universitaet Muenchen (Germany)

    2015-07-01

    In the family of iron-based superconductors, where the superconducting dome is usually separated from the magnetic phase, only few compounds show ferromagnetism arising in the superconducting state. The so far discovered examples show ferromagnetic ordering of Eu{sup 2+} ions. In this context, the presented ordering of iron orbitals in (Li{sub 1-x}Fe{sub x}OH)(Fe{sub 1-y}Li{sub y}Se) is unique. We performed a wealth of experimental methods to characterize the physics in this system, including dc resistivity and magnetization. With use of local probes (μSR,NMR,Moessbauer), we are able to describe the emergence of bulk ferromagnetism and superconductivity in a microscopic scale. Both phenomena can coexist, though they compete with each other, due to a spatial separation in the multilayer system.

  2. Mechanosynthesis and structural characterization of nanocrystalline Ce{sub 1x}Y{sub x}O{sub 2–δ} (x=0.1–0.35) solid solutions

    Energy Technology Data Exchange (ETDEWEB)

    Fabián, Martin, E-mail: fabianm@saske.sk [Institute of Nanotechnology, Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen (Germany); Institute of Geotechnics, Slovak Academy of Sciences, Watsonova 45, 04001 Košice (Slovakia); Antić, Bratislav [“Vinča” Institute of Nuclear Sciences, University of Belgrade, P.O. Box 522, 11001 Belgrade (Serbia); Girman, Vladimír [Institute of Physics, P. J. Šafárik University, Park Angelinum 9, 04154 Košice (Slovakia); Vučinić-Vasić, Milica [Faculty of Technical Sciences, University of Novi Sad, Trg D. Obradovića 6, 21000 Novi Sad (Serbia); Kremenović, Aleksandar [Laboratory of Crystallography, Faculty of Mining and Geology, University of Belgrade, Djusina 7, 11001 Belgrade (Serbia); Suzuki, Shigeru [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Katahira 2-1-1, Aoba-ku, 980-8577 Sendai (Japan); Hahn, Horst [Institute of Nanotechnology, Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen (Germany); Šepelák, Vladimír [Institute of Nanotechnology, Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen (Germany); Institute of Geotechnics, Slovak Academy of Sciences, Watsonova 45, 04001 Košice (Slovakia)

    2015-10-15

    A series of nanostructured fluorite-type Ce{sub 1x}Y{sub x}O{sub 2–δ} (0≤x≤0.35) solid solutions, prepared via high-energy milling of the CeO{sub 2}/Y{sub 2}O{sub 3} mixtures, are investigated by XRD, HR-TEM, EDS and Raman spectroscopy. For the first time, complementary information on both the long-range and short-range structural features of mechanosynthesized Ce{sub 1x}Y{sub x}O{sub 2–δ}, obtained by Rietveld analysis of XRD data and Raman spectroscopy, is provided. The lattice parameters of the as-prepared solid solutions decrease with increasing yttrium content. Rietveld refinements of the XRD data reveal increase in microstrains in the host ceria lattice as a consequence of yttrium incorporation. Raman spectra are directly affected by the presence of oxygen vacancies; their existence is evidenced by the presence of vibration modes at ~560 and ~600 cm{sup –1}. The detailed spectroscopic investigations enable us to separate extrinsic and intrinsic origin of oxygen vacancies. It is demonstrated that mechanosynthesis can be successfully employed in the one-step preparation of nanocrystalline Ce{sub 1x}Y{sub x}O{sub 2–δ} solid solutions. - Graphical abstract: Mechanosynthesis of nanocrystalline Ce{sub 1x}Y{sub x}O{sub 2–δ} (x=0.1–0.35) solid solutions. - Highlights: • One-step mechanosynthesis of nanoscale Ce{sub 1x}Y{sub x}O{sub 2–δ} (0≤x≤0.35) solid solutions. • Complementary information on the long-range and short-range structural features of mechanosynthesized Ce{sub 1x}Y{sub x}O{sub 2–δ} is provided. • Structural variations as a response to the yttrium doping. • Separation of extrinsic and intrinsic origin of the induced oxygen vacancies.

  3. Robust s± pairing in CaK (Fe1-xNix) 4As4 (x =0 and 0.05) from the response to electron irradiation

    Science.gov (United States)

    Teknowijoyo, S.; Cho, K.; Kończykowski, M.; Timmons, E. I.; Tanatar, M. A.; Meier, W. R.; Xu, M.; Bud'ko, S. L.; Canfield, P. C.; Prozorov, R.

    2018-04-01

    Controlled pointlike disorder introduced by 2.5-MeV electron irradiation was used to probe the superconducting state of single crystals of CaK (Fe1-xNix) 4As4 superconductor at x =0 and 0.05 doping levels. Both compositions show an increase of the residual resistivity and a decrease of the superconducting transition temperature, Tc, at the rate of d Tc/d ρ (Tc) ≈0.19 K/(μ Ω cm ) for x =0 and 0.38 K/(μ Ω cm ) for x =0.05 , respectively. In the Ni-doped compound (x =0.05 ), the coexisting spin-vortex crystal (SVC) magnetic phase is suppressed at the rate of d TN/d ρ (TN) ≈ 0.16 K/(μ Ω cm ). The low-temperature variation of London penetration depth is well approximated by the power-law function, Δ λ (T ) =A Tn , with n ≈2.5 for x =0 and n ≈1.9 for x =0.05 in the pristine state. Detailed analysis of λ (T ) and Tc evolution with disorder is consistent with two effective nodeless energy gaps in the density of states due to robust s± pairing. Overall the behavior of CaK (Fe1-xNix) 4As4 at x =0 is similar to a slightly overdoped Ba1 -yKyFe2As2 at y ≈ 0.5, and at x =0.05 to an underdoped composition at y ≈ 0.2.

  4. Magnetic properties of Y3+ doped Bi4-xTi2FeO12 aurivillius phase ceramics

    Science.gov (United States)

    Tirupathi, Patri; Reddy, H. Satish Kumar; Babu, P. D.

    2018-05-01

    In the present paper reports a comprehensive investigation of structural, microstructural and magnetic phase transition in Y3+ doped BITF Aurivillius phase compounds. The study of surface morphology by scanning electron microscope reveals the growth of plate-like grains and further the grain size increase with increasing Y3+ composition. Low temperature magnetic studies reveals enhanced magnetic property with doping of Y3+ in BITF. It was explained by considering exchange interaction between the neighboring Fe+3 ions via electron trapped electrons at oxygen vacancies. Temperature dependent dc-magnetic studies exhibit a magnetic transitions TC = 750 K for x=0.0 TC ˜ 674 K for x=1.0 & TC ˜ 645 K for x=1.50 ceramics respectively in high temperature magnetization studies

  5. Synthesis, structure and magnetic properties of distorted Y{sub x}La{sub 1-x}FeO{sub 3}: Effects of mechanochemical activation and composition

    Energy Technology Data Exchange (ETDEWEB)

    Cristobal, A.A. [Instituto de Investigaciones en Ciencia y Tecnologia de Materiales, INTEMA (CONICET-UNMdP), J.B. Justo 4302 B7608FDQ, Mar del Plata (Argentina); Botta, P.M., E-mail: pbotta@fi.mdp.edu.ar [Instituto de Investigaciones en Ciencia y Tecnologia de Materiales, INTEMA (CONICET-UNMdP), J.B. Justo 4302 B7608FDQ, Mar del Plata (Argentina); Aglietti, E.F.; Conconi, M.S. [Centro de Tecnologia de Recursos Minerales y Ceramica, CETMIC (CIC-CONICET), Camino P. Centenario y 506 B1897ZCA, Gonnet (Argentina); Bercoff, P.G. [Facultad de Matematica, Astronomia y Fisica, FaMAF UNC and IFEG (CONICET), Ciudad Universitaria (5000), Cordoba (Argentina); Porto Lopez, J.M. [Instituto de Investigaciones en Ciencia y Tecnologia de Materiales, INTEMA (CONICET-UNMdP), J.B. Justo 4302 B7608FDQ, Mar del Plata (Argentina)

    2011-11-01

    Highlights: {yields} Y{sub x}La{sub 1-x}FeO{sub 3} phases (0 {<=} x {<=} 1) were prepared at RT by mechanochemical treatment. {yields} The obtained materials showed an anisotropic distortion of its crystal structure. {yields} Combination of Y-doping and mechanochemistry produced weak ferromagnetic materials. {yields} Thermal treatments improved the structural order, leading to antiferromagnetic solids. {yields} Neel temperature decreased with x due to less stable magnetic structures. - Abstract: The influence of mechanochemical treatment on the synthesis and properties of Y{sub x}La{sub 1-x}FeO{sub 3} (0 {<=} x {<=} 1) orthoferrites is studied. Solid mixtures of the corresponding metal oxides were treated in a high-energy ball-mill. X-ray diffraction revealed that during the milling the disappearance of the reactants and a fast conversion to orthoferrite phase take place. Magnetic measurements showed a weak ferromagnetic behavior of the obtained materials, observing higher magnetization for larger x. The activated powders heated at 600 and 800 deg. C showed a progressive crystalline ordering together with a significant drop of magnetization. Thermal treatments at 1000 deg. C produced the formation of the phase Y{sub 3}Fe{sub 5}O{sub 12} for the samples richer in yttrium, increasing the magnetization. Rietveld refinements of the diffraction patterns and dynamical scanning calorimetry were used respectively to determine the lattice parameters and Neel temperatures for the formed orthoferrites. The effect of the composition on the structure and magnetic behavior is discussed.

  6. Composition and carrier-concentration dependence of the electronic structure of InyGa1-yAs1-xNx films with nitrogen mole fraction of less than 0.012

    International Nuclear Information System (INIS)

    Kang, Youn-Seon; Robins, Lawrence H.; Birdwell, Anthony G.; Shapiro, Alexander J.; Thurber, W. Robert; Vaudin, Mark D.; Fahmi, M.M.E.; Bryson, Damian; Mohammad, S. Noor

    2005-01-01

    The electronic structure of Si-doped In y Ga 1-y As 1-x N x films on GaAs substrates, grown by nitrogen-plasma-assisted molecular-beam epitaxy, was examined by photoreflectance (PR) spectroscopy at temperatures between 20 and 300 K. The films were approximately 0.5 μm thick and had nitrogen mole fraction between x=0.0014 and x=0.012, measured indirectly by a secondary-ion-mass spectrometry calibration; indium mole fraction between y=0.052 and y=0.075, measured by electron-dispersive x-ray spectroscopy; and carrier concentration between 2x10 16 and 1.1x10 18 cm -3 , measured by Hall effect. Three critical-point transitions were identified by PR: the fundamental band gap (highest valence band to the lowest conduction band); the spin-orbit split valence band to the lowest conduction band; and the highest valence band to a nitrogen impurity band (above the lowest conduction band). The measured critical-point energies were described by a band anticrossing (BAC) model with the addition of a Burstein-Moss band-filling term. The fitted BAC parameters were similar to previously reported values. The N impurity level was located 0.3004±0.0101 eV above the conduction-band edge at 20 K and 0.3286±0.0089 eV above the conduction-band edge at 295 K. The BAC interaction parameter was 2.588±0.071 eV. From the small magnitude of the Burstein-Moss energy shift with increasing carrier concentration, it was inferred that the carrier concentration probed by PR is reduced from the bulk (Hall-effect) carrier concentration by a reduction factor of 0.266±0.145. The PR lines broadened with increasing carrier concentration; the line broadening tracked the predicted Burstein-Moss energy shift for the bulk carrier concentration. The surface-normal lattice constants of the films were measured by x-ray diffraction. Comparison of the measured lattice constants with Vegard's law showed the presence of tensile strain (in the surface-normal direction) with magnitude between 1.5x10 -3 and 3.0x10

  7. Bandgap engineering of the Lu{sub x}Y{sub 1x}PO{sub 4} mixed crystals

    Energy Technology Data Exchange (ETDEWEB)

    Levushkina, V.S., E-mail: viktoriia.levushkina@ut.ee [Institute of Physics, University of Tartu, Ravila 14c, 50411 Tartu (Estonia); Physics Faculty, Moscow State University, Leninskiye Gory 1-2, 11991 Moscow (Russian Federation); Spassky, D.A. [Institute of Physics, University of Tartu, Ravila 14c, 50411 Tartu (Estonia); Skobeltsyn Institute of Nuclear Physics, Moscow State University, Leninskiye Gory 1-2, 11991 Moscow (Russian Federation); Aleksanyan, E.M. [Institute of Physics, University of Tartu, Ravila 14c, 50411 Tartu (Estonia); A. Alikhanyan National Science Laboratory, Yerevan Physics Institute, Alikhanyan Yeghbayrneri St. 2, 0036 Yerevan (Armenia); Brik, M.G. [Institute of Physics, University of Tartu, Ravila 14c, 50411 Tartu (Estonia); College of Sciences, Chongqing University of Posts and Telecommunications, 400065 Chongqing (China); Institute of Physics, Jan Dlugosz University, Armii Krajowej 13/15, PL-42200 Czestochowa (Poland); Institute of Physics, Polish Academy of Sciences, Al. Lotników 32/46, 02-668 Warsaw (Poland); Tretyakova, M.S.; Zadneprovski, B.I. [Central Research and Development Institute of Chemistry and Mechanics, Nagatinskaya St. 16a, 115487 Moscow (Russian Federation); Belsky, A.N. [Institute of Light and Matter, CNRS, University Lyon1, 69622 Villeurbanne (France)

    2016-03-15

    Bandgap modification of the Lu{sub x}Y{sub 1x}PO{sub 4} mixed crystals has been studied by thermostimulated luminescence (TSL) and ab-initio calculation methods. Doping of Lu{sub x}Y{sub 1x}PO{sub 4} with Ce{sup 3+} allowed to follow up the changes of electron traps depth, caused by the modification of the bottom of conduction band. The observed gradual shift of the most intensive TSL peaks to higher temperatures with increase of x value was connected with the high-energy shift of the conduction band bottom. According to the band structure calculations the bottom of the conduction band is formed by the 5d and 4d states of Lu and Y, respectively. Therefore, substitution of one cation by another is responsible for the observed variation of the electronic and optical properties. Doping with Eu{sup 3+} was used to study the modification of the hole traps and the top of the valence band in Lu{sub x}Y{sub 1x}PO{sub 4}. The independence of the TSL peaks position on x value in Lu{sub x}Y{sub 1x}PO{sub 4}:Eu{sup 3+} allows to conclude that the top of the valence band is negligibly affected by the cation substitution. According to the band structure calculations the top of the valence band is formed by the O 2p electronic states, which are not affected by the cation substitution. The resulting increase of the bandgap with x value is confirmed by the data of ab-initio calculations. - Highlights: • Band structure modification with x in Lu{sub x}Y{sub 1x}PO{sub 4}:RE{sup 3+} (RE=Ce, Eu) is studied. • Depth of electron traps is affected by the bandgap modification. • Increase of bandgap with x is due to the shift of conduction band bottom.

  8. Transformation from an easy-plane to an easy-axis antiferromagnetic structure in the mixed rare-earth ferroborates Pr x Y1-x Fe3(BO3)4: magnetic properties and crystal field calculations.

    Science.gov (United States)

    Pankrats, A I; Demidov, A A; Ritter, C; Velikanov, D A; Semenov, S V; Tugarinov, V I; Temerov, V L; Gudim, I A

    2016-10-05

    The magnetic structure of the mixed rare-earth system Pr x Y1-x Fe3(BO3)4 (x  =  0.75, 0.67, 0.55, 0.45, 0.25) was studied via magnetic and resonance measurements. These data evidence the successive spin reorientation from the easy-axis antiferromagnetic structure formed in PrFe3(BO3)4 to the easy-plane one of YFe3(BO3)4 associated with the weakening of the magnetic anisotropy of the Pr subsystem due to its diamagnetic dilution by nonmagnetic Y. This reorientation occurs through the formation of an inclined magnetic structure, as was confirmed by our previous neutron research in the range of x  =  0.67 ÷ 0.45. In the compounds with x  =  0.75 and 0.67 whose magnetic structure is close to the easy-axis one, a two-step spin reorientation takes place in the magnetic field H||c. Such a peculiarity is explained by the formation of an interjacent inclined magnetic structure with magnetic moments of Fe ions located closer to the basal plane than in the initial state, with these intermediate states remaining stable in some ranges of the magnetic field. An approach based on a crystal field model for the Pr(3+) ion and the molecular-field approximation is used to describe the magnetic characteristics of the system Pr x Y1-x Fe3(BO3)4. With the parameters of the d-d and f-d exchange interactions, of the magnetic anisotropy of the iron subsystem and of the crystal field parameters of praseodymium thus determined, it is possible to achieve a good agreement between the experimental and calculated temperature and field dependences of the magnetization curves (up to 90 kOe) and magnetic susceptibilities (2-300 K).

  9. Nanopowders Y1yNdyV1xCrxO4 with y=0 and 1; x=0, 0.1, 0.2 and 0.5 synthesized by a sol–gel process. Relationship between morphological characteristics and optical properties

    International Nuclear Information System (INIS)

    Alcaraz, L.; Isasi, J.; Caballero, A.C.; Izquierdo, J.G.; Bañares, L.

    2015-01-01

    Y 1y Nd y V 1x Cr x O 4 nanopowders with y=0 and 0.1; x=0, 0.1, 0.2 and 0.5, have been synthetized by a sol–gel process followed by heating in an oxygen flow. This second treatment was done only in the case of samples containing chromium. The samples have been characterized by X-ray diffraction (XRD), Fourier Transform Infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The structural analysis revealed that when chromium was inserted at vanadium-sites in Y 0.9 Nd 0.1 VO 4 , the host retained the tetragonal symmetry corresponding to a zircon-type structure, attributed to the space group I4 1 /amd. In addition, a loss of crystallinity was observed when chromium substitutes vanadium into the Y 0.9 Nd 0.1 VO 4 host. The morphological studies revealed agglomerates of spherical particles whose size is increased with the Cr content and confirmed the composition of all synthetized samples. FTIR spectra of these samples exhibit a broadening and a slight shift of the bands around 830 cm −1 towards higher values of frequency when the chromium content increases. The effect of vanadium substitution by chromium on the optical properties was also evaluated by UV–vis absorption and photoluminescence (PL) spectroscopies. The broad UV band absorption is due to the presence of Cr 5+ . A decrease of PL emission is found when chromium substitutes vanadium in the YVO 4 host. - Highlights: • Nanophosphors Y 1y Nd y V 1x Cr x O 4 with y=0, 0.1 and x=0, 0.1, 0.2 and 0.5 have been synthesized. • Structural analysis reveals structural distortions associated to chromium insertion. • Morphological studies confirm the nanocristalline size and the stoichiometry of synthesized samples. • Chromium insertion causes a decrease of the PL emission intensity

  10. Magnetic structures of (Co2-xNix)(OH)PO4 (x = 0.1,0.3) spin glass-like state in antiferromagnetically ordered phases

    International Nuclear Information System (INIS)

    Pedro, I de; Rojo, J M; Pizarro, J L; Fernandez, J RodrIguez; Marcos, J Sanchez; Fernandez-DIaz, M T; Arriortua, M I; Rojo, T

    2006-01-01

    Compounds of the general formula Co 2-x Ni x (OH)PO 4 (x = 0.1, 0.3) have been synthesized under mild hydrothermal conditions. Neutron powder diffraction, susceptibility and heat capacity measurements were carried out on polycrystalline samples. The cobalt-nickel compounds are ordered as three-dimensional antiferromagnets with ordering temperatures of 70 and 64 K for x = 0.1 and x = 0.3, respectively. The magnetic study shows a spin glass-like state below 11 and 5 K for Co 1.9 Ni 0.1 (OH)PO 4 and Co 1.7 Ni 0.3 (OH)PO 4 , respectively. Specific heat data present peaks at 68 and 61 K for Co 1.9 Ni 0.1 and Co 1.7 Ni 0.3 , respectively. These peaks show broad shoulders between approximately 15 and 40 K. The lack of any distinguishable anomaly below 10 K supports the spin glass nature of the low temperature transitions. Refinement of room temperature neutron diffraction data indicates that the Ni(II) ions are in octahedral co-ordination with the practical absence of these ions in the trigonal bipyramidal sites. The magnetic structures of Co 2-x Ni x (OH)PO 4 consist of ferromagnetic arrangements between the octahedral chains and trigonal bipyramidal dimers within the xz plane with the magnetic moments along the z axis. The ferromagnetic layers are disposed antiparallel to one another along the y direction establishing the three-dimensional antiferromagnetic order (T N ∼70 K for Co 1.9 Ni 0.1 and ∼64 K for Co 1.7 Ni 0.3 ). The different exchange pathways, the anisotropy of the Co(II) ions and the frustration of the magnetic moments in the trigonal bipyramidal geometry could be responsible for the freezing process

  11. X-ray photoemission studies of Zn doped Cu1-xTl xBa2Ca2Cu 3-yZn yO10-δ (y = 0, 2.65) superconductors

    International Nuclear Information System (INIS)

    Khan, Nawazish A.; Mumtaz, M.; Ahadian, M.M.; Iraji-zad, Azam

    2007-01-01

    The X-ray photoemission (XPS) measurements of Cu 1-x Tl x Ba 2 Ca 2 Cu 3-y Zn y O 10-δ (y = 0, 2.65) superconductors have been performed and compared. These studies revealed that the charge state of thallium in the Cu 0.5 Tl 0.5 Ba 2 O 4-δ charge reservoir layer in Zn doped samples is Tl 1+ , while it is a mix of Tl 1+ and Tl 2+ in Zn free samples. The binding energy of Ba atoms in the Zn doped samples is shifted to higher energy, which when considered along with the presence of Tl 1+ suggested that it more efficiently directed the carriers to ZnO 2 and CuO 2 planes. The evidence of improved inter-plane coupling witnessed in X-ray diffraction is also confirmed by XPS measurements of Ca atoms in the Zn doped samples. The shift of the valance band spectrum in these Zn doped samples to higher energies suggested that the electrons at the top edge of the valance band were tied to a higher binding energy (relative to samples without Zn doping), which most likely resulted in a much lower energy state of the system in the superconducting state. The stronger superconducting state arising out of these effects is witnessed in the form of increased T c (R 0), J c and the extent of diamagnetism in the final compound

  12. Tunable metal-insulator transition in Nd{sub 1x}Y{sub x}NiO{sub 3} (x = 0.3, 0.4) perovskites thin film at near room temperature

    Energy Technology Data Exchange (ETDEWEB)

    Shao, Tao; Qi, Zeming, E-mail: zmqi@ustc.edu.cn; Wang, Yuyin; Li, Yuanyuan; Yang, Mei; Zhang, Guobin [National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, Anhui 230029 (China); Wang, Yu [Shanghai Synchrotron Radiation Facility, Shanghai Institute of Applied Physics, Chinese Academy of Science, Shanghai 201204 (China); Liu, Miao [Environmental Energy Technologies Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)

    2015-07-13

    Metal-insulator transition (MIT) occurs due to the charge disproportionation and lattice distortions in rare-earth nickelates. Existing studies revealed that the MIT behavior of rare-earth nickelates is fairly sensitive to external stress/pressure, suggesting a viable route for MIT strain engineering. Unlike applying extrinsic strain, the MIT can also be modulated by through rare-earth cation mixing, which can be viewed as intrinsic quantum stress. We choose Nd{sub 1X}Y{sub X}NiO{sub 3} (x = 0.3, 0.4) perovskites thin films as a prototype system to exhibit the tunable sharp MIT at near room temperature. By adjusting Y concentration, the transition temperature of the thin films can be changed within the range of 340–360 K. X-ray diffraction, X-ray absorption fine structure (XAFS), and in situ infrared spectroscopy are employed to probe the structural and optical property variation affected by composition and temperature. The infrared transmission intensity decreases with temperature across the MIT, indicating a pronounced thermochromic effect. Meanwhile, the XAFS result exhibits that the crystal atomistic structure changes accompanying with the Y atoms incorporation and MIT phase transition. The heavily doped Y atoms result in the pre-edge peak descent and Ni-O bond elongation, suggesting an enhanced charge disproportionation effect and the weakening of hybridization between Ni-3d and O-2p orbits.

  13. Magnetism and superconductivity in Ru{sub 1-x}Sr{sub 2}RECu{sub 2+x}O{sub 8-d} (RE=Gd, Eu) and RuSr{sub 2}Gd{sub 1-y}Ce{sub y}Cu{sub 2}O{sub 8} compounds

    Energy Technology Data Exchange (ETDEWEB)

    Klamut, P.W. [Dept. of Physics, Northern Illinois Univ., DeKalb, IL (United States)]|[Inst. of Low Temperature and Structure Research of Polish Academy of Sciences, Wroclaw (Poland); Dabrowski, B.; Mini, S.M.; Kolesnik, S.; Maxwell, M.; Mais, J. [Dept. of Physics, Northern Illinois Univ., DeKalb, IL (United States); Shengelaya, A.; Keller, H. [Physik-Inst., Univ. Zuerich, Zuerich (Switzerland); Khazanov, R. [Physik-Inst., Univ. Zuerich, Zuerich (Switzerland)]|[Lab. for Muon-Spin Spectroscopy, Paul Scherrer Inst., Villigen PSI (Switzerland); Savic, I. [Physik-Inst., Univ. Zuerich, Zuerich (Switzerland)]|[Faculty of Physics, Univ. of Belgrade, Belgrade (Yugoslavia); Sulkowski, C.; Wlosewicz, D.; Matusiak, M. [Inst. of Low Temperature and Structure Research of Polish Academy of Sciences, Wroclaw (Poland); Wisniewski, A.; Puzniak, R.; Fita, I. [Inst. of Physics of Polish Academy of Sciences, Warszawa (Poland)

    2002-07-01

    We discuss the properties of new superconducting compositions of ruthenocuprates Ru{sub 1-x}Sr{sub 2}RECu{sub 2+x}O{sub 8-d} (RE=Gd, Eu) that were synthesized at 600 atm. of oxygen at 1080 C. By changing ratio between the Ru and Cu, the temperature of superconducting transition (T{sub C}) raises up to T{sub C}{sup max} = 72 K for x=0.3, 0.4. The hole doping achieved along the series increases with Cu{yields}Ru substitution. For x {ne} 0, T{sub C} can be subsequently tuned between T{sub C}{sup max} and 0 K by changing oxygen content in the compounds. The magnetic characteristics of the RE=Gd and Eu based compounds are interpreted as indicative of constrained dimensionality of the superconducting phase. Muon spin rotation experiments reveal the presence of the magnetic transitions at low temperatures (T{sub m}=14-2 K for x=0.1-0.4) that can originate in the response of Ru/Cu sublattice. RuSr{sub 2}Gd{sub 1-y}Ce{sub 1-y}Cu{sub 2}O{sub 8} (0 {<=} y {<=} 0.1) compounds show the simultaneous increase of T{sub N} and decrease of T{sub C} with y. The effect should be explained by the electron doping that occurs with Ce{yields}Gd substitution. Properties of these two series allow us to propose phase diagram for 1212-type ruthenocuprates that links their properties to the hole doping achieved in the systems. Non-superconducting single-phase RuSr{sub 2}GdCu{sub 2}O{sub 8} and RuSr{sub 2}EuCu{sub 2}O{sub 8} are reported and discussed in the context of the properties of substituted compounds. (orig.)

  14. Interband Stark effects in InxGa1-xAs/InyAl1-yAs coupled step quantum wells

    International Nuclear Information System (INIS)

    Kim, J.H.; Kim, T.W.; Yoo, K.H.

    2005-01-01

    The effects of an electric field on the interband transitions in In x Ga 1-x As/In y Al 1-y As coupled step quantum wells have been investigated both experimentally and theoretically. A In x Ga 1-x As/In y Al 1-y As coupled step quantum well sample consisted of the two sets of a 50 Aa In 0.53 Ga 0.47 As shallow quantum well and a 50 Aa In 0.65 Ga 0.35 As deep step quantum well bounded by two thick In 0.52 Al 0.48 As barriers separated by a 30 Aa In 0.52 Al 0.48 As embedded potential barrier. The Stark shift of the interband transition energy in the In x Ga 1-x As/In y Al 1-y As coupled step quantum well is larger than that of the single quantum well, and the oscillator strength in the In x Ga 1-x As/In y Al 1-y As coupled step quantum well is larger than that in a coupled rectangular quantum well. These results indicate that In x Ga 1-x As/In y Al 1-y As coupled step quantum wells hold promise for potential applications in optoelectron devices, such as tunable lasers

  15. Single crystal growth and structural evolution across the 1st order valence transition in (Pr1-yYy)1-xCaxCoO3

    Science.gov (United States)

    Schreiber, N. J.; Zhang, Junjie; Zheng, Hong; Freeland, J. W.; Chen, Yu-Sheng; Mitchell, J. F.; Phelan, D.

    2017-10-01

    Praseodymium-containing cobalt perovskites, such as (Pr1-yYy)1-xCaxCoO3-δ, have been argued to undergo a first-order charge shift between Pr and hybridized Co-O orbitals that leads to a metal-insulator transition at a temperature, TVT. Magnetization and x-ray absorption spectroscopy measurements on single crystals of (Pr0.85Y0.15)0.7Ca0.3CoO3-δ grown in an IR image furnace under 40-60 bar of oxygen confirm the presence of this valence transition. Single crystal x-ray synchrotron diffraction measurements are consistent with an isomorphic phase transition at TVT. No evidence of charge ordering was revealed by the single crystal diffraction. Dissimilar to analytical transmission electron microscopy measurements performed on a grain from a polycrystalline sample that revealed an oxygen vacancy order-disorder transition at TVT, the present single-crystal measurements did not evidence such a transition, likely reflecting a lower density of oxygen vacancies in the high-pO2 grown single crystals.

  16. Structural and magnetic properties of Sr{sub 2}Y{sub 1+x}Ir{sub 1-x}O{sub 6} materials

    Energy Technology Data Exchange (ETDEWEB)

    Aslan Cansever, Gizem; Geyer, Maximilian; Blum, Christian G.F.; Gass, Sebastian; Corredor, Laura T.; Maljuk, Andrey; Wolter, A.U.B. [Leibniz Institute for Solid State and Materials Research Dresden, IFW Dresden (Germany); Manna, Kaustuv [Max-Planck-Institute for Chemical Physics of Solids, Dresden (Germany); Hammerath, Franziska; Wurmehl, Sabine; Buechner, Bernd [Leibniz Institute for Solid State and Materials Research Dresden, IFW Dresden (Germany); Institute for Solid State Physics, TU Dresden (Germany)

    2016-07-01

    Ir-based materials have attracted a lot of attention because of the competition between the spin-orbit coupling, Coulomb interaction and crystal field. Sr{sub 2}YIrO{sub 6} double perovskites with Ir{sup +5} (5d{sup 4}) ions are generally considered to have a nonmagnetic ground state (J=0). However, Sr{sub 2}YIrO{sub 6} double perovskites have been reported to exhibit long-range magnetic order at low temperature and the distorted IrO{sub 6} octahedra were discussed to cause the magnetism in this compound [2]. In this study Sr{sub 2}Y{sub 1+x}Ir{sub 1-x}O{sub 6} materials were investigated in relation to structural and magnetic properties with varying Y and Ir concentrations. The samples were prepared by solid-state chemical reaction method. Magnetic susceptibility measurements were performed down to 0.4 K.

  17. Optical investigation of the valency of Pr in Y1-xPrxBa2Cu3O7-δ

    International Nuclear Information System (INIS)

    Kircher, J.; Cardona, M.; Gopalan, S.; Habermeier, H.; Fuchs, D.

    1991-01-01

    We have investigated the dependence of the visible-ultraviolet dielectric function of Y 1-x Pr x Ba 2 Cu 3 O 7 on the Pr content x using rotating analyzer ellipsometry. Based on recently published band-structure calculations, we believe that the valency of Pr can be deduced from the optical properties in this spectral region. Interband transitions should shift to higher energies for Pr 4+ and to lower energies for Pr 3+ when compared to the optical spectra of YBa 2 Cu 3 O 7 . In the case of tetravalent Pr ions, transitions into unoccupied Pr 5d levels should be observable. Since the experimental energies for interband transitions shift down with increasing x and no additional structure can be seen, we conclude that Pr is trivalent in Y 1-x Pr x Ba 2 Cu 3 O 7

  18. High frequencies of Y chromosome lineages characterized by E3b1, DYS19-11, DYS392-12 in Somali males

    DEFF Research Database (Denmark)

    Sanchez Sanchez, Juan Jose; Hallenberg, Charlotte; Børsting, Claus

    2005-01-01

    We genotyped 45 biallelic markers and 11 STR systems on the Y chromosome in 201 male Somalis. In addition, 65 sub-Saharan Western Africans, 59 Turks and 64 Iraqis were typed for the biallelic Y chromosome markers. In Somalis, 14 Y chromosome haplogroups were identified including E3b1 (77.6%) and K2...... (10.4%). The haplogroup E3b1 with the rare DYS19-11 allele (also called the E3b1 cluster gamma) was found in 75.1% of male Somalis, and 70.6% of Somali Y chromosomes were E3b1, DYS19-11, DYS392-12, DYS437-14, DYS438-11 and DYS393-13. The haplotype diversity of eight Y-STRs ('minimal haplotype') was 0......f2) (27.1%), R1b3*(xR1b3d, R1b3f) (20.3%), E3b3 and R1a1*(xR1a1b) (both 11.9%). In Iraqis, 12 haplogroups were identified including J2*(xJ2f2) (29.7%) and J*(xJ2) (26.6%). The data suggest that the male Somali population is a branch of the East African population - closely related to the Oromos...

  19. Crystalline electric field at the rare-earth sites in RxY1-xCo5+y compounds (R= Dy and Tb)

    International Nuclear Information System (INIS)

    Han Xiufeng; Jin Hanmin; Chen Hong; Guo Guanghua; Zhao Tiesong

    1992-01-01

    The magnetic properties of R x Y 1-x Co 5+y compounds are reproduced well by a calculation based on the single-ion model. The values of the exchange field H cx and crystalline-electric-field parameters A m n at the rare-earth ion sites in R x Y 1-x Co 5+y (R = Dy and Tb) are evaluated by fitting the calculations to the experiments. The experiments include the temperature dependence of the spontaneous magnetization, the temperature dependence of the normalized magnetic moments of the rare-earth ions, the temperature dependence of the cone angle, the magnetization curves along the crystal axes at 4.2 K, and the hyperfine field at the Dy ion site

  20. Crystallisation kinetics of amorphous Fe72.5-xCu1Nb4.5Si10+x+yB12-y alloy

    International Nuclear Information System (INIS)

    Miglierini, M.; Lipka, J.; Sitek, J.

    1994-01-01

    Fe 73.5 Cu 1 Nb 3 Si 13.5 B 9 and Fe 72.5-x Cu 1 Nb 4.5 Si 10+x+y B 12-y alloys are compared from the point of view of crystallisation behaviour and changes in the short-range order in the amorphous reminder. The increase in Nb to 4.5 at.% in the latter system slows down the formation of nanocrystals to approximately 40% even after 16 hours of anneal at 550 C for x = 0.5, y = 3. Segregation-induced changes in the short-range order are manifested via hyperfine field distributions corresponding to the amorphous reminder. (orig.)

  1. Complete titanium substitution by boron in a tetragonal prism: exploring the complex boride series Ti(3-x)Ru(5-y)Ir(y)B(2+x) (0 ≤ x1 and 1 theory.

    Science.gov (United States)

    Fokwa, Boniface P T; Hermus, Martin

    2011-04-18

    Polycrystalline samples and single crystals of four members of the new complex boride series Ti(3-x)Ru(5-y)Ir(y)B(2+x) (0 ≤ x1 and 1 X-ray diffraction as well as energy- and wavelength-dispersive X-ray spectroscopy analyses. They crystallize with the tetragonal Ti(3)Co(5)B(2) structure type in space group P4/mbm (No. 127). Tetragonal prisms of Ru/Ir atoms are filled with titanium in the boron-poorest phase (Ti(3)Ru(2.9)Ir(2.1)B(2)). Gradual substitution of titanium by boron then results in the successive filling of this site by a Ti/B mixture en route to the complete boron occupation, leading to the boron-richest phase (Ti(2)Ru(2.8)Ir(2.2)B(3)). Furthermore, both ruthenium and iridium share two sites in these structures, but a clear Ru/Ir site preference is found. First-principles density functional theory calculations (Vienna ab initio simulation package) on appropriate structural models (using a supercell approach) have provided more evidence on the stability of the boron-richest and -poorest phases, and the calculated lattice parameters corroborate very well with the experimentally found ones. Linear muffin-tin orbital atomic sphere approximation calculations further supported these findings through crystal orbital Hamilton population bonding analyses, which also show that the Ru/Ir-B and Ru/Ir-Ti heteroatomic interactions are mainly responsible for the structural stability of these compounds. Furthermore, some stable and unstable phases of this complex series could be predicted using the rigid-band model. According to the density of states analyses, all phases should be metallic conductors, as was expected from these metal-rich borides.

  2. A new set of K3Fe3(PO4)4·yH2O (0 ≤ y1) layered phases obtained by topotactic reactions

    Science.gov (United States)

    Trad, Khiem; Wattiaux, Alain; Ben Amara, Mongi; Delmas, Claude; Carlier, Dany

    2018-06-01

    K3Fe3(PO4)4·H2O powder was synthesized by Na+/K+ exchange reaction from Na3Fe3(PO4)4 in aqueous medium. The replacement of the sodium cations by the potassium larger ones and water molecules causes a structural distortion leading to P2/n monoclinic K3Fe3(PO4)4·H2O. This new layered phase was characterized by XRD, Mössbauer spectroscopy and magnetic measurements. The study of its thermal stability reveals that other new layered K3Fe3(PO4)4·yH2O with (0 ≤ y1) phases can be stabilized up to 600 °C and finally at higher temperature a new K3Fe3(PO4)4 polymorph with a different structural type is irreversibility formed.

  3. Structural and magnetotransport properties of the Y doped A-site deficient double layered manganites La{sub 1.2−x}□{sub 0.2}Y{sub x}Ca{sub 1.6}Mn{sub 2}O{sub 7}

    Energy Technology Data Exchange (ETDEWEB)

    Mahamdioua, N., E-mail: mahamdioua.nabil@gmail.com [LEND, Faculty of Science and Technology, Jijel University, Jijel 18000 (Algeria); Amira, A. [LEND, Faculty of Science and Technology, Jijel University, Jijel 18000 (Algeria); Altintas, S.P. [Department of Physics, Faculty of Arts and Sciences, AIB University, Bolu 14280 (Turkey); Koc University, Surface Science and Technology Center (KUYTAM), 34450-Sariyer, Istanbul (Turkey); Varilci, A.; Terzioglu, C. [Department of Physics, Faculty of Arts and Sciences, AIB University, Bolu 14280 (Turkey)

    2016-08-15

    We present structural, magnetic and electrical properties of the polycrystalline A-site-deficient yttrium doped double layered manganites La{sub 1.2−x}□{sub 0.2}Y{sub x}Ca{sub 1.6}Mn{sub 2}O{sub 7} (x=0.2, 0.3 and 0.4) prepared by a solid state reaction method. The samples crystallize in the tetragonal structure with the space group I4/mmm. Doping with Y decreases the cell parameters and causes a decrease of the metal-insulator transition temperature. The same evolution with doping is also seen for the deduced Curie temperature from susceptibility curves which present a clear paramagnetic-ferromagnetic transition. The significant positive intrinsic magnetoresistance, shown in all samples, reaches 85% at 122 K under 7 T for 0.3 doped sample and can be attributed to the suppression of spin fluctuations via aligning the spins under external magnetic field, while the extrinsic one is attributed to the inter-grain spin-polarized tunneling across the grain boundaries. The simulation of the resistivity curves in the entire temperature range show that the percolation model is suitable to fit our results. The applied magnetic field increases the density of states near the Fermi level, which is in accordance with the observed decrease of resistivity. - Graphical abstract: Resistivity and magnetoresistance of La{sub 1.2−x}□{sub 0.2}Y{sub x}Ca{sub 1.6}Mn{sub 2}O{sub 7} (x=0.2, 0.3, 0.4). Solid lines correspond to the fitting results. Display Omitted.

  4. Transport (electrical and thermal) properties and surface morphology of Y1-xCaxFeO3 (where x = 0.03 and 0.05) ceramics

    Science.gov (United States)

    Suthar, Lokesh; Bhadala, Falguni; Roy, M.; Jha, V. K.

    2018-05-01

    The electrical transport behaviour of polycrystalline Calcium doped Yttrium orthoferrite (Y1-xCaxFeO3, where x = 0.03 and 0.05) have been synthesized by high temperature Solid state reaction route. The I-V characteristics have been measured which revels that Y1-xCaxFeO3 (where x = 0.03 and 0.05), behaves like semiconductor and its conductivity increases with increase in doping concentration. The thermal analysis experiment shows no phase change with the minor weight loss which reflects the high temperature thermal stability of the materials. The surface morphology was analyzed using the AFM. The results are discussed in detail.

  5. La temperatura de transición en SrxBa1-xHfO3

    Directory of Open Access Journals (Sweden)

    López-García, A.

    2002-02-01

    Full Text Available In this contribution the transition temperature TC to the cubic phase in SrxBa1-xHfO3 compounds with x = 0.12, 0.25, 0.50, 0.75 and 0.88 is presented. These temperatures were deduced from the measurements of the perturbed angular correlation on tantalum probes. The purpose of this work is to study how the Sr substitution by Ba affect this temperature. The oxides BaHfO3 and SrHfO3 have at RT cubic and orthorhombic structures, respectively. The Sr-compound transform from tetragonal to cubic at TC1 ≈ 1400. From TC2 ≈ 1000K and up to TC1 the oxygen octahedra are tilted and the tilt angle decreases steadily as T approaches TC1. This rotation is originated by the interaction of strontium with oxygen because the Sr ionic radius (rSr ≈ 1.13 Å allows to be closer than Ba (rBa ≈ 1.35 Å. Then in SrxBa1-xHfO3 compounds a competition between the Ba-O interaction, 2.9502 Å apart and Sr-O interaction at a distance of 2.9098 Å in their respective pure compounds, is established.En este trabajo se presenta las temperaturas de transición TC a la estructura cúbica, en la familia de compuestos SrXBa1-XHfO3 donde x es igual a 0.12, 0.25, 0.50, 0.75 y 0.88, determinadas por medidas de la Correlación Angular Perturbada y usando al tantalio como sonda. El interés es estudiar como la sustitución de estroncio por bario modifica dicha temperatura. El BaHfO3 es cúbico a temperatura ambiente. En cambio, el SrHfO3 presenta una transición estructural de tetragonal a cúbica cuando TC1 ≈ 1400 K. Por debajo de esta temperatura y hasta TC2 ≈ 1000 K los octaedros de oxígeno están rotados uno con respecto al consecutivo, en un ángulo φ alrededor del eje z de la red tetragonal que disminuye a cero a medida que T→TC. Esta rotación está relacionada con la interacción del estroncio con el oxígeno, ya que el radio iónico del catión rSr (≈ 1.13 Å permite un mayor acercamiento entre ambos que el bario al oxígeno, pues rBa (≈ 1.35 Å. Entonces, en

  6. Neutron powder diffraction investigation of magnetic structure and spin reorientation transition of HoFe{sub 1-x}Cr{sub x}O{sub 3} solid solutions

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Xinzhi [Department of Nuclear Physics, China Institute of Atomic Energy, Beijing 102413 (China); Hao, Lijie, E-mail: haolijie@ciae.ac.cn [Department of Nuclear Physics, China Institute of Atomic Energy, Beijing 102413 (China); Liu, Yuntao; Ma, Xiaobai; Meng, Siqin; Li, Yuqing; Gao, Jianbo; Guo, Hao; Han, Wenze; Sun, Kai; Wu, Meimei [Department of Nuclear Physics, China Institute of Atomic Energy, Beijing 102413 (China); Chen, Xiping; Xie, Lei [Institute of Nuclear Physics and Chemistry, CAEP, Mianyang 621900 (China); Klose, Frank [Australian Nuclear Science and Technology Organization, Lucas Heights, New South Wales 2234 (Australia); Department of Physics and Materials Science, The City University of Hong Kong, Hong Kong (China); Chen, Dongfeng, E-mail: dongfeng@ciae.ac.cn [Department of Nuclear Physics, China Institute of Atomic Energy, Beijing 102413 (China)

    2016-11-01

    Orthoferrite solid solution HoFe{sub 1x}Cr{sub x}O{sub 3} (x=0, 0.2,…,1.0) was synthesized via solid state reaction methods. The crystal structure, magnetism and spin reorientation properties of this system were investigated by X-ray diffraction, neutron powder diffraction and magnetic measurements. For compositions of x≤0.6, the system exhibits similar magnetic properties to HoFeO{sub 3}. With increasing Cr-doping, the system adopts a Γ{sub 4}(G{sub x}A{sub y}F{sub z}) magnetic configuration with a decreased Neel temperature from 640 K to 360 K. A Γ{sub 42} spin reorientation of Fe(Cr){sup 3+} was also observed in this system with an increase in transition temperature from 56 K to about 200 K due to competition between the Fe(Cr)–Fe(Cr) and Ho–Fe(Cr) interactions. For the x≥0.8, the system behaves more like HoCrO{sub 3} which adopts a Γ{sub 2}(F{sub x}C{sub y}G{sub z}) configuration with no spin reorientation below the Neel temperature T{sub N}. Throughout the whole substitution range, we found that the saturated moment of Fe(Cr) was less than the ideal value for a free ion, which implies the existence of spin fluctuation in this system. A systematic magnetic structure variation with Cr-substitution is revealed by Rietveld refinement. A phase diagram combining the results of the magnetic measurements and neutron powder diffraction results was obtained. - Highlights: • With Cr-substitution in the HoFe{sub 1x}Cr{sub x}O{sub 3} system, A Γ{sub 42} spin reorientation of Fe(Cr){sup 3+} was observed with an increase in transition temperature from 56 K to about 200 K for x=0−0.6. • The saturated moment of Fe(Cr) position was found to be systematically less than the ideal value of free ion, and thus implies the presence of spin quantum fluctuation. • A composition–temperature phase diagram throughout x=0–1 for HoFe{sub 1x}Cr{sub x}O{sub 3} system was established.

  7. X-ray photo-emission studies of Cu1-xTlxBa2Ca3Cu4O12-y superconductor thin films

    International Nuclear Information System (INIS)

    Khan, Nawazish A.; Mumtaz, M.; Ahadian, M.M.; Iraji-zad, Azam

    2006-01-01

    X-ray photo-emission spectroscopy (XPS) studies of Cu 1-x Tl x Ba 2 Ca 3 Cu 4 O 12-y superconductor thin films have been carried out for understanding the mechanism of superconductivity and to find out the reasons for the increase of zero resistivity critical temperature T c (R = 0) with post-annealing in a nitrogen atmosphere. It is observed from these studies that reduction of charge state of thallium is a source of doping of carriers to the CuO 2 planes. The reduced charge state of thallium (i.e. Tl 1+ ) promotes lower oxygen concentration in the charge reservoir layer, which possibly results in movement of electrons to the conducting CuO 2 planes. The higher density of electrons in the CuO 2 planes optimizes the hole concentration 'n p ' in these planes. The reduced charge state of thallium in the Cu 1-x Tl x Ba 2 O 4-δ charge reservoir layer is also supported by a shift of the Ba 3d 5/2 and Ba 3d 3/2 XPS lines to lower binding energies with post-annealing in nitrogen atmosphere. Moreover, the movement of the valance band spectrum to lower binding energies suggested that the electronic density of states changes in the valance band with the post-annealing in nitrogen, which possibly becomes a source of doping of carriers to the CuO 2 planes. The increased doping of electrons to the CuO 2 planes optimizes the Fermi-vector K F and Fermi-velocity V F of the carriers and increases the T c (R = 0) of final compound

  8. Neutron scattering studies of nuclear and magnetic structures of YBa2(Cu1-yZny)3O6+x

    International Nuclear Information System (INIS)

    Villeneuve, R.; Mirebeau, I.; Collin, G.; Bouree, F.

    1994-01-01

    Structural effects of zinc substitution in YBCO have been studied by neutron diffraction in order to determine the substitution site of zinc atoms. Electron neutron diffraction experiments are performed on YBa 2 (Cu 1-y Zn y ) 3 O 6+x powders. Nuclear structures have been refined using the Rietveld method on powders of compositions x=1 and y ranging from 0.01 to 0.06. The results suggest a solubility limit of zinc in the copper planes at y ≅ 0.04 and zinc may start to substitute for chain copper sites for higher y values. Magnetic structure of a y=0.02 and x=0.05 powder has been studied by neutron elastic diffraction. The antiferromagnetic structure is not affected by non-magnetic zinc atoms but the ordering temperature is strongly reduced. 2 figs., 11 refs

  9. Giant magnetoresistance on low field in non-stoichiometric La2/3Ca1/3Mn1-xO3

    International Nuclear Information System (INIS)

    Zhao Lifeng; Chen Wei; Shang Jingling; Chen Lei; Liu Sheng; Xia Zhengcai; Yuan Songliu

    2005-01-01

    Electrical transport and low field magnetoresistance (MR) are reported in the La 2/3 Ca 1/3 Mn 1-x O 3 (x = 0-0.16) samples, which are prepared by the sol-gel method followed by a sintering treatment at 1100 0 C. Experimental results show, for x = 0.06, an MR platform is observed in a temperature ∼200 K under the magnetic field of 0.5 T. With an increase in x, the MR effect gets augmented. For the sample with x = 0.16, its MR peak is as high as 50%

  10. Magnetocaloric effect in (La1-xAx)2/3Ba1/3Mn1.05O3

    DEFF Research Database (Denmark)

    Ancona-Torres, Carlos Eugenio; Menon, Mohan; Bahl, Christian Robert Haffenden

    Recently, a large magnetocaloric effect has been reported in La2/3Ba1/3MnO3-δ at about 300 K. In this paper, we investigate the effect of the ion size distribution at the A site on the magnetocaloric effect of this perovskite material. This is accomplished by replacing the lanthanum by Ce, Pr......, and Nd, which allows us to study the effect of both the average size, , and the distribution, σrA, on the magnetic properties of the system. Using magnetization and heat capacity measurements, we determine the important magnetocaloric parameters ΔSM and ΔTad of (La1-xAx)2/3Ba1/3Mn1.05O3-δ powders...

  11. System Ba/sub 2/Gdsub(2/3)vacantsub(1/3)Usub(1-x)Wsub(x)O/sub 6/ and hexagonal perovskites of an 18-layer type

    Energy Technology Data Exchange (ETDEWEB)

    Wischert, W; Schittenhelm, H J; Kemmler-Sack, S [Tuebingen Univ. (Germany, F.R.). Inst. fuer Chemie

    1978-04-01

    In the system Ba/sub 2/Gdsub(2/3)vacantsub(1/3)Usub(1-x)Wsub(x)O/sub 6/ the formation of a continuous solid solution series is observed. With x <= 0.9 the mixed crystals have a cubic 1:1 ordered perovskite structure. With x >= 0.95 the compounds are polymorphic: besides an cubic 1:1 ordered perovskite type for x = 0.95; 0.99 and 1.00 one hexagonal layer structure exists. This lattice is in all cases rhombohedral (space group R3m) and represents an 18 L-type. Likewise the compounds Ba/sub 2/Bsub(2/3)sup(III)vacantsub(1/3)Wsup(VI)O/sub 6/ with Bsup(III) Tb-Lu and Y belong to the 18 L-type.

  12. Superconductivity in Na{sub 1-x}CoO{sub 2}.yH{sub 2}O thin films

    Energy Technology Data Exchange (ETDEWEB)

    Hildebrandt, Sandra; Komissinkiy, Philipp; Alff, Lambert [Institute for Materials Science, TU Darmstadt (Germany); Fritsch, Ingo; Habermeier, Hanns-Ulrich [Max-Planck-Institute for Solid State Research, Stuttgart (Germany); Lemmens, Peter [Institute for Condensed Matter Physics, TU Braunschweig (Germany)

    2010-07-01

    Sodium cobaltate (Na{sub 1-x}CoO{sub 2}) is a novel material with thermoelectric behavior, charge and spin ordered states dependent on the sodium content in the composition. A superconducting phase was found in water intercalated sodium cobaltate (Na{sub 1-x}CoO{sub 2}.yH{sub 2}O) with x=0.65-0.7 and y=0.9-1.3. The pairing state is still under debate, but there are some indications for a spin-triplet or p-wave superconducting pairing state. First films of Na{sub 1-x}CoO{sub 2}.yH{sub 2}O with a superconducting transition temperature near 5 K have been successfully grown. Here we report on thin films of Na{sub 1-x}CoO{sub 2} grown by pulsed laser deposition technique. The deposition parameters, sodium deintercalation and water intercalation conditions are tuned in order to obtain the superconducting phase. The instability of this phase might be an indication for triplet superconductivity, which is known to be affected strongly by impurities and defects.This observation is in agreement with the fact that so far also no superconducting thin films of the most famous triplet superconductor Sr{sub 2}RuO{sub 4} have been reported.

  13. Improved dielectric properties and grain boundary response in neodymium-doped Y_2_/_3Cu_3Ti_4O_1_2 ceramics

    International Nuclear Information System (INIS)

    Liang, Pengfei; Yang, Zupei; Chao, Xiaolian

    2016-01-01

    Rare earth element neodymium was adopted to refine grain and in turn increase the volume of grain boundary of Y_2_/_3Cu_3Ti_4O_1_2 ceramics, which could strongly increase the resistance of grain boundary. Proper amount of Nd substitution in Y_2_/_3_−_xNd_xCu_3Ti_4O_1_2 ceramics could significantly depress the low-frequency dielectric loss. When the doping level is 0.06 and 0.09, the samples exhibited a relatively low dielectric loss (below 0.050 between 0.3 and 50 kHz) and high dielectric constant above 11000 over a wide frequency range from 40 Hz to 100 kHz. Based on the ε′-T plots, dielectric relaxation intensity was substantially weakened by Nd doping so that the temperature stability of dielectric constant was improved obviously. The correlations between low-frequency dielectric loss and the resistance of grain boundary were revealed. After Nd doping, the activation energies for the conduction behavior in grain boundaries were significantly enhanced, and the activation energies for the dielectric relaxation process in grain boundaries were slightly influenced. - Highlights: • Significant decrease in dielectric loss of Y_2_/_3_−_xNd_xCu_3Ti_4O_1_2 ceramics was realized. • The enhanced grain boundary density is responsible for the lowered dielectric loss. • Nd doping could improve the temperature stability of dielectric constant. • Oxygen vacancies contribute to conduction and relaxation process of grain boundaries.

  14. Single crystal neutron diffraction study of SrFeOsub(3-x)(x=0. 1)

    Energy Technology Data Exchange (ETDEWEB)

    Oda, H; Yamaguchi, Y; Takei, H; Watanabe, H [Tohoku Univ., Sendai (Japan). Research Inst. for Iron, Steel and Other Metals

    1977-01-01

    Neutron diffraction study was carried out on single crystals of the perovskite oxide SrFeOsub(3-x)(x=0.1). SrFeOsub(3-x)(x=0.1) has a proper screw spin structure with the propagation vector parallel to (111) direction and its Neel temperature is 118 K. The electron configuration of Fe/sup 4 +/(3d/sup 4/) ion is close to the low-spin state (tsub(2g)sup(4)) and the oxygen ion has the unpaired electron with the magnetic moment of 0.3..mu..sub(B) antiparallel to the vector sum of the magnetic moments of two iron ions lying on the neighbouring planes perpendicular to the screw axis. The absolute value of the propagation vector is almost constant. 0.130x..sqrt..3.2..pi../a A/sup -1/, at temperatures below 50 K, while it decreases gradually at higher temperatures reaching 0.118x..sqrt..3.2..pi../a A/sup -1/ at Tsub(N).

  15. Phase composition and superconducting properties of (Pb sub 0 sub . sub 6 Sn sub y Cu sub 0 sub . sub 4 sub - sub y)Sr sub 2 (Y sub 1 sub - sub x Ca sub x)Cu sub 2 O sub z

    CERN Document Server

    Balchev, N; Kunev, B; Souleva, A; Tsacheva, T

    2001-01-01

    The effect of Sn-doping in (Pb sub 0 sub . sub 6 Sn sub y Cu sub 0 sub . sub 4 sub - sub y)Sr sub 2 (Y sub 1 sub - sub x Ca sub x)Cu sub 2 O sub z for 0 <= y <= 0.3 and 0 <= x <= 0.7 was investigated. It was established that a nearly pure 1212 phase could be obtained at 0 <= y <= 0.1 and 0 <= x <= 0.3. The obtained X-ray diffraction (XRD) patterns as well as the results of the inductively coupled plasma atomic emission spectrometry (ICP-AES) and energy-dispersive X-ray (EDX) analysis showed that the Sn-substitution was possible in the (Pb,Cu)-1212 phase. Superconductivity was observed at 0.4 <= x <= 0.7. The onset of the diamagnetic transitions varied from 10 to 30 K. The influence of the strong Pb deficiency on the superconducting properties of the samples was discussed. (authors)

  16. Heat-capacity measurement on (Zr1-ySny)Ox from 325 to 905 K

    International Nuclear Information System (INIS)

    Tsuji, Toshihide; Amaya, Masaki; Naito, Keiji

    1993-01-01

    Heat capacities of (Zr 1-y Sn y )O 0.17 and (Zr 1-y Sn y )O 0.28 (y=0-0.07) having α''-ZrO ∼1/6 and α''-ZrO x type crystal structures, respectively, were measured from 325 to 905 K by using an adiabatic scanning calorimeter. Two kinds of heat capacity anomalies were observed for all samples. The anomaly at lower temperatures is attributed to a nonequilibrium phenomenon. Another anomaly at higher temperatures is assigned to an order-disorder rearrangement of oxygen atoms. The transition temperature, transition enthalpy and entropy changes due to the order-disorder transition decreased with increasing tin content, indicating that arrangement of oxygen atoms in the lower temperature phase may be partially disordered by substituting tin for zirconium. The entropy change due to the order-disorder transition for (Zr 1-y Sn y )O 0.17 and (Zr 1-y Sn y )O 0.28 solid solutions is compared with the theoretical value. The solubility limits of (Zr 1-y Sn y )O 0.17 and (Zr 1-y Sn y )O 0.28 were determined from the variation of lattice constants, transition temperature, transition enthalpy and entropy changes against tin content. (orig.)

  17. Magnetic and transport properties of the (Tb{sub 1-} {sub x} Y {sub x} )Mn{sub 2}Si{sub 2} and TbMn{sub 2}(Si{sub 1-} {sub y} Ge {sub y} ){sub 2} systems

    Energy Technology Data Exchange (ETDEWEB)

    Granovsky, S.A. [Department of Physics, M.V. Lomonosov Moscow State University, Leninskie Gory GSP-2 119992 Moscow (Russian Federation) and TU Dresden, Institut fuer Festkoerperphysik, D-01062, Dresden (Germany)]. E-mail: ser@plms.phys.msu.ru; Gaidukova, I.Yu. [Department of Physics, M.V. Lomonosov Moscow State University, Leninskie Gory GSP-2 119992 Moscow (Russian Federation); Doerr, M. [TU Dresden, Institut fuer Festkoerperphysik, D-01062, Dresden (Germany); Loewenhaupt, M. [TU Dresden, Institut fuer Festkoerperphysik, D-01062, Dresden (Germany); Markosyan, A.S. [Department of Physics, M.V. Lomonosov Moscow State University, Leninskie Gory GSP-2 119992 Moscow (Russian Federation)

    2005-04-15

    Magnetic and transport characteristics of pseudo-ternary compounds (Tb{sub 1-} {sub x} Y {sub x} )Mn{sub 2}Si{sub 2} and TbMn{sub 2}(Si{sub 1-} {sub y} Ge {sub y} ){sub 2} have been studied. The role of the 4f-3d exchange and Mn-Mn distances in the formation of the magnetic structure of these compounds is discussed.

  18. Optical properties of lattice matched InxGa1-xP1-yNy heteroepitaxial layers on GaP

    International Nuclear Information System (INIS)

    Imanishi, T.; Wakahara, A.; Kim, S.M.; Yonezu, H.; Furukawa, Y.

    2005-01-01

    Optical constants and band structure of In x Ga 1-x P 1-y N y lattice matched to GaP (100) substrate are investigated. Nitrogen concentration in the film estimated by X-ray diffraction and X-ray photoelectron spectroscopy, was 1.4%, 1.8% and 3.5%. Refractive index and transition critical points E 0 (Γ v to Γ c ), E 1 (L v to L c ) and E 2 (X v to X c ) are evaluated by spectroscopic ellipsometry. When N composition increases from 1.4% to 3.5%, both photoluminescence (PL) peak energy, E PL , and E 0 shift to lower energy, and the energy difference ΔE=E 0 -E PL decrease from 380 meV to 110 meV. The large red-sift of E PL from the E 0 suggest that the luminescence is of defect-related luminescence, and crossover point of indirect band structure estimated by the extrapolation of N-composition dependence of ΔE is estimated to be around in In 0.1 Ga 0.9 P 0.96 N 0.04 . (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  19. As-Deposited (La1-xSrx)(Ga1-y-zMgyCoz)O3-(x+y+z)/2 Crystallized Thin Films Prepared by Pulsed Laser Deposition for Application to Solid Oxide Fuel Cell Electrolyte

    Science.gov (United States)

    Mitsugi, Fumiaki; Kanazawa, Seiji; Ohkubo, Toshikazu; Nomoto, Yukiharu; Ishihara, Tatsumi; Takita, Yusaku

    2004-01-01

    Doped lanthanum gallate (La1-xSrx)(Ga1-y-zMgyCoz)O3-(x+y+z)/2 (LSGMCO) perovskite oxide films were deposited on a quartz glass, LaAlO3 single-crystal substrate and porous anode electrode of a solid oxide fuel cell (SOFC) by pulsed laser deposition. It was necessary to increase the substrate temperature up to 800°C for a crystallization of the LSGMCO films. The film deposited on the LaAlO3 single-crystal substrate grew along the c-axis. The as-deposited LSGMCO thick film fabricated on the porous substrate at 800°C and at an oxygen pressure of 20Pa was formed from polycrystal columns and showed a high conductivity of 0.7S/cm at a measurement temperature of 800°C. The activation energies were 0.72 eV at 600-800°C and 1.05 eV at 400-600°C.

  20. Polycrystalline (TbXY1-X)2O3 Faraday rotator.

    Science.gov (United States)

    Ikesue, Akio; Aung, Yan Lin; Makikawa, Shinji; Yahagi, Akira

    2017-11-01

    We have succeeded for the first time in synthesizing an optical grade (Tb X Y 1-X ) 2 O 3 (X=0.5-1.0) ceramic Faraday rotator, which greatly exceeds the basic characteristics of the commercial terbium gallium garnet (TGG) (Tb 3 Ga 5 O 12 ) crystal. The Faraday rotation angle increased as the Tb concentration increased, and the Verdet constant increased from 2.1 (82  rad T -1  m -1 at X=0.5) to 3.8 times (154  rad T -1  m -1 at X=1.0) than the TGG single crystal, which is regarded as highest class. Therefore, it is possible to minimize the Faraday rotator length and the magnet in building an optical isolator. It was also confirmed that its optical quality was very comparable to the commercial TGG crystal.

  1. The complex metal-rich boride Ti{sub 1+x}Rh{sub 2-x+y}Ir{sub 3-y}B{sub 3} (x=0.68, y=1.06) with a new structure type containing B{sub 4} zigzag fragments: Synthesis, crystal chemistry and theoretical calculations

    Energy Technology Data Exchange (ETDEWEB)

    Goerens, Christian [Institute of Inorganic Chemistry, RWTH Aachen University, Landoltweg 1, 52064 Aachen (Germany); Fokwa, Boniface P.T., E-mail: boniface.fokwa@ac.rwth-aachen.de [Institute of Inorganic Chemistry, RWTH Aachen University, Landoltweg 1, 52064 Aachen (Germany)

    2012-08-15

    Polycrystalline samples and single crystals of the new complex boride Ti{sub 1+x}Rh{sub 2-x+y}Ir{sub 3-y}B{sub 3} (x=0.68; y=1.06) were synthesized by arc-melting the elements in a water-cooled copper crucible under an argon atmosphere and characterized by X-Ray diffraction as well as EDX measurements. The crystal structure was refined on the basis of single crystal data. The new phase, which represents a new structure type containing trans zigzag B{sub 4} fragments as well as isolated boron atoms crystallizes in the orthorhombic space group Pbam (Nr. 55) with the lattice parameters a=8.620(1) A, b=14.995(2) A and c=3.234(1) A. First-principles density functional theory calculations using the Vienna ab-initio simulation package (VASP) were performed on an appropriate structural model (using a supercell approach) and the experimental crystallographic data could be reproduced accurately. Based on this model, the density of states and crystal orbital Hamilton population (for bonding analysis) were calculated, using the linear muffin-tin orbital atomic sphere approximation (LMTO-ASA) method. According to these calculations, this metal-rich compound should be metallic, as expected. Furthermore, very strong boron-boron interactions are observed in the trans zigzag B{sub 4} fragment, which induce a clear differentiation of two types of metal-boron contacts with different strength. The observed three-dimensional metal-metal interaction is in good agreement with the predicted metallic behavior. - graphical abstract: The structure of Ti{sub 1.68(2)}Rh{sub 2.38(6)}Ir{sub 1.94(4)} B{sub 3}, a new structure type containing planar trans zigzag B{sub 4} units, is another example which illustrates the tendency of metal-rich borides to form B-B bonds with increasing boron content. Beside the B{sub 4} fragment it exhibits one-dimensional chains of titanium atoms and hold one-dimensional strings of face-sharing empty tetrahedral and square pyramidal clusters (see figure). Highlights

  2. Synthesis and thermal expansion study of (Th1-xGdx)O2-y

    International Nuclear Information System (INIS)

    Keskar, Meera; Sali, S.K.; Dahale, N.D.; Krishnan, K.; Kannan, S.

    2012-01-01

    Thermal expansion of (Th 1-x Gd x )O 2-y (x = 0, 0.15, 0.3, 0.86 and 1) was studied using high temperature X-ray diffraction (HTXRD) technique. Synthesis of the solid solutions was carried out by gel combustion method using citric acid as fuel

  3. Effect of Ca2+ Ions on Electrical Properties of Ba1-x Ca x Ti0.90Sn0.10O3-0.05Y2O3 Ceramics

    Science.gov (United States)

    Chen, Zhi-hui; Li, Zhi-wei; Ding, Jian-ning; Zhao, Tian-xiang; Qiu, Jian-hua; Zhu, Ke-qian; Xu, Jiu-jun; Zhang, Bing

    2018-03-01

    Ba1-x Ca x Ti0.90Sn0.10O3-0.05Y2O3 (BCTSY) lead-free piezoceramics with x = 0.02 to 0.10 have been fabricated by solid-state sintering method at 1420°C. The effects of Ca2+ ions on the microstructure and electrical properties of the samples were studied. X-ray diffraction analysis showed that all samples possessed pure perovskite structure with Ca2+ ions diffused into the matrix lattice. The rhombohedral phase and tetragonal phase coexisted in the composition range of 0.02 ceramic became more homogeneous with addition of Ca2+ ions, and the average grain size of the samples decreased from 97 μm (x = 0.02) to 18 μm (x = 0.10). Addition of Ca2+ remarkably improved the piezoelectric properties, enhanced the dielectric frequency dispersion, and increased the Curie temperature of the ceramics. The piezoelectric properties of the ceramics were optimized at x = 0.04 with d 33 and K p values of 579 pC/N and 52.7%, respectively.

  4. Syntheses of optically efficient (La{sub 1-x-y}Ce{sub x}Tb{sub y})F{sub 3} nanocrystals via a hydrothermal method

    Energy Technology Data Exchange (ETDEWEB)

    Wang Qiang [Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, NJ 08544 (United States); You Yumin; Ludescher, Richard D. [Department of Food Science, Rutgers University, New Brunswick, NJ 08901 (United States); Ju Yiguang, E-mail: yju@princeton.ed [Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, NJ 08544 (United States)

    2010-06-15

    Optically efficient cerium and terbium doped lanthanide fluoride (La{sub 1-x-y}Ce{sub x}Tb{sub y})F{sub 3} nanocrystals with different doping concentrations have been synthesized by a hydrothermal route in the presence of ethylenediamine tetraacetic acid disodium salt (EDTA). The results showed that the formation of nanocrystals with different morphologies depends on terbium ion Tb{sup 3+} doping concentration, but independent of cerium ion Ce{sup 3+} doping concentration. With increase in Tb{sup 3+} doping concentration, the morphologies of nanocrystals evolved from a spherical shape to a plated-like one. In addition, both the photoluminescence quantum yield (PL QY) and the fluorescence lifetime of nanocrystals increased with the increase in Ce{sup 3+} doping concentration in cerium and terbium co-doped system. The PL QY reached up to 55%, and the lifetime up to 7.3 ms. Transmission electron microscopy (TEM), X-ray diffraction (XRD), selected area electron diffraction (SAED), X-ray fluorescence (XRF), energy dispersive spectroscopy (EDS), ultraviolet-visible (UV-vis) absorption, photoluminescence (PL) and infrared (IR) spectroscopies were employed to characterize the properties of nanocrystals. The growth mechanism of nanocrystals with different morphologies and optical properties of nanocrystals with different doping concentrations were investigated.

  5. Improved thermal stability and hole mobilities in a strained-Si/strained-Si1-yGe y/strained-Si heterostructure grown on a relaxed Si1-xGe x buffer

    International Nuclear Information System (INIS)

    Gupta, Saurabh; Lee, Minjoo L.; Isaacson, David M.; Fitzgerald, Eugene A.

    2005-01-01

    A dual channel heterostructure consisting of strained-Si/strained-Si 1-y Ge y on relaxed Si 1-x Ge x (y > x), provides a platform for fabricating metal-oxide-semiconductor field-effect transistors (MOSFETs) with high hole mobilities (μ eff ) which depend directly on Ge concentration and strain in the strained-Si 1-y Ge y layer. Ge out-diffuses from the strained-Si 1-y Ge y layer into relaxed Si 1-x Ge x during high temperature processing, reducing peak Ge concentration and strain in the strained-Si 1-y Ge y layer and degrades hole μ eff in these dual channel heterostructures. A heterostructure consisting of strained-Si/strained-Si 1-y Ge y /strained-Si, referred to as a trilayer heterostructure, grown on relaxed Si 1-x Ge x has much reduced Ge out-flux from the strained-Si 1-y Ge y layer and retains higher μ eff after thermal processing. Improved hole μ eff over similar dual channel heterostructures is also observed in this heterostructure. This could be a result of preventing the hole wavefunction tunneling into the low μ eff relaxed Si 1-x Ge x layer due to the additional valence band offset provided by the underlying strained-Si layer. A diffusion coefficient has been formulated and implemented in a finite difference scheme for predicting the thermal budget of the strained SiGe heterostructures. It shows that the trilayer heterostructures have superior thermal budgets at higher Ge concentrations. Ring-shaped MOSFETs were fabricated on both platforms and subjected to various processing temperatures in order to compare the extent of μ eff reduction with thermal budget. Hole μ eff enhancements are retained to a much higher extent in a trilayer heterostructure after high temperature processing as compared to a dual channel heterostructure. The improved thermal stability and hole μ eff of a trilayer heterostructure makes it an ideal platform for fabricating high μ eff MOSFETs that can be processed over higher temperatures without significant losses in hole

  6. The (p, ρ, T, x) properties for {x propane + (1 - x) isobutane} with x = (1.0000, 0.2765, 0.5052, and 0.7468) in the temperature range from (280 to 440) K at pressures from (1 to 200) MPa

    International Nuclear Information System (INIS)

    Miyamoto, H.; Shigetoyo, K.; Uematsu, M.

    2007-01-01

    The (p, ρ, T, x) properties for {x propane + (1 - x) isobutane} with x = (1.0000, 0.2765, 0.5052, and 0.7468) in the compressed liquid phase were measured by means of a metal-bellows variable volumometer in the temperature range from (280 to 440) K at pressures from (1 to 200) MPa. The mole fraction purities of the propane and isobutane used in the measurements were 0.9999 and 0.9999, respectively. The expanded uncertainties (k = 2) in temperature, pressure, density, and composition measurements have been estimated to be less than ±3 mK; 1.4 kPa (p ≤ 7 MPa), 0.06% (7 MPa 150 MPa); 0.09%; and 1.3 . 10 -4 , respectively. In the region above 100 MPa at T (280 and 440) K, the uncertainty in density measurements increases from 0.09% to 0.13% and 0.22%, respectively. Comparisons of the available equation of state with the present measurements are reported. On the basis of the present results, the excess molar volume V m E of the mixtures was calculated and illustrated as a function of temperature and pressure

  7. Improved current transport properties of post annealed Y1Ba2Cu3O7-x thin films using Ag doping

    DEFF Research Database (Denmark)

    Clausen, Thomas; Skov, Johannes; Jacobsen, Claus Schelde

    1996-01-01

    The influence of Ag doping on the transport properties of Y1Ba2Cu3O7–x thin films prepared by Y, BaF2, and Cu co-evaporation and optimized ex situ post annealing has been investigated. Both undoped and Ag doped films have values of Tc above 90 K, but Jc (77 K) is highly dependent on the nominal...... thickness (tnom) of the as-deposited film. For undoped films with tnom>106 A/cm2) decreases monotonically with increasing film thickness. Above 300 nm Jc (77 K) decreases rapidly to values below 5×105 A/cm2. Ag doped films with tnom>=200 nm have higher Jc (77 K) values than those of undoped films. Ag doped...... films have a maximum in Jc (77 K) around 250 nm. As for the undoped films, there is a large decrease in Jc (77 K) for Ag doped films with tnom>=300 nm. It was found that the higher values of Jc (77 K) for the Ag doped films were due to a better epitaxial growth of the YBCO compound. The low values of Jc...

  8. Structural properties of CaTi{sub 1-x}(Nb{sub 2/3}Li{sub 2/3}){sub x}O{sub 3-d}elta (CNLTO) and CaTi{sub 1-x}(Nb{sub 1/2}Ln{sub 1/2}){sub x}O{sub 3} (Ln=Fe (CNFTO), Bi (CNBTO)), modified dielectric ceramics for microwave applications

    Energy Technology Data Exchange (ETDEWEB)

    Costa, R.C.S. [Laboratorio de Telecomunicacoes e Ciencia e Engenharia dos Materiais (LOCEM), Departamento de Fisica, Universidade Federal do Ceara, Caixa Postal 6030, CEP 60455-760, Fortaleza, Ceara (Brazil); Departamento de Engenharia de Teleinformatica, CP 6007, Universidade Federal do Ceara, CEP 60455-760, Fortaleza, Ceara (Brazil); Bruno Costa, A.D.S. [Departamento de Engenharia de Teleinformatica, CP 6007, Universidade Federal do Ceara, CEP 60455-760, Fortaleza, Ceara (Brazil); Freire, F.N.A.; Santos, M.R.P.; Almeida, J.S.; Sohn, R.S.T.M. [Laboratorio de Telecomunicacoes e Ciencia e Engenharia dos Materiais (LOCEM), Departamento de Fisica, Universidade Federal do Ceara, Caixa Postal 6030, CEP 60455-760, Fortaleza, Ceara (Brazil); Sasaki, J.M. [Laboratorio de Raios-X, Departamento de Fisica, Universidade Federal do Ceara, Caixa Postal 6030, CEP 60455-760, Fortaleza, Ceara (Brazil); Sombra, A.S.B., E-mail: sombra@fisica.ufc.b [Laboratorio de Telecomunicacoes e Ciencia e Engenharia dos Materiais (LOCEM), Departamento de Fisica, Universidade Federal do Ceara, Caixa Postal 6030, CEP 60455-760, Fortaleza, Ceara (Brazil)

    2009-05-01

    This paper presents an investigation of the structural characteristics of Nb{sub 1/2}Bi{sub 1/2} (CNBTO), Nb{sub 1/2}Fe{sub 1/2} (CNFTO) and Nb{sub 2/3}Li{sub 1/3} (CNLTO) substitution into the B-site of calcium titanate ceramics. The modified CaTiO{sub 3} (CTO) ceramics were prepared by the conventional solid-state method. The compounds were investigated, by X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDXS). The X-ray analysis shows that all samples have an orthorhombic structure. The refinement analysis of all samples were also performed and discussed in this paper. For all studied samples, a Raman mode at 805 cm{sup -1} was detected and its intensity increases as the substitution increases. The dielectric permittivity and loss at microwave frequencies (MW) were investigated. The CNLTO phase, present the highest dielectric constant (k=35.8) at 3.9 GHz with loss (tg alpha=7x10{sup -3}). The lowest value of k=25.7 (f=4.8 GHz) and tg alpha=3x10{sup -3}, was obtained for the CNFTO phase. These measurements confirm the possible use of such material for microwave devices like dielectric resonator antennas.

  9. Nitrogen lattice location in MOVPE grown Ga1-xInxNyAs1-y films using ion beam channeling

    International Nuclear Information System (INIS)

    Nebiki, Takuya; Narusawa, Tadashi; Kumagai, Akiko; Doi, Hideyuki; Saito, Tadashi; Takagishi, Shigenori

    2006-01-01

    We have investigated the nitrogen lattice location in MOVPE grown Ga 1-x In x N y As 1-y with x=0.07 and y=0.025 by means of ion beam channeling technique. In this system, the lattice constant of the Ga 1-x In x N y As 1-y film is equal to GaAs lattice. Therefore, we can grow apparently no strain, high quality and very thick GaInNAs film on GaAs substrate. The quality of the films as well as the lattice location of In and N were characterized by channeling Rutherford backscattering spectrometry and nuclear reaction analysis using 3.95 MeV He 2+ beam. The fraction of substitutional nitrogen in the film was measured using the 14 N(α,p) 17 O endothermic nuclear reaction. Our results indicate that more than 90% of In and N atoms are located the substitutional site, however, N atoms are slightly displaced by ∼0.2 A from the lattice site. We suggest that the GaInNAs film has a local strain or point defects around the N atoms. (author)

  10. Hyperfine fields at 89Y nuclei in Y(Fesub(1-x)Tsub(x))2 (T=V, Mn, Co, Ni, Al) with low concentrations x

    International Nuclear Information System (INIS)

    Ichinose, Kazuyoshi; Yoshie, Hiroshi; Nagai, Hiroyuki; Tsujimura, Akira; Fujiwara, Katsuyuki.

    1983-01-01

    NMR of 89 Y nuclei in Y(Fesub(1-x)Tsub(x)) 2 (T=V, Mn, Co, Ni, Al) has been observed at 4.2K. Well-resolved satellite structures of Y resonance appear in these compounds. This shows that the Y hyperfine field is mainly due to the magnetic nearest neighbor atoms. The magnetic moment of T atoms is estimated by two methods: (i) the contribution of T atoms to the hyperfine field is proportional to the magnetic moments of Fe and T atoms and (ii) the well known empirical relation between the hyperfine field and the mean magnetic moment of alloys is used. These results are in good agreement with those in dilute T-Fe alloys except for T=Mn. The intensity ratio of satellite peaks is discussed based upon a statistical distribution of Fe and T atoms. (author)

  11. {sup 57}Fe Mössbauer spectroscopic studies of single-crystalline K{sub x}Fe{sub 2-y}S{sub 2} and K{sub x}Fe{sub 2-y}Se{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Tsuchiya, Yuu, E-mail: tsuchiya.yuu1990@gmail.com; Ikeda, Shugo; Kobayashi, Hisao [University of Hyogo (Japan)

    2016-12-15

    We have investigated the physical properties of single-crystalline K{sub x}Fe{sub 2-y}S{sub 2} and K{sub x}Fe{sub 2-y}Se{sub 2} samples using {sup 57}Fe Mössbauer spectroscopy. The observed {sup 57}Fe Mössbauer spectra were reconstructed using a major antiferromagnetic ordered K{sub 2}Fe{sub 4}Se{sub 5} phase and a minor paramagnetic phase down to 5 K, despite being superconducting below 32.2 K in K{sub x}Fe{sub 2-y}Se{sub 2}. The analysis of {sup 57}Fe Mössbauer spectrum for K{sub x}Fe{sub 2-y}S{sub 2} at 290 K confirms the presence of a major antiferromagnetic ordered K{sub 2}Fe{sub 4}S{sub 5} phase and a minor paramagnetic phase in the K{sub x}Fe{sub 2-y}S{sub 2} single crystal. The derived hyperfine interaction parameters of the paramagnetic phase in K{sub x}Fe{sub 2-y}S{sub 2} suggest that the microstructure of this phase in K{sub x}Fe{sub 2-y}S{sub 2} is similar to that of the superconducting phase in K{sub x}Fe{sub 2-y}Se{sub 2} although the K{sub x}Fe{sub 2-y}S{sub 2} single crystals exhibit no superconductivity down to 5 K.

  12. Electrical conductivity and thermo-EMF of cobaltite gallates LaCo_1_-_xGa_xO_3

    International Nuclear Information System (INIS)

    Lubinskij, N.N.; Shevchenko, S.V.; Bashkirov, L.A.; Petrov, G.S.; Slonskaya, S.V.

    2015-01-01

    It has been found that in LaCo_1_-_xGa_xO_3 system increase of the substitution degree x from 0 to 0,95 leads to the gradual electrical conductivity (σ) decrease. Within 300-1050 K temperature range for samples LaCo_1_-_xGa_xO_3 with x≤0,5 there are three linear parts on the curve lnσ - T"-"1, where electrical conductivity activation energies have been calculated for the low, intermediate and high temperature ranges. Electrical conductivity activation energy (E_A) for samples at different temperatures has been also estimated using derivatives d(lnσ)/d(T"-"1). The E_A temperature dependence for LaCo_1_-_xGa_xO_3 at 0≤x≤0,5 passes through a maximum that indicates the temperature for beginning of semiconductor-metal phase transition (T_E__A___m___a___x). It has been shown that the thermo-EMF coefficient (S) for LaCo_1_-_xGa_xO_3 (0,1≤x≤0,3) at room temperature is negative, increasing with temperature rising, going through zero at 435-530 K, reaching the maximum at 500-650 K and then dropping down. It has been established that the temperatures corresponding to the maximum S and E_A values are identical. (authors)

  13. Mechanosynthesis of nanocrystalline CaTi1-xMnxO3

    Directory of Open Access Journals (Sweden)

    Figueiredo, F. M.

    2008-08-01

    Full Text Available The mechanosynthesis of nanocrystalline CaTi1-xMnxO3-δ is reported for the first time. Powdered CaO, TiO2 anatase and Mn2O3 (Aldrich were weighed in the appropriate stoichiometric quantities in order to obtain CaTi1-xMnxO3-δ (x=0.05, 0.10, 0.15, 0.20, 0.30, 0.50 and 0.80 and dry milled in a planetary high-energy ball mill, using zirconia containers and balls, with a 10:1 ball/mass ratio. The planetary rotation was kept constant at 650 rpm and the container at 1300 rpm, in the opposite direction. Powder XRD patterns revealed a perovskite forming from the early milling stages and a completed reaction after 180 min, with no apparent crystalline or amorphous intermediates, indicating significant Mn solubility in CaTiO3. Patterns show a decrease in lattice volume upon Mn substitution, as expected from the lower Mn3+ or Mn4+ ionic radii when compared to Ti4+. The average crystallite size is in the range 5-30 nm, as determined from Williamson-Hall plots and confirmed by high resolution transmission electron microscopy.La mecanosíntesis de CaTi1-xMnxO3-δ nanocristalino es presentada por primera vez. Polvos reactivos de CaO, TiO2 anatasa y Mn2O3 (Aldrich fueron pesados en las cantidades estequiométricas adecuadas para obtener CaTi1-xMnxO3-δ (x=0.05, 0.10, 0.15, 0.20, 0.30, 0.50 y 0.80 por molienda en seco en un molino planetario de alta energía utilizando contenedores y bolas de circona, en una relación masa de bolas : masa de polvo de 10:1. La rotación del planetario se mantuvo constante a 650 revoluciones por minuto (rpm y la del contenedor a 1300 rpm, en el sentido inverso. La formación de una fase con estructura de perovskita fue identificada a través del análisis de los polvos por difracción de rayos X, siendo esta fase claramente mayoritaria en los polvo molidos durante 180 min y sin observarse la formación de compuestos intermediarios. Los patrones de difracción de rayos X también indicaron una disminución de los parámetro de red

  14. Irreversibility Curve on Y1xLuxBa2Cu3O7–δ (x=0.4, 0.5 and 0.6) superconducting

    International Nuclear Information System (INIS)

    Grimaldos, J F Cepeda; Supelano G, I; Santos, A Sarmiento; Chiquillo, M V; Martínez B, D; Vargas, C A Parra

    2014-01-01

    The irreversibility line in the H–T plane divides the irreversible and reversible behaviour of the magnetization which is of importance for the characterization of high T c superconductors. In this work, we report the production of Y 1X Lu X Ba 2 Cu 3 O 7–δ (X=0.4, 0.5 and 0.6) superconducting system using the usual solid state reaction method. The irreversibility line H–T plane for the Y 1X Lu X Ba 2 Cu 3 O 7–δ polycrystalline sample was investigated. The curves of magnetization ZFC (cero field cooled)- FC (field cooled) were measured in magnetic fields between 100 Oe and 4000 Oe, and allowed to obtain the values for irreversibility and critical temperatures

  15. Pressure effect on thermopower of Y1-xGdxCo2 alloy system

    International Nuclear Information System (INIS)

    Nakama, T.; Takaesu, Y.; Uchima, K.; Yagasaki, K.; Hedo, M.; Uwatoko, Y.; Burkov, A.T.

    2007-01-01

    Thermopower of Y 1-x Gd x Co 2 pseudobinary compounds has been measured at temperatures from 1.5 to 300K under hydrostatic pressure up to 2GPa and in magnetic field 0-15T. In the inhomogeneous and paramagnetic regions of the phase diagram the main contribution to the electronic transport is related to the strong static magnetic fluctuations, which arise due to interplay of structural disorder within Gd-sublattice and Co-3d itinerant electron metamagnetism. This complex magnetic disorder brings about novel transport phenomena, such as anomalous positive magnetoresistance found in ferrimagnetic state of the alloys. The low-temperature thermopower is almost independent of alloy composition in the ferrimagnetic range of the phase diagram (x>0.3) indicating that the alloying does not change electronic structure of the compounds in a close vicinity of Fermi energy. However, the thermopower shows substantial variation with the composition in the inhomogeneous and in the paramagnetic regions of the phase diagram reflecting evolution of the magnetic structure with the composition

  16. Interacciones hiperfinas en BaxSr1-xHfO3

    Directory of Open Access Journals (Sweden)

    López García, A.

    1999-10-01

    Full Text Available In order to determine the microscopic role of cation A in ABO3 perovskites the hyperfine interaction in the Sr1-xBaxHfO3 system using Perturbed Angular Correlation spectroscopy (PAC is studied. As a previous result the compositions x = 0.50 and 0.25 are shown. The PAC spectra were obtained in the temperature range from 20 to 1000ºC. In both compounds a phase transition to higher symmetry structure was observed at T≈400 and 200ºC, respectively. This structure is proposed to be cubic in both compositions. The results are compared with those obtained in SrHfO3 and BaHfO3.Con el fin de determinar el papel microscópico que juega el catión A en las perovskitas ABO3 se estudia la interacción hiperfina el sistema Sr1-xBaxHfO3 usando la espectroscopia Correlaciones Angulares Perturbadas (PAC en función de la temperatura y la composición. Como resultado previo se muestra en este trabajo, el estudio de las composiciones x = 0.5 y 0.75. Las medidas PAC se realizaron en el intervalo de temperaturas que va desde 20 a 1000ºC. Para x=0.50 y 0.75 se determinó una transición a una fase de mayor simetría a T≈400 y 200ºC, respectivamente. Se propone que esta fase de mayor simetría es cúbica en ambas composiciones. Los resultados obtenidos son comparados con los compuestos puros SrHfO3 y BaHfO3.

  17. Manifestation of vortex depinning transition in nonlinear current-voltage characteristics of polycrystalline superconductor Y1-xPrxBa2Cu3O7-δ

    International Nuclear Information System (INIS)

    Rivera, V.A.G.; Stari, C.; Sergeenkov, S.; Marega, E.; Araujo-Moreira, F.M.

    2008-01-01

    We present our recent results on the temperature dependence of current-voltage characteristics for polycrystalline Y 1-x Pr x Ba 2 Cu 3 O 7-δ superconductors with x=0.0, 0.1 and 0.3. The experimental results are found to be reasonably well fitted for all samples by a power like law of the form V=R(I-I c ) a(T) . Here, we assume that a(T)=1+Φ 0 I C (T)/2πk B T and I C (T)=I C (0)(1-T/T C ) 3/2 for the temperature dependences of the power exponent and critical current, respectively. According to the theoretical interpretation of the obtained results, nonlinear deviation of our current-voltage characteristics curves from Ohmic behavior (with a(T C )=1) below T C is attributed to the manifestation of dissipation processes. They have a characteristic temperature T p defined via the power exponent as a(T p )=2 and are related to the current induced depinning of Abrikosov vortices. Both T C (x) and T p (x) are found to decrease with an increase of Pr concentration x reflecting deterioration of the superconducting properties of the doped samples

  18. Thermochemistry of 1,1,3,3-tetramethylguanidine and 1,1,3,3-tetramethylguanidinium nitrate

    International Nuclear Information System (INIS)

    Vitorino, Joana; Agapito, Filipe; Piedade, M. Fátima M.; Bernardes, Carlos E.S.; Diogo, Hermínio P.; Leal, João P.

    2014-01-01

    Graphical abstract: - Highlights: • The enthalpy of formation of 1,1,3,3-tetramethylguanidinium nitrate was determined by combustion calorimetry. • The cohesive energy of liquid 1,1,3,3-tetramethylguanidinium nitrate was evaluated. • The crystal structure of 1,1,3,3-tetramethylguanidinium nitrate was determined by single crystal X-ray diffraction. • Δ f H m o (l/g) of 1,1,3,3-tetramethylguanidine (tmg) were obtained by solution and Calvet calorimetry. • Δ f H m o (g) calculated by the W1-F12 procedure was in excellent agreement with the corresponding experimental value. - Abstract: Considerable efforts have recently been made to investigate how the structure of protic ionic liquids determines some of their most important properties for technological applications (e.g. low vapour pressure, conductivity). In contrast, the assessment of cohesive energies (which are also linked to those properties) based on thermodynamic results is still practically unexplored. This problem is addressed here for 1,1,3,3-tetramethylguanidinium nitrate, [Htmg][NO 3 ], through a combination of experimental and computational chemistry results at the reference temperature of 298.15 K. The standard molar enthalpies of formation, Δ f H m o ([Htmg][NO 3 ],cr)=-(311.8±2.3)kJ·mol -1 , and fusion, Δ fus H m o ([Htmg][NO 3 ])=16.2±3.8kJ·mol -1 , of solid 1,1,3,3-tetramethylguanidinium nitrate (form I polymorph) were obtained by combustion and differential scanning calorimetry, respectively. From these results Δ f H m o ([Htmg][NO 3 ],l)=-(295.6±4.4)kJ·mol -1 could be derived. Also determined were the standard molar enthalpies of formation, Δ f H m o (tmg, l)=7.7±2.8kJ·mol -1 , and vaporisation, Δ vap H m o (tmg,l)=50.0±1.2kJ·mol -1 , of 1,1,3,3-tetramethylguanidine, by reaction solution and Calvet-drop microcalorimetry, respectively, leading to Δ f H m o (tmg,g)=57.7±3.0kJ·mol -1 . This result is in excellent agreement with Δ f H m o (tmg,g)=58.4±4.0kJ·mol -1

  19. Structural complexity and thermoelectric properties of quaternary and quinary tellurides (Ge{sub x}Sn{sub 1-x}){sub 0.8}(In{sub y}Sb{sub 1-y}){sub 0.13}Te with 0 ≤ x,y1

    Energy Technology Data Exchange (ETDEWEB)

    Neudert, Lukas; Scheel, Manuel [Department Chemie, Ludwig-Maximilians-Universitaet Muenchen (Germany); Schwarzmueller, Stefan; Welzmiller, Simon; Oeckler, Oliver [Institut fuer Mineralogie, Kristallographie und Materialwissenschaft, Fakultaet fuer Chemie und Mineralogie, Universitaet Leipzig (Germany)

    2017-12-13

    Starting from stoichiometric mixtures of the elements, quaternary and quinary solid solutions (Ge{sub x}Sn{sub 1-x}){sub 0.8}(In{sub y}Sb{sub 1-y}){sub 0.13}Te were obtained. Concerning the ratio Ge/Sn and Sb/In, respectively, lattice parameters of the metastable phases with rocksalt-type average structures approximately obey Vegard's law. Stable phases correspond to a disordered rocksalt type at high temperature and to trigonal layered structures with van der Waal gaps at lower temperature as shown by temperature-dependent powder X-ray diffraction combined with TEM, which reveals layer-like vacancy ordering, whose extent depends on composition and thermal treatment. In the long-periodically ordered model compounds 21R-Ge{sub 0.5}Sn{sub 0.5}InSbTe{sub 4} and 9P-GeSnInSbTe{sub 5} studied by resonant scattering data at K-absorption edges, Sb and Sn concentrate near the van der Waals gaps. Compared to Ge{sub 0.8}Sb{sub 0.13}Te and Sn{sub 0.8}Sb{sub 0.13}Te, the simultaneous presence of In and Sn combines increased electrical conductivity with low thermal conductivity and enhanced thermoelectric properties in certain temperature ranges. Phase transitions correlate with changes of the thermoelectric properties. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  20. Effect of layer composition on band spectrum of CdxHg1-xTe - CdyHg1-yTe-type superlattices

    International Nuclear Information System (INIS)

    Gerchikov, L.G.; Subashiev, A.V.; Salman Dalla

    1993-01-01

    Evolution of energy spectrum of Cd x Hg 1-x Te -Cd y Hg 1-y Te superlattices at variation of layer composition is considered. Transition from 3 type superlattice to 1 type superlattice occurring for y=0.16 is studied comprehensively. In this case, dependence of the width of superlattice forbidden zone on layer thickness is shown to become more smooth, than in CdTe - HgTe superlattice and it gives more possibilities to use such superlattices for making IR phototransistors. 10 refs., 4 figs

  1. Electronic property and structure of double-doping Y1-2xPrxCaxBa2Cu3O7-δ with 0 ≤ x ≤ 0.14

    International Nuclear Information System (INIS)

    Wang Yang; Shi Lei; Chu Songnan

    2010-01-01

    Equal amount Pr and Ca double-doping Y 1-2x Pr x Ca x Ba 2 Cu 3 O 7-δ with 0 ≤ x ≤ 0.14 have been investigated by X-ray diffraction, resistivity, and X-ray photoemission spectroscopy (XPS). The deviation of the linearly decreasing of T c vs. x curve was observed when x 1-2x Pr x Ca x Ba 2 Cu 3 O 7-δ with low Pr content (x 0.10), which suggests a change of Pr valence with the Pr content. XPS measurement shows that the relative amount of Pr 3+ and Pr 4+ is closely related to the total Pr content x. The valence of Pr is close to +3 when x 0.10, which implies a different mechanism for depression of superconductivity of Pr content x 0.10 in Pr doping Y-123.

  2. Magnetic properties of (Mn1-xRux)3Ga alloys

    International Nuclear Information System (INIS)

    Hori, T.; Akimitsu, M.; Miki, H.; Ohoyoama, K.; Yamaguchi, Y.

    2002-01-01

    We found that the pseudo binary alloys Mn 1-x Ru x 3 Ga, with 0.33≤x≤0.67, have an ordered b.c.c. structure. The lattice constant a is almost constant with respect to x: a=6.000 A for x=0.33 and a=5.992 A for x=0.67. For the alloy with x=0.33, i.e. Mn 2 RuGa, the magnetization is almost saturated in a field of 20 kOe. The saturation magnetization at 4.2 K is 23 emu/g, and the Curie temperature, T C , is 460 K. The T C of (Mn 1-x Ru x ) 3 Ga decreases almost linearly with increasing x, and it vanishes around x=0.67 (MnRu 2 Ga). We also determined atomic and magnetic structures from neutron diffraction experiments. The alloy Mn 2 RuGa (x=0.33) has an ordered structure of CuHg 2 Ti type; the magnetic Mn atoms mainly occupy the 4a (0,0,0) and 4d (3/4,3/4,3/4) sites. We also observed that the magnetic moments of Mn atoms on the 4a and 4d sites are antiparallel to each other; values of the magnetic moment are μ a =4.6 and μ d =3.3 μ B per Mn atom. (orig.)

  3. Millimeter wave surface resistance of grain-aligned Y1Ba2Cu3O(x) bulk material

    International Nuclear Information System (INIS)

    Wosik, J.; Kranenburg, R.A.; Wolfe, J.C.; Selvamanickam, V.; Salama, K.

    1990-04-01

    Measurements are reported of the millimeter-wave surface resistance of grain-aligned YBa2Cu3O(x) bulk material grown by a liquid-phase process. The measurements were performed by replacing the endplate of a TE(011) cylindrical copper cavity with the superconducting sample. Surface resistance was measured for samples with surfaces oriented perpendicular and parallel to the c-axis of the grains. For the parallel configuration, the surface resistance at 77 K and 80 GHz is given. For a very well-aligned sample with a very low density of Y2BaCuO(y) precipitates, measured in the perpendicular configuration, the transition width (10-90 percent) is about 2 K and the surface resistance is derived at 88 K. The effect of microstructure on surface resistance is discussed. 19 refs

  4. Ammonium dynamics in the disordered α-phase of K1-x(NH4)xY (Y = Cl, Br, I). A neutron scattering study

    International Nuclear Information System (INIS)

    Natkaniec, I.; Smirnov, L.S.; Shuvalov, L.A.

    2002-01-01

    The effect of temperature and concentration on the lattice parameters and amplitude-weighted phonon density of states in mixed salts of ammonium-potassium halides is investigated by neutron powder diffraction and incoherent inelastic neutron scattering. In the disordered α-phase (NaCl type) ammonium ions exhibit a fast stochastic reorientation at phonon frequency rates down to ca. 80 K. At 10 K, the incoherent inelastic neutron scattering spectra display four distinct ammonium excitations: two (resonant) modes below and two (localized) above the Debye cut-off energy of potassium halides. High-frequency localized modes correspond to translational and librational vibrations of NH 4 ions. These modes are typical for the ordered phases of ammonium halides. The effect of ammonium concentration on localized and resonant modes is studied for the K 1-x (NH 4 ) x I mixed salts. The harmonic excitations of ammonium in a hypothetical low-temperature α-phase of NH 4 I are approximated to ca. 30, 95, 155 and 250 cm -1 . In a real low-temperature ordered γ-phase of NH 4 I, translational ammonium vibrations are observed at ca. 140-160 cm -1 and librational vibrations at ca.300 cm -1

  5. Thermoelectric and Transport Properties of N-Type Bi{sub 2−x}Sb{sub x}Te{sub 3y}Se{sub y} Solid Solutions

    Energy Technology Data Exchange (ETDEWEB)

    Eum, A-Young; Kim, Il-Ho [Korea National University of Transportation, Chungju (Korea, Republic of)

    2017-03-15

    Bi{sub 2−x}Sb{sub x}Te{sub 3y}Se{sub y} (x = 0.1, 0.2 and y = 0.15, 0.3) solid solutions were prepared using encapsulated melting and hot pressing. The lattice constants decreased with increases in the Sb and the Se contents, which revealed the successful formation of solid solutions. The relative densities of the hot-pressed specimens were 95 - 98%. All specimens exhibited n-type conduction at temperatures from 323 K to 523 K, and the electrical conductivity slightly decreased with increasing temperature. With an increase in the Se content, the Seebeck coefficient increased while the electrical and the thermal conductivities decreased; thus, the dimensionless figure of merit could be improved. The maximum dimensionless figure of merit ZT{sub max} = 0.89 was obtained at 423 K for Bi{sub 1.8}Sb{sub 0.2}Te{sub 2.7}Se{sub 0.3}. An increase in the Sb content resulted in a decrease in the lattice thermal conductivity because of an increase in alloy scattering, but its effect on the electrical properties was not superior to the effect of Se substitution. Therefore, Sb substitution could effectively control the thermal properties while Se substitution could effectively control the electrical properties.

  6. Pr:Ca1-xRxF2+x (R=Y or Gd) crystals: Modulated blue, orange and red emission spectra with the proportion of R3+ ions

    Science.gov (United States)

    Yu, Hao; Qian, Xiaobo; Guo, Linyang; Jiang, Dapeng; Wu, Qinghui; Tang, Fei; Su, Liangbi; Ju, Qiangwen; Wang, Jingya; Xu, Jun

    2018-04-01

    The spectroscopic properties of 0.6at.%:Pr:Ca1-xRxF2+x (R = Y, Gd; x = 0,0.006, 0.012, 0.03, 0.06) crystals were investigated and compared. The XRD tests were conducted and the cell dimensions of the crystals were calculated. Room temperature absorption spectra have been registered and analyzed. The emission spectra and decay curves of the crystals were obtained at room temperature. Increasing the proportion of the lattice regulators of Y3+ or Gd3+ ions could significantly enhance the luminescence intensity of all visible emission bands with different ratios. Particularly, the emission intensity ratio of orange to red increased from 0.15 to 1.9 in Pr:Ca1-xYxF2+x crystals and to 1.02 in Pr:Ca1-xGdxF2+x crystals, respectively. Furthermore, Pr:Ca1-xGdxF2+x crystals have substantially strong emission at orange and red region of 580-660 nm, comparable with blue light at 482 nm. The quantum efficiency of the crystals increased rapidly with the increment of R3+ concentration, and finally tend to be 100%.

  7. Two-step photoconductivity in LiY x Lu1 - x F4:Ce,Yb crystals

    Science.gov (United States)

    Nurtdinova, L. A.; Korableva, S. L.; Leontiev, A. V.

    2016-10-01

    Photoconductivity of LiY x Lu1- x F4:Ce,Yb ( x = 0-1) crystals is measured under one- and two-step excitation. It is established that the photoconductivity is due to intra-center transitions from excited states of Ce3+ ions. The position of the ground 4 f-state of Ce3+ ion relative to the bottom of the conduction band is determined. The choice of pumping conditions to obtain the lasing on the 5 d-4 f transitions of trivalent cerium in these active media is substantiated.

  8. Neuropharmacology of Purinergic Receptors in Human Submucous Plexus: Involvement of P2X1, P2X2, P2X3 Channels, P2Y and A3 Metabotropic Receptors in Neurotransmission

    Science.gov (United States)

    Liñán-Rico, A.; Wunderlich, JE.; Enneking, JT.; Tso, DR.; Grants, I.; Williams, KC.; Otey, A.; Michel, K.; Schemann, M.; Needleman, B.; Harzman, A.; Christofi, FL.

    2015-01-01

    Rationale The role of purinergic signaling in the human ENS is not well understood. We sought to further characterize the neuropharmacology of purinergic receptors in human ENS and test the hypothesis that endogenous purines are critical regulators of neurotransmission. Experimental Approach LSCM-Fluo-4-(Ca2+)-imaging of postsynaptic Ca2+ transients (PSCaTs) was used as a reporter of neural activity. Synaptic transmission was evoked by fiber tract electrical stimulation in human SMP surgical preparations. Pharmacological analysis of purinergic signaling was done in 1,556 neurons from 234 separate ganglia 107 patients; immunochemical labeling for P2XRs of neurons in ganglia from 19 patients. Real-time MSORT (Di-8-ANEPPS) imaging was used to test effects of adenosine on fast excitatory synaptic potentials (fEPSPs). Results Synaptic transmission is sensitive to pharmacological manipulations that alter accumulation of extracellular purines. Apyrase blocks PSCaTs in a majority of neurons. An ecto-NTPDase-inhibitor 6-N,N-diethyl-D-β,γ-dibromomethyleneATP or adenosine deaminase augments PSCaTs. Blockade of reuptake/deamination of eADO inhibits PSCaTs. Adenosine inhibits fEPSPs and PSCaTs (IC50=25μM), sensitive to MRS1220-antagonism (A3AR). A P2Y agonist ADPβS inhibits PSCaTs (IC50=111nM) in neurons without stimulatory ADPβS responses (EC50=960nM). ATP or a P2X1,2,2/3 (α,β-MeATP) agonist evokes fast, slow, biphasic Ca2+ transients or Ca2+ oscillations (EC50=400μM). PSCaTs are sensitive to P2X1 antagonist NF279. Low (20nM) or high (5μM) concentrations of P2X antagonist TNP-ATP block PSCaTs in different neurons; proportions of neurons with P2XR-ir follow the order P2X2>P2X1≫P2X3; P2X1+ P2X2 and P2X3+P2X2 are co-localized. RT-PCR identified mRNA-transcripts for P2X1-7,P2Y1,2,12-14R. Responsive neurons were also identified by HuC/D-ir. Conclusions Purines are critical regulators of neurotransmission in the human enteric nervous system. Purinergic signaling involves

  9. SISTEMA DE CROMOSSOMOS SEXUAIS MÚLTIPLOS X1X1X2X2/X1X2Y NA MOSCA-DAS-FRUTAS Anastrepha sororcula (DIPTERA: TEPHRITIDAE

    Directory of Open Access Journals (Sweden)

    Inês Regina de Araújo Moura Cunha

    2014-08-01

    Full Text Available Sistemas de cromossomos sexuais simples estão difundidos entre os Tephritidae do gênero Anastrepha. Espécies deste gênero apresentam enorme importância pelo impacto que causam em frutíferas cultivadas, sobretudo no nordeste do Brasil. Análises citogenéticas desenvolvidas em Anastrepha sororcula, através da análise da estrutura cariotípica e bandamento C revelaram a presença de um sistema de cromossomos sexuais múltiplos do tipo X1X1X2X2/X1X2Y nesta espécie. Enquanto as fêmeas apresentam um cariótipo homomórfico com 2n=12, os machos possuem 2n=11, onde se destaca um grande cromossomo Y despareado. O nível de divergência cariotípica da espécie A. sororcula do nordeste, com a presença de um sistema de cromossomos sexuais múltiplos, em relação às regiões central e sudeste do Brasil, podem indicar a ocorrência de impedimentos reprodutivos entre os exemplares das duas áreas e que possivelmente, como outros exemplos que existem neste gênero, A. sororcula constitua um complexo de espécies ainda não inteiramente definido. Palavras-chave: Alossomos, peste agrícola, citogenética de insetos, heterocromatina. DOI: http://dx.doi.org/10.18561/2179-5746/biotaamazonia.v4n2p1-4

  10. Formation of Y(x)Nd(1-x) Ba2Cu3O(7-delta) (0 = or Acoustic Levitation

    Science.gov (United States)

    Gustafson, D. E.; Hofmeister, W. H.; Bayuzick, R. J.

    2001-01-01

    Melt processing of RE123 superconductors has gained importance in recent years. While the first high temperature superconductors (HTSCs) were made using traditional ceramic press and sinter technology, recent fabrication efforts have employed alternate processing techniques including laser ablation and ion beam assisted deposition for thin film fabrication of tapes and wires and melt growth for bulk materials. To optimize these techniques and identify other potential processing strategies, phase relation studies on HTSCs have been conducted on a wide variety of superconducting compounds using numerous processing strategies. This data has enhanced the understanding of these complex systems and allowed more accurate modeling of phase interactions. All of this research has proved useful in identifying processing capabilities for HTSCs but has failed to achieve a breakthrough for wide spread application of these materials. This study examines the role of full to partial substitution of Nd in the Y123 structure under rapid solidification conditions. Aero-acoustic levitation (AAL) was used to levitate and undercool RE123 in pure oxygen binary alloys with RE = Nd an Y along a range of compositions corresponding to Y(x)Nd(1-x) Ba2Cu3O(7-delta) (0 = or < x < or = 0.7) which were melted by a CO2 laser. Higher Y content spheres could not be melted in the AAL and were excluded from this report. Solidification structures were examined using scanning electron microscopy, electron dispersive spectroscopy, and powder x-ray diffraction to characterize microstructures and identify phases.

  11. Core-Shell Zn x Cd1- x Se/Zn y Cd1- y Se Quantum Dots for Nonvolatile Memory and Electroluminescent Device Applications

    Science.gov (United States)

    Al-Amoody, Fuad; Suarez, Ernesto; Rodriguez, Angel; Heller, E.; Huang, Wenli; Jain, F.

    2011-08-01

    This paper presents a floating quantum dot (QD) gate nonvolatile memory device using high-energy-gap Zn y Cd1- y Se-cladded Zn x Cd1- x Se quantum dots ( y > x) with tunneling layers comprising nearly lattice-matched semiconductors (e.g., ZnS/ZnMgS) on Si channels. Also presented is the fabrication of an electroluminescent (EL) device with embedded cladded ZnCdSe quantum dots. These ZnCdSe quantum dots were embedded between indium tin oxide (ITO) on glass and a top Schottky metal electrode deposited on a thin CsF barrier. These QDs, which were nucleated in a photo-assisted microwave plasma (PMP) metalorganic chemical vapor deposition (MOCVD) reactor, were grown between the source and drain regions on a p-type silicon substrate of the nonvolatile memory device. The composition of QD cladding, which relates to the value of y in Zn y Cd1- y Se, was engineered by the intensity of ultraviolet light, which controlled the incorporation of zinc in ZnCdSe. The QD quality is comparable to those deposited by other methods. Characteristics and modeling of the II-VI quantum dots as well as two diverse types of devices are presented in this paper.

  12. Structural and electronic properties of zinc blende B{sub x}Al{sub 1-x}N{sub y}P{sub 1-y} quaternary alloys via first-principle calculations

    Energy Technology Data Exchange (ETDEWEB)

    Abdiche, A., E-mail: abdiche_a@yahoo.fr [Engineering Physics Laboratory, Tiaret University, 14000 Tiaret (Algeria); Baghdad, R. [Engineering Physics Laboratory, Tiaret University, 14000 Tiaret (Algeria); Khenata, R., E-mail: khenata_rabah@yahoo.fr [Laboratoire de Physique Quantique et de Modelisation Mathematique (LPQ3M), Departement de Technologie, Universite de Mascara, 29000 Mascara (Algeria); Department of Physics and Astronomy, King Saud University, P.O Box 2455, Riyadh 11451 (Saudi Arabia); Riane, R. [Computational Materials Science Laboratory, University Research of Sidi-Bel-Abbes, 22000 Algeria (Algeria); Al-Douri, Y. [Institute of Nono Electronic Engineering, University Malaysia Perlis, 01000 Kangar, Perlis (Malaysia); Guemou, M. [Engineering Physics Laboratory, Tiaret University, 14000 Tiaret (Algeria); Bin-Omran, S. [Department of Physics and Astronomy, King Saud University, P.O Box 2455, Riyadh 11451 (Saudi Arabia)

    2012-02-01

    The structural and electronic properties of cubic zinc blende BN, BP, AlN and AlP compounds and their B{sub x}Al{sub 1-x}N{sub y}P{sub 1-y} quaternary alloys, have been calculated using the non relativistic full-potential linearized-augmented plane wave FP-LAPW method. The exchange-correlation potential is treated with the local density approximation of Perdew and Wang (LDA-PW) as well as the generalized gradient approximation (GGA) of Perdew-Burke and Ernzerhof (GGA-PBE). The calculated structural properties of BN, BP, AlN and AlP compounds are in good agreement with the available experimental and theoretical data. A nonlinear variation of compositions x and y with the lattice constants, bulk modulus, direct and indirect band gaps is found. The calculated bowing of the fundamental band gaps is in good agreement with the available experimental and theoretical value. To our knowledge this is the first quantitative theoretical investigation on B{sub x}Al{sub 1-x}N{sub y}P{sub 1-y} quaternary alloy and still awaits experimental confirmations.

  13. Features of the core-valence luminescence and electron energy band structure of A1-xCsxCaCl3 (A = K,Rb) crystals

    International Nuclear Information System (INIS)

    Chornodolskyy, Ya; Stryganyuk, G; Syrotyuk, S; Voloshinovskii, A; Rodnyi, P

    2007-01-01

    From luminescence spectroscopy of CsCaCl 3 , Rb 1-x Cs x CaCl 3 and K 1-x Cs x CaCl 3 crystals, we have found evidence for intrinsic and impurity core-valence luminescence due to the radiative recombination of valence electrons with the holes of intrinsic or impurity 5p Cs + core states. The structural similarity of core-valence luminescence spectra has been revealed for the A 1-x Cs x CaCl 3 (A = K,Rb) crystals investigated. The electron energy structure of the CsCaCl 3 crystal has been calculated using the pseudopotential approach taking into account the gradient corrections for the exchange-correlation energy. The calculated density of the electronic states of CsCaCl 3 has been compared with corresponding parameters obtained from the analysis of core-valence luminescence spectra

  14. Neutron diffraction and magnetic study of the Nd0.7Pb0.3Mn1-xFexO3 (0=<x=<0.1) perovskites

    International Nuclear Information System (INIS)

    Blanco, J.J.; Insausti, M.; Gil de Muro, I.; Lezama, L.; Rojo, T.

    2006-01-01

    The effect of Fe doping on the ferromagnetic Nd 0.7 Pb 0.3 Mn 1-x Fe x O 3 (x=0, 0.025, 0.05, 0.075, 0.1) phases has been studied in order to analyze the double-exchange interaction. The structural and magnetic study has been carried out by neutron powder diffraction and susceptibility measurements between 1.7 and 300K. The substitution of Fe at the Mn site results in reductions in both the Curie temperature T c and the magnetic moment per Mn ion without appreciable differences in the crystal structures. All the compounds crystallize in Pnma space group. The thermal evolution of the lattice parameters of the Nd 0.7 Pb 0.3 Mn 1-x Fe x O 3 (x=0.025, 0.05, 0.075) compounds shows discontinuities in volume and lattice parameters close to the magnetic transition temperature. Increasing amounts of Fe 3+ reduces the double exchange interactions and no magnetic contribution for x=0.1 is observed. The magnetic structures of Nd 0.7 Pb 0.3 Mn 1-x Fe x O 3 (x=0, 0.025, 0.05, 0.075) compounds show that the Nd and Mn ions are ferromagnetically ordered

  15. Magnetocaloric properties of LaFe13-x-yCoxSiy and commercial grade Gd

    International Nuclear Information System (INIS)

    Bjork, R.; Bahl, C.R.H.; Katter, M.

    2010-01-01

    The magnetocaloric properties of three samples of LaFe 13-x-y Co x Si y have been measured and compared to measurements of commercial grade Gd. The samples have (x=0.86, y=1.08), (x=0.94, y=1.01) and (x=0.97, y=1.07) yielding Curie temperatures in the range 276-288 K. The magnetization, specific heat capacity and adiabatic temperature change have been measured over a broad temperature interval. Importantly, all measurements were corrected for demagnetization, allowing the data to be directly compared. In an internal field of 1 T the maximum specific entropy changes were 6.2, 5.1 and 5.0 J/kg K, the specific heat capacities were 910, 840 and 835 J/kg K and the adiabatic temperature changes were 2.3, 2.1 and 2.1 K for the three LaFeCoSi samples respectively. For Gd in an internal field of 1 T the maximum specific entropy change was 3.1 J/kg K, the specific heat capacity was 340 J/kg K and the adiabatic temperature change was 3.3 K. The adiabatic temperature change was also calculated from the measured values of the specific heat capacity and specific magnetization and compared to the directly measured values. In general an excellent agreement was seen.

  16. Metallic and semi-conducting resistivity behaviour of La0.7Ca0.3- x K x MnO3 ( x = 0.05, 0.1) manganites

    Science.gov (United States)

    Varshney, Dinesh; Dodiya, Neha

    2015-12-01

    The temperature dependence of electrical resistivity, ρ, of ceramic La0.7Ca0.3- x K x MnO3 ( x = 0.05, 0.1) is investigated in metallic and semi-conducting phase. The metallic resistivity is attributed to be caused by electron-phonon, electron-electron and electron-magnon scattering. Substitutions affect average mass and ionic radii of A-site resulting in an increase in Debye temperature θ D attributed to hardening of lattice with K doping. The optical phonon modes shift gradually to lower mode frequencies leading to phonon softening. Estimated resistivity compared with reported metallic resistivity, accordingly ρ diff. = [ ρ exp. - { ρ 0 + ρ e-ph (= ρ ac + ρ op)}], infers electron-electron and electron-magnon dependence over most of the temperature range. Semi-conducting nature is discussed with variable range hopping and small polaron conduction model. The decrease in activation energies and increase in density of states at the Fermi level with enhanced Ca doping is consistently explained by cationic disorder and Mn valence.

  17. Effect of doping of trivalent cations Ga{sup 3+}, Sc{sup 3+}, Y{sup 3+} in Li{sub 1.3}Al{sub 0.3}Ti{sub 1.7} (PO{sub 4}){sub 3} (LATP) system on Li{sup +} ion conductivity

    Energy Technology Data Exchange (ETDEWEB)

    Kothari, Dharmesh H.; Kanchan, D.K., E-mail: dkkanchan.ssi@gmail.com

    2016-11-15

    We report the effect of trivalent cations dopants in the Li{sub 1.3}Al{sub 0.3x}R{sub x}Ti{sub 1.7}(PO{sub 4}){sub 3} (R=Ga{sup 3+}, Sc{sup 3+}, Y{sup 3+}) NASICON ceramic system in the concentration range x=0.01,0.03,0.05,0.07, on the Li{sup +} ion conducting properties using impedance spectroscopy. The samples were prepared by solid state reaction method and characterized by X-Ray Diffraction and density measurements. The electrical properties were studied using impedance spectroscopy in frequency range 10 Hz to 20 MHz and temperature range 303 K to 423 K. Although the porosity of the material decreased with doping, the overall Li{sup +} ion conductivity of the system did not improve with doping. Ionic radii of the dopant cations was found to be an important factor in formation of impurity phases and low Li{sup +} ion conductivity. Gallium doped samples exhibited a higher Li{sup +} ion conductivity compared to its scandium and yttrium doped counterparts.

  18. Millimeter wave surface resistance of grain-aligned Y1Ba2Cu3O(x) bulk material

    Science.gov (United States)

    Wosik, J.; Kranenburg, R. A.; Wolfe, J. C.; Selvamanickam, V.; Salama, K.

    1991-01-01

    Measurements of the millimeter wave surface resistance of grain-aligned YBa2Cu3O(x) bulk material grown by a liquid phase process are reported. The measurements were performed by replacing the endplate of a TE011 cylindrical copper cavity with the superconducting sample. Surface resistance was measured for samples with surfaces oriented perpendicular and parallel to the c-axis of the grains. It is shown that, for the parallel configuration, the surface resistance at 77 K and 80 GHz is typically near 100 milliohms. For a very well-aligned sample with a very low density of Y2BaCuO(y) precipitates, measured in the perpendicular configuration, the transition width (10-90 percent) is about 2 K, and the surface resistance is less than 50 milliohms at 88 K. The effect of microstructure on surface resistance is discussed.

  19. Electroluminescence in quantum well heterostructures p-Al{sub x}Ga{sub 1-x}As/GaAs{sub 1-y}P{sub y}/n-Al{sub x}Ga{sub 1-x}As under uniaxial stress

    Energy Technology Data Exchange (ETDEWEB)

    Berman, Irina V. [Physics Department, San Jose State University, CA (United States); Bogdanov, Evgeniy V.; Minina, Natalia Ya.; Shirokov, Stanislav S.; Yunovich, Alexander E. [Physics Department, Lomonosov Moscow State University (Russian Federation); Kissel, Heiko [R and D Department, DILAS Diodenlaser GmbH, (Germany)

    2009-03-15

    We present new results on the influence of uniaxial stress up to P=4 kbar on the electroluminescence spectra and current-voltage characteristics of p-Al{sub x}Ga{sub 1-x}As/GaAs{sub 1-y}P{sub y}/n-Al{sub x}Ga{sub 1-x}As double heterostructures usually used in TM emitting 808 nm high-power diode lasers. With increasing stress, the emission spectra demonstrate a blue shift of up to 25 meV at a pressure of P=4 kbar, while the electroluminescence intensity increases under compression. The different behavior of the current-voltage characteristics under uniaxial stress along[110] and[1 anti 10] directions is mainly determined by the arising piezoelectric field. The results are also discussed in terms of changes in the band structure under uniaxial compression. The construction of the cryostat for optical measurements under uniaxial stress at liquid nitrogen temperature is described in the paper. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  20. Transformaciones de fase en aleaciones Zn-22%Al-2%Cu y Zn-22%Al-2%Cu-X (X = 1, 2 y 3%Ag envejecidas isotérmicamente

    Directory of Open Access Journals (Sweden)

    Flores-Ramos, Alfredo

    2014-12-01

    Full Text Available The study of phase transformations that take place in Zn-22%Al-2%Cu and Zn-22%Al-2%Cu-X (X = 1, 2 and 3%Ag alloys was carried out using X-Ray Diffraction (XRD and Scanning Electron Microscopy (SEM. Alloys were homogenized at 350 °C during 10 days and quenched at ~2 °C. Subsequently, samples were aged at 200 °C for different times. The initial microstructure consists in a matrix of fine equiaxial grains of α and η phases for all the alloys. Besides isolated particles of ε and Φ were observed without and with Ag addition, respectively. During the aging, the four phase reaction, α + ε→η + τ’, takes place to obtain the equilibrium η, α and τ’ phases. However, the Ag addition promotes the formation of the Φ phase, which retards or inhibits the four phase reaction. The stability of the Φ phase is obtained with 3%Ag, which could improve the dimensional stability of the alloy for future industrial applications.En el presente estudio sobre las transformaciones de fase en las aleaciones Zn-22%Al-2%Cu y Zn-22%Al-2%Cu-X (X = 1, 2 y 3%Ag se utilizó Difracción de Rayos X (DRX y Microscopía Electrónica de Barrido (MEB. Las aleaciones fueron homogeneizadas a 350 °C durante 10 días, templadas a ~2 °C y posteriormente envejecidas a 200 °C durante diferentes tiempos. Todas las aleaciones ensayadas presentaron una microestructura inicial formada por una matriz de granos finos y equiaxiales de las fases α y η. Además, para las aleaciones sin Ag se observa la presencia de partículas de la fase ε (CuZn4 y de Φ ((Ag, Cu Zn4 en las que se adicionó Ag. Durante el envejecido, ocurre la reacción de cuatro fases, α + ε→η + τ’, para obtener las fases de equilibrio η, α y τ’. Sin embargo, la adición de Ag promueve la formación de la fase Φ, la cual retarda e incluso inhibe la reacción de cuatro fases. La estabilidad de la fase Φ se obtiene con 3%Ag, lo que podría mejorar la estabilidad dimensional de la aleación para

  1. Microstructure and superconducting properties of Ca substituted Y(Ba1xCax2Cu3O7−δ ceramics prepared by thermal treatment method

    Directory of Open Access Journals (Sweden)

    Mustafa Mousa Dihom

    Full Text Available The effect of Ca substitution in Ba site of Y(Ba1xCax2Cu3O7−δ, (x = 0.00, 0.04, 0.08, 0.1 and 0.125, ceramics prepared by thermal treatment method was investigated. Surface morphology, structural and superconducting were studied using field emission electron microscope (FESEM, X-ray Diffraction (XRD and four-probe method. FESEM analysis showed an increasing of samples’ grain size, homogeneity and compactness with increasing of Ca substitution. From XRD, the samples had orthorhombic crystal structure of space group Pmmm besides small amount of unknown peaks. The critical temperature (Tc R=zero decreased from 87 K for the pure sample to 80 K for sample with x = 0.08, and it remained the same for samples with x ⩾ 0.08. Sample with x = 0.04 showed the sharpest superconducting transition (ΔTc, which could be due to good microstructure morphology and better crystallinity. Keywords: YBa2Cu3O7−δ, Ca substitution, Thermal treatment, X-ray Diffraction, Orthorhombic, Critical temperature

  2. Microwave dielectric properties and microstructure of Ba{sub 6−3x}Nd{sub 8+2x}Ti{sub 18−y}(Cr{sub 1/2}Nb{sub 1/2}){sub y}O{sub 54} ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Xia [State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Jianshe Road, Chengdu 610054 (China); Tang, Bin, E-mail: tangbin@uestc.edu.cn [State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Jianshe Road, Chengdu 610054 (China); Liu, Jiaqin [Sichuan Special Equipment Inspection Institute, Dongfeng Road, Chengdu 610061 (China); Chen, Hetuo; Zhang, Shuren [State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Jianshe Road, Chengdu 610054 (China)

    2015-10-15

    The microwave dielectric properties and the morphology of Ba{sub 6−3x}Nd{sub 8+2x}Ti{sub 18−y}(Cr{sub 1/2}Nb{sub 1/2}){sub y}O{sub 54} (x = 0.75, 0 ≤ y3.0) ceramics prepared under different sintering conditions were investigated in this work. The effects of substitutions on the microstructure and microwave dielectric properties were discussed. The X-ray diffraction (XRD) patterns of the sintered samples revealed a single-phase formation BaNd{sub 2}Ti{sub 4}O{sub 12} with a tungsten bronze type structure in the system. The results of energy dispersive spectrometer (EDS) and lattice parameters calculated on XRD data could confirm the substitution at B-site. A small amount of substitutions improved quality factor value (Q × f) and the temperature coefficient of resonant frequency (τ{sub f}) but led to a decrease of the permittivity. The temperature coefficient of resonant frequency (τ{sub f}) was found to decrease with increasing substitutions because of the declination of tolerance factor (t). And the τ{sub f} could be adjusted from +62.4 ppm/°C to −7.3 ppm/°C with increment of substitutions. Finally, excellent dielectric properties were obtained as y was 0.5 sintered at 1400 °C for 2 h in air: ε{sub r} = 88.6, Q × f = 11486 GHz, τ{sub f} = +37.1 ppm/°C. - Graphical abstract: It was evident that the tendency of the τ{sub f} was consistent with the variation of tolerance factor (t). The τ{sub f} was much affected by the titling of Ti–O octahedral that bigger ionic radius of (Cr{sub 1/2}Nb{sub 1/2}){sup 4+} substituted for Ti{sup 4+} would significantly reduce the temperature coefficient of resonant frequency. - Highlights: • (Cr{sub 1/2}Nb{sub 1/2}){sup 4+} substitution for Ti{sup 4+} would low down the τ{sub f} of the samples. • The Cr{sup 3+} substitution for Ti{sup 4+} would promote the quality factor. • (Cr{sub 1/2}Nb{sub 1/2}){sup 4+} substitution for Ti{sup 4+} makes the permittivity maintain a high value. • The high Q × f

  3. Increased transient Na+ conductance and action potential output in layer 2/3 prefrontal cortex neurons of the fmr1-/y mouse.

    Science.gov (United States)

    Routh, Brandy N; Rathour, Rahul K; Baumgardner, Michael E; Kalmbach, Brian E; Johnston, Daniel; Brager, Darrin H

    2017-07-01

    Layer 2/3 neurons of the prefrontal cortex display higher gain of somatic excitability, responding with a higher number of action potentials for a given stimulus, in fmr1 -/y mice. In fmr1 -/y L2/3 neurons, action potentials are taller, faster and narrower. Outside-out patch clamp recordings revealed that the maximum Na + conductance density is higher in fmr1 -/y L2/3 neurons. Measurements of three biophysically distinct K + currents revealed a depolarizing shift in the activation of a rapidly inactivating (A-type) K + conductance. Realistic neuronal simulations of the biophysical observations recapitulated the elevated action potential and repetitive firing phenotype. Fragile X syndrome is the most common form of inherited mental impairment and autism. The prefrontal cortex is responsible for higher order cognitive processing, and prefrontal dysfunction is believed to underlie many of the cognitive and behavioural phenotypes associated with fragile X syndrome. We recently demonstrated that somatic and dendritic excitability of layer (L) 5 pyramidal neurons in the prefrontal cortex of the fmr1 -/y mouse is significantly altered due to changes in several voltage-gated ion channels. In addition to L5 pyramidal neurons, L2/3 pyramidal neurons play an important role in prefrontal circuitry, integrating inputs from both lower brain regions and the contralateral cortex. Using whole-cell current clamp recording, we found that L2/3 pyramidal neurons in prefrontal cortex of fmr1 -/y mouse fired more action potentials for a given stimulus compared with wild-type neurons. In addition, action potentials in fmr1 -/y neurons were significantly larger, faster and narrower. Voltage clamp of outside-out patches from L2/3 neurons revealed that the transient Na + current was significantly larger in fmr1 -/y neurons. Furthermore, the activation curve of somatic A-type K + current was depolarized. Realistic conductance-based simulations revealed that these biophysical changes in Na

  4. Towards the large scale production of (La{sub 1-z}Ce{sub z})(Fe{sub 1-x-y}Mn{sub y}Si{sub x}){sub 13}H{sub n} products for room temperature refrigeration

    Energy Technology Data Exchange (ETDEWEB)

    Mayer, Charlotte; Dubrez, Alexandra; Pierronnet, Michel; Vikner, Peter [Erasteel SAS, Tour Maine Montparnasse, Paris (France)

    2014-05-15

    In this paper, we present a novel process based on gas atomization and powder metallurgy techniques to produce reliable and stable (La{sub 1-z}Ce{sub z})(Fe{sub 1-x-y}Mn{sub y}Si{sub x}){sub 13}H{sub n} materials, with 0.08 ≤ x ≤ 0.15, 0 ≤ y ≤ 0.05, 0 ≤ z ≤ 0.3 and 1.5 ≤ n ≤ 3. With this process, shaped pieces ready-to-use into refrigeration devices can be produced. Gas atomisation is a rapid solidification technique that prevents the La-Fe-Si-type alloy from forming very large α-Fe dendrites during cooling, allowing to easily and efficiently heat treat the obtained powder to form the magnetocaloric NaZn{sub 13}-type intermetallic. In this process, a batch of 500 kg of alloy was first gas atomized into powder. The powder was then annealed at 1373 K under Ar for one hour to reach around 95% of magnetocaloric phase, and subsequently hydrogenated. Finally, the powder was shaped into composite shaped products containing 91.5 wt.% of powder, by extrusion. This process induces no loss of matter and allows producing non fragile pieces comprising thin portions. Our first results on the stability of partially hydrogenated (La,Ce)(Fe,Mn,Si){sub 13} materials are shown and we discuss on the possible existence of conditions of instability liked to both the composition of the magnetocaloric phase and the level of hydrogenation. (copyright 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  5. Photoluminescence in Pb{sub 0.95}Sr{sub 0.05}(Zr{sub 1x}Ti{sub x}){sub 1y}Cr{sub y}O{sub 3} ferroelectric ceramic system

    Energy Technology Data Exchange (ETDEWEB)

    Hernández-García, M.; Costa-Marrero, J. [Departamento de Física Aplicada, Instituto de Cibernética, Matemática y Física, 15 # 551, Vedado, Ciudad Habana, CP 10400 (Cuba); Durruthy-Rodríguez, M. D., E-mail: dolores@icmf.inf.cu [Departamento de Física Aplicada, Instituto de Cibernética, Matemática y Física, 15 # 551, Vedado, Ciudad Habana, CP 10400 (Cuba); CINVESTAV-Unidad Querétaro, IPN, Libramiento Norponiente No. 2000, Fracc. Real de Juriquilla, CP. 76230 Querétaro, Querétaro (Mexico); Calderón-Piñar, F. [Laboratorio de Magnetismo, Instituto de Ciencia y Tecnología de Materiales, Universidad de La Habana, La Habana, CP 10400 (Cuba); CINVESTAV-Unidad Querétaro, IPN, Libramiento Norponiente No. 2000, Fracc. Real de Juriquilla, CP. 76230 Querétaro, Querétaro (Mexico); Guerra, J. D. S. [Grupo de Ferroelétricos e Materiais Multifuncionais, Instituto de Física, Universidade Federal de Uberlândia, MG (Brazil); Yañez-Limón, J. M. [CINVESTAV-Unidad Querétaro, IPN, Libramiento Norponiente No. 2000, Fracc. Real de Juriquilla, CP. 76230 Querétaro, Querétaro (Mexico)

    2014-07-28

    Over the past several years, there has been a remarkable growth and development in new ceramic and/or composite materials to be used in the electro-electronic industry. Ferroelectric materials have been recognized for their multifunctional physical properties; also, their optical properties are a subject of intense research effort due to their possible electro-optic applications. In this work, the visible photoluminescence effect is analyzed at room temperature in a sintered Pb{sub 0.95}Sr{sub 0.05}(Zr{sub 1x}Ti{sub x}){sub 1y}Cr{sub y}O{sub 3} perovskite-type structure system, doped with Sr and Cr. The excitation bands used were 267, 325, 373, 457, 635, and 680 nm, but the best result was obtained at 373 nm. The intensity and energy of such emission in this system have been studied by changing the molar Cr concentration (0 < y < 0.005) and the Ti content (x), with x = 0.20, 0.40, 0.53, 0.60, and 0.80, on both sides of the morphotropic phase boundary (MPB) zone. The principal emission bands are at the energies 1.73, 1.87, and 3.03 eV. The changes that were caused by Zr or Ti ions in the symmetry presented in the rhombohedral or tetragonal side of the MPB are more important. Additionally, structural and micro-structural measurements were performed by the x-ray diffraction and scanning electron microscopy techniques, respectively. The micro-Raman technique is also used in the study of this set of samples, which allows finding the Raman shift modes and the influence on the structural changes of the dopants.

  6. Magnetic and transport properties of EuNi(Si1-xGex)3 compounds

    International Nuclear Information System (INIS)

    Uchima, K; Takaesu, Y; Akamine, H; Kakihana, M; Tomori, K; Uejo, T; Teruya, A; Nakamura, A; Hedo, M; Nakama, T; Yagasaki, K; Matsubayashi, K; Uwatoko, Y

    2014-01-01

    The magnetization M, electrical resistivity ρ, thermopower S and specific heat C of EuNi(Si 1-x Ge x ) 3 compounds have been measured at temperatures from 2 to 300 K. For the compounds of EuNi(Si 1-x Ge x ) 3 , we obtained an effective magnetic moment of μ eff ∼ 7.7 μ B , which is close to the divalent Eu value of μ eff =7.94 μ B . All compounds of EuNi(Si 1-x Ge x ) 3 order antiferromagnetically. The Néel temperature T N decreases monotonously with increasing the Ge concentration x from T N =49 K for EuNiSi 3 to T N =14 K for EuNiGe 3 . In the low temperature region below T N , anomalies corresponding to an additional magnetic phase transition into ferromagnetic state for compounds with x < 0.3, and into another antiferromagnetic for x > 0.3 were observed. The Curie temperature T C rapidly decreases with increasing x and vanishes at x ≈ 0.3. It is found that the magnetic phase transition temperatures of T N and T C in EuNi(Si 1-x Ge x ) 3 are strongly connected with the change of volume induced by the atomic substitution of Si by Ge

  7. Site-selective doping and superconductivity in (La/sub 1-//sub y/Pr/sub y/)(Ba/sub 2-//sub x/La/sub x/)Cu3O/sub 7+//sub δ/

    International Nuclear Information System (INIS)

    Mitzi, D.B.; Feffer, P.T.; Newsam, J.M.; Webb, D.J.; Klavins, P.; Jacobson, A.J.; Kapitulnik, A.

    1988-01-01

    Samples in the quaternary system (La/sub 1-//sub y/Pr/sub y/)(Ba/sub 2-//sub x/La/sub x/)Cu 3 O/sub 7+//sub δ/ have been prepared and characterized using x-ray and neutron diffraction, thermogravimetric analysis, and transport and magnetic measurements. Pr substitutes on the oxygen-depleted La layers for y>0.0, while La substitutes on the Ba sites for x>0.0. The effect of doping on each site is inferred to be primarily local, affecting immediately adjacent Cu-O layers. The similar suppression of superconductivity that accompanies doping on each of the two distinct sites apparently correlates with the degree of oxidation of the Cu-O sheets (and not the chains), indicating that the sheets support the high temperature superconductivity. Comparison of orthorhombic and tetragonal samples with similar Ba:La ratios (and y = 0) demonstrates that the orthorhombic phase yields the largest Meissner signals and highest transition temperatures in the La(Ba/sub 2-//sub x/La/sub x/)Cu 3 O/sub 7+//sub δ/ system

  8. Microstructure analyses and thermoelectric properties of Ag1xPb18Sb1+yTe20

    International Nuclear Information System (INIS)

    Perlt, S.; Höche, Th.; Dadda, J.; Müller, E.; Bauer Pereira, P.; Hermann, R.; Sarahan, M.; Pippel, E.; Brydson, R.

    2012-01-01

    This study reports microstructural investigations of long-term annealed Ag 1x Pb m Sb 1+y Te 2+m (m=18, x=y=0, hereinafter referred to as AgPb 18 SbTe 20 ) (Lead–Antimony–Silver–Tellurium, LAST-18) as well as of Ag 1x Pb 18 Sb 1+y Te 20 , i.e. Ag-deficient and Sb-excess LAST-18 (x≠0,y≠0), respectively. Two different length scales are explored. The micrometer scale was evaluated by SEM to analyze the volume fraction and the number of secondary phases as well as the impact of processing parameters on the homogeneity of bulk samples. For AgPb 18 SbTe 20 , site-specific FIB liftout of TEM lamellae from thermoelectrically characterized samples was accomplished to investigate the structure on the nanometer scale. High-resolution TEM and energy-filtered TEM were performed to reveal shape and size distribution of nanoprecipitates, respectively. A hypothesis concerning the structure–property relationship is set out within the frame of a gradient annealing experiment. This study is completed by results dealing with inhomogeneities on the micrometer scale of Ag 1x Pb 18 Sb 1+y Te 20 and its electronic properties. Highlights: ► SEM and TEM microstructure investigation of long-term annealed AgPb 18 SbTe 20 . ► SEM and thermoelectric studies on Ag 1x Pb 18 Sb 1+y Te 20 . ► Discussion concerning structure–property relationship in long-term annealed AgPb 18 SbTe 20 . ► Correlation between Ag 1x Pb 18 Sb 1+y Te 20 microscale structure and electronic properties.

  9. Studies on the KTa1-xFe xO3-δ system

    International Nuclear Information System (INIS)

    Ciriaco, M. Lurdes F.; Silva Pereira, M.I. da; Nunes, M.R.; Mendonca, M.H.; Costa, F.M.

    2006-01-01

    In this work we have prepared by ceramic route, polycrystalline powders samples derived from the KTaO 3 perovskite by the partial replacement of tantalum by iron with nominal composition KTa 1-x Fe x O 3-δ (0 ≤ x1), in order to evaluate the consequence of these substitution on the properties of the compounds. Two synthesis temperatures were used, 973 and 1373 K. From the powders (x = 0.1) iron coatings were prepared and tested, as electrode materials, in alkaline solutions. The characterisation of the powder samples was made by X-ray diffraction (XRD), scanning electron microscopy (SEM) and electrical conductivity measurements. Cyclic voltammetry was used in the electrodes characterisation. The results show that the partial replacement of Ta by Fe and the synthesis temperature affect the properties of the system

  10. Synthesis and piezoelectric properties of KxNa1-xNbO3 ceramic by molten salt method

    International Nuclear Information System (INIS)

    Li Yueming; Wang Jinsong; Liao Runhua; Huang Dan; Jiang Xiangping

    2010-01-01

    K x Na 1-x NbO 3 ceramic powder with perovskite structure was synthesized in molten salt with a Na 2 CO 3 /K 2 CO 3 molar ratio of 1:1, under different salt-to-oxide weight ratios of 1:10, 1:5, 1:3, 1:2.5 and 1:2 in the temperatures range of 650-900 o C. It is found that the synthesizing temperature and salt-to-oxide ratios had significant effects on the morphology of K x Na 1-x NbO 3 powder. The X-ray diffraction analysis indicated that a pure perovskite structure of K x Na 1-x NbO 3 powder could be synthesized at 650 o C. The microstructure observation revealed that the crystal morphology of K x Na 1-x NbO 3 powder changed from spheroid to cube, and then became irregular after further increasing temperature. The grain size of the synthesized powder increased by an increment of the molten salt content. The K x Na 1-x NbO 3 ceramics were prepared at x = 0.345 by adding 1.0 mol% ZnO as sintering aid, and the optimized dielectric and piezoelectric properties are obtained as following: d 33 = 120 pC/N, T c = 406 o C, Q m = 126 and k p = 0.302.

  11. Structural and superconducting properties of epitaxial Fe{sub 1+y}Se{sub 1-x}Te{sub x} thin films

    Energy Technology Data Exchange (ETDEWEB)

    Richter, Stefan; Yuan, Feifei; Grinenko, Vadim; Huehne, Ruben [Institute for Metallic Materials, IFW Dresden (Germany); Sala, Alberto; Putti, Marina [Dipartimento di Fisica, Universita di Genova (Italy)

    2015-07-01

    The iron based superconductor Fe(Se,Te) is in the center of much ongoing research. The reason for this is on the one hand its simple crystal structure, that consists only of stacked Fe(Se,Te) layers so that structural and superconducting properties can be connected more easily, on the other hand FeSe itself shows a high sensibility for strain and changes in stoichiometry and can have potentially very high critical temperatures under hydrostatic pressure or in monolayers. We investigate epitaxial thin films of Fe{sub 1+y}Se{sub 1-x}Te{sub x} grown by pulsed laser deposition on different single crystalline substrates. A high crystalline quality and a superconducting transition of up to about 20 K can be achieved using optimized deposition parameters. The influence of growth conditions, Te-doping, film thickness and post growth oxygen treatment on the structural and superconducting properties on these films will be presented in detail.

  12. Crystallization behavior of ZrO{sub 2}−3Y{sub 2}O{sub 3}−xSrO precursor powders synthesized by a coprecipitation process

    Energy Technology Data Exchange (ETDEWEB)

    Chu, Hsueh-Liang [Department of Materials Science and Engineering, National Cheng Kung University, 1 Ta- Hsueh Road, Tainan 70101, Taiwan (China); Hwang, Weng-Sing [Department of Materials Science and Engineering, National Cheng Kung University, 1 Ta- Hsueh Road, Tainan 70101, Taiwan (China); Institute of Nanotechnology and Microsystems Engineering, National Cheng Kung University, 1 Ta- Hsueh Road, Tainan 70101, Taiwan (China); Du, Je-Kang [Department of Dentistry, Kaohsiung Medical University, 100 Shih-Chuan 1st Road, Kaohsiung 80708, Taiwan (China); Department of Dentistry, Kaohsiung Medical University, Chung Ho Memorial Hospital, 100 Tzyou 1st Road, Kaohsiung 80708, Taiwan (China); Chen, Ker-Kong, E-mail: enamel@kmu.edu.tw [Department of Dentistry, Kaohsiung Medical University, 100 Shih-Chuan 1st Road, Kaohsiung 80708, Taiwan (China); Department of Dentistry, Kaohsiung Medical University, Chung Ho Memorial Hospital, 100 Tzyou 1st Road, Kaohsiung 80708, Taiwan (China); Wang, Moo-Chin, E-mail: mcwang@kmu.edu.tw [Department of Fragrance and Cosmetic Science, Kaohsiung Medical University, 100 Shih-Chuan 1st Road, Kaohsiung 80708, Taiwan (China)

    2016-09-05

    Crystallization behaviors of ZrO{sub 2}−3Y{sub 2}O{sub 3}−xSrO precursor powders were studied with zirconium nitrate (Zr(NO{sub 3}){sub 4}·xH{sub 2}O), yttrium nitrate (Y(NO{sub 3}){sub 3}·6H{sub 2}O) and strontium nitrate (Sr(NO{sub 3}){sub 2}) constituting the initial materials. Differential thermal analysis (DTA), X-ray diffraction (XRD), transmission electron microscopy (TEM), selected area electron diffraction (SAED), nano beam electron diffraction (NBED) and high-resolution TEM (HRTEM) were utilized to characterize the crystallization behavior of ZrO{sub 2}−3Y{sub 2}O{sub 3}−xSrO precursor powders. The activation energies of tetragonal ZrO{sub 2} (t-ZrO{sub 2}) crystallization were 389.1, 327.6, and 315.1 kJ/mol with SrO content for 1, 2, and 3 mol%, respectively, obtained with a non-isothermal method. The growth morphology parameter and growth mechanism index were close to 2.0 and 1.0, respectively, showing that t-ZrO{sub 2} had a plate-like morphology. - Highlights: • The single phase of tetragonal ZrO{sub 2} formed when calcined at 923 K for 2 h. • ZrO{sub 2}−3Y{sub 2}O{sub 3}−2SrO precursor powders crystallization is at 765.6 K. • The activation energy of t-ZrO{sub 2} crystallization was 389.1 kJ/mol with 1 mol% SrO. • The growth morphology and index of crystallization were close to 2.0 and 1.0.

  13. Impurity quadrupole Kondo ground state in a dilute Pr system Y1-xPrxIr2Zn20

    Science.gov (United States)

    Yamane, Yu; Onimaru, Takahiro; Uenishi, Kazuto; Wakiya, Kazuhei; Matsumoto, Keisuke T.; Umeo, Kazunori; Takabatake, Toshiro

    2018-05-01

    The electrical resistivity ρ and specific heat C of a dilute Pr system Y1-xPrxIr2Zn20 for 0 ≤ x ≤ 0.44 were measured to study the phenomena arising from active quadrupoles of the Pr3+ ion with 4f2 configuration. On cooling, ρ's of all samples monotonically decrease, while the residual resistivity ratio ρ(300 K)/ρ(3 K) drastically decreases with x. In the whole range x ≤ 0.44, the magnetic contribution to the specific heat divided by temperature Cm/T shows a broad maximum at around 10 K, which can be reproduced by a two-level model with a first-excited triplet separated by 30 K from a ground state doublet. This indicates that the crystalline electric field ground state of the Pr ions remains in the Γ3 doublet for the cubic Td point group. On cooling, the Cm/T data for x = 0.085 and 0.44 approach constant values at Texpected from the random two-level model. By contrast, Cm/T for x = 0.044 increases continuously down to 0.08 K, suggesting a non-Fermi liquid state due to the impurity quadrupole Kondo effect.

  14. Heterojunction laser operation of N-free and N-doped GaAs/sub 1-y/P/sub y/ (y=0.42--0.43, lambdaapprox.6200 A, 77 degreeK) near the direct-indirect transition (yapprox.y/subc/approx. =0.46)

    International Nuclear Information System (INIS)

    Coleman, J.J.; Holonyak, N. Jr.; Ludowise, M.J.; Wright, P.D.; Groves, W.O.; Keune, D.L.; Craford, M.G.

    1975-01-01

    The successful LPE growth of In/sub 1-x/Ga/sub x/P/sub 1-z/As/sub z//GaAs/sub 1-y/P/sub y/ single heterojunctions on VPE substrates makes possible the study of stimulated emission in N-free and N-doped GaAs/sub 1-y/P/sub y/ in a region (y=0.42--0.43) much closer to the direct-indirect transition (yequivalenty/subc/=0.46, 77 degreeK) than previously. Laser operation in N-free GaAs/sub 1-y/P/sub y/ on the GAMMA-Zn (E/sub Gamma/-E)) recombination transition has been achieved at energies as high as 2.00 eV (lambda=6200 A), and some line narrowing has been observed at energies as high as 2.01 eV (lambda=6170 A, y=0.43). In contrast to diodes made on lower composition substrates, the diodes of this work do not change their threshold current densities in the range 77--4.2 degreeK, indicating that laser operation occurs on direct transitions lying within approx.kT of the indirect donor states (Te) associated with the X conduction-band minima. From E/sub Gamma/+kTapprox.E/subX/-E/subd/ (y=0.42- []0.43), the depth of indirect Te donor states in GaAs/sub 1-y/P/sub y/ is estimated to fall in the range E/subd/=22--32 meV. Nitrogen doping in these laser diodes increases the threshold current densities since the N impurity is an efficient trap and introduces competing indirect recombination. For y=0.42--0.43 GaAs/sub 1-y/P/sub y/, heterojunction laser operation on the N trap lies approx.10 meV lower in energy than on the GAMMA-Zn transition. Beyond y=0.42--0.43, the N trap may be required for stimulated emission, but in this range diode operation at high currents becomes difficult because of the large change in carrier mobility

  15. Multielectronic conduction in La1-xSrxGa1/2Mn1/2O3-δ as solid oxide fuel cell cathode

    Science.gov (United States)

    Iguchi, E.; Hashimoto, Y.; Kurumada, M.; Munakata, F.

    2003-08-01

    Four-probe dc conductivities, capacitances, and thermopower have been measured in the temperature range of 80-1123 K for La1-xSrxGa1/2Mn1/2O3-δ, which is a desirable cathode material for lanthanum-gallate electrolytes of solid oxide fuel cells. The dc conductivities in the specimens (0.1⩽x⩽0.3) are insensitive to x but the thermopower is very sensitive to x, although the x=0 specimen exhibits a somewhat different conduction behavior. At T500 K, the band conduction dominates the electronic transports. The ionic conduction due to O2- migration seems difficult to contribute directly to the dc conduction even at high temperature.

  16. Versatile electronic behavior of the Li{sub x}Mn{sub 3−x−y}Fe{sub y}O{sub 4} spinels

    Energy Technology Data Exchange (ETDEWEB)

    Alonso-Domínguez, D. [Departamento de Química Inorgánica, Facultad de Ciencias Químicas, Universidad Complutense de Madrid, Avda. Complutense s/n, 28040 Madrid (Spain); CEI Moncloa, UCM-UPM, Madrid (Spain); Álvarez-Serrano, I., E-mail: ias@quim.ucm.es [Departamento de Química Inorgánica, Facultad de Ciencias Químicas, Universidad Complutense de Madrid, Avda. Complutense s/n, 28040 Madrid (Spain); López, M.L.; Veiga, M.L.; Pico, C. [Departamento de Química Inorgánica, Facultad de Ciencias Químicas, Universidad Complutense de Madrid, Avda. Complutense s/n, 28040 Madrid (Spain); Mompeán, F.; García-Hernández, M. [Instituto de Ciencia de Materiales, CSIC, Cantoblanco, 28049 Madrid (Spain); Cuello, G.J. [Institut Laue-Langevin, 6 rue Jules Horowitz, F-38042 Grenoble (France)

    2013-11-15

    Highlights: •The Li{sub x}Mn{sub 3−x−y}Fe{sub y}O{sub 4} spinels show a versatile electronic behavior. •Optimal compositional ranges for different application fields are proposed. •Frustrated ferromagnetic response is compositionally driven. •High ε′ values are obtained when B sites are occupied by both Mn and Fe cations. •High lithium contents are linked to the electrochemical behavior. -- Abstract: The detailed structural and electronic characterization of microcrystalline powders of new spinels Li{sub x}Mn{sub 3−x−y}Fe{sub y}O{sub 4} (0.4 ⩽ x1.33; 0 ⩽ y1.30), obtained by the “liquid mix” method, is reported. Compositional characterization was carried out by means of thermogravimetric analysis, energy-dispersive X-ray spectroscopy and electron energy loss spectroscopy, and their structure was refined from neutron and X-ray diffraction showing a cubic symmetry between 5 and 550 K, Space Group Fd3{sup ¯}m. However, at temperatures above ca. 950 K, a reversible transformation, probably implying the formation of an ordered vacant phase, has been detected. The magnetic behavior, analyzed from neutron diffraction data and magnetization measurements, is interpreted considering an “incomplete” ferrimagnetic response, due to magnetic frustration in the B sites. Potential applications have been evaluated from the magnetocaloric, electrochemical and dielectric behavior in selected compositional ranges.

  17. The Application of CPA to Calculations of the Mean Magnetic Moment in the Gd1-xNi, Gd1-xFe, Gd1xCox, and Y1-xCox Intermetallic Compounds

    DEFF Research Database (Denmark)

    Szpunar, B.; Kozarzewski, B.

    1977-01-01

    with a narrow d-band is considered. The magnetic moment of the alloy at zero temperature is calculated within the molecular field and Hartree-Fock approximations. Disorder is treated in the coherent potential approximation. Results are in good agreement with the experimental data obtained for the crystalline......Calculations are made of the mean magnetic moment per atom of the transition metal and the rare-earth metal in the intermetallic compounds, Gd1-x,Nix, Gd1-x Fex, Gd1-x Cox, and Y1-x Cox. A simple model of the disordered alloy consisting of spins localized on the rare-earth atoms and interacting...

  18. Effect of grain boundary on electrical characteristics in B- and P-doped polycrystalline Si1-x-yGe xC y film deposited by ultraclean LPCVD

    International Nuclear Information System (INIS)

    Shim, Hyunyoung; Sakuraba, Masao; Murota, Junichi

    2006-01-01

    The effect of grain boundary on electrical characteristics in B- and P-doped polycrystalline (poly) Si 1-x -y Ge x C y films was investigated. Poly-Si 1-x -y Ge x C y films were deposited on thermally oxidized Si(100) at 500-650 deg. C in a SiH 4 -GeH 4 -SiH 3 CH 3 -H 2 gas mixture by an ultraclean hot-wall low-pressure chemical vapor deposition. B and P were doped into the films by ion implantation and diffusion by heat-treatment. The electrical properties are characterized by grain size, width of disordered region near grain boundaries, carrier trap density and the amount of impurity segregation at grain boundaries. In the B-doped poly-Si 1-x -y Ge x C y films heat-treated at 900 deg. C, the increase of carrier concentration n poly and the decrease of resistivity ρ poly with Ge addition are caused by the narrowing of the width of disordered regions, i.e., crystallization of disordered regions induced by Ge atoms. The decrease of n poly and the increase of ρ poly with C addition are explained by the suppression of crystallization of disordered region due to C atom segregation at grain boundaries. In the P-doped poly-Si 1-x -y Ge x C y films, it is found that n poly and ρ poly are influenced by P atom segregation at grain boundaries due to lowering solid solubility of P in grain by the existence of Ge

  19. Efficient UV-emitting X-ray phosphors: octahedral Zr(PO4)6 luminescence centers in potassium hafnium-zirconium phosphates K2Hf1-xZrx(PO4)2 and KHf2(1-x)Zr2x(PO4)3

    International Nuclear Information System (INIS)

    Torardi, C.C.; Miao, C.R.; Li, J.

    2003-01-01

    Potassium hafnium-zirconium phosphates, K 2 Hf 1-x Zr x (PO 4 ) 2 and KHf 2(1-x) Zr 2x (PO 4 ) 3 , are broad-band UV-emitting phosphors. At room temperature, they have emission peak maxima at approximately 322 and 305 nm, respectively, under 30 kV peak molybdenum X-ray excitation. Both phosphors demonstrate luminescence efficiencies that make them up to ∼60% as bright as commercially available CaWO 4 Hi-Plus. The solid-state and flux synthesis conditions, and X-ray excited UV luminescence of these two phosphors are discussed. Even though the two compounds have different atomic structures, they contain zirconium in the same active luminescence environment as that found in highly efficient UV-emitting BaHf 1-x Zr x (PO 4 ) 2 . All the three materials have hafnium and zirconium in octahedral coordination via oxygen-atom corner sharing with six separate PO 4 tetrahedra. This octahedral Zr(PO 4 ) 6 moiety appears to be an important structural element for efficient X-ray excited luminescence, as are the edge-sharing octahedral TaO 6 chains for tantalate emission

  20. Luminescent properties of the potassium zinc phosphates of composition K1-xTlxZn(PO3)3

    International Nuclear Information System (INIS)

    El Abiad, A.; Mesnaoui, M.; Maazaz, M.; Parent, C.; Le Flem, G.

    2003-01-01

    Crystalline and glassy K 1-x Tl x Zn(PO 3 ) 3 polyphosphates have been synthesized and characterized. UV-visible spectroscopy was systematically used in order to analyze the optical properties of Tl + ions both in crystalline and glassy forms with the similar compositions. The investigated polyphosphates can be considered as a model system since the spectroscopic properties of Tl + ions in the glasses could be deduced by comparison with those in crystals. From structural point of view, in the crystalline forms the thallium ions are six-fold coordinated in a dissymmetrical oxygenated sites. Three luminescences (α, A X , A T ) have been then observed and were attributed to the isolated Tl + ions. In the glassy forms, an additional luminescence (D) has been detected in the low-energy range and was assigned to the Tl + pairs formation. The relationship between the Tl + site symmetry and its optical properties is discussed in the context of the Fukuda's model

  1. Conductividad eléctrica en corriente alterna de materiales cerámicos aurivillius de composición PbxBi4Ti3+xO12+3x, x=0,1,2 y 3

    Directory of Open Access Journals (Sweden)

    Moure, C.

    2004-04-01

    Full Text Available The ac electric conductivity of both textured and non textured Aurivillius ferroelectric ceramics PbxBi4Ti3+xO12+3x, where x = 0,1,2 and 3, has been studied by impedance measurements. The electrical conductivity decreases approximately one order of magnitude with the incorporation of a mol of lead titanate into the bismuth titanate structure. The anisotropy of the conductivity is kept between the ab plane and the c axis. The response seems to be related to the number of oxygen vacancies present in the crystalline structure of the materials, as well as to the aspect ratio of the grains. The activation energy values of the electrical conduction process are presented for both the ferroelectric and paraelectric phases.Se ha estudiado la conductividad eléctrica en corriente alterna (ca de la serie de materiales cerámicos ferroeléctricos con estructura Aurivillius: PbxBi4Ti3+xO12+3x, donde x = 0,1,2 y 3. El estudio se realiza a partir de la medida de la impedancia sobre muestras texturadas y no texturadas. La conductividad eléctrica disminuye sucesiva y aproximadamente en un orden de magnitud con el incremento sucesivo de un mol de titanato de plomo en la estructura del titanato de bismuto. Se mantiene la anisotropía de la conductividad entre el plano ab y el eje c de la estructura cristalina. La respuesta parece estar relacionada tanto con la variación del número de vacantes de oxígeno presentes en la estructura cristalina de los materiales, como con la variación de la relación de esbeltez de las placas que componen la microestructura de las muestras. Se presentan también los valores de energía de activación del proceso de conducción eléctrica en diferentes rangos de temperatura, tanto en la fase ferroeléctrica como en la paraeléctrica.

  2. Thermoelectric properties of p-type pseudo-binary (Ag0.365Sb0.558Te) x -(Bi0.5Sb1.5Te3)1-x (x=0-1.0) alloys prepared by spark plasma sintering

    International Nuclear Information System (INIS)

    Cui, J.L.; Xue, H.F.; Xiu, W.J.; Jiang, L.; Ying, P.Z.

    2006-01-01

    In this paper, pseudo-binary (Ag 0.365 Sb 0.558 Te) x -(Bi 0.5 Sb 1.5 Te 3 ) 1- x (x=0-1.0) alloys were prepared using spark plasma sintering technique, and the composition-dependent thermoelectric properties were evaluated. Electrical conductivities range from 7.9x10 4 to 15.6x10 4 Ω -1 m -1 at temperatures of 507 and 318 K, respectively, being about 3.0 and 8.5 times those of Bi 0.5 Sb 1.5 Te 3 alloy at the corresponding temperatures. The optimal dimensionless figure of merit (ZT) of the sample with molar fraction x=0.025 reaches 1.1 at 478 K, whereas that of the ternary Bi 0.5 Sb 1.5 Te 3 alloy is 0.58 near room temperature. The results also reveal that a direct introduction of Ag 0.365 Sb 0.558 Te in the Bi-Sb-Te system is much more effective to the property improvement than naturally precipitated Ag 0.365 Sb 0.558 Te in the Ag-doped Ag-Bi-Sb-Te system. - Graphical abstract: The temperature dependence of the dimensionless thermoelectric figure of merit ZT for different (Ag 0.365 Sb 0.558 Te) x -(Bi 0.5 Sb 1.5 Te 3 ) 1- x (x=0-1.0) alloys prepared by spark plasma sintering

  3. Synthesis–property relationship in thermoelectric Sr 1x Yb x TiO 3− δ ceramics

    KAUST Repository

    Bhattacharya, S

    2014-08-22

    The electronic transport properties of a series of Sr1-xYbxTiO3-delta (x = 0.05, 0.1) ceramics are investigated as a function of solid-state reaction (SSR) parameters, specifically calcination steps. It was found that the electrical conductivity (sigma) increases almost by a factor of 6, through the optimization of SSR parameters. The enhancement in the electrical conductivity leads to an enhancement in the thermoelectric power factor by a factor of 3. In addition, the lattice thermal conductivity (k(L)) of the Sr1-xYbxTiO3-delta ceramics is suppressed with increasing Yb-doping, supposedly due to heavier atomic mass of Yb substituted at the Sr site and a smaller ionic radii of Yb+3 with respect to Sr+2 ions. However, our model calculations indicate that strain-field effect, which occurs due to the difference in ionic radii, is the more prominent phonon scattering mechanism in the Yb-doped SrTiO3. This work is an extension of our previous study on the underlying phonon scattering mechanisms in the Y-doped SrTiO3, which would provide new insight into thermal transport in doped SrTiO3 and could be used as a guideline for more effective material synthesis.

  4. Architectural Processes and Physicochemical Properties of CoO/ZnO and Zn 1x Co x O/Co 1y Zn y O Nanocomposites

    KAUST Repository

    Yao, Ke Xin

    2009-01-29

    In this work we synthesized two inverse kinds of cobalt and zinc oxide nanocomposites (CoO/ZnO and Zn1-xCoxO/Co 1-yZnyO) and compared methodologistic features observed from the syntheses. The binary oxide system chosen herein is because divalent cobalt and zinc have very similar ion radii, and they interdiffuse easily when forming doped structures. A "two-pot" process was devised for the CoO/ZnO composites, in which mesocrystalline cores of CoO were formed first, followed by introduction of an overlayer of ZnO nanoparticles to the core surfaces. In contrast, a "one-pot" process was developed for the Zn1-xCoxO/Co1-yZnyO composites. In particular, hollow and/or multishelled Zn1-xCoxO cores (in wurtzite phase) serve as a support for the nanospheres of Co 1-yZnyO (in rock-salt phase) in this latter method. Our findings indicate that while "multi-pot" synthesis is a prevailing methodology for composite nanoparticles, simpler "one-pot" synthesis can be an effective approach for preparation of more complex nanocomposite materials, especially for interdoped metal oxides. As an example, our as-prepared binary oxide composites Zn1-xCoxO/Co 1-yZnyO have shown good catalytic activity for oxidation of carbon monoxide at relatively low reaction temperatures. © 2009 American Chemical Society.

  5. Microscopic theory of magnetization processes in Y (Co sub 1 sub - sub x Al sub x) sub 2

    CERN Document Server

    Khmelevskyi, S; Mohn, P

    2002-01-01

    Employing ab initio electronic structure calculations we study the development of the magnetic properties in Y (Co sub 1 sub - sub x Al sub x) sub 2 for varying Al concentration. The effect of substitutional disorder is treated in the coherent-potential approximation implemented within a tight-binding linear muffin-tin orbital method. The experimentally observed reduction of the critical field of the itinerant electron metamagnetic phase transition with increasing content of non-magnetic Al is explained. It is shown, on the basis of a T = 0 K Stoner type itinerant magnetism theory, that the alloying-induced changes in the shape of the calculated density of states, caused by the Al substitution, lead to (i) a stabilization of the magnetic state, (ii) a smoothening of the first-order metamagnetic transition and (iii) a subsequent suppression of the metamagnetic transition around x 0.15. Analysing the magnetization processes in Y (Co sub 1 sub - sub x Al sub x) sub 2 by varying the strength of the exchange inter...

  6. Effect of silver doping on infrared reflectance and Tc of superconducting GdBa2Cu(1 - x)3Ag3xO7

    International Nuclear Information System (INIS)

    Memon, A.; Khan, M.N.; Al-Dallal, S.; Tanner, D.B.; Porter, C.D.

    1990-01-01

    This paper reports on infrared reflectance of GdBa 2 Cu(1 - x) 3 Ag 3x O 7 ceramic superconductor with the composition of x = 0.025 and 0.05 performed in the frequency range of 100--5000 cm -1 . All the infrared active phonon modes allowed by the selection rules were observed in the reflection spectra of these compounds. The optical conductivity as calculated from K--K analysis further confirms the existence of these optical phonons. Besides the increase of the reflectivity in the silver doped samples, an extra phonon mode is observed, which is normally not seen at room temperature reflectance of GdBa 2 Cu 3 O 7 compounds. The four probe resistivity measurement show zero resistance at 88 K for x = 0, and 78 K for x = 0.025 in GdBa 2 Cu(1 - x) 3 Ag 3x O 7 compound

  7. Oxygen potential of Th1-yUyO2+x

    International Nuclear Information System (INIS)

    Schram, R.P.C.; Cordfunke, E.H.P.

    1996-03-01

    Oxygen potentials of UO 2 -ThO 2 solid solutions (Th 1-y U y O 2+x ) were retrieved from literature and stored in a database. For each datapoint the oxygen pressure p O 2 the nonstoichiometry x, the temperature T and the uranium concentration y was specified. The data were analyzed using a defect model, which includes electronic disorder, point defects and cluster formation. In addition, the thermochemical representation of Lindemer and Besmann for UO 2+x was extended for the analysis of the Th 1-y U y O 2+x data. The solid solution is regarded as an ideal ternary mixture of UO 2 , ThO 2 and a hypothetical compound U a O b . The thermodynamic properties of this compound U a O b were determined in two oxygen pressure ranges of the database. In both the defect model and thermochemical approach ThO 2 is treated as an inert compound that does not participate in any of the chemical equilibria describing the oxygen potential. (orig.)

  8. Temperature-dependent photoluminescence and contactless electroreflectance characterization of a ZnxCd1-xSe/Znx'Cdy'Mg1-x'-y'Se asymmetric coupled quantum well structure

    International Nuclear Information System (INIS)

    Wu, J.D.; Huang, Y.S.; Lin, D.Y.; Charles, W.O.; Shen, A.; Tamargo, M.C.; Tiong, K.K.

    2011-01-01

    Research highlights: → We report a detailed study of a ZnxCd 1-x Se/Znx'Cdy'Mg 1-x '-y'Se asymmetric coupled quantum well structure by using temperature-dependent photoluminescence (PL) and contactless electroreflectance (CER) techniques. → The PL peak position yielded information of the fundamental excitonic recombinations. → Analysis of the CER spectra led to the identification of various interband transitions. →Study of the temperature dependence of the excitonic transition energies indicated that main influence of temperature on the quantized transitions is through temperature dependence of the constituent material band gap in the well. - Abstract: Temperature-dependent photoluminescence (PL) and contactless electroreflectance (CER) were used to characterize a Zn x Cd 1-x Se/Zn x' Cd y' Mg 1-x'-y' Se asymmetric coupled quantum well (ACQW) structure in the range of 10-300 K. The PL peak position yielded information of the fundamental excitonic recombinations. A detailed analysis of the CER spectra led to the identification of various interband transitions. The intersubband transitions were then estimated and found to be in a good agreement with the previous report of Fourier-transform infrared absorption measurements. At low temperature, the PL spectra of the sample showed an asymmetric behavior with an exponential tail at the lower-energy side and were attributed to the localized excitonic recombinations due to potential fluctuations. Detailed study of the temperature dependence of the excitonic transition energies indicated that the main influence of temperature on the quantized transitions is through the temperature dependence of the band gap of the constituent material in the well.

  9. Structural chemistry and magnetic properties of Pr3-xSr1+xCrNiO8

    International Nuclear Information System (INIS)

    Dutton, Sian E.; Bahout, Mona; Battle, Peter D.; Tonus, Florent; Demange, Valerie

    2008-01-01

    Polycrystalline samples of the n=1 Ruddlesden-Popper system Pr 3-x Sr 1+x CrNiO 8 have been synthesized over the composition range 0.0 0.1 adopt the tetragonal space group I4/mmm; Pr 2.9 Sr 1.1 CrNiO 8 adopts the orthorhombic space group Fmmm. There is no evidence of Cr/Ni cation ordering in any composition. A maximum in the zero-field cooled magnetic susceptibility is observed at a temperature T f that decreases with increasing Sr content; 52≤T f (K)≤13. The frequency dependence of T f observed in a.c. susceptibility measurements, together with the analysis of neutron diffraction data, suggests that the atomic magnetic moments in these compositions adopt a spin-glass-like state below T f . - Graphical abstract: The n=1 Ruddlesden-Popper system Pr 3-x Sr 1+x CrNiO 8 (0.0< x≤1.0) has been characterized by diffraction methods and magnetometry. There is no evidence of Cr/Ni cation ordering in any composition. The atomic magnetic moments adopt a spin-glass-like state below a transition temperature that decreases from 52 K (x=0.1) to 13 K (x=1.0)

  10. Critical Temperature of Randomly Diluted Two-Dimensional Heisenberg Ferromagnet, K2CuxZn(1-x)F4

    Science.gov (United States)

    Okuda, Yuichi; Tohi, Yasuto; Yamada, Isao; Haseda, Taiichiro

    1980-09-01

    The susceptibility of randomly diluted two-dimensional Heisenberg-like ferromagnet K2CuxZn(1-x)F4 was measured down to 50 mK, using the 3He-4He dilution refrigerator and a SQUID magnetometer. The ferromagnetic critical temperature Tc(x) was obtained for x{=}0.98, 0.94, 0.85, 0.82, 0.68, 0.60, 0.54, 0.50 and 0.42. The value of [1/Tc(1)][(d/dx)Tc(x)]x=1 was approximately 3.0. The critical temperature versus x curve exhibits a noticeable tail near the critical concentration, which may stem from the second nearest-neighbor interaction. The critical concentration xc, below which concentration there is no long range order down to T{=}0 K, was estimated to be 0.45˜0.50. The susceptibility of sample with x{=}0.42 behaves as if it obeys the Curie law down to 50 mK.

  11. Thermal behaviour of GdCo1-xMnxO3 cobaltates

    Science.gov (United States)

    Thakur, Rasna; Thakur, Rajesh K.; Gaur, N. K.

    2018-05-01

    With the objective of exploring the unknown thermodynamic behavior of GdCo1-xMnxO3 family, we present here an investigation of the temperature-dependent (10K≤T≤1000K) thermodynamic properties of GdCo1-xMnxO3 (x=0.1 to 0.8). The specific heat of GdCoO3 with Mn doping in the perovskite structure at B-site has been studied by means of a Modified Rigid Ion Model (MRIM). The cohesive energy, specific heat (C), volume thermal expansion (α) and Gruneisen parameter (γ) of GdCo1-xMnxO3 compounds are also discussed.

  12. Study Of Hysteresis Curve Characteristic On The YBa2Cu3O7-x Superconductor

    International Nuclear Information System (INIS)

    Adi, Wisnu; S W, Didin; Purwanto S; Yamaguchi, Yasuo

    2003-01-01

    The measurements of magnetic moment (m) on the superconductor YBa 2 Cu 3 O 7-x as function of temperature (T) and applied magnetic field (H) have been performed by using superconducting quantum interference device magnetometer (SQUID). The samples measured consist of pellet from sintering and melting products. The m-T curve is used to measure critical temperature (Tc), and the m-H curve is used to measure critical field, critical current density, and pinning force. Analysis results of both curves found that Tc is about 90.16 K and 90,15 K for samples of sintering and melting products, respectively. Hc 2 and Hc 2 of both samples are 1 k Oe and 20 k Oe, respectively. J c (H = 0) are 1.88 x 10 2 A.cm -2 ; 2.80 x 10 4 A.m -2 ; 2.02 x 10 3 A.m -2 ; and 5.70 x 10 5 A.cm -2 for Y S-2 (T = 77 K), Y S-2 (T = 5 K), Y M-2 (T = 77 K), and Y M-2 (T = 5 K) products, respectively. The F p maximum are 5.8 x 10 5 Nm -3 (H = 17 k Oe); 2.1 x 10 8 Nm -3 (H = 17 k Oe); 5.1 x 10 6 Nm -3 (H = 14 k Oe); and 8.3 x 10 9 Nm -3 (H = 14 k Oe) for Y S-2 (T = 77 K), Y S-2 (T= 5 K), Y M-2 (T= 77 K), and Y M-2 (T= 5 K), respectively

  13. Weak mixing angle and the SU(3)CxSU(3) model on M4xS1/(Z2xZ'2)

    International Nuclear Information System (INIS)

    Li Tianjun; Wei Liao

    2002-05-01

    We show that the desirable weak mixing angle sin 2 θ W =0.2312 at m Z scale can be generated naturally in the SU(3) C xSU(3) model on M 4 xS 1 /(Z 2 x Z 2 ') where the gauge symmetry SU(3) is broken down to SU(2) L xU(1) Y by orbifold projection. For a supersymmetric model with a TeV scale extra dimension, the SU(3) unification scale is about hundreds of TeVs at which the gauge couplings for SU(3) C and SU(3) can also be equal in the mean time. For the non-supersymmetric model, SU(2) L xU(1) Y are unified at order of 10 TeV. These models may serve as good candidates for physics beyond the SM or MSSM. (author)

  14. The electronic and optical properties of quaternary GaAs1-x-y N x Bi y alloy lattice-matched to GaAs: a first-principles study.

    Science.gov (United States)

    Ma, Xiaoyang; Li, Dechun; Zhao, Shengzhi; Li, Guiqiu; Yang, Kejian

    2014-01-01

    First-principles calculations based on density functional theory have been performed for the quaternary GaAs1-x-y N x Bi y alloy lattice-matched to GaAs. Using the state-of-the-art computational method with the Heyd-Scuseria-Ernzerhof (HSE) hybrid functional, electronic, and optical properties were obtained, including band structures, density of states (DOSs), dielectric function, absorption coefficient, refractive index, energy loss function, and reflectivity. It is found that the lattice constant of GaAs1-x-y N x Bi y alloy with y/x =1.718 can match to GaAs. With the incorporation of N and Bi into GaAs, the band gap of GaAs1-x-y N x Bi y becomes small and remains direct. The calculated optical properties indicate that GaAs1-x-y N x Bi y has higher optical efficiency as it has less energy loss than GaAs. In addition, it is also found that the electronic and optical properties of GaAs1-x-y N x Bi y alloy can be further controlled by tuning the N and Bi compositions in this alloy. These results suggest promising applications of GaAs1-x-y N x Bi y quaternary alloys in optoelectronic devices.

  15. Magnetic tri-axial orientation in (Y1-xErx)2Ba4Cu7O15-y superconductors

    International Nuclear Information System (INIS)

    Horii, S.; Okuhira, S.; Yamaki, M.; Haruta, M.; Maeda, T.; Shimoyama, J.

    2011-01-01

    (Y 1-x Er x ) 2 Ba 4 Cu 7 O 15-y [(Y,Er)247] was synthesized for clarifying a magnetic role of Er ion. The three magnetization axes of (Y,Er)247 were obtained from tri-axial orientation using a modulated rotation magnetic field. Magnetic anisotropy of Er ion is roughly ten times higher than that for Y247 at room temperature. Importance of rare-earth ions was shown for reduction of required magnetic fields in the tri-axial magnetic orientation. We report the tri-axial grain-orientation effects under a modulated rotation magnetic field for (Y 1-x Er x ) 2 Ba 4 Cu 7 O y [(Y, Er)247]. The magnetic easy axis at room temperature was drastically changed around x ∼ 0.1; however, the Er-doping levels for the conversion of magnetic easy axes from the c-axis to the ab-direction and from the a- to b-axes were quite different. Tri-axial single-ion magnetic anisotropy of Er 3+ was roughly 10 times greater than tri-axial magnetic anisotropy generated by both the superconducting CuO 2 plane and the blocking Cu-O chain layer. An appropriate choice of rare-earth (RE) ions in RE-based cuprate superconductors enables the reduction of the required magnetic field for the production of bulks and thick films based on the magnetic orientation technique.

  16. Study of TiO2(1 1 0)-p(1x1), p(1x2) and p(1x3) surface structures by impact collision ion scattering spectroscopy (ICISS)

    International Nuclear Information System (INIS)

    Asari, E.; Souda, R.

    2000-01-01

    The surface structure of TiO 2 (1 1 0)-p(1x1), p(1x2) and p(1x3) were studied using impact collision ion scattering spectroscopy (ICISS). We found that (i) the height of bridging oxygen for the p(1x1) is comparative to that of bulk structure, (ii) the p(1x2) surface has the added Ti 2 O 3 unit rows proposed by Onishi et al. and also the oxygen atoms rows between Ti 2 O 3 unit rows and (iii) the p(1x3) surface is constructed with the same added Ti 2 O 3 unit rows as that in the p(1x2) surface, but the bridging oxygen rows exist between the Ti 2 O 3 unit rows

  17. Magnetic susceptibilities of Ca/sub y/U/sub 1-y/O/sub 2+x/ solid solutions

    International Nuclear Information System (INIS)

    Hinatsu, Y.; Fujino, T.

    1988-01-01

    Magnetic susceptibilities of Ca/sub y/U/sub 1-y/O/sub 2+x/ solid solutions with fluorite structure were measured from 4.2 K to room temperature. An antiferromagnetic transition was observed for all the solid solutions examined in this study (y ≤ 0.33). The Neel temperature of the oxygen-hypostoichiometric solid solutions (x 2 solid solutions, but different from that of (U,Th)O 2 solid solutions. The effective magnetic moment decreased with increasing calcium concentration, which indicates the oxidation of uranium in the solid solutions. From the analysis of the magnetic susceptibility data, it was found that the oxidation state of uranium was either tetravalent or pentavalent. The Neel temperature of the hyperstoichiometric solid solutions (x > 0) did not change appreciably with calcium concentrations. From the comparison of the magnetic susceptibility data of the hypostoichiometric solid solutions with those of the hyperstoichiometric solid solutions, the effect of oxygen vacancies is more significant than that of interstitial oxygens on the decrease of magnetic interactions between uranium ions

  18. Characterization of photoluminescent (Y{sub 1{minus}x}Eu{sub x}){sub 2}O{sub 3} thin-films prepared by metallorganic chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    McKittrick, J.; Bacalski, C.F.; Hirata, G.A. [Univ. of California, San Diego, La Jolla, CA (United States); Hubbard, K.M.; Pattillo, S.G.; Salazar, K.V.; Trkula, M. [Los Alamos National Lab., NM (United States). Materials Science and Technology Div.

    1998-12-01

    Europium doped yttrium oxide, (Y{sub 1{minus}x}Eu{sub x}){sub 2}O{sub 3}, thin-films were deposited on silicon and sapphire substrates by metallorganic chemical vapor deposition (MOCVD). The films were grown in a MOCVD chamber reacting yttrium and europium tris(2,2,6,6-tetramethyl-3,5,-heptanedionates) precursors in an oxygen atmosphere at low pressures (5 Torr) and low substrate temperatures (500--700 C). The films deposited at 500 C were flat and composed of nanocrystalline regions of cubic Y{sub 2}O{sub 3}, grown in a textured [100] or [110] orientation to the substrate surface. Films deposited at 600 C developed from the flat, nanocrystalline morphology into a plate-like growth morphology oriented in the [111] with increasing deposition time. Monoclinic Y{sub 2}O{sub 3}:Eu{sup 3+} was observed in x-ray diffraction for deposition temperatures {ge}600 C on both (111) Si and (001) sapphire substrates. This was also confirmed by the photoluminescent emission spectra.

  19. Structural, dielectric and magnetic properties of Bi{sub 1x}Y{sub x}FeO{sub 3} (0⩽x⩽0.2) obtained by acid–base co-precipitation

    Energy Technology Data Exchange (ETDEWEB)

    Medina, Leila María Saleh [Instituto de Química Física de Materiales, Ambiente y Energía (INQUIMAE), Departamento de Química Inorgánica, Analítica y Química Física, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires (Argentina); Jorge, Guillermo A. [Instituto de Ciencias, Universidad Nacional de General Sarmiento, Buenos Aires (Argentina); Martín Negri, R., E-mail: rmn@qi.fcen.uba.ar [Instituto de Química Física de Materiales, Ambiente y Energía (INQUIMAE), Departamento de Química Inorgánica, Analítica y Química Física, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires (Argentina)

    2014-04-01

    Highlights: • Yttrium-substituted bismuth-iron oxides were prepared by co-precipitation synthesis. • Single-phase materials with absence of other bismuth-oxides were obtained. • Strong dependence of magnetic and electrical properties with yttrium percentage at RT. • Magnetic and electric properties are related to particle size and structural changes. - Abstract: Bismuth–iron oxides with partial substitution of bismuth by yttrium, referred as (Bi{sub 1x}Y{sub x})FeO{sub 3}, were synthesized by simple-low cost acid–base co-precipitation method, which constitutes a difference with the currently used synthetic methods for obtaining BiFeO{sub 3}-doped compounds (e.g. polymer assisted sol–gel, solid state, microwave, etc.) Samples were characterized by XRD, EDS, SEM, TEM, DSC and FTIR. The influence of yttrium (Y) substitution on magnetization curves of (Bi{sub 1x}Y{sub x})FeO{sub 3} powders were studied at room temperature by VSM. The particle size systematically decreases with the Y percentage. Ferromagnetic curves were obtained at room temperature for Y-percentage lower than 20% with relatively large values of the coercive field, H{sub c}, which increases with Y-substitution, while for 20% yttrium a superparamagnetic behavior is observed. The electrical impedance of compressed disks were investigated also by impedance analysis in the range 1Hz–1MHz and the results were successfully fitted by a simple parallel R–C model. The dc-leakage currents are lower than previously reported for (Bi{sub 1x}Y{sub x})FeO{sub 3} compounds and for most of the doped-BiFeO{sub 3} ceramics. As a difference with the influence on the magnetic behavior, the doping with yttrium does not seem to have a large influence on the dielectrical properties. These results suggest that magnetization can be systematically modified by the relatively simple co-precipitation synthesis while keeping invariable the dielectrical properties.

  20. Structural and electrical properties of (1-x)(Na1/2Bi1/2)TiO3-xPb(Mg1/3Nb2/3)O3 solid solution

    International Nuclear Information System (INIS)

    Lee, J.-K.; Yi, J.Y.; Hong, K.S.

    2004-01-01

    Structural, dielectric and piezoelectric properties of (1-x)(Na 1/2 Bi 1/2 )TiO 3 -xPb(Mg 1/3 Nb 2/3 )O 3 (NBT-xPMN) solid solution have been investigated. An addition of PMN into NBT transformed the structure of sintered samples from rhombohedral to pseudocubic phase where x is larger than 0.1. In calcined powders, however, the intermediate structure were observed between rhombohedral and cubic phases near x=0.1. The formation of solid solution between NBT and PMN modified the dielectric and piezoelectric properties of NBT to be suitable for high temperature dielectric and piezoelectric material. With increasing the content of PMN, the temperature-stability of ε r (T) increased and the high temperature dielectric loss decreased. In addition, the piezoelectric property of NBT-xPMN was enhanced, for the decrease of coercive field and conductivity promoted the domain reversal under the high electric field of the poling process

  1. Effect of Fe substitution on magnetocaloric effect in La{sub 0.7}Sr{sub 0.3}Mn{sub 1-x}Fe{sub x}O{sub 3} (0.05{<=}x{<=}0.20)

    Energy Technology Data Exchange (ETDEWEB)

    Barik, S K; Krishnamoorthi, C [Department of Physics and NUS Nanoscience and Nanotechnology Initiative, 2 Science Drive 3, National University of Singapore, Singapore 117542, Singapore. (Singapore); Mahendiran, R [Department of Physics and NUS Nanoscience and Nanotechnology Initiative, 2 Science Drive 3, National University of Singapore, Singapore 117542, Singapore. (Singapore)

    2011-04-15

    We have studied the effect of Fe substitution on magnetic and magnetocaloric properties in La{sub 0.7}Sr{sub 0.3}Mn{sub 1-x}Fe{sub x}O{sub 3} (x=0.05, 0.07, 0.10, 0.15, and 0.20) over a wide temperature range (T=10-400 K). It is shown that substitution by Fe gradually decreases the ferromagnetic Curie temperature (T{sub C}) and saturation magnetization up to x=0.15 but a dramatic change occurs for x=0.2. The x=0.2 sample can be considered as a phase separated compound in which both short-range ordered ferromagnetic and antiferromagnetic phases coexist. The magnetic entropy change (-{Delta}S{sub m}) was estimated from isothermal magnetization curves and it decreases with increase of Fe content from 4.4 J kg{sup -1} K{sup -1} at 343 K (x=0.05) to 1.3 J kg{sup -1} K{sup -1} at 105 K (x=0.2), under {Delta}H=5 T. The La{sub 0.7}Sr{sub 0.3}Mn{sub 0.93}Fe{sub 0.07}O{sub 3} sample shows negligible hysteresis loss, operating temperature range over 60 K around room temperature with refrigerant capacity of 225 J kg{sup -1}, and magnetic entropy of 4 J kg{sup -1} K{sup -1} which will be an interesting compound for application in room temperature refrigeration. - Research highlights: > We report magnetocaloric effect in La{sub 0.7}Sr{sub 0.3}Mn{sub 1-x}Fe{sub x}O{sub 3} (x=0-0.2). > Magnetic entropy change ({Delta}S{sub m}) decreases with increasing x. > A large {Delta}S{sub m} and refrigeration capacity are found around 300 K in x=0.07.

  2. SU(3)_C× SU(2)_L× U(1)_Y( × U(1)_X ) as a symmetry of division algebraic ladder operators

    Science.gov (United States)

    Furey, C.

    2018-05-01

    We demonstrate a model which captures certain attractive features of SU(5) theory, while providing a possible escape from proton decay. In this paper we show how ladder operators arise from the division algebras R, C, H, and O. From the SU( n) symmetry of these ladder operators, we then demonstrate a model which has much structural similarity to Georgi and Glashow's SU(5) grand unified theory. However, in this case, the transitions leading to proton decay are expected to be blocked, given that they coincide with presumably forbidden transformations which would incorrectly mix distinct algebraic actions. As a result, we find that we are left with G_{sm} = SU(3)_C× SU(2)_L× U(1)_Y / Z_6. Finally, we point out that if U( n) ladder symmetries are used in place of SU( n), it may then be possible to find this same G_{sm}=SU(3)_C× SU(2)_L× U(1)_Y / Z_6, together with an extra U(1)_X symmetry, related to B-L.

  3. Visible light water oxidation using a co-catalyst loaded anatase-structured Ti(1-(5x/4))Nb(x)O(2-y-δ)N(y) compound.

    Science.gov (United States)

    Breault, Tanya M; Brancho, James J; Guo, Ping; Bartlett, Bart M

    2013-08-19

    The photocatalytic activity of anatase-structured Ti(1-(5x/4))Nb(x)O(2-y-δ)N(y) (x = 0.25, y = 0.02; NbN-25) was examined for water oxidation under UV and visible light irradiation. The semiconductor was prepared by sol-gel processing followed by nitridation in flowing ammonia and exhibits an indirect optical gap of 2.2 eV. Ti(1-(5x/4))Nb(x)O(2-y-δ)N(y) was loaded with RuO2 by an impregnation technique, and optimized conditions reveal that 1 wt % RuO2 generates 16 μmol O2 from water with concomitant IO3(-) reduction after 3 h of illumination under simulated solar radiation at a flux of 600 mW/cm(2) illumination, which corresponds to 6-sun AM1.5G illumination (compared to no detectible O2 without the RuO2 cocatalyst). A series of cut-on filters shows that the catalyst-loaded semiconductor evolves O2 for λ ≤ 515 nm, and a gas-phase mass spectrometry isotope labeling experiment shows that irradiating an iodate solution in H2(18)O in the presence of 1 wt % RuO2 loaded on NbN-25 gives rise to catalytic water oxidation: both (36)O2 and (34)O2 are observed. It is unclear whether (16)O arises from IO3(-) or surface reconstruction on the photocatalyst, but ICP-AES analysis of the postirradiated solution shows no dissolved metal ions.

  4. Magnetization reversal and tunable exchange bias in GdCr{sub 1x}Mn{sub x}O{sub 3} (x=0−0.50)

    Energy Technology Data Exchange (ETDEWEB)

    Dash, Bibhuti B.; Ravi, S., E-mail: sravi@iitg.ernet.in

    2017-05-01

    Single phase samples of GdCr{sub 1-x}Mn{sub x}O{sub 3} (x=0−0.50) were prepared and their magnetic properties were studied by measuring temperature and field variations of magnetization. The Neel temperature, T{sub N} is found to decrease from T{sub N}=174 K for x=0 to 91 K for x=0.50. The magnetization reversal persists upto 5 at% of Mn substitution with a magnetic compensation temperature, T{sub comp} of 136 K and 139 K for x=0 and 0.05 respectively. However, spin reorientation induced magnetization reversal emerges for x=0.40 and 0.50 samples around 30 K. Tunable positive and negative exchange bias fields in the range of −1.0 kOe to +1.6 kOe have been observed. The origin of magnetization reversal and exchange bias field is explained in terms of antiparallel alignment of canted ferromagnetic component of Cr{sup 3+} ions and the paramagnetic moments of Gd{sup 3+} and Mn{sup 3+} ions under the influence of negative internal field due to antiferromagnetically ordered Cr{sup 3+} ions. - Highlights: • Magnetization reversal and bipolar switching in Mn substituted GdCrO{sub 3} • Tunable exchange bias field in the range of −1.0 kOe to +1.6 kOe. • Low temperature spin reorientation transition is observed.

  5. Magnetism and superconductivity of CePt3Si and Ce1+xPt3+ySi1+z

    International Nuclear Information System (INIS)

    Motoyama, Gaku; Yamamoto, Suguru; Takezoe, Hiroaki; Oda, Yasukage; Ueda, Ko-ichi; Kohara, Takao

    2006-01-01

    We measured the dc magnetization, electrical resistivity, and ac magnetic susceptibility of a series of polycrystalline CePt 3 Si samples whose compositions vary slightly from the stoichiometric composition. The sample that showed the most distinct anitiferromagnetic transition at 2.2K was found to be Ce 1.01 Pt 3 Si annealed. This sample showed a clear bulk antiferromagnetic order at 2.2 K even in both electrical resistivity and dc magnetization measurements, although the characteristic change in dc magnetization at 2.2 K was found to be small and to be easily masked in other magnetic anomalies if they exist. Moreover, it had the largest residual resistivity ratio. We concluded that Ce 1.01 Pt 3 Si annealed has the intrinsic bulk properties of ideal CePt 3 Si. In addition, we revealed that some anomalies arise as a result of the variation in composition. One is a ferromagnetic anomaly at 3.0 K in the Pt-rich samples, and the other is an antiferromagnetic anomaly at 4.0 K in the Pt-poor samples. The two magnetic anomalies seemed to appear in small domains in the samples that exhibited an antiferromagnetic order at 2.2 K. To reveal the relationship between these magnetisms and superconductivity, we measured ac magnetic susceptibility down to ∼14mK. We found that the superconducting transition temperature is suppressed by the ferromagnetic anomaly. (author)

  6. Magnetic ordering and charge transport in electron-doped La1-yCeyMnO3 (0.1y ≤ 0.3) films

    International Nuclear Information System (INIS)

    Prokhorov, V.G.; Kaminsky, G.G.; Flis, V.S.; Hyun, Y.H.; Park, S.Y.; Lee, Y.P.; Svetchnikov, V.L.

    2009-01-01

    The microstructure and the magnetic and transport properties of as-deposited La 10-y Ce y MnO 3 (0.1≤ y≤ 0.3) films prepared by pulsed laser deposition are investigated in a wide region of temperature and magnetic field. The microstructure analysis reveals that all films have a high c-oriented texture, an orthorhombic crystal lattice, and a negligible quantity of CeO 2 inclusions. The observed strip-domain phase with a periodic spacing of about 3c, the crystal lattice of which is the same as for the basic film phase, exhibits magnetic behavior typical for the Griffiths phase. Regions of the double-period modulated phase are found at room temperature in the y=0.1 film, which is interpreted as Mn 3+ /Mn 2+ ordering with a partial ferromagnetic → antiferromagnetic transition at T N ≤ 80 K. At the same time, the investigation reveals that the magnetic and transport properties of the electron-doped La 1-y Ce y MnO 3 films, driven by cation doping, are similar to those for the hole-doped La/Ca manganites. Therefore, one can conclude that there is no fundamental difference between the mechanisms of spin ordering and charge transport in the hole-doped and electron-doped manganites

  7. K1-xMn1+x/2[Fe(CN)6]·yH2O Prussian blue analogues as an anode material for lithium-ion batteries

    Science.gov (United States)

    Zhou, Feng-Chen; Sun, Yan-Hui; Li, Jie-Qiong; Nan, Jun-Min

    2018-06-01

    Hexacyanoferrate, KMn[Fe(CN)6]·yH2O (KMnHCF), a Prussian blue analogue (PBA), is synthesized by a solution precipitation method under alkaline condition at room temperature. After treated with diluted hydrochloride acid, the KMnHCF is turned into Mn3[Fe(CN)6]2·yH2O (MnHCF). Then both synthesized KMnHCF and MnHCF are applied as anode material for lithium ion batteries (LIBs). The KMnHCF anode exhibits a super electrochemical performance than MnHCF. It shows a very low discharge voltage plateau of 0.6 V, an initial capacity of 777 mAh g-1, and a reversible capacity of 434 mAh g-1 after 50 cycles at a current density of 50 mA g-1. Furthermore, it keeps 425 mAh g-1 after 100 cycles at 100 mA g-1 and 215 mAh g-1 after 200 cycles even at 500 mA g-1. It is remarkable that the coulombic efficiency can be maintained larger than 98.4% from the 5th cycle at 50 mA g-1, 99.2% at 100 mA g-1, and 96.8% even at 500 mA g-1. In addition, the original structure of the KMnHCF has no obvious change after lithiation/de-lithiation based on the ex-situ X-ray powder diffraction (XRD) and Fourier transform infrared spectrometer (FT-IR) characterization, indicating large channels and interstitial sites in the open-framework can allow rapid insertion and extraction of Li+ and constrain volume expansion during charge/discharge process.

  8. A study on magnetoelastic properties of Tb3 (Fe28-xCox) V1.0 (x=0, 3, 6) compounds

    International Nuclear Information System (INIS)

    Gholizadeh, A.; Tajabor, N.; Pourarian, F.

    2012-01-01

    In this work, The magnetoelastic properties of polycrystalline samples of Tb 3 (Fe 28-x Co x ) V 1.0 (x=0, 3, 6) intermetallic compounds are investigated by means of linear thermal expansion and magnetostriction measurements in the temperature range of 77-515 K under applied magnetic fields up to 1.5 T. The linear thermal expansion increases with the Co content. The well-defined anomalies observed in the linear thermal expansion coefficients for Tb 3 (Fe 28-x Co x ) V 1.0 (x=0, 3, 6) compounds are associated with the magnetic ordering temperature for x=0 and spin reorientation temperatures for x=3, 6. Below transition temperatures, the value of the longitudinal magnetostriction (λ Pa ) at 1.6 T increases with Co content.

  9. Crystal structure and high-temperature properties of the Ruddlesden–Popper phases Sr{sub 3x}Y{sub x}(Fe{sub 1.25}Ni{sub 0.75})O{sub 7−δ} (0≤x≤0.75)

    Energy Technology Data Exchange (ETDEWEB)

    Samain, Louise; Amshoff, Philipp [Department of Materials and Environmental Chemistry, Stockholm University, S-106 91 Stockholm (Sweden); Biendicho, Jordi J. [Department of Materials and Environmental Chemistry, Stockholm University, S-106 91 Stockholm (Sweden); The ISIS Facility, STFC Rutherford Appleton Laboratory, Didcot OX11 0QX, Oxfordshire (United Kingdom); Tietz, Frank [Institute of Energy and Climate Research, IEK-1, Forschungszentrum Jülich GmbH, D-52425 Jülich (Germany); Mahmoud, Abdelfattah [Jülich Centre for Neutron Science JCNS and Peter Grünberg Institut PGI, JARA-FIT, Forschungszentrum Jülich GmbH, D-52425 Jülich (Germany); Hermann, Raphaël P. [Jülich Centre for Neutron Science JCNS and Peter Grünberg Institut PGI, JARA-FIT, Forschungszentrum Jülich GmbH, D-52425 Jülich (Germany); Faculty of Science, University of Liège, B-4000 Liège (Belgium); Istomin, Sergey Ya. [Department of Materials and Environmental Chemistry, Stockholm University, S-106 91 Stockholm (Sweden); Department of Chemistry, M.V. Lomonosov Moscow State University, 119991 Moscow (Russian Federation); Grins, Jekabs [Department of Materials and Environmental Chemistry, Stockholm University, S-106 91 Stockholm (Sweden); Svensson, Gunnar, E-mail: gunnar.svensson@mmk.su.se [Department of Materials and Environmental Chemistry, Stockholm University, S-106 91 Stockholm (Sweden)

    2015-07-15

    Ruddlesden–Popper n=2 member phases Sr{sub 3x}Y{sub x}Fe{sub 1.25}Ni{sub 0.75}O{sub 7−δ}, 0≤x≤0.75, have been investigated by X-ray and neutron powder diffraction, thermogravimetry and Mössbauer spectroscopy. Both samples as-prepared at 1300 °C under N{sub 2}(g) flow and samples subsequently air-annealed at 900 °C were studied. The as-prepared x=0.75 phase is highly oxygen deficient with δ=1, the O1 atom site being vacant, and the Fe{sup 3+}/Ni{sup 2+} ions having a square pyramidal coordination. For as-prepared phases with lower x values, the Mössbauer spectral data are in good agreement with the presence of both 5- and 4-coordinated Fe{sup 3+} ions, implying in addition a partial occupancy of the O3 atom sites that form the basal plane of the square pyramid. The air-annealed x=0.75 sample has a δ value of 0.61(1) and the structure has Fe/Ni ions in both square pyramids and octahedra. Mössbauer spectroscopy shows the phase to contain only Fe{sup 3+}, implying that all Ni is present as Ni{sup 3+}. Air-annealed phases with lower x values are found to contain both Fe{sup 3+} and Fe{sup 4+}. For both the as-prepared and the air-annealed samples, the Y{sup 3+} cations are found to be mainly located in the perovskite block. The high-temperature thermal expansion of as-prepared and air-annealed x=0.75 phases were investigated by high-temperature X-ray diffraction and dilatometry and the linear thermal expansion coefficient determined to be 14.4 ppm K{sup −1}. Electrical conductivity measurements showed that the air-annealed samples have higher conductivity than the as-prepared ones. - Highlights: • Ruddlesden–Popper, n=2, Sr{sub 3x}Y{sub x}Fe{sub 1.25}Ni{sub 0.75}O{sub 7−δ}, 0≤x≤0.75, have been synthesised. • The crystal structures of the phases have been determined. • Sr{sub 2.25}Y{sub 0.75}Fe{sub 1.25}Ni{sub 0.75}O{sub 6}, made in N{sub 2}(g) has Fe{sup 3+}/Ni{sup 2+} in square pyramides. • Sr{sub 2.25}Y{sub 0.75}Fe{sub 1.25}Ni

  10. Transport and superconducting properties of Fe-based superconductors: a comparison between SmFeAsO1-xFx and Fe1+yTe1-xSex

    Science.gov (United States)

    Tropeano, M.; Pallecchi, I.; Cimberle, M. R.; Ferdeghini, C.; Lamura, G.; Vignolo, M.; Martinelli, A.; Palenzona, A.; Putti, M.

    2010-05-01

    In this paper we carry out a direct comparison between transport and superconducting properties—namely resistivity, magnetoresistivity, Hall effect, Seebeck effect, thermal conductivity, upper critical field—of two different families of Fe-based superconductors, which can be viewed in many respects as end members: SmFeAsO1 - xFx with the largest Tc and the largest anisotropy and Fe1 + yTe1 - xSex, with the largest Hc2, the lowest Tc and the lowest anisotropy. In the case of the SmFeAsO1 - xFx series, we find that a single-band description allows us to extract an approximate estimation of band parameters such as carrier density and mobility from experimental data, although the behaviour of the Seebeck effect as a function of doping demonstrates that a multiband description would be more appropriate. On the contrary, experimental data for the Fe1 + y(Te1 - x, Sex) series exhibit a strongly compensated behaviour, which can be described only within a multiband model. In the Fe1 + y(Te1 - x, Sex) series, the role of the excess Fe, tuned by Se stoichiometry, is found to be twofold: on one hand it dopes electrons in the system and on the other hand it introduces localized magnetic moments, responsible for Kondo like scattering and likely pairbreaking of Cooper pairs. Hence, Fe excess also plays a crucial role in determining superconducting properties such as the Tc and the upper critical field Hc2. The huge Hc2 values of the Fe1 + yTe1 - xSex samples are described by a dirty limit law, opposed to the clean limit behaviour of the SmFeAsO1 - xFx samples. Hence, magnetic scattering by excess Fe seems to drive the system in the dirty regime, but its detrimental pairbreaking role seems not to be as severe as predicted by theory. This issue has yet to be clarified, addressing the more fundamental issue of the interplay between magnetism and superconductivity.

  11. Unconventional antiferromagnetic correlations of the doped Haldane gapsystem Y 2 BaNi 1 - x Zn x O 5

    Science.gov (United States)

    Villar, V.; Mélin, R.; Paulsen, C.; Souletie, J.; Janod, E.; Payen, C.

    2002-01-01

    We make a new proposal to describe the very low temperature susceptibility of the doped Haldane gap compound Y2BaNi1-xZnxO5. We propose a new mean field model relevant for this compound. The ground state of this mean field model is unconventional because antiferromagnetism coexists with random dimers. We present new susceptibility experiments at very low temperature. We obtain a Curie-Weiss susceptibility χ(T) C/(Θ + T) as expected for antiferromagnetic correlations but we do not obtain a direct signature of antiferromagnetic long range order. We explain how to obtain the ``impurity'' susceptibility (T) by subtracting the Haldane gap contribution to the total susceptibility. In the temperature range [1 K, 300 K] the experimental data are well fitted by T (T) = Cimp 1 + Timp/T . In the temperature range [100 mK, 1 K] the experimental data are well fitted by T (T) = A ln(T/Tc), where Tc increases with x. This fit suggests the existence of a finite Néel temperature which is however too small to be probed directly in our experiments. We also obtain a maximum in the temperature dependence of the ac-susceptibility (T) which suggests the existence of antiferromagnetic correlations at very low temperature.

  12. An X-ray absorption spectroscopic study of the metal site preference in Al1xGaxFeO3

    International Nuclear Information System (INIS)

    Walker, James D.S.; Grosvenor, Andrew P.

    2013-01-01

    Magnetoelectric materials have potential for being introduced into next generation technologies, especially memory devices. The AFeO 3 (Pna2 1 ; A=Al, Ga) system has received attention to better understand the origins of magnetoelectric coupling. The magnetoelectric properties this system exhibits depend on the amount of anti-site disorder present, which is affected by the composition and the method of synthesis. In this study, Al 1x Ga x FeO 3 was synthesized by the ceramic method and studied by X-ray absorption spectroscopy. Al L 2,3 -, Ga K-, and Fe K-edge spectra were collected to examine how the average metal coordination number changes with composition. Examination of XANES spectra from Al 1x Ga x FeO 3 indicate that with increasing Ga content, Al increasingly occupies octahedral sites while Ga displays a preference for occupying the tetrahedral site. The Fe K-edge spectra indicate that more Fe is present in the tetrahedral site in AlFeO 3 than in GaFeO 3 , implying more anti-site disorder is present in AlFeO 3 . - Graphical abstract: Al 1x Ga x FeO 3 has been investigated by XANES. Through examination of Al L 2,3 -, Ga K-, and Fe K-edge XANES spectra, it was found that more anti-site disorder of the Fe atoms is present in AlFeO 3 compared to in GaFeO 3 . Highlights: ► Al 1x Ga x FeO 3 was investigated by X-ray absorption spectroscopy. ► Ga prefers to occupy the tetrahedral site in Al 1x Ga x FeO 3 . ► Fe prefers to occupy the octahedral sites in Al 1x Ga x FeO 3 as x increases. ► More anti-site disorder is present in AlFeO 3 compared to in GaFeO 3.

  13. The thermal expansion coefficient of Ga/sub x/In/sub 1-x/As/sub y/P/sub 1-y/ epitaxial layers grown on InP substrate

    International Nuclear Information System (INIS)

    Pietsch, U.; Marlow, D.

    1986-01-01

    The amount of the measured room temperature thermal expansion coefficient of tetragonal strained layers grown lattice matched on the InP substrate used is about 30% greater the expected one for a cubic 'relaxed' material. This issue has to be taken into account for the determination of the composition of the quarternary Ga/sub x/In/sub 1-x/As/sub y/P/sub 1-y/ layers from both X-ray and photoluminescence data as well as for the estimation of the thermally created stress field of optoelectronic devices. (author)

  14. Structure and electrical conduction of the system La sub(1-x)Ca sub(x)FeO sub(3-α)

    International Nuclear Information System (INIS)

    Hombo, Jukichi; Urabe, Noriake; Hiroshige, Gota; Hamada, Kotaro.

    1982-01-01

    Perovskite phases in the system, La sub(1-x)Ca sub(x)FeO sub(3-α) were prepared with La 2 O 3 , CaCO 3 , and Fe 2 O 3 by firing in air and in vacuo. The compositions of samples fired in vacuo and in air are represented as La sub(1-x)Ca sub(x)FeO sub(3-x 2) and La sub(1-x)Ca sub(x)Fe sub(1-y)sup(3+)Fe sub(y)sup(4+)O sub(3-x/2+y/2), respectively. That is, samples fired in vacuo contain some oxygen vacancies and no tetravalent iron; in contrast, samples fired in air contain both oxygen vacancies and tetravalent iron in the structures. The electrical conductivities of these synthesized oxides depended extensively upon the content of tetravalent iron. For instance, the conductivity of the sample x = 0.6 fired in air was larger by 10 6 than that of the sample fired in vacuo. In this system, except for the two terminal compositions of x = 0 and x = 1.0, the values of activation energy for conduction are considerably small, and from the results of thermo-electromotive force measurement, the charge carrier was positive. Furthermore, the conductivity increased somewhat with time during the conductivity measurement by the direct-current method. These facts suggest that the electrical conducted would not be ionic but electronic. The electrical conduction would then be carried out by the so-called hopping mechanism by which the positive charge is transferred. (author)

  15. Synthesis and photoluminescence properties of Sm{sup 3+}substituted glaserite-type orthovanadates K{sub 3}Y[VO{sub 4}]{sub 2} with monoclinic structure

    Energy Technology Data Exchange (ETDEWEB)

    Duke John David, A., E-mail: dukejohndavid02@gmail.com [Voorhees College, Vellore, Tamil Nadu (India); Muhammad, G. Shakil [Islamiah College, Vaniyambadi, Tamil Nadu (India); Sivakumar, V. [National Institute of Technology (NIT), Rourkela (India)

    2016-09-15

    A novel phosphor of Glaserite type Orthovanadate K{sub 3}Y[VO{sub 4}]{sub 2} substituted with the trivalent rare-earth Sm{sup 3+} ions were synthesized by the conventional high temperature solid-state reaction method, their structural characterization and photoluminescent properties were investigated by X-ray diffraction and spectrofluorimetry. The phase-purity of glaserite structure in the synthesized compound was verified by XRD study. The morphology was measured by FESEM. Host lattice emits broad-band green color and it is originated from the [VO{sub 4}]{sup 3−}. Photoluminescence studies of Sm{sup 3+} activated samples show orange red emission. The charge transfer behaviours from [VO{sub 4}]{sup 3−} to Sm{sup 3+} ions (host to activator) in K{sub 3}Y{sub (1x)}[VO{sub 4}]{sub 2}: {sub x}Sm{sup 3+} phosphors have been confirmed by photoluminescence and PL decay life time measurement. No concentration quenching was observed even for higher concentration of the dopant Sm{sup 3+} ions. The CIE chromaticity color coordinate values were calculated and it is very much closer to the NTSC standards. All the results clearly indicate that self-activated K{sub 3}Y{sub 1x}[VO{sub 4}]{sub 2} with the rare earth {sub x}Sm{sup 3+} activated phosphors show great potential as a phosphor material for near-UV based white LEDs.

  16. Alloying as a Route to Monolayer Transition Metal Dichalcogenides with Improved Optoelectronic Performance: Mo(S1xSex)2 and Mo1yWyS2

    KAUST Repository

    Shi, Zhiming; Zhang, Qingyun; Schwingenschlö gl, Udo

    2018-01-01

    xSex)2 and Mo1yWyS2 with x = 1/3, 2/3 and y = 1/3, 1/2, 2/3 are stable according to phonon calculations and realize 1T′ or 1T″ phases. The transition barriers from the 2H phase are lower than for monolayer MoS2, implying that the 1T′ or 1T″ phases

  17. Structure, chemistry and luminescence properties of dielectric La{sub x}Hf{sub 1-x}O{sub y} films

    Energy Technology Data Exchange (ETDEWEB)

    Kaichev, V.V., E-mail: vvk@catalysis.ru [Boreskov Institute of Catalysis, Novosibirsk (Russian Federation); Novosibirsk State University, Novosibirsk (Russian Federation); Smirnova, T.P.; Yakovkina, L.V. [Nikolaev Institute of Inorganic Chemistry, Novosibirsk (Russian Federation); Ivanova, E.V.; Zamoryanskaya, M.V. [Ioffe Physical-Technical Institute, St. Petersburg (Russian Federation); Saraev, A.A. [Boreskov Institute of Catalysis, Novosibirsk (Russian Federation); Novosibirsk State University, Novosibirsk (Russian Federation); Pustovarov, V.A. [Ural State Technical University, Ekaterinburg (Russian Federation); Perevalov, T.V.; Gritsenko, V.A. [Novosibirsk State University, Novosibirsk (Russian Federation); Rzhanov Institute of Semiconductor Physics, Novosibirsk (Russian Federation)

    2016-06-01

    Dielectric films of La{sub 2}O{sub 3}, HfO{sub 2}, and La{sub x}Hf{sub 1-x}O{sub y} were synthesized by metal-organic chemical vapor deposition. Structural, chemical, and luminescence properties of the films were studied using X-ray photoelectron spectroscopy, methods of X-ray diffraction and selected area electron diffraction, high-resolution transmission electron microscopy, and a cathodoluminescence technique. It was found that doping of hafnium oxide with lanthanum leads to the formation of a continuous series of solid solutions with a cubic structure. This process is accompanied by the formation of oxygen vacancies in the HfO{sub 2} lattice. Cathodoluminescence spectra of the La{sub x}Hf{sub 1-x}O{sub y}/Si films exhibited a wide band with the maximum near 2.4–2.5 eV, which corresponds to the blue emission. Quantum-chemical calculations showed that this blue band is due to oxygen vacancies in the HfO{sub 2} lattice. - Highlights: • HfO{sub 2} and solid solution La{sub x}Hf{sub 1-x}O{sub y} films were synthesized by MOCVD. • The continuous series of solid solutions with a cubic structure was formed at La doping of HfO{sub 2}. • Cathodoluminescence band at 2.4–2.5 eV is observed due to the oxygen vacancies in La{sub x}Hf{sub 1-x}O{sub y}. • The cathodoluminescence decreases in intensity when the La concentration increases.

  18. Judd–Ofelt analysis and transition probabilities of Er{sup 3+} doped KY{sub 1−x−y}Gd{sub x}Lu{sub y}(WO{sub 4}){sub 2} crystals

    Energy Technology Data Exchange (ETDEWEB)

    Martínez de Mendívil, Jon, E-mail: jon.martinez@uam.es [Departamento de Física de Materiales, Universidad Autónoma de Madrid, 28049 Madrid (Spain); Lifante, Ginés [Departamento de Física de Materiales, Universidad Autónoma de Madrid, 28049 Madrid (Spain); Pujol, Maria Cinta; Aguiló, Magdalena; Díaz, Francesc [Física i Cristalografia de Materials i Nanomaterials (FiCMA-FiCNA), Universitat Rovira i Virgili, Tarragona (Spain); Cantelar, Eugenio [Departamento de Física de Materiales, Universidad Autónoma de Madrid, 28049 Madrid (Spain)

    2015-09-15

    In this work the transition probabilities, radiative lifetimes and branching ratios of Er{sup 3+} ions in KY{sub 1−x−y}Gd{sub x}Lu{sub y}(WO{sub 4}){sub 2} crystals have been determined. With this aim, Er{sup 3+} doped KY{sub 1−x−y}Gd{sub x}Lu{sub y}(WO{sub 4}){sub 2} crystals have been grown by means of the high temperature Top-Seeded Solution Growth. A spectroscopic analysis of Er{sup 3+} ions in this crystal has been performed following anisotropic Judd–Ofelt analysis to obtain basic spectroscopic properties. A quantum efficiency over 97% has been determined for the {sup 4}I{sub 13/2}→{sup 4}I{sub 15/2} transition, indicating that this material is adequate for the development of lasers and amplifiers working in the third telecommunication window. - Highlights: • Er{sub 0.01}:KY{sub 1−x−y}Gd{sub x}Lu{sub y}(WO{sub 4}){sub 2} crystals have been grown. • Anisotropic Judd Ofelt analysis has been carried out. • Optical transition probabilities and branching ratios have been calculated. • Radiative and non-radiative lifetimes have been obtained.

  19. Modulation of electronic and optical properties in mixed halide perovskites CsPbCl3xBr3(1-x) and CsPbBr3xI3(1-x)

    Science.gov (United States)

    Zhou, Ziqi; Cui, Yu; Deng, Hui-Xiong; Huang, Le; Wei, Zhongming; Li, Jingbo

    2017-03-01

    The recent discovery of lead halide perovskites with band gaps in the visible presents important potential in the design of high efficient solar cells. CsPbCl3, CsPbBr3 and CsPbI3 are stable compounds within this new family of semiconductors. By performing the first-principles calculation, we explore the structural, electronic and optical properties of CsPbCl3xBr3(1-x) and CsPbBr3xI3(1-x) with various compositions of halide atoms. Structural stability is demonstrated with halide atoms distributing randomly at the halide atomic sites. CsPbCl3xBr3(1-x) and CsPbBr3xI3(1-x) exhibit the modulation of their band gaps by varying the halide composition. Our results also indicate that CsPbCl3xBr3(1-x) and CsPbBr3xI3(1-x) with different halide compositions are suitable to application to solar cells for the general features are well preserved. Good absorption to lights of different wavelengths has been obtained in these mixed halide perovskites.

  20. Structural, Dielectric, and Electrical Properties of Bi1- x Pb x Fe1- x (Zr0.5Ti0.5) x O3

    Science.gov (United States)

    Panda, Niranjan; Pattanayak, Samita; Choudhary, R. N. P.

    2015-12-01

    Polycrystalline samples of Bi1- x Pb x Fe1- x (Zr0.5Ti0.5) x O3 (BPFZTO) with x = 0.0, 0.2, 0.3, and 0.4 were prepared by high-temperature solid-state reaction. Preliminary structural analysis of calcined powders of the materials by use of x-ray powder diffraction confirmed formation of single-phase systems with the tetragonal structure. Room-temperature scanning electron micrographs of the samples revealed uniform distribution of grains of low porosity and different dimensions on the surface of the samples. The frequency-temperature dependence of dielectric and electric properties was studied by use of dielectric and complex impedance spectroscopy over a wide range of frequency (1 kHz to 1 MHz) at different temperatures (25-500°C). The dielectric constant of BiFeO3 (BFO) was enhanced by substitution with Pb(Zr0.5Ti0.5)O3 (PZT) whereas the dielectric loss of the BPFZTO compounds decreased with increasing PZT content. A significant contribution of both grains and grain boundaries to the electrical response of the materials was observed. The frequency-dependence of the ac conductivity of BPFZTO followed Jonscher's power law. Negative temperature coefficient of resistance behavior was observed for all the BPFZTO samples. Conductivity by thermally excited charge carriers and oxygen vacancies in the materials was believed to be of the Arrhenius-type.

  1. Phase stability predictions of Cr1x, Mx)2(Al1y, Ay)(C1−z, Xz) (M = Ti, Hf, Zr; A = Si, X = B)

    International Nuclear Information System (INIS)

    Shang, Lin; Music, Denis; Baben, Moritz to; Schneider, Jochen M

    2014-01-01

    The phase stability of (Cr 1x , M x ) 2 (Al 1y , A y )(C 1−z , X z ) (M = Ti, Hf, Zr; A = Si, X = B, space group P6 3 /mmc, prototype Cr 2 AlC) was studied using ab initio calculations. Based on the energy of mixing data as well as the density of states (DOS) analysis, (Cr 1x , Zr x ) 2 AlC and (Cr 1x , Hf x ) 2 AlC are predicted to be unstable, whereas (Cr 1x , Ti x ) 2 AlC, Cr 2 (Al 1y , Si y )C and Cr 2 Al(C 1−z , B z ) are predicted to be stable or metastable. The density of states analysis reveals that small differences in the position of the Fermi level alters the phase stability: (Cr 1x , Zr x ) 2 AlC and (Cr 1x , Hf x ) 2 AlC are predicted to be unstable or metastable as the Fermi level lies at a peak position. While the Cr dominated DOS for (Cr 1x , Ti x ) 2 AlC plateaus at the Fermi level indicating stability. Implications of these results for the vapour phase condensation of self-healing Cr 2 AlC based materials are discussed. (paper)

  2. The Calculation Spontaneous Polarization and Quadrupole Moment of Electric Potential PIZT (PbInxZryTi1-x-yO3-x/2

    Directory of Open Access Journals (Sweden)

    Irzaman

    2004-12-01

    Full Text Available ZT (PbZr1-xTixO3 is a perovskite crystal that can be used for IR sensor. Small amount of dopant can drastically change the specific characteristic of ferroelectric ceramic such as spontaneous polarization, dielectric constant, electromechanical and also electro-optic properties. The addition of In3+ ion (called as hard doping has been applied in this research. Thin film of PIZT (PbInxZryTi1-x-yO3-x/2 has been deposited on Si(100 substrate with Chemical Solution Deposition (CSD method. The concentration of solution is 0,5 M and the angular speed applied of spin coating is 3000 rpm. The PIZT sample has been analyzed with x-ray diffraction method. Rietveld analyses using GSAS-EXPGUI software resulted lattice parameter of crystal and phase compositions of PIZT samples. The values of all sample PIZT spontaneous polarization (Ps have been calculated lower than PZT. The optimally Ps was reached at 0,5% to 1% In2O3 doping. Quadrupole moment of electric potential (ΦQ(r at point P (0,0,2a reached optimum at 6% In2O3 doping and they also showed that PIZT thin film have ΦQ(r higher value than their bulk form for In2O3 doping >1%.

  3. X-ray and neutron single-crystal diffraction on [Rbx(NH4)1-x]3H(SO4)2. I. Refinement of crystal structure of phase II with x=0.11 at 300 K

    International Nuclear Information System (INIS)

    Loose, A.; Wozniak, K.; Dominiak, P.; Smirnov, L.S.; Natkaniec, I.; Frontas'eva, M.V.; Pomyakushina, E.V.; Baranov, A.I.; Dolbinina, V.V

    2006-01-01

    The study of [Rb x (NH 4 ) 1-x ] 3 H(SO 4 ) 2 mixed crystals by X-ray single-crystal diffraction is known up to now only for x=0.57 at the temperatures 293 and 180 K. The crystal structures at these temperatures as was determined [1] belong to monoclinic phase II (C2/c sp. gr., Z=4). In accordance with this work, ammonium ions should be considered as deformed tetrahedra. Monoclinic phase II on the x-T phase diagram of [Rb x (NH 4 ) 1-x ] 3 H(SO 4 ) 2 mixed crystals, which has earlier been determined by the dielectric spectroscopy, is stabilized below room temperature if Rb concentration exceeds 9%. The presented results of X-ray and neutron single-crystal diffraction of the [Rb 0.11 (NH 4 ) 0.89 ] 3 H(SO 4 ) 2 mixed crystal at T= 300 K show that ammonium ions could be considered as regular tetrahedra

  4. CEXE INCEXE, 1 Group 3-D Time-Dependent Xe Oscillations in X-Y-Z Geometry with Feedback

    International Nuclear Information System (INIS)

    Kern, R.; Pacino, S.

    1973-01-01

    1 - Description of problem or function: CEXE solves the three- dimensional xyz time-dependent xenon spatial oscillation problem using a modified one energy group theory and a nodal representation. 2 - Method of solution: CEXE solves for the spatial neutron source distribution with coupled Doppler and moderator temperature feedbacks. The time dependence of the iodine and xenon concentrations are based on the assumption of constant power during each time-step interval. 3 - Restrictions on the complexity of the problem: Maximum reactor core size representation is restricted to a nodal configuration of 19 x 19 x 10 in the x, y, z directions, respectively

  5. Magnetic and electrical transport properties of Pb1-xLaxTi1-xMnxO3 ceramics

    Directory of Open Access Journals (Sweden)

    Jie Xu

    2012-09-01

    Full Text Available Pb1-xLaxTi1-xMnxO3 (PLTM100x, x = 0.20, 0.40, 0.50, 0.60, and 0.80 ceramics have been prepared and investigated. X-ray diffractions show all ceramics are crystallized into perovskite structures with tetragonal symmetry for PLTMO20 and orthorhombic symmetry for the other compositions. X-ray photoelectron spectroscopy results confirm that the Mn cations in PLTMO20 and PLTMO40 have the valence state of +3, whereas in other compositions, the Mn cations have mixed valences states of +3 and +4. With increasing x from 0.20 to 0.80, the materials change from superparamagnetic to coexisting ferromagnetic and antiferromagnetic magnetic behaviour whereas all compositions persist insulating behaviour, as confirmed by the magnetization-magnetic field (M-H, the temperature dependent magnetization (M-T and transport measurements. Especially, the PLTMO80 has a large negative magnetoresistance of −41.5% at 10 K with the applied filed of 2 T. By considering the chemical states of Mn cations, these results are attributed to that the coexistence of metallic ferromagnetic and insulating non-ferromagnetic phases.

  6. Magnetic properties of NdMn{sub 1x}Fe{sub x}O{sub 3+δ} (0≤x≤0.3) system

    Energy Technology Data Exchange (ETDEWEB)

    Mihalik, Matúš, E-mail: matmihalik@saske.sk [Institute of Experimental Physics SAS, Watsonova 47, 040 01 Košice (Slovakia); Mihalik, Marián [Institute of Experimental Physics SAS, Watsonova 47, 040 01 Košice (Slovakia); Fitta, M.; Bałanda, M. [Institute of Nuclear Physics Polish Academy of Sciences, Radzikowskiego 152, 31-342 Kraków (Poland); Vavra, M. [Institute of Experimental Physics SAS, Watsonova 47, 040 01 Košice (Slovakia); P.J. Šafárik University, Moyzesova 11, 041 54 Košice (Slovakia); Gabáni, S.; Zentková, M. [Institute of Experimental Physics SAS, Watsonova 47, 040 01 Košice (Slovakia); Briančin, J. [Institute of Geotechnics SAS, Watsonova 45, 043 53 Košice (Slovakia)

    2013-11-15

    We have studied the effect of Fe for Mn substitution on magnetic properties of NdMn{sub 1x}Fe{sub x}O{sub 3+δ} compounds. Our heat capacity, AC susceptibility and magnetization measurements revealed that the transition from paramagnetic to magnetically ordered state of the Mn sublattice decreases linearly from T{sub N}=74.9 K to T{sub N}=49 K with doping up to x=0.25. The ordering temperature T{sub 1} of Nd sublattice varies in a non-monotonous way in the temperature range 11–16 K. For x=0.3, the ordering of the Mn/Fe sublattice is residual, while the magnetism in Nd sublattice seems to be intact. The broad maximum in heat capacity C(T) at about 10 K was ascribed by 2-level Schottky contribution (Δ=21(1) K) for x=0, but this description failed for Fe-doped samples. An upturn of C(T) at temperatures below 0.5 K was observed on NdMnO{sub 3} and can be accounted to nuclear contribution. A more detailed study of AC susceptibility performed on samples with x=0.1 and 0.2 revealed a shift of both peaks to higher temperature with increasing frequency. The compensation temperature and a large negative field-cooled magnetization was observed for concentrations x=0.2 and x=0.25. - Highlights: • Fe substitution into NdMnO{sub 3} compound decreases T{sub N} by 10 K for 10% of Fe. • In this compound: Nd and Mn ions both order magnetically. • “Butterfly-type” hysteresis loops in the ordered state.

  7. Magnetotransport, structural and optical characterization of p-type modulation doped heterostructures with high Ge content Si1-xGex channel grown by SS-MBE on Si1-yGey/Si(001) virtual substrates

    International Nuclear Information System (INIS)

    Myronov, M.

    2001-04-01

    This thesis is a report on experimental investigations of magnetotransport, structural and optical properties of p-type modulation doped (MOD) heterostructures with Si 1-x Ge x channel of high Ge content (0.6 1-y Ge y /Si(001) virtual substrate (VS). The active layers of MOD heterostructures were grown by solid source molecular beam epitaxy (SS-MBE). The VSs were grown either by SS-MBE or low-pressure chemical vapour deposition (LP-CVD). The influence of thermal annealing on magnetotransport, structural and optical properties of Si 1-x Ge x /Si 1-y Ge y heterostructures was studied by performing the post growth furnace thermal annealing (FTA) treatments in the temperature range of 600-900C for 30min and rapid thermal annealing (RTA) treatments at temperature 750C for 30sec. Structural and optical analysis of p-type MOD Si 1-x Ge x /Si 1-y Ge y heterostructures involved the techniques of cross-sectional transmission electron microscopy, ultra low energy secondary ion mass spectrometry, photoluminescence spectroscopy, micro-Raman spectroscopy and scanning white-light interferometry. From the combinations of experimental results obtained by these techniques the Ge composition in the SiGe heteroepilayers, their thicknesses, state of strain in the heteroepilayers and dislocations microstructure in VSs were obtained. After post growth thermal annealing treatments were observed broadening of the Si 1-x Ge x channel accompanied with the reduction of Ge content in the channel and smearing of Si 1-x Ge x /Si 1-y Ge y interfaces. The Si 0.7 Ge 0.3 on low-temperature Si buffer VSs with very good structural properties were designed and grown by SS-MBE. These include: relatively thin 850nm total thickness of VS, 4-6nm Peak-to-Valley values of surface roughness, less than 10 5 cm -2 threading dislocations density and more than 95% degree of relaxation in the top layers of VS. The Hall mobility and sheet carrier density of as-grown and annealed p-type MOD Si 1-x Ge x /Si 1-y Ge y

  8. Structure, magnetism and electronic properties in 3d-5d based double perovskite (Sr1-xYx)2FeIrO6.

    Science.gov (United States)

    Kharkwal, Kishor Chandra; Pramanik, Ashim Kumar

    2017-10-17

    The 3$d$-5$d$ based double perovskites are of current interest as they provide model system to study the interplay between electronic correlation ($U$) and spin-orbit coupling (SOC). Here we report detailed structural, magnetic and transport properties of doped double perovskite material (Sr$_{1-x}$Y$_x$)$_2$FeIrO$_6$ with $x$ $\\leq$ 0.2. With substitution of Y, system retains its original crystal structure but structural parameters modify with $x$ in nonmonotonic fashion. The magnetization data for Sr$_2$FeIrO$_6$ show antiferromagnetic type magnetic transition around 45 K, however, a close inspection in data indicates a weak magnetic phase transition around 120 K. No change of structural symmetry has been observed down to low temperature, although the lattice parameters show sudden changes around the magnetic transitions. Sr$_2$FeIrO$_6$ shows an insulating behavior over the whole temperature range which yet does not change with Y substitution. Nature of charge conduction is found to follow thermally activated Mott's variable range hopping and power law behavior for parent and doped samples, respectively. Interestingly, evolution of structural, magnetic and transport behavior in (Sr$_{1-x}$Y$_x$)$_2$FeIrO$_6$ is observed to reverse with $x$ $>$ 0.1 which is believed to arise due to change in transition metal ionic state. © 2017 IOP Publishing Ltd.

  9. Crystallisation kinetics of amorphous Fe{sub 72.5-x}Cu{sub 1}Nb{sub 4.5}Si{sub 10+x+y}B{sub 12-y} alloy

    Energy Technology Data Exchange (ETDEWEB)

    Miglierini, M. [Komenskeho Univ., Bratislava (Czechoslovakia). Dept. of Nuclear Physics and Technics; Lipka, J. [Komenskeho Univ., Bratislava (Czechoslovakia). Dept. of Nuclear Physics and Technics; Sitek, J. [Komenskeho Univ., Bratislava (Czechoslovakia). Dept. of Nuclear Physics and Technics

    1994-11-01

    Fe{sub 73.5}Cu{sub 1}Nb{sub 3}Si{sub 13.5}B{sub 9} and Fe{sub 72.5-x}Cu{sub 1}Nb{sub 4.5}Si{sub 10+x+y}B{sub 12-y} alloys are compared from the point of view of crystallisation behaviour and changes in the short-range order in the amorphous reminder. The increase in Nb to 4.5 at.% in the latter system slows down the formation of nanocrystals to approximately 40% even after 16 hours of anneal at 550 C for x = 0.5, y = 3. Segregation-induced changes in the short-range order are manifested via hyperfine field distributions corresponding to the amorphous reminder. (orig.)

  10. CaMn(1-x)Nb(x)O3 (x < or = 0.08) perovskite-type phases as promising new high-temperature n-type thermoelectric materials.

    Science.gov (United States)

    Bocher, L; Aguirre, M H; Logvinovich, D; Shkabko, A; Robert, R; Trottmann, M; Weidenkaff, A

    2008-09-15

    Perovskite-type CaMn(1-x)Nb(x)O(3+/-delta) (x = 0.02, 0.05, and 0.08) compounds were synthesized by applying both a "chimie douce" (SC) synthesis and a classical solid state reaction (SSR) method. The crystallographic parameters of the resulting phases were determined from X-ray, electron, and neutron diffraction data. The manganese oxidations states (Mn(4+)/Mn(3+)) were investigated by X-ray photoemission spectroscopy. The orthorhombic CaMn(1-x)Nb(x)O(3+/-delta) (x = 0.02, 0.05, and 0.08) phases were studied in terms of their high-temperature thermoelectric properties (Seebeck coefficient, electrical resistivity, and thermal conductivity). Differences in electrical transport and thermal properties can be correlated with different microstructures obtained by the two synthesis methods. In the high-temperature range, the electron-doped manganate phases exhibit large absolute Seebeck coefficient and low electrical resistivity values, resulting in a high power factor, PF (e.g., for x = 0.05, S(1000K) = -180 microV K(-1), rho(1000K) = 16.8 mohms cm, and PF > 1.90 x 10(-4) W m(-1) K(-2) for 450 K 0.3) make these phases the best perovskitic candidates as n-type polycrystalline thermoelectric materials operating in air at high temperatures.

  11. The (x, T) magnetic phase diagram of Y2Co17-xCrx (1.17-bar x-bar 3) compounds by neutron diffraction

    International Nuclear Information System (INIS)

    Schobinger-Papamantellos, P.; Buschow, K.H.J.; Fuquan, B.; Tegus, O.; Brueck, E.; Boer, F.R. de; Ritter, C.

    2006-01-01

    We present the (x, T) phase diagram of the ferromagnetic Y 2 Co 17-x Cr x (x=1.17, 1.76, 2.34, 3) compounds with rhombohedral structure (space group R3-bar m, Th 2 Zn 17 -type), determined for the entire magnetically ordered regime from high-resolution neutron-diffraction data. Substitution of small amounts of Cr for Co was found to have drastic effects on the magnetic properties such as a decrease of the Curie (T C ) and spin reorientation (T SR ) temperatures as well as a decrease of the ordered-moment values. These effects could be brought into connection to the fact that Cr was found to have a preference for the four Co sites in the following order 6c>18f>9d>18h. The number of Cr atoms found occupying the latter two sites, however, is within experimental error negligible. The magnetic phase diagram comprises three distinct regions of magnetic order in addition to the paramagnetic state: (a) the HT range (easy axis) (b) the LT (easy plane) for 0 C and T SR . It also leads to the formation of varying portions of the hexagonal Th 2 Ni 17 -modification (with similar magnetic properties) in samples with x>=1.76. The crystal and magnetic structure of both modifications were refined simultaneously

  12. Effect of the manganese in (Pb1-x Lax) TiO3 piezoelectric ceramics

    International Nuclear Information System (INIS)

    Garcia, D.; Eiras, J.A.

    1990-01-01

    Measurements of the relative dielectric constant K, the electric dissipation factor tan δ and the electrochemical coupling factors of the thickness k t and planar K p vibration modes were realized in lead titanate piezoelectric ceramics, with batched composition (Pb 1-3/2x La x )TiO 3 , 0,025 ≤ x ≤0,20. The same parameters were determined in these compositions after the addition of 1%mol of Mn. The results shown clearly that manganese increases the electrochanical anisotropy (K t /K p ) and decreases the dielectric constant and the electric dissipation factor of these materials. (author) [pt

  13. Defect chemistry modelling of oxygen-stoichiometry, vacancy concentrations, and conductivity of (La1-xSrx)(y)MnO3 +/-delta

    DEFF Research Database (Denmark)

    Poulsen, F.W.

    2000-01-01

    model, based on delocalised electrons, electron holes and all B-ions being trivalent is given in Appendix A. The sequential mathematical method allows us to calculate the high temperature oxygen partial pressure dependent properties of (La1-xSrx)(y)MnO3+/-delta in a unified manner irrespective...... are calculated by the small polaron model containing only ionic species - the B-ion may be Mn-B' (Mn2+), Mn-B(x) (Mn3+), and Mn-B(Mn4+). The A/B-ratio = y greatly influences the oxygen stoichiometry, oxygen ion vacancy- and cation vacancy concentrations and the total conductivity. Calculations are given...

  14. Thermochemistry of rare earth doped uranium oxides Ln{sub x}U{sub 1x}O{sub 2−0.5x+y} (Ln = La, Y, Nd)

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Lei; Navrotsky, Alexandra, E-mail: anavrotsky@ucdavis.edu

    2015-10-15

    Lanthanum, yttrium, and neodymium doped uranium dioxide samples in the fluorite structure have been synthesized, characterized in terms of metal ratio and oxygen content, and their enthalpies of formation measured by high temperature oxide melt solution calorimetry. For oxides doped with 10–50 mol % rare earth (Ln) cations, the formation enthalpies from constituent oxides (LnO{sub 1.5}, UO{sub 2} and UO{sub 3} in a reaction not involving oxidation or reduction) become increasingly exothermic with increasing rare earth content, while showing no significant dependence on the varying uranium oxidation state. The oxidation enthalpy of Ln{sub x}U{sub 1x}O{sub 2−0.5x+y} is similar to that of UO{sub 2} to UO{sub 3} for all three rare earth doped systems. Though this may suggest that the oxidized uranium in these systems is energetically similar to that in the hexavalent state, thermochemical data alone can not constrain whether the uranium is present as U{sup 5+}, U{sup 6+}, or a mixture of oxidation states. The formation enthalpies from elements calculated from the calorimetric data are generally consistent with those from free energy measurements. - Highlights: • We synthesize, characterize Ln{sub x}U{sub 1x}O{sub 2−0.5x+y} solid solutions (Ln = La, Y, Nd). • Formation enthalpies become more exothermic with increasing rare earth content. • Oxidation enthalpy of Ln{sub x}U{sub 1x}O{sub 2−0.5x+y} is similar to that of UO{sub 2} to UO{sub 3}. • Direct calorimetric measurements are in good agreement with free energy data.

  15. On the simultaneous Pell equations x 2 - (4m 2 - 1)y 2 = y 2 - pz 2 ...

    African Journals Online (AJOL)

    Let m be a positive integer, and let p be an odd prime. By using certain properties of Pell and quartic diophantine equations with some elementary number theory methods, we prove that the system of equations x2 - (4m2 - 1)y2 = 1 and y2 - pz2 = 1 has positive integer solutions (x, y, z) if and only if p ≡ 7(mod 8) and m = 1/4 ...

  16. Superconducting energy gap of BaPb/sub 1-//sub x/Bi/sub x/O3

    International Nuclear Information System (INIS)

    Schlesinger, Z.; Collins, R.T.; Scott, B.A.; Calise, J.A.

    1988-01-01

    We report the first infrared measurement of the superconducting energy gap of BaPb/sub 1-//sub x/Bi/sub x/O 3 . In our polycrystalline samples with T/sub c/≅9.5 K (x≅0.2) we obtain 2Δ≅3.2kT/sub c/, roughly in agreement with the weak-coupling Bardeen-Cooper-Schrieffer prediction, 2Δ = 3.5kT/sub c/, and with tunneling measurements of the gap. We do not observe any structure above the gap energy associated with strong coupling

  17. Comparación productiva de vacas holstein y F1 blanco orejinero (BON x holstein 1. producción y calidad de la leche.

    Directory of Open Access Journals (Sweden)

    Quijano Bernal Jorge H.

    2000-12-01

    Full Text Available Se estimaron los porcentajes de heterosis para la producción de leche, duración de la lactancia y calidad de la leche ( porcentaje de grasa y proteína, en vacas Holstein y F1 (BON x HOLSTEIN del Centro Paysandú, propiedad de la Universidad Nacional de Colombia, situado en el corregimiento Santa Elena, municipio de Medellín, a 2600 m.s.n.m., con temperatura promedio de 12,5C, correspondiendo a la formación bosque muy húmedo montano bajo (bmh-MB. La producción de leche fue afectada significativamente (P 0,01 y proteína (2,8 y 2,9%; P >0,01 para Holstein y F1 BON x Holstein respectivamente. En el BON estos valores fueron 278 kg, 114 días de lactancia, 4,6% de grasa y 3,9% de proteína en la leche. Los porcentajes de heterosis con base en el promedio de razas fueron: 4,20%, 16,70%, -12,80% y -12.20% para producción de leche, duración de lactancia, porcentaje de grasa y porcentaje de proteína respectivamente, todos altamente significativos (P<0,01. Los porcentajes de heterosis tomando como referencia la raza Holstein fueron: -45,20%, -21,50%, 6,25% y 5,35% en el mismo orden de las características anteriormente citadas. En general, los porcentajes de heterosis fueron menores a los reportados en la literatura. Se concluye que el F1 ha desempeñado un papel preponderante en el mejoramiento de la calidad de la leche en el Centro Paysandú, presentado porcentajes de heterosis medios para la calidad de la leche con referencia a la raza Holstein. Esto puede ser confirmado al analizar el porcentaje de grasa desde 1994, cuando parieron las primeras vacas F1, presentado coeficiente de regresión y correlación de 0,02 y 0,55 respectivamente. En la actualidad, el promedio para el porcentaje de grasa y proteína en el hato es de 3,45% y 3,03% respectivamente. Si sólo se tuviese la raza Holstein, estos porcentajes serían de 3,20% y 2,80%, significativamente menores.

  18. The (p, ρ, T, x) properties of (x1 propane + x2n-butane) with x1 (0.0000, 0.2729, 0.5021, and 0.7308) over the temperature range from (280 to 440) K at pressures from (1 to 200) MPa

    International Nuclear Information System (INIS)

    Miyamoto, H.; Uematsu, M.

    2008-01-01

    The (p, ρ, T, x) properties for (x 1 propane + x 2 n-butane) with x 1 = (0.0000, 0.2729, 0.5021, and 0.7308) in the compressed liquid phase were measured by means of a metal-bellows variable volumometer over the temperature range from (280 to 440) K at pressures from (1 to 200) MPa. The mole fraction purities of the propane and n-butane used in the measurements were 0.9999 and 0.9997, respectively. The expanded uncertainties (k = 2) in temperature, pressure, density, and composition measurements have been estimated to be less than ±3 mK; 1.4 kPa (p ≤ 7 MPa), 0.06% (7 MPa 150 MPa); 0.09%; and 4.4 . 10 -4 , respectively. In the region above 100 MPa at T = (280 and 440) K, the uncertainty in density measurements increases from 0.09% to 0.13% and 0.22%, respectively. Comparisons of the available equation of state with the present measurements are reported. On the basis of the present results, the excess molar volume v m E of the mixtures was calculated and illustrated as a function of temperature and pressure

  19. Effect of cationic substitution on the double-well hydrogen-bond potential in [K1-x(NH4)x]3H(SO4)2 proton conductors: a single-crystal neutron diffraction study.

    Science.gov (United States)

    Choudhury, R R; Chitra, R; Selezneva, E V; Makarova, I P

    2017-10-01

    The structure of the mixed crystal [K 1-x (NH 4 ) x ] 3 H(SO 4 ) 2 as obtained from single-crystal neutron diffraction is compared with the previously reported room-temperature neutron structure of crystalline K 3 H(SO 4 ) 2 . The two structures are very similar, as indicated by the high value of their isostructurality index (94.8%). It was found that the replacement of even a small amount (3%) of K + with NH 4 + has a significant influence on the short strong hydrogen bond connecting the two SO 4 2- ions. Earlier optical measurements had revealed that the kinetics of the superionic transition in the solid solution [K 1-x (NH 4 ) x ] 3 H(SO 4 ) 2 are much faster than in K 3 H(SO 4 ) 2 ; this reported difference in the kinetics of the superionic phase transition in this class of crystal is explained on the basis of the difference in strength of the hydrogen-bond interactions in the two structures.

  20. Phase transitions and electrical properties of Bi2W1xNbxO6−y and Bi2W1xTaxO6−y

    International Nuclear Information System (INIS)

    Kharitonova, E.P.; Voronkova, V.I.; Gagor, A.B.; Pietraszko, A.P.; Alekseeva, O.A.

    2013-01-01

    Highlights: •The limit of Bi 2 W 1x Me x O 6−y solid solutions is at x = 0.1, 0.15 for Me = Nb, Ta. •Ta and Nb substitutions for W suppress the reconstructive phase transition. •Bi 2 W 0.9 Nb 0.1 O 6−y samples belong to Aurivillius-type structure up to their melting. •Nb and Ta doping shifts ferroelectric transition to low temperatures up to 200 °C. •The highest conductivity reaches 10 −1 S/cm at 800 °C (x = 0.05, 0.1; Me = Nb, Ta). -- Abstract: Polycrystalline samples of Bi 2 W 1x Me x O 6−y (Me = Nb, Ta) solid solutions have been prepared by solid-state reactions, and the influence of Nb and Ta substitutions for W on the polymorphism and electrical properties of Bi 2 WO 6 has been studied. The limit of the solid solutions is at x = 0.1 for Me = Nb and at x = 0.15 for Me = Ta. The distinctive features of the polymorphism of the Nb- and Ta-doped materials have been identified. According to differential scanning calorimetry data, tantalum and niobium substitutions for tungsten increase the temperature of the high-temperature, orthorhombic-to-monoclinic reconstructive phase transition and suppress the transition starting at x = 0.05 for Me = Nb and x = 0.10 for Me = Ta. As a result, the Bi 2 W 1x Nb x O 6−y samples have an orthorhombic Aurivillius-type structure up to their melting point. The Bi 2 W 1x Ta x O 6−y solid solutions at high temperatures consist of a mixture of an orthorhombic and a monoclinic phase. Nb and Ta doping shifts the ferroelectric phase transition to lower temperatures by more than 200 °C, thus markedly extending the stability range of the nonpolar orthorhombic paraelectric phase, which exists in a temperature range as narrow as 930–960 °C in the case of undoped Bi 2 WO 6 . The increase in oxygen vacancy concentration due to heterovalent substitutions of Nb 5+ and Ta 5+ for W 6+ leads to an increase in conductivity by two orders of magnitude relative to the unsubstituted compound

  1. Influencia de las condiciones de procesamiento sobre las propiedades dieléctricas y microestructurales de cerámicos de K1/2Na1/2NbO3

    Directory of Open Access Journals (Sweden)

    Castro, M. S.

    2011-02-01

    Full Text Available The objective of this work was to analyze different processing condition of Na1/2K1/2NbO3 (KNN in order to obtain a material with good properties and without secondary phases. Solid state reaction method was used and the influence of milling time, calcination temperature and time, and sintering temperature was analyzed. It was found that sintering temperatures were limited by the component decomposition. Also, it was observed that samples sintered at 1125 ºC showed the highest density and permittivity with a homogeneous structure. In general, samples calcined at higher temperatures and times showed the best properties.El objetivo de este trabajo es analizar diferentes condiciones de procesamiento del K1/2Na1/2NbO3 (KNN que permitan obtener un material con buenas propiedades y libre de fases secundarias. Se implementó el método de activación mecanoquímica de los precursores y posterior reacción en estado sólido. Se analizaron las principales condiciones de procesamiento (tiempo de molienda, temperaturas de calcinación y sinterizado, y se determinaron las propiedades dieléctricas y microestructurales de cada sistema. Se encontró que las temperaturas máximas de calcinación estuvieron limitadas por la descomposición de los constituyentes. También se observó que las pastillas sinterizadas a 1125ºC registraron mayor densidad, mayor permitividad y una microestructura homogénea. En general, se observó que los sistemas calcinados a mayores temperaturas y por tiempos mayores tuvieron mejores propiedades.

  2. Hole doping and pressure effects on the II-II-V-based diluted magnetic semiconductor (Ba1-xKx)(Zn1-yMny)2As2

    International Nuclear Information System (INIS)

    Sun, F.; Zhao, G. Q.; Escanhoela, C. A. Jr.

    2017-01-01

    We investigate doping- and pressure-induced changes in the electronic state of Mn 3d and As 4p orbitals in II-II-V based diluted magnetic semiconductor (Ba_1_-_x,K_x)(Zn_1_-_y,Mn_y)_2As_2 to shed light into the mechanism of indirect exchange interactions leading to high ferromagnetic ordering temperature (T_c = 230 K in optimally doped samples). A suite of x-ray spectroscopy experiments (emission, absorption and dichroism) show that the emergence, and further enhancement of ferromagnetic interactions with increased hole doping into the As 4p band is accompanied by a decrease in local 3d spin density at Mn sites. This is a result of increasing Mn 3d - As 4p hybridization with hole doping which enhances indirect exchange interactions between Mn dopants and gives rise to induced magnetic polarization in As 4p states. On the contrary, application of pressure suppresses exchange interactions. While Mn Kβ emission spectra show a weak response of 3d state to pressure, clear As 4p band broadening (hole delocalization) is observed under pressure ultimately leading to loss of ferromagnetism concomitant with a semiconductor to metal transition. The pressure response of As 4p and Mn 3d states is intimately connected with the evolution of the As-As interlayer distance and the geometry of the MnAs_4 tetrahedral units, which we probed with X-ray diffraction. Our results indicate that hole doping increases the degree of covalency between the anion (As) p states and cation (Mn) d states in the MnA_s_4 tetrahedron, a crucial ingredient to promote indirect exchange interactions between Mn dopants and high T_c ferromagnetism. As a result, the instability of ferromagnetism and semiconducting state against pressure is mainly dictated by delocalization of anion p states.

  3. Czochralski growth and optical properties of Li 6Gd 1-xEu x(BO 3) 3 ( x=0-1) single crystals

    Science.gov (United States)

    Yavetskiy, R. P.; Dolzhenkova, E. F.; Dubovik, M. F.; Korshikova, T. I.; Tolmachev, A. V.

    2005-04-01

    It was shown that a continuous series of Li 6Gd 1-xEu x(BO 3) 3 solid solutions exist within the whole concentration range ( x=0-1). Li 6Gd 1-xEu x(BO 3) 3 ( x=0-0.03; 1) single crystals up to 25 mm in length and up to 20 mm in diameter have been grown by the Czochralski method. The structural perfection of the crystals has been estimated from etch patterns and XPA analysis results. The optical absorption and thermally stimulated luminescence of the grown crystals has been studied.

  4. Magnetic properties and magnetocaloric effect in the HoNi1xCuxIn (x=0, 0.1, 0.3, 0.4) intermetallic compounds

    International Nuclear Information System (INIS)

    Mo, Zhao-Jun; Shen, Jun; Yan, Li-Qin; Tang, Cheng-Chun; He, Xiao-Nan; Zheng, Xinqi; Wu, Jian-Feng; Sun, Ji-Rong; Shen, Bao-Gen

    2014-01-01

    The magnetic properties and magnetocaloric effect (MCE) in HoNi 1x Cu x In (x=0, 0.1, 0.3, 0.4) compounds have been investigated. With the substitution of Cu for Ni, the Ho magnetic moment will cant from the c-axis, and form a complicated magnetic structure. These compounds exhibit two successive magnetic transitions with the increase in temperature. The large reversible magnetocaloric effects have been observed in HoNi 1x Cu x In compounds around T ord , with no thermal and magnetic hysteresis loss. The large reversible isothermal magnetic entropy change (−ΔS M ) is 20.2 J/kg K and the refrigeration capacity (RC) reaches 356.7 J/kg for field changes of 5 T for HoNi 0.7 Cu 0.3 In. Especially, the value of −ΔS M (12.5 J/kg K) and the large RC (132 J/kg) are observed for field changes of 2 T for HoNi 0.9 Cu 0.1 In. Additionally, the values of RC are improved to 149 J/K for the field changes of 2 T due to a wide temperature span for the mix of HoNi 0.9 Cu 0.1 In and HoNi 0.7 Cu 0.3 In compounds with the mass ratio of 1:1. These compounds with excellent MCE are expected to have effective applications in magnetic refrigeration around 20 K. - Highlights: • For magnetic-field changes of 2 T, the values of RC are improved to 149 J/K. • MCEs of these compounds show no thermal and magnetic hysteresis. • Compounds show two successive magnetic transitions with the increase in temperature. • With the substitution of Cu for Ni, compounds form a complicated magnetic structure

  5. Effect of substituted rare earth element in (Yb1-xNd x)Ba2Cu3O y thin film on growth orientation and superconducting properties

    International Nuclear Information System (INIS)

    Honda, R.; Ichino, Y.; Yoshida, Y.; Takai, Y.; Matsumoto, K.; Ichinose, A.; Kita, R.; Mukaida, M.; Horii, S.

    2005-01-01

    We studied the orientation and superconducting properties in (Yb 1-x Nd x )Ba 2 Cu 3 O y (Yb/Nd123) thin films as a function of Yb/Nd composition ratio x. As a results, we needed so high oxygen pressure as to increase x for obtaining the c-axis oriented films. J c -B curves in the Yb/Nd123 thin films were superior to that in YBa 2 Cu 3 O y thin film. Since a RE fluctuation in a composition in the Yb/Nd123 thin films was observed with TEM-EDX, we speculated the pinning centers in the Yb/Nd123 thin films were strongly affected by the RE fluctuation

  6. Ionic conductivity of the lithium titanium phosphate (Li/sub 1+x/M/sub x/Ti/sub 2-x/(PO/sub 4/)/sub 3/, M=Al, Sc, Y, and La) systems

    International Nuclear Information System (INIS)

    Aono, H.; Sugimoto, E.; Sadaaka, Y.; Imanaka, N.; Adachi, G.Y.

    1989-01-01

    High lithium ionic conductivity was obtained in Li/sub 1+X/M/sub X/Ti/sub 2-X/(PO/sub 4/)/sub 3/ (M=Al, Sc, Y, and La) systems. Lithium titanium phosphate, LiTi/sub 2/(PO/sub 4/)/sub 3/, is composed of both TiO/sub 6/ octahedra and PO/sub 4/ tetrahedra, which are linked by corners to form a three dimensional network, with a space group R3-barC. Some workers have already described that the conductivity increased considerably if Ti/sup 4+/ in LiTi/sub 2/(PO/sub 4/)/sub 3/ was substituted by slightly larger cations such as Ga/sup 3+/(1),Sc/sup 3+/(2), and In/sup 3+/(3,4). These results are similar to each other because of their close ionic radii. In this communication, substitution effects of Ti/sup 4+/ in LiTi/sub 2/(PO/sub 4/)/sub 3/ by various ions (Al/sup 3+/, Sc/sup 3+/, Y/sup 3+/, and La/sup 3+/) on their conductivities are reported

  7. Structure and electrical conduction of the system La sub(1-x)Ca sub(x)FeO sub(3-. cap alpha. )

    Energy Technology Data Exchange (ETDEWEB)

    Hombo, Jukichi; Urabe, Noriake [Kumamoto Univ. (Japan). Faculty of Engineering; Hiroshige, Gota; Hamada, Kotaro

    1982-08-01

    Perovskite phases in the system, La sub(1-x)Ca sub(x)FeO sub(3-..cap alpha..) were prepared with La/sub 2/O/sub 3/, CaCO/sub 3/, and Fe/sub 2/O/sub 3/ by firing in air and in vacuo. The compositions of samples fired in vacuo and in air are represented as La sub(1-x)Ca sub(x)FeO sub(3-x 2) and La sub(1-x)Ca sub(x)Fe sub(1-y)sup(3+)Fe sub(y)sup(4+)O sub(3-x/2+y/2), respectively. That is, samples fired in vacuo contain some oxygen vacancies and no tetravalent iron; in contrast, samples fired in air contain both oxygen vacancies and tetravalent iron in the structures. The electrical conductivities of these synthesized oxides depended extensively upon the content of tetravalent iron. For instance, the conductivity of the sample x = 0.6 fired in air was larger by 10/sup 6/ than that of the sample fired in vacuo. In this system, except for the two terminal compositions of x = 0 and x = 1.0, the values of activation energy for conduction are considerably small, and from the results of thermo-electromotive force measurement, the charge carrier was positive. Furthermore, the conductivity increased somewhat with time during the conductivity measurement by the direct-current method. These facts suggest that the electric conduction would not be ionic but electronic. The electrical conduction would then be carried out by the so-called hopping mechanism by which the positive charge is transferred.

  8. Solid solubility, phase transitions, thermal expansion, and compressibility in Sc{sub 1x}Al{sub x}F{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Morelock, Cody R.; Gallington, Leighanne C. [School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, GA 30332-0400 (United States); Wilkinson, Angus P., E-mail: angus.wilkinson@chemistry.gatech.edu [School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, GA 30332-0400 (United States); School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, GA 30332-0245 (United States)

    2015-02-15

    With the goal of thermal expansion control, the synthesis and properties of Sc{sub 1x}Al{sub x}F{sub 3} were investigated. The solubility limit of AlF{sub 3} in ScF{sub 3} at ∼1340 K is ∼50%. Solid solutions (x≤0.50) were characterized by synchrotron powder diffraction at ambient pressure between 100 and 900 K and at pressures <0.414 GPa while heating from 298 to 523 K. A phase transition from cubic to rhombohedral is observed. The transition temperature increases smoothly with Al{sup 3+} content, approaching 500 K at the solid solubility limit, and also upon compression at fixed Al{sup 3+} content. The slope of the pressure–temperature phase boundary is ∼0.5 K MPa{sup −1}, which is steep relative to that for most symmetry-lowering phase transitions in perovskites. The volume coefficient of thermal expansion (CTE) for the rhombohedral phase is strongly positive, but the cubic-phase CTE varies from negative (x<0.15) to near-zero (x=0.15) to positive (x>0.20) between ∼600 and 800 K. The cubic solid solutions elastically stiffen on heating, while Al{sup 3+} substitution causes softening at a given temperature. - Graphical abstract: The cubic-phase coefficient of thermal expansion for Sc{sub 1x}Al{sub x}F{sub 3}(solubility limit ∼50% at ∼1340 K) becomes more positive with increased Al{sup 3+} substitution, but the average isothermal bulk modulus decreases (elastic softening). - Highlights: • The solubility limit of AlF{sub 3} in ScF{sub 3} at ∼1340 K is ∼50%. • The phase transition temperature of Sc{sub 1x}Al{sub x}F{sub 3} increases smoothly with x. • The cubic-phase volume CTE varies from negative to positive with increasing x. • The cubic solid solutions elastically stiffen on heating. • Al{sup 3+} substitution causes softening at a given temperature.

  9. Synthesis and electrochemical properties of xLiMn0.9Fe0.1PO4·yLi3V2(PO4)3/C composite cathode materials for lithium–ion batteries

    International Nuclear Information System (INIS)

    Wu, Ling; Lu, JiaJia; Wei, Gui; Wang, Pengfei; Ding, Hao; Zheng, Junwei; Li, Xiaowei; Zhong, Shengkui

    2014-01-01

    Highlights: • xLiMn 0.9 Fe 0.1 PO4·yLi 3 V 2 (PO 4 ) 3 /C composites are prepared by a solid-state method. • The addition of Li 3 V 2 (PO 4 ) 3 can improve the properties of LiMn 0.9 Fe 0.1 PO 4 . • Mutual doping occurrs between the LiMn 0.9 Fe 0.1 PO 4 and Li 3 V 2 (PO 4 ) 3 phases. • 5LiMn 0.9 Fe 0.1 PO 4 ·Li 3 V 2 (PO 4 ) 3 /C shows the best electrochemical properties. - Abstract: The xLiMn 0.9 Fe 0.1 PO 4 ·yLi 3 V 2 (PO 4 ) 3 /C (x:y=1:0, 9:1 5:1, 3:1, 1:1 and 0:1) cathode materials are synthesized by a ball–milling and post–calcination method. XRD results reveal that the xLiMn 0.9 Fe 0.1 PO 4 ·yLi 3 V 2 (PO 4 ) 3 /C (x,y≠0) composites are composed of LiMn 0.9 Fe 0.1 PO 4 and Li 3 V 2 (PO 4 ) 3 phases, and no impurities are detected. In LiMn 0.9 Fe 0.1 PO 4 –Li 3 V 2 (PO 4 ) 3 system, most of the manganese, iron and vanadium elements in the raw materials tend to form the two major phases, and only small amounts of V, Mn and Fe as dopants enter into the lattice of LiMn 0.9 Fe 0.1 PO 4 and Li 3 V 2 (PO 4 ) 3 . Electrochemical tests show that the xLiMn 0.9 Fe 0.1 PO 4 ·yLi 3 V 2 (PO 4 ) 3 /C (x,y≠0) composites exhibit much better performance than the single LiMn 0.9 Fe 0.1 PO 4 /C. Among the samples, 5LiMn 0.9 Fe 0.1 PO 4 ·Li 3 V 2 (PO 4 ) 3 /C shows the best electrochemical performance. The sample delivers the specific capacities of 158.1, 140.7 and 100.2 mAh g −1 at 0.05, 1 and 4 C rates in the potential range of 2.5–4.5 V, and exhibits very long and flat discharge plateau around 4.0 V up to 1 C rate. The sample also shows good cycling performance at various C–rates

  10. Transport properties of the rare earth disordered systems (R1-xYbx)Ba2Cu3O7 (R = Y, Sm)

    International Nuclear Information System (INIS)

    Hwang, J.R.; Tai, M.F.; Ku, H.C.; Lii, K.H.

    1989-01-01

    Electrical and magnetic measurements have been carried out for the rare earth disordered superconducting copper oxide systems (Y 1-x Yb x )Ba 2 Cu 3 O 7 (substitution with large rare earth mass difference) and (Sm 1-x Yb x )Ba 2 Cu 3 O 7 (substitution with large rare earth ionic size difference). Effect of compositional variation upon room temperature electrical resistivity shows no disorder scattering contribution from the randomly distributed rare earth ions located on the (1/2, 1/2, 1/2) site of the space group Pmmm. This result indicates very low conduction electron density of states surrounding rare earth ions. On the contrary, negative deviation of electrical resistivity from the linear Vegard law was observed. This reduced conduction electron scattering was discussed through the variation of packing density, grain size and/or twin structure

  11. Phenomenology of the spontaneous C P violation in SU(3)L x U(1)Y electroweak models

    International Nuclear Information System (INIS)

    Epele, Luis N.; Gomez Dumm, Daniel A.

    1994-01-01

    This work studies the phenomenological consequence of the spontaneous C P violation in a SU(3) L x U(1) Y model with three Higgs triplets and one sextuplet, which has been recently proposed. Since this C P-violating effects are due to the presence of complex vacuum expectation values in the Higgs sector, our analysis requires a detailed study of the enlarged potential

  12. Fabrication and characterization of Ba sub x Sr sub 1 sub - sub x TiO sub 3 /YBa sub 2 Cu sub 3 O sub x /SrTiO sub 3 structure

    CERN Document Server

    Choi, J; Park, S Y; Lee Jae Sik; No, K; Sung, T H; Park, Y

    2002-01-01

    Ba sub x Sr sub 1 sub - sub x TiO sub 3 (BST)/YBa sub 2 Cu sub 3 O sub x (YBCO)/SrTiO sub 3 (STO) structures were deposited, and the microstructure, orientation and electrical characteristics were investigated. (00l) oriented YBCO thin films were deposited on STO substrates using pulsed laser deposition, and (h00) oriented BST thin films were deposited on YBCO/STO substrates using electron cyclotron resonance (ECR) plasma assisted metal organic chemical vapor deposition (MOCVD). A new phase was formed at the interface between YBCO and BST films and was speculated to be (Ba sub x Y sub 1 sub - sub x)(Ti sub y Y sub 1 sub - sub y)O sub 3. Ba-rich BST films showed a higher dielectric loss than Sr-rich BST films did, which indicates that Sr-rich BST films are more suited for application to microwave devices. The dielectric loss of the films was reduced as temperature decreased, which may be due to the conductivity change of YBCO film and the formation of a conduction path rather than a dielectric property change ...

  13. Superconductivity at 43K in SmFeAsO1-xFx

    Science.gov (United States)

    Chen, X. H.; Wu, T.; Wu, G.; Liu, R. H.; Chen, H.; Fang, D. F.

    2008-06-01

    Since the discovery of high-transition-temperature (high-Tc) superconductivity in layered copper oxides, extensive effort has been devoted to exploring the origins of this phenomenon. A Tc higher than 40K (about the theoretical maximum predicted from Bardeen-Cooper-Schrieffer theory), however, has been obtained only in the copper oxide superconductors. The highest reported value for non-copper-oxide bulk superconductivity is Tc = 39K in MgB2 (ref. 2). The layered rare-earth metal oxypnictides LnOFeAs (where Ln is La-Nd, Sm and Gd) are now attracting attention following the discovery of superconductivity at 26K in the iron-based LaO1-xFxFeAs (ref. 3). Here we report the discovery of bulk superconductivity in the related compound SmFeAsO1-xFx, which has a ZrCuSiAs-type structure. Resistivity and magnetization measurements reveal a transition temperature as high as 43K. This provides a new material base for studying the origin of high-temperature superconductivity.

  14. Properties of Y Ba2 Cu3 O7-x-Ag prepared by the citrate technique

    International Nuclear Information System (INIS)

    Fonseca, Fabio Coral

    1996-01-01

    Y Ba 2 Cu 3 O 7-x (Y123) ceramic superconductor and YBa 2 Cu 3 O 7-x- Ag composite superconductors have been prepared by the citrate technique. Microstructural analysis has been done by X-ray diffractometry and optical ceramography. The superconducting behavior has been studied by 4 probe dc electrical resistivity in the 77 K - 140 K temperature range. Silver percolation in the ceramic matrix was studied by electrical resistivity measurements at room temperature; the percolation threshold was found to be approximately 25 vol. % (35.5 wt. %) Ag. Specimens with silver addition showed improvement in the flexural strength of the Y123 compound. The main results show that the critical temperatures does not depend on the silver content in the composite specimens, the normal state electrical behavior of the superconductor is affected by silver addition and approximately 3 wt. % (1.8 vol. %) Ag doping yields and optimized composite superconductor from the electrical, mechanical and microstructural pont of view, with platelet-like grain shapes. (author)

  15. Effect of elevated concentrations of strontium and iron on the structural and dielectric characteristics of Ba{sub (1-x-y)}Sr{sub (x)}Ti Fe{sub (y)}O{sub 3} prepared through sol-gel technique

    Energy Technology Data Exchange (ETDEWEB)

    Nur, Omer; Willander, Magnus; Israr, Muhammad Q. [Department of Science and Technology, Campus Norrkoeping, Linkoeping University, SE-60174, Norrkoeping (Sweden); Desouky, Fawzy G. El; Salem, Mohamed A.; Abou Hamad, Ali B. [National Research Center (NRC), Solid State Physics Department, Giza (Egypt); Battisha, Inas K., E-mail: szbasha@yahoo.com [National Research Center (NRC), Solid State Physics Department, Giza (Egypt)

    2012-07-15

    Nano-composite Ba{sub 1-x}Sr{sub (x)}TiO{sub 3} (BST), where x=0.01-0.50 and doped with different concentrations of iron Ba{sub (1-x-y)}Sr{sub (x)}TiFe {sub (y)}O{sub 3} (BSTF), where x=0.01 and y=0.01-0.05 powders were prepared by sol-gel method. The effect of increasing the iron and strontium concentrations substituted in Barium strontium titanate system will be studied. The prepared samples have a tetragonal crystalline phase after sintering for 1 h at 750 Degree-Sign C in air. The structural and the morphological features of the systems have been studied using X-ray diffraction (XRD), transmission electron microscope (TEM) and scanning electron microscope (SEM). The dielectric properties of the BST and BSTF systems have been investigated as a function of temperature and frequency. The dielectric measurements are carried out in the frequency range 42 Hz-1 MHz, at a temperature ranging between 25 and 250 Degree-Sign C. The results showed a decrease in T{sub c} temperature giving the following values 90 and 85 Degree-Sign C for B{sub 10}ST and B{sub 10}ST{sub 5}F prepared powder samples, respectively, implying tetragonal, feroelectric phase at lower temperature into cubic, para-electric phase at temperature higher than T{sub c}.

  16. Triple-axis X-ray reciprocal space mapping of In{sub y}Ga{sub 1-y}As thermophotovoltaic diodes grown on (1 0 0) InP substrates

    Energy Technology Data Exchange (ETDEWEB)

    Dashiell, M.W.; Ehsani, H.; Sander, P.C. [Lockheed Martin Corporation, Schenectady, NY 12301-1072 (United States); Newman, F.D. [Emcore Corporation, Albuquerque, NM 87123 (United States); Wang, C.A. [MIT Lincoln Laboratory, Lexington, MA 02420 (United States); Shellenbarger, Z.A. [Sarnoff Corporation, Princeton NJ, 08543-5300 (United States); Donetski, D.; Gu, N.; Anikeev, S. [Department of Electrical Engineering, State University of New York, Stony Brook, NY 11794-2350 (United States)

    2008-09-15

    Analysis of the composition, strain-relaxation, layer-tilt, and the crystalline quality of In{sub y}Ga{sub 1-y}As/InP{sub 1-x}As{sub x} thermophotovoltaic (TPV) diodes grown by metal-organic vapor phase epitaxy (MOVPE) is demonstrated using triple-axis X-ray reciprocal space mapping techniques. In{sub 0.53}Ga{sub 0.47}As (E{sub gap}=0.74 eV) n/p junction diodes are grown lattice matched (LM) to InP substrates and lattice-mismatched (LMM) In{sub 0.67}Ga{sub 0.33}As (E{sub gap}=0.6 eV) TPV diodes are grown on three-step InP{sub 1-x}As{sub x} (0<x<0.32) buffer layers on InP substrates. X-ray reciprocal space maps about the symmetric (4 0 0) and asymmetric (5 3 3) reciprocal lattice points (RELPs) determine the in-plane and out-of-plane lattice parameters and strain of the In{sub y}Ga{sub 1-y}As TPV active layer and underlying InP{sub 1-x}As{sub x} buffers. Triple-axis X-ray rocking curves about the LMM In{sub 0.67}Ga{sub 0.33}As RELP show an order of magnitude increase of its full-width at half-maximum (FWHM) compared to that from the LM In{sub 0.53}Ga{sub 0.47}As (250 vs. 30 arcsec). Despite the significant RELP broadening, the photovoltaic figure of merits show that the electronic quality of the LMM In{sub 0.67}Ga{sub 0.33}As approaches that of the LM diode material. This indicates that misfit-related crystalline imperfections are not dominating the photovoltaic response of the optimized LMM In{sub 0.67}Ga{sub 0.33}As material compared with the intrinsic recombination processes and/or recombination through native point defects, which would be present in both LMM and LM diode material. However, additional RELP broadening in non-optimized LMM In{sub 0.67}Ga{sub 0.33}As n/p junction diodes does correspond to significant degradation of TPV diode open-circuit voltage and minority carrier lifetime demonstrating that there is correlation between X-ray FWHM and the electronic performance of the LMM TPV diodes. (author)

  17. Superconductivity in Ba sub 1 sub - sub x K sub x BiO sub 3 : possible scenario of spatially separated Fermi-Bose mixture

    CERN Document Server

    Menushenkov, A P; Kuznetsov, A V; Kagan, M Y

    2001-01-01

    A new scenario for the metal-insulator phase transition and superconductivity in the perovskite-like bismuthates Ba sub 1 sub - sub x K sub x BiO sub 3 (BKBO) is proposed. It is shown that two types of charge carriers, the local pairs (real-space bosons) and the itinerant electrons, exist in the metallic compound BKBO (x >= 0.37). The real-space bosons are responsible for the charge transport in semiconducting BaBiO sub 3 and for superconductivity in the metallic BKBO. The appearance of the Fermi-liquid state as the percolation threshold is overcome (x >= 0.37) explains the observed metal-insulator phase transition. Because bosons and fermions occupy different types of the octahedral BiO sub 6 complexes, they are separated in real space, and therefore, the spatially separated Fermi-Bose mixture of a new type is likely to be realized in the bismuthates. The nature of superconductivity is consistently explained in the framework of this scenario. A new superconducting oxide Ba sub 1 sub - sub x La sub x PbO sub ...

  18. Low-energy optics of Sr{sub 1-x}Ca{sub x}RuO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Geiger, Diana; Scheffler, Marc; Dressel, Martin [1. Physikalisches Institut, Universitaet Stuttgart (Germany); Schneider, Melanie; Gegenwart, Philipp [I. Physikalisches Institut, Georg-August-Universitaet, Goettingen (Germany)

    2012-07-01

    The pseudo-cubic perovskite ruthenates SrRuO{sub 3} and CaRuO{sub 3} have recently attracted interest due to their unconventional electronic properties. For both materials, non-Fermi liquid behavior has been reported in previous optical studies at infrared frequencies. In addition to these two pure compounds, the doping series Sr{sub 1-x}Ca{sub x}RuO{sub 3} offers a rich phase diagram: going from the itinerant ferromagnet SrRuO{sub 3} to the paramagnet CaRuO{sub 3}, indications for a quantum phase transition at x{approx}0.8 have been found. Using THz spectroscopy at frequencies between 5 cm{sup -1} and 45 cm{sup -1}, we have studied thin-film samples of the Sr{sub 1-x}Ca{sub x}RuO{sub 3} system, which were prepared by metalorganic aerosol deposition. From transmission and phase measurements we have determined the frequency-dependent conductivity for a set of temperatures between 5 K and 300 K, and we discuss it in the framework of the extended Drude model with frequency-dependent relaxation rate and effective mass. While for pure SrRuO{sub 3} as well as for doped systems approaching the quantum phase transition we find conventional metallic Drude behavior, CaRuO{sub 3} exhibits highly unusual optical properties which we compare to results of dc measurements on these thin films, which also revealed temperature ranges with non-Fermi liquid behavior.

  19. Magnetic susceptibility of LaxCe1-xF3 single crystals

    International Nuclear Information System (INIS)

    Paradowski, M.L.; Pacyna, A.W.; Bombik, A.; Korczak, W.; Korczak, S.Z.

    2000-01-01

    The magnetic susceptibility of La x Ce 1-x F 3 single crystals, for 0 eff and paramagnetic Curie temperature θ p have been obtained, using the Curie-Weiss law in the temperature range 100-300 K. The interconfiguration excited energy E ex , the spin-fluctuation temperature T sf , and the g-values, corresponding to three Kramers doublets in the 2 F 5/2 ground multiplet of Ce 3+ ion in La x Ce 1-x F 3 have been determined, using quantum theory of paramagnetic susceptibility. The mixed-valent and crystal field effects influence significantly the g-values. The effect of the dilution of the paramagnetic Ce 3+ ions with diamagnetic La 3+ ions is also discussed

  20. Nature of anomalous magnetic properties of yttrium ferrite-chromites. [Y Fe/sub 1-X/Cr/sub x/0/sub 3/, x=0 to 1. 0

    Energy Technology Data Exchange (ETDEWEB)

    Kadomtseva, A M [Moskovskij Gosudarstvennyj Univ. (USSR); Moskvin, A S; Bostrem, I G [Ural' skij Gosudarstvennyj Univ., Sverdlovsk (USSR)

    1977-06-01

    The theoretical results of an analysis of the Fe/sup 3 +/-Fe/sup 3 +/,Cr/sup 3 +/ -Cr/sup 3 +/nd Fe/sup 3 +/-Cr/sup 3 +/ exchange interactions are successfully employed to explain the anomalous magnetic properties of yttrium ferrite-chromite single crystals YFesub(1-x)Crsub(x)Osub(3) (where x=0; 0.05; 0.15; 0.2; 0.5; 0.65; 0.85; 0.95; 1). It is shown that these compounds are weak ferrimagnets with the mixed Dzyaloshinsky interaction. A qualitative explanation of the complex concentration and temperature dependences of the weak-ferrimagnetic moment is presented. The nature of the spin reorientation phenomenon is discussed.

  1. Lattice parameters and thermal expansion of delta-VNsub(1-x) from 298-1000 K

    International Nuclear Information System (INIS)

    Lengauer, W.; Ettmayer, P.

    1986-01-01

    The thermal expansion of VNsub(1-x) was determined from measurements of the lattice parameters in the temperature range of 298-1000 K and in the composition range of VNsub(0.707) - VNsub(0.996). Within the accuracy of the results the expansion of the lattice parameter with temperature is not dependent on the composition. The lattice parameter as a function of composition ([N]/[V] = 0.707-0.996) and temperature (198-1000 K) is given by a([N]/[V], T) = 0.38872+0.02488 ([N]/[V]) - (1.083+-0.021) x 10 -4 Tsup(1/2) + (6.2+-0.1) x 10 - sup6T. The coefficient of linear thermal expansion as a function of temperature (in the same range) is given by α(T) = a([N]/[V], T) -1 [(-5.04+-0.01) x 10 -5 Tsup(1/2) + (6.2+-0.1) x 10 -6 ]. The average linear thermal expansion coefficient is αsub(av) = 9.70 +- 0.15 x 10 -6 K -1 (298-1000 K). The data are compared with those of several fcc transition metal nitrides collected and evaluated from the literature. (Author)

  2. Correlation of the superconducting transition to oxygen stoichiometry in single-crystal Ba1-xKxBiO3-y

    Science.gov (United States)

    Mosley, W. D.; Dykes, J. W.; Klavins, P.; Shelton, R. N.; Sterne, P. A.; Howell, R. H.

    1993-07-01

    Temperature-dependent positron-lifetime experiments have been performed from room temperature to 15 K on single crystals of the oxide superconductor Ba1-xKxBiO3-y. Results indicate that the filling of oxygen vacancies has a marked impact on the superconducting properties of this system. Cation defect concentrations were below the detectable limit of positron-annihilation-analysis techniques in this material, which is in sharp contrast to identical studies on polycrystalline samples. We find that the positron lifetime in these electrochemically deposited single crystals is determined by the oxygen stoichiometry of the lattice, but there is no experimental signature of strong positron localization. By performing a subsequent oxygen anneal on the crystals, the superconducting transition is sharpened and the onset is raised. The observed change in positron lifetime associated with this annealing procedure is in quantitative agreement with theory.

  3. Synthesis and properties of La1-x Cax Al O3

    Directory of Open Access Journals (Sweden)

    Omari, M.

    2012-12-01

    Full Text Available La1x Cax Al O3 (0 ≤ x ≤ 0.6 perovskite-type oxides were prepared by co-precipitation method using metal nitrate salts as cation precursors and NaOH solution as the precipitating agent. Differential thermal analysis (DTA and thermogravimetric analysis (TGA results indicate that decomposition of the precursor to the oxide begins at ~ 800°C. Powder X-ray diffraction (XRD patterns confirm the formation of the perovskite phase. Both undoped and doped lanthanum aluminates show two IR active vibrational modes at 450 and 670 cm−1 which are assigned to AlO6 octahedra of the oxide matrix. The microstructure and morphology of the compounds show that the particles are nearly spherical in shape and are agglomerated. Electrochemical measurements indicate that the catalytic activity is strongly influenced by lanthanum doping. The highest electrode performance is achieved with large calcium content.Se prepararon diferentes óxidos tipo perovskita con formulación La1x Cax Al O3 (0 ≤ x ≤ 0.6 mediante método de coprecipitación empleando sales nitrato como precursores catiónicos y NaOH como agente precipitante. Los resultados de análisis térmico diferencial (DTA y análisis termogravimétrico (TGA indican que la descomposición del precursor del óxido comienza a ~ 800°C. Los patrones de difracción de rayos-X de polvo (XRD confirman la formación de la fase perovskita. Los aluminatos de lantano, tanto dopado como no dopado, muestran dos modos vibracionales activos a 450 y 670 cm-1 que se asignan a octahedros AlO6 de la matriz del óxido. La microestructura y morfología de los compuestos muestran que las partículas son de forma próxima a la esférica y aparecen en forma de aglomerados. Las medidas electroquímicas indican que actividad catalítica se ven fuertemente influenciadas por el dopaje con lantano. La mayor actividad del electrodo se alcanza con altos contenidos de calcio.

  4. Growth and structural characterization of single crystals of the magnetic superconductor Ru1-xSr2-yGd1+yCu2+xO8-δ (RuGd-1212) obtained by the partial melting technique

    Science.gov (United States)

    Yamaki, K.; Bamba, Y.; Mochiku, T.; Funahashi, S.; Matsushita, Y.; Irie, A.

    2018-05-01

    In this study, cubic single crystals of the magnetic superconductor Ru1-xSr2-yGd1+yCu2+xO8-δ (RuGd-1212) with typical dimensions of 100-150 μm in length were grown by the partial melting technique. Multiple 00l reflections were first observed by XRD measurements of the bulk RuGd-1212 single crystals. The resistivity of the obtained crystals was roughly estimated to be ∼24-80 mΩ cm and no superconducting transition was observed down to 4.2 K. From the XRD measurements and refinement of the crystal structure, it was apparent that the Ru and Sr sites of the single-crystal RuGd-1212 were partially substituted by Cu and Gd, respectively. Oxygen defects were found to be minor (δ ≈ 0.1). The lattice parameters a and c of the single crystals were found to be larger and smaller, respectively, than those of a polycrystalline sample.

  5. Improvement of photoluminescence properties and thermal stability of Y2.9Ce0.1Al5−xSixO12 phosphors with Si3N4 addition

    International Nuclear Information System (INIS)

    Zhang, Fangfang; Song, Kaixin; Jiang, Jun; Wu, Song; Zheng, Peng; Huang, Qingming; Xu, Junming; Qin, Huibin

    2014-01-01

    Highlights: • Y 2.9 Ce 0.1 Al 5−x Si x O 12 phosphors were prepared by solid-state reaction in reduced air ambience. • Si 4+ could be incorporated into the host lattice of Y 3 Al 5 O 12 through partial occupation of the Al 3+ sites. • Si 3 N 4 addition can improve photoluminescence efficiency and thermal stability of Y 3 Al 5 O 12 :Ce. - Abstract: A series of Si 3 N 4 doping Y 2.9 Ce 0.1 Al 5−x Si x O 12−3x/2 N 4x/3 phosphors were prepared by solid-state reaction in 95%N 2 –5%H 2 reduced air ambience. The XRD characteristics plus Rietveld refinement results shows that the as-sintered powders are unique crystal phase with the same crystal structure of Y 3 Al 5 O 12 (PDF No. 79-1891). The N element was not detected by the analysis of X-ray photoelectron spectroscopy (XPS) and energy dispersive X-ray spectrum (EDS). The photoluminescence spectra (PL and PLE) tests show that the exciting and emitting intensity of PLE and PL gradually increase due to the increase of Si 3 N 4 concentration. Meanwhile, the phosphorescence decay times are prolonged from 45 ns (x = 0) to 78 ns (x = 0.3), under the monitor of 530 nm wavelength. The thermoluminescence tests (TL) confirm the thermal stability of as-phosphors with Si 3 N 4 addition is much better than that of the pristine Y 2.9 Ce 0.1 Al 5 O 12 phosphors

  6. Thermoelectric properties of n-type Bi{sub 2}(Te{sub 1{minus}x}Se{sub x}){sub 3} fabricated by mechanical alloying and hot pressing

    Energy Technology Data Exchange (ETDEWEB)

    Kim, H J; Choi, J S; Oh, T S; Hyun, D B

    1997-07-01

    Thermoelectric properties of polycrystalline Bi{sub 2}(Te{sub 1{minus}x}Se{sub x}){sub 3} (0.05 {le} x {le} 0.25), fabricated by mechanical alloying and hot pressing, have been investigated. Formation of n-type Bi{sub 2}(Te{sub 0.9}Se{sub 0.1}){sub 3} alloy powders was completed by mechanical alloying for 3 hours at ball-to-material ratio of 5:1, and processing time for Bi{sub 2}(Te{sub 1{minus}x}Se{sub x}){sub 3} formation increased with Bi{sub 2}Se{sub 3} content x. Figure-of-merit of Bi{sub 2}(Te{sub 0.9}Se{sub 0.1}) was markedly increased by hot pressing at temperatures above 450 C, and maximum value of 1.9 x 10{sup {minus}3}/K was obtained by hot pressing at 550 C. With addition of 0.015 wt% Bi as acceptor dopant, figure-of-merit of Bi{sub 2}(Te{sub 0.9}Se{sub 0.1}){sub 3} was hot pressed at 550 C, could be improved to 2.1 x 10{sup {minus}3}/K. When Bi{sub 2}(Te{sub 1{minus}x}Se{sub x}){sub 3} was hot pressed at 550 C, figure-of-merit increased from 1.14 x 10{sup {minus}3}/K to 1.92 x 10{sup {minus}3}/K with increasing Bi{sub 2}Se{sub 3} content x from 0.05 to 0.15, and then decreased to 1.30 x 10{sup {minus}3}/K for x = 0.25 composition.

  7. Photoluminescence and optical absorption spectra of {gamma}{sub 1}-(Ga{sub x}In{sub 1-x}){sub 2}Se{sub 3} mixed crystals

    Energy Technology Data Exchange (ETDEWEB)

    Kranjcec, M. [Department of Geotechnics, University of Zagreb, 7 Hallerova Aleja, Varazdin, 42000 (Croatia); Ruder Boskovic Institute, 54 Bijenicka Cesta, Zagreb, 10000 (Croatia); Studenyak, I.P. [Uzhhorod National University, 46 Pidhirna Str., Uzhhorod, 88000 (Ukraine); Azhniuk, Yu. M. [Institute of Electron Physics, Ukr. Nat. Acad. Sci., 21 Universytetska Str., Uzhhorod, 88000 (Ukraine)

    2005-08-01

    Temperature and compositional studies of photoluminescence and optical absorption edge spectra of {gamma}{sub 1}-(Ga{sub x}In{sub 1-x}){sub 2}Se{sub 3} mixed crystals with x=0.1-0.4 are performed. Exciton and impurity-related photoluminescence bands are revealed at low temperatures and Urbach shape of the absorption edge is observed in the temperature range 77-300 K. Temperature and compositional dependences of the photoluminescence band spectral positions and halfwidths as well as optical pseudogap and absorption edge energy width are investigated. Mechanisms of radiative recombination and optical absorption as well as crystal lattice disordering processes in {gamma}{sub 1}-(Ga{sub x}In{sub 1-x}){sub 2}Se{sub 3} solid solutions are studied. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  8. Composition dependence of electric-field-induced structure of Bi{sub 1/2}(Na{sub 1x}K{sub x}){sub 1/2}TiO{sub 3} lead-free piezoelectric ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Khansur, Neamul H. [School of Materials Science and Engineering, UNSW Australia, 2052 Sydney (Australia); Department of Materials Science, University of Erlangen-Nürnberg, Erlangen 91058 (Germany); Benton, Rachel [Department of Chemical and Biomolecular Engineering, North Carolina State University, North Carolina 27695 (United States); Dinh, Thi Hinh; Lee, Jae-Shin [School of Materials Science and Engineering, University of Ulsan, Ulsan 680-749 (Korea, Republic of); Jones, Jacob L. [Department of Materials Science and Engineering, North Carolina State University, North Carolina 27695 (United States); Daniels, John E. [School of Materials Science and Engineering, UNSW Australia, 2052 Sydney (Australia)

    2016-06-21

    Microscopic origins of the electric-field-induced strain for three compositions of Bi{sub 1/2}(Na{sub 1x}K{sub x}){sub 1/2}TiO{sub 3} (x = 0.14, 0.18, and 0.22) (BNKT100x) ceramics have been compared using in situ high-energy (87.12 keV) X-ray diffraction. In the as-processed state, average crystallographic structure of BNKT14 and BNKT18 were found to be of rhombohedral symmetry, while BNKT22 was tetragonal. Diffraction data collected under electric field showed that both the BNKT14 and BNKT18 exhibit induced lattice strain and non-180° ferroelectric domain switching without any apparent phase transformation. The BNKT22 composition, in addition to the lattice strain and domain switching, showed an electric-field-induced transformation from a tetragonal to mixed tetragonal-rhombohedral state. Despite the difference in the origin of microscopic strain responses in these compositions, the measured macroscopic poling strains of 0.46% (BNKT14), 0.43% (BNKT18), and 0.44% (BNKT22) are similar. In addition, the application of a second poling field of opposite polarity to the first increased the magnitude of non-180° ferroelectric domain texture. This was suggested to be related to the existence of an asymmetric internal bias field.

  9. Exciton-related nonlinear optical response and photoluminescence in dilute nitrogen In{sub x}Ga{sub 1x}N{sub y}As{sub 1y}/GaAs cylindrically shaped quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Duque, C.M.; Morales, A.L. [Grupo de Materia Condensada-UdeA, Instituto de Física, Facultad de Ciencias Exactas y Naturales, Universidad de Antioquia UdeA, Calle 70 No. 52-21, Medellín (Colombia); Mora-Ramos, M.E. [Grupo de Materia Condensada-UdeA, Instituto de Física, Facultad de Ciencias Exactas y Naturales, Universidad de Antioquia UdeA, Calle 70 No. 52-21, Medellín (Colombia); Facultad de Ciencias, Universidad Autónoma del Estado de Morelos, Av. Universidad 1001, CP 62209 Cuernavaca, Morelos (Mexico); Duque, C.A. [Grupo de Materia Condensada-UdeA, Instituto de Física, Facultad de Ciencias Exactas y Naturales, Universidad de Antioquia UdeA, Calle 70 No. 52-21, Medellín (Colombia)

    2014-10-15

    An investigation of the effects of the dilute nitrogen contents in the exciton states of cylindrical In{sub x}Ga{sub 1x}N{sub y}As{sub 1y}/GaAs quantum dots is presented. The exciton states in the system are obtained within the effective mass theory and the band anti-crossing model. Exciton-related nonlinear optical absorption and refractive index change, as well as excitonic photoluminescence are studied with the help of the calculated exciton states. - Highlights: • Theoretical study of excitons in cylindrical In{sub x}Ga{sub 1x}N{sub y}As{sub 1y}/GaAs quantum dots. • Calculations of binding energy for different configurations of electron-hole pairs. • Nonlinear optical absorption and refractive index changes. • Dependence of photoluminescence energy transitions with several inputs.

  10. Spin Triplet Nematic Pairing Symmetry and Superconducting Double Transition in U1-xThxBe13

    Science.gov (United States)

    Machida, Kazushige

    2018-03-01

    Motivated by a recent experiment on U1-xThxBe13 with x = 3%, we develop a theory to narrow down the possible pair symmetry to consistently describe the double transition utilizing various theoretical tools, including group theory and Ginzburg-Landau theory. It is explained in terms of the two-dimensional representation Eu with spin triplet. Symmetry breaking causes the degenerate Tc to split into two. The low-temperature phase is identified as the cyclic p wave: d(k) = \\hat{x}kx + ɛ \\hat{y}ky + ɛ 2\\hat{z}kz with ɛ3 = 1, whereas the biaxial nematic phase: d(k) = √{3} (\\hat{x}kx - \\hat{y}ky) is the high-temperature one. This allows us to simultaneously identify the uniaxial nematic phase: d(k) = 2\\hat{z}kz - \\hat{x}kx - \\hat{y}ky for UBe13, which spontaneously breaks the cubic symmetry of the system. Those pair functions are fully consistent with this description and existing data. We comment on the accidental scenario in addition to this degeneracy scenario and the intriguing topological nature hidden in this long-known material.

  11. Effect of Al/Ga substitution on the structural and luminescence properties of Y3(Al1-xGax)5O12: Ce3+ phosphors

    Science.gov (United States)

    Fu, Sheng; Tan, Jin; Bai, Xin; Yang, Shanjie; You, Lei; Du, Zhengkang

    2018-01-01

    As candidates for display and lighting materials, a series of gallium-substituted cerium-doped yttrium aluminum garnet (Y3(GaxAl1-x)5O12: Ce3+) phosphors were synthesized by high temperature solid-state reaction. The phases, morphology, luminescence spectra and thermal stability of the phosphors were investigated. The volatilization of Ga2O3 induces the constituents out of stoichiometric ratio and different impurities in the system. The excitation and emission spectra occur red shift (339 nm - 351 nm) and blue shift (465 nm - 437 nm), and blue shift (541 nm - 517 nm), respectively. The spectra have no further blue shift and the luminescence intensity decrease with x over 0.4. Combining crystal structure with PL spectrum, the distortion of dodecahedron and crystal field splitting of 5d level of Ce3+ are influenced by Ga3+ in octahedral coordination polyhedron rather than tetrahedron. The crystalline perfection and Ga3+ occupying the tetrahedron induce less garnet phase formation, more impurities and the 5d level located in the conductive bands, thus accounting for the x = 0.4 turning points of the PL and PLE intensity. Based on the thermal quenching and CIE, the Y3(GaxAl1-x)5O12: Ce3+0.06 phosphors have great potential for use on the w-LED.

  12. Neutron scattering study of La1-xCaxMnO3 with x=0.15

    International Nuclear Information System (INIS)

    Begum, Shahnaz; Ono, Yasuhiro; Miyazaki, Yuzuru; Kajitani, Tsuyoshi; Tomioka, Yasuhide; Tokura, Yoshinori

    2001-01-01

    Elastic and inelastic neutron scattering measurements have been made on a perovskite hole doped manganite La 1-x Ca x MnO 3 with x=0.15 for both powder and single crystal samples to understand the magnetic properties of this compound. Strong diffuse scattering observed in the paramagnetic phase, originates from the ferromagnetic spin fluctuations. New peaks have been observed at 001, 100 and 1/2 0 1/2 from 15 K to the ambient temperature indicating the long-range and/or short-range charge and magnetic spin ordering. An anomalous temperature dependent inelastic scattering intensities were observed by the TOF neutron spectrometer AGNES at 2θ=57-64deg (close to 101 Bragg peak) at temperatures from 17 to 220 K for powder sample. The peak at about 1.0 meV was only observed at 17 and 98 K in the ferromagnetic region and smeared in the paramagnetic region which is possibly the indication of spin gap formation in the ferromagnetic region. The peak at about 1.0 meV at lower temperatures were also observed for single crystal sample close to 1/2 0 1/2 reciprocal point. (author)

  13. Structural characteristics of Mg-doped (1-x)(K0.5Na0.5)NbO3-xLiSbO3 lead-free ceramics as revealed by Raman spectroscopy

    International Nuclear Information System (INIS)

    Zhu, W L; Meng, Y; Pezzotti, G; Zhu, J L; Wang, M S; Zhu, B; Zhu, X H; Zhu, J G; Xiao, D Q

    2011-01-01

    This paper presents a Raman spectroscopic study of compositional-change-induced structure variation and of the related mechanism of Mg doping in LiSbO 3 (LS)-modified (K 0.5 Na 0.5 )NbO 3 (KNN) ceramics. With increasing LS content from 0 to 0.06, a discontinuous shift towards higher wavenumbers was found for the band position of the A 1g (v 1 ) stretching mode of KNN, accompanied by a clearly nonlinear broadening of this band and a decrease in its intensity. Such morphological changes in the Raman spectrum result from two factors: (i) changes in polarizability/binding strength of the O-Nb-O vibration upon incorporation of Li ions in the KNN perovskitic structure and (ii) a polymorphic phase transition (PPT) from orthorhombic to tetragonal (O → T) phase at x > 0.04. Upon increasing the amount, w, of Mg dopant incorporated into the (1-x)KNN-xLS ceramic structure, the intensity of the Raman bands are enhanced, while the peak position and the full width at half maximum of the A 1g (v 1 ) mode was found to experience a clear dependence on both w and x. Raman characterization revealed that the mechanism of Mg doping is strongly correlated with the concentration of Li in the perovskite structure: Mg 2+ ions will preferentially replace Li + ions for low Mg doping while replace K/Na ions for higher doping of Mg. The PPT O → T was also found to be altered by the introduction of Mg and the critical value of LS concentration, x O-T , for incipient O → T transition in the KNN-xLS-wMT system was strongly dependent on Mg content, with x O→T being roughly equal to 0.04 + 2w, for the case of dilute Mg alloying. (paper)

  14. Synthesis and crystal structure of K{sub 2}NiF{sub 4}-type novel Gd{sub 1+x}Ca{sub 1x}AlO{sub 4−x}N{sub x} oxynitrides

    Energy Technology Data Exchange (ETDEWEB)

    Masubuchi, Yuji, E-mail: yuji-mas@eng.hokudai.ac.jp; Hata, Tomoyuki; Motohashi, Teruki; Kikkawa, Shinichi

    2014-01-05

    Highlights: • Novel gadolinium calcium aluminum oxynitride was prepared by solid state reaction. • Crystal structure of the oxynitride was refined by using synchrotron X-ray diffraction. • Gd{sub 1.2}Ca{sub 0.8}AlO{sub 3.8}N{sub 0.2} has a layered K{sub 2}NiF{sub 4}-type structure with the I4mm space group. • Nitride ions preferentially occupy the apical site of aluminum octahedron. -- Abstract: Novel gadolinium calcium aluminum oxynitrides, Gd{sub 1+x}Ca{sub 1x}AlO{sub 4−x}N{sub x}, were prepared in x = 0.15–0.25 by the solid state reaction of a nitrogen–rich mixture with AlN as an aluminum source; the mixture was sintered twice at 1500 °C for 5 h under 0.5 MPa of nitrogen gas. Shift in the optical absorption edge was observed in their diffuse reflectance spectra from 4.46 eV for the oxide (x = 0) to 2.94 eV for the oxynitride at x = 0.2. The crystal structure of Gd{sub 1.2}Ca{sub 0.8}AlO{sub 3.8}N{sub 0.2} at x = 0.2 was refined using a synchrotron X-ray diffraction data as a layered K{sub 2}NiF{sub 4}-type structure with the I4mm space group. Longer Al–O/N bond lengths in the oxynitride than those in GdCaAlO{sub 4} suggest that the nitride ions are in the apical site of aluminum polyhedron, similar to those in Nd{sub 2}AlO{sub 3}N.

  15. Structural and electronic properties of Ga{sub 1-x}In{sub x} As{sub 1-y}N{sub y} quaternary semiconductor alloy on GaAs substrate

    Energy Technology Data Exchange (ETDEWEB)

    Aslan, Metin, E-mail: maslan@sakarya.edu.tr [Sakarya University, Art, Science Faculty, Department of Physics, Esentepe Campus, 54187 Sakarya (Turkey); Yalc Latin-Small-Letter-Dotless-I n, Battal G.; Uestuendag, Mehmet [Sakarya University, Art, Science Faculty, Department of Physics, Esentepe Campus, 54187 Sakarya (Turkey)

    2012-04-05

    Highlights: Black-Right-Pointing-Pointer In this study we used DFT in the frame of LDA approach to determine electronic and structural properties of GaInAsN alloy. Black-Right-Pointing-Pointer We calculated lattice parameter and band gap energy of binary (GaAs, InAs, and GaN), ternary (GaInAs, GaAsN) and quaternary (GaInAsN) semiconductor alloys. Black-Right-Pointing-Pointer We formulated lattice parameter of GaInAsN respect to In and N composition. Black-Right-Pointing-Pointer We investigated different In and N composition of GaInAsN/GaAs heterostructure for various device applications. - Abstract: We have presented structural and electronic properties of binary (GaAs, GaN and InAs), ternary (Ga{sub 1-x}In{sub x}As and GaAs{sub 1-y}N{sub y}) and quaternary (Ga{sub 1-x}In{sub x}As{sub 1-y}N{sub y}) semiconductor alloys by using a first-principles pseudopotential technique. The structural and electronic properties of Zinc-Blende phase of these materials have been calculated by using the local density approximation (LDA) of the density-functional theory (DFT). To obtain the lattice parameter and band gap energy of the (GaInAsN) quaternary semiconductor alloy we separately calculated the lattice constant and band gap energies of ternary semiconductor alloys, namely GaAsN and GaInAs. The calculated lattice constant, bulk modulus and the direct band gaps for studied semiconductors showed great parallelism with the previous available theoretical and experimental studies.

  16. Elliptic Curve Integral Points on y2 = x3 + 3x ‑ 14

    Science.gov (United States)

    Zhao, Jianhong

    2018-03-01

    The positive integer points and integral points of elliptic curves are very important in the theory of number and arithmetic algebra, it has a wide range of applications in cryptography and other fields. There are some results of positive integer points of elliptic curve y 2 = x 3 + ax + b, a, b ∈ Z In 1987, D. Zagier submit the question of the integer points on y 2 = x 3 ‑ 27x + 62, it count a great deal to the study of the arithmetic properties of elliptic curves. In 2009, Zhu H L and Chen J H solved the problem of the integer points on y 2 = x 3 ‑ 27x + 62 by using algebraic number theory and P-adic analysis method. In 2010, By using the elementary method, Wu H M obtain all the integral points of elliptic curves y 2 = x 3 ‑ 27x ‑ 62. In 2015, Li Y Z and Cui B J solved the problem of the integer points on y 2 = x 3 ‑ 21x ‑ 90 By using the elementary method. In 2016, Guo J solved the problem of the integer points on y 2 = x 3 + 27x + 62 by using the elementary method. In 2017, Guo J proved that y 2 = x 3 ‑ 21x + 90 has no integer points by using the elementary method. Up to now, there is no relevant conclusions on the integral points of elliptic curves y 2 = x 3 + 3x ‑ 14, which is the subject of this paper. By using congruence and Legendre Symbol, it can be proved that elliptic curve y 2 = x 3 + 3x ‑ 14 has only one integer point: (x, y) = (2, 0).

  17. Characterization of Y1-xCaxBa2Cu4O8 (x=0.0˜ 0.1) with Double Cu-O Chains by Raman Spectra

    Science.gov (United States)

    Kodama, Yasuharu; Tanemura, Sakae; Ikeda, Teruki

    1991-08-01

    Raman spectra of Y1-xCaxBa2Cu4O8 (x=0.0, 0.02, 0.05 and 0.1) ceramic samples synthesized under high oxygen pressure were investigated. Seven clear peaks assigned to Ag modes were observed for the sample with x=0. With increasing x, the peaks at 238 cm-1, 332 cm-1, 430 cm-1 and 590 cm-1 were broadened. The origin of the broadening of the peaks at 238 cm-1 and 590 cm-1 is considered to be the destruction of the double Cu-O chains due to the substitution of Ca for Y.

  18. Structural, magnetic and magnetocaloric properties of La{sub 0.7}Ca{sub 0.2}Sr{sub 0.1}Mn{sub 1x}Cr{sub x}O{sub 3} compounds with x = 0, 0.05 and 0.1

    Energy Technology Data Exchange (ETDEWEB)

    Dhahri, Ah., E-mail: dhahri.ahmad@outlook.fr [Laboratoire de Physique Appliquée, Faculté des Sciences de Sfax, BP 1171, Université de Sfax, 3000 (Tunisia); Jemmali, M. [Laboratoire des Sciences des Matériaux et de l’Environnement, Faculté des Sciences de Sfax, BP 1171, Université de Sfax, 3000 (Tunisia); Taibi, K. [Département SDM, FGMGP/USTHB, 16311 (Algeria); Dhahri, E. [Laboratoire de Physique Appliquée, Faculté des Sciences de Sfax, BP 1171, Université de Sfax, 3000 (Tunisia); Hlil, E.K. [Institut Néel, CNRS et Université J. Fourier, BP 166, 38042 Grenoble (France)

    2015-01-05

    Highlights: • The samples crystallize in the rhombohedral structure with the R3{sup ¯}c space group. • Enhancement of T{sub C} for the rhombohedral samples. • The relative cooling power increases with Cr-doping. • All samples exhibit a large magnetocaloric effect. • High values of the magnetoresistance in all samples. - Abstract: Structural, magnetic and magnetocaloric properties of La{sub 0.7}Sr{sub 0.1}Ca{sub 0.2}Mn{sub 1x}Cr{sub x}O{sub 3} compounds with x = 0, 0.05 and 0.1 have been investigated to shed light on Cr-doping influence. X-ray diffraction studies show that all samples crystallize in the rhombohedral symmetry with R3{sup ¯}c space group. Rietveld refinement structure shows that the insertion of Cr in Mn network modifies the structural parameters such as the volume, Mn–O–Mn angles and the Mn–O bond length. The substitution of Mn by Cr decreases the 2p-3d hybridization between O and Mn ions, reduces the bandwidth and increases the electron–phonon coupling. The investigation of magnetic and magnetocaloric properties reveals that the samples exhibit a paramagnetic(PM)–ferromagnetic (FM) transition with decreasing Curie temperature (T{sub C}) from 294 K to 255 K when Cr doping level increases. The magnetic entropy change (ΔS{sub M}{sup max}) also decreases from 6.20 J kg{sup −1} K{sup −1} for x = 0 to3.80 J kg{sup −1} K{sup −1} for x = 0.1, while the relative cooling power (RCP) increases from 234.5 to 240 J kg{sup −1}, respectively, under a magnetic field of 5 T. These outcomes suggest that Mn-site Cr doping inhibits the enhancement of the magnetocaloric effect in some perovskite manganites. This is explained by the weakening of the ferromagnetic double-exchange interaction between Mn{sup 3+} and Mn{sup 4+} ions.

  19. Growth, thermal and laser properties of Yb:YxLu1xVO4 mixed crystal

    International Nuclear Information System (INIS)

    Zhong, Degao; Teng, Bing; Kong, Weijin; Li, Jianhong; Zhang, Shiming; Li, Yuyi; Cao, Lifeng; Yang, Liting; He, Linxiang; Huang, Wanxia

    2015-01-01

    New mixed crystal of Yb: Y 0.78 Lu 0.22 VO 4 with Yb ion concentration of 0.3 at% was grown by Czochralski method. Transmission synchrotron X-ray topography implies that this mixed crystal follows a rotational growth pattern. Crystal structure of this crystal was determined by X-ray diffraction. It showed that this crystal possesses a tetragonal zircon structure (ZrSiO 4 , space group I41/amd), as YVO 4 and LuVO 4 do. Thermal properties of this crystal were characterized by measuring its specific heat, thermal expansion coefficients and thermal conductivities. The specific heat was determined to be 0.500 J g −1 K1 at 293 K. The average linear thermal expansion coefficients were calculated to be α 11 = 1.73 × 10 −6 K1 and α 33 = 9.43 × 10 −6 K1 , over the temperature range of 300–777 K. The thermal conductivities were calculated to be κ 11 = 5.47 W m −1 K1 and κ 33 = 6.64 W m −1 K1 at 303 K. Continuous-wave (cw) laser test on Yb: Y 0.78 Lu 0.22 VO 4 was conducted at room temperature in the wavelength range of 1035.7–1048.3 nm, and a 13.5% optical-to-optical efficiency was achieved. The good thermal properties of Yb:Y 0.78 Lu 0.22 VO 4 mixed crystal and its attractive cw laser performance make it very suitable for practical applications. - Highlights: • New Yb:Y 0.78 Lu 0.22 VO 4 mixed laser crystals were grown. • The thermal expansion, thermal diffusivity and specific heat were measured. • Cw laser operation was realized at room temperature in the range of 1035.7–1048.3 nm

  20. Electronic band structure calculations for GaxIn1xASyP1y alloys lattice matched to InP

    International Nuclear Information System (INIS)

    Bechiri, A; Benmakhlouf, F; Allouache, H; Bacha, S; Bouarissa, N

    2012-01-01

    A pseudopotential formalism coupled with the virtual crystal approximation are applied to study the effect of compositional disorder upon electronic band structure of cubic Ga x In 1x As y P 1y quarternary alloys lattice matched to InP. The effects of compositional variations are properly included in the calculations. Very good agreement is obtained between the calculated values and the available experimental data for the lattice–matched alloy to InP. The absorption at the fundamental optical gaps is found to be direct within a whole range of the y composition whatever the lattice-matching to the substrate of interest. The alloy system Ga x In 1x As y P 1y lattice matched to InP is suggested to be suitable for an efficient light emitting device (ELED) material.

  1. Low-temperature specific heat measurements on the NdCoxFe1-xO3 system

    International Nuclear Information System (INIS)

    Bartolome, F.; Kuz'min, M.D.; Bartolome, J.; Blasco, J.; Garcia, J.

    1995-01-01

    Low-temperature specific heat measurements have been carried out on the NdCo x Fe 1-x O 3 perovskite system (x=0, 0.25, 0.5, 0.9, 1). Magnetic ordering of Nd 3+ ions have been observed in NdCoO 3 (at 1.20 K) and NdFeO 3 (at 1.05 K). The studied dilutions, unlike the pure Fe or Co compounds, do not show a magnetic order of the Nd ions due to the stronger molecular field caused by decompensation of the internal field upon the introduction of the (Co 3+ ) magnetic vacancies in the antiferromagnetically ordered Fe subsystem. The specific heat curve of the system at x=0.9 resembles spin-glass behaviour. ((orig.))

  2. Formation of Y{sub x}Nd{sub 1-x}Ba{sub 2}Cu{sub 3}O{sub 7-{delta}} (0{<=}x{<=}0.9) superconductors from an undercooled melt via aero-acoustic levitation

    Energy Technology Data Exchange (ETDEWEB)

    Gustafson, D.E.; Hofmeister, W.H.; Bayuzick, R.J.; Nagashio, K.; Kuribayashi, K

    2003-01-20

    This paper presents the results of rapid solidification experiments performed on the copper oxide superconductors Y{sub x}Nd{sub 1-x}Ba{sub 2}Cu{sub 3}O{sub 7-{delta}} (0{<=}x{<=}0.9). Spherical rare earth (RE) 123 specimens were levitated in O{sub 2} using aero-acoustic levitation (AAL), melted with a laser, undercooled, and solidified. The peritectic transformation temperature for the reaction RE{sub 2}BaCuO{sub 5}+liquid{yields}REBa{sub 2}Cu{sub 3}O{sub 7-{delta}} corresponding to the maximum recalescence temperature during solidification was determined. RE123 was formed directly from the melt for Y-Nd binary alloy compositions with Nd concentration greater than 20% (Y concentration less than 80%). A minimum in the peritectic transformation temperature for the Nd/Y123 system corresponding to a composition Y{sub 0.3}Nd{sub 0.7}123 was determined at 66 deg. C below the peritectic of pure Nd123.

  3. Electrical transport of (1-x)La0.7Ca0.3MnO3+xAl2O3 composites

    International Nuclear Information System (INIS)

    Phong, P.T.; Khiem, N.V.; Dai, N.V.; Manh, D.H.; Hong, L.V.; Phuc, N.X.

    2009-01-01

    We report the resistivity (ρ)-temperature (T) patterns in (1-x)La 0,7 Ca 0,3 MnO 3 +xAl 2 O 3 composites (0≤x≤0.05) over a temperature regime of 50-300 K. Al 2 O 3 addition has increased the resistivity of these composites. The Curie temperature (T C ) is almost independent on the Al 2 O 3 content and is about 250 K for all the samples, while the metal-insulator transition temperature (T MI ) decreases with increasing Al 2 O 3 content. Based on the phenomenological equation for conductivity under a percolation approach, which is dependent on the phase segregation of ferromagnetic metallic clusters and paramagnetic insulating regions, we fitted the experimental data (ρ-T) from 50 to 300 K and find that the activation barrier increases as Al 2 O 3 content increases.

  4. Al x Ga1x N-based semipolar deep ultraviolet light-emitting diodes

    Science.gov (United States)

    Akaike, Ryota; Ichikawa, Shuhei; Funato, Mitsuru; Kawakami, Yoichi

    2018-06-01

    Deep ultraviolet (UV) emission from Al x Ga1x N-based light-emitting diodes (LEDs) fabricated on semipolar (1\\bar{1}02) (r-plane) AlN substrates is presented. The growth conditions are optimized. A high NH3 flow rate during metalorganic vapor phase epitaxy yields atomically flat Al y Ga1y N (y > x) on which Al x Ga1x N/Al y Ga1y N multiple quantum wells with abrupt interfaces and good periodicity are fabricated. The fabricated r-Al x Ga1x N-based LED emits at 270 nm, which is in the germicidal wavelength range. Additionally, the emission line width is narrow, and the peak wavelength is stable against the injection current, so the semipolar LED shows promise as a UV emitter.

  5. Magnetic phase diagram of ErGe 1-xSi x (0<x<1)

    Science.gov (United States)

    Thuéry, P.; El Maziani, F.; Clin, M.; Schobinger-Papamantellos, P.; Buschow, K. H. J.

    1993-10-01

    The composition-temperature magnetic phase diagram of ErGe 1- xSi x (0 0.40. For 0.17 ≥ x ≤ 0.55, a first-order transition occurs as function of the temperature between these two phases. For x ≥ 0.65, a lock-in transition takes place at TIC, leading from the wavevector ( k' x,0, k' z) to (1/2,0,1/2), as was already observed in ErSi. Finally, for x < 0.17 or 0.55 < x < 0.65, the wavevectors of the incommensurate phases characterized by (0,0, kz) or ( k' x,0, k' z) respectively remain unchanged in the whole temperature range below TN. For x≥0.65, a small amount of a magnetic phase characterized by the wavevector (0,0, 1/2) coexists with the main phases, below a Néel temperature T' N slightly lower than TN. In all cases, the erbium magnetic moments are colinear along the orthorhombic α-axis; the arrangement of the moments in the commensurate phases is the same as in ErSi and the incommensurate orderings correspond to sine-wave amplitude modulations. A brief account on the theoretical interpretation of this phase diagram is finally given.

  6. Alloying as a Route to Monolayer Transition Metal Dichalcogenides with Improved Optoelectronic Performance: Mo(S1xSex)2 and Mo1yWyS2

    KAUST Repository

    Shi, Zhiming

    2018-04-26

    On the basis of first-principles and cluster expansion calculations, we propose an effective approach to realize monolayer transition metal dichalcogenides with sizable band gaps and improved optoelectronic performance. We show that monolayer Mo(S1xSex)2 and Mo1yWyS2 with x = 1/3, 2/3 and y = 1/3, 1/2, 2/3 are stable according to phonon calculations and realize 1T′ or 1T″ phases. The transition barriers from the 2H phase are lower than for monolayer MoS2, implying that the 1T′ or 1T″ phases can be achieved experimentally. Furthermore, it turns out that the 1T″ monolayer alloys with x = 1/3, 2/3 and y = 1/3, 2/3 are semiconductors with band gaps larger than 1 eV, due to trimerization. The visible light absorption and carrier mobility are strongly improved as compared to 2H monolayer MoS2, MoSe2, and WS2. Thus, the 1T″ monolayer alloys have the potential to expand the applications of transition metal dichalcogenides, for example, in solar cells.

  7. Facile synthesis of Ba1-xKxFe₂As₂ superconductors via hydride route

    Energy Technology Data Exchange (ETDEWEB)

    Zaikina, Julia V. [Univ. of California at Davis, Davis, CA (United States); Batuk, Maria [Univ. of Antwerp, Antwerp (Belgium); Abakumov, Artem M. [Univ. of Antwerp, Antwerp (Belgium); Navrotsky, Alexandra [Univ. of California at Davis, Davis, CA (United States); Kauzlarich, Susan M. [Univ. of California at Davis, Davis, CA (United States)

    2014-12-03

    We have developed a fast, easy, and scalable synthesis method for Ba1-xKxFe₂As₂ (0 ≤ x1) superconductors using hydrides BaH₂ and KH as a source of barium and potassium metals. Synthesis from hydrides provides better mixing and easier handling of the starting materials, consequently leading to faster reactions and/or lower synthesis temperatures. The reducing atmosphere provided by the evolved hydrogen facilitates preparation of oxygen-free powders. By a combination of methods we have shown that Ba1-xKxFe₂As₂ obtained via hydride route has the same characteristics as when it is prepared by traditional solid-state synthesis. Refinement from synchrotron powder X-ray diffraction data confirms a linear dependence of unit cell parameters upon K content as well as the tetragonal to orthorhombic transition at low temperatures for compositions with x < 0.2. Magnetic measurements revealed dome-like dependence of superconducting transition temperature Tc upon K content with a maximum of 38 K for x close to 0.4. Electron diffraction and high-resolution high-angle annular dark-field scanning transmission electron microscopy indicates an absence of Ba/K ordering, while local inhomogeneity in the Ba/K distribution takes place at a scale of several angstroms along [110] crystallographic direction.

  8. Photoluminescence of heterostructures with GaP1xNx and GaP1−x−yNxAsy layers grown on GaP and Si substrates by molecular-beam epitaxy

    International Nuclear Information System (INIS)

    Lazarenko, A. A.; Nikitina, E. V.; Sobolev, M. S.; Pirogov, E. V.; Denisov, D. V.; Egorov, A. Yu.

    2015-01-01

    The structural and optical properties of heterostructures containing GaP 1x N x ternary and GaP 1−x−y N x As y quaternary alloy layers are discussed. The heterostructures are grown by molecular-beam epitaxy on GaP and Si substrates. The structures are studied by the high-resolution X-ray diffraction technique and photoluminescence measurements in a wide temperature range from 10 to 300 K. In the low-temperature photoluminescence spectra of the alloys with a low nitrogen fraction (x < 0.007), two clearly resolved narrow lines attributed to the localized states of nitrogen pairs and the phonon replicas of these lines are observed

  9. Magnetic and magnetocaloric properties of La{sub 0.7}Ca{sub 0.3}Mn{sub 1x}Zn{sub x}O{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Ho, T.A. [Department of Materials Science and Engineering, Korea University, Seoul 02841 (Korea, Republic of); Lim, S.H., E-mail: sangholim@korea.ac.kr [Department of Materials Science and Engineering, Korea University, Seoul 02841 (Korea, Republic of); Tho, P.T.; Phan, T.L. [Department of Physics and Oxide Research Center, Hankuk University of Foreign Studies, Yongin 17035 (Korea, Republic of); Yu, S.C. [Department of Physics, Chungbuk National University, Cheongju 28644 (Korea, Republic of)

    2017-03-15

    The magnetic Mn{sup 3+} ions in La{sub 0.7}Ca{sub 0.3}MnO{sub 3} are partially replaced by nonmagnetic Zn{sup 2+} ions to form La{sub 0.7}Ca{sub 0.3}Mn{sub 1x}Zn{sub x}O{sub 3} compounds (x=0.0, 0.06, 0.08, and 0.1), and their magnetic and magnetocaloric properties are investigated. The Curie temperature decreases drastically from 245 to 70 K as x increases from 0 to 0.1. An analysis using the Banerjee's criterion of the experimental results for magnetization as a function of temperature and magnetic field indicates that the first-to-second order magnetic phase transformation occurs at a threshold composition of x=0.06, which is further supported by the universal curves of the normalized entropy change versus reduced temperature. The maximum magnetic entropy change measured at a magnetic field span of 50 kOe, which occurs near the Curie temperature, decreases from 10.30 to 2.15 J/kg K with the increase of x from 0.0 to 0.1. However, the relative cooling power, an important parameter for practical applications, shows a maximum value of 404 J/kg at x=0.08, which is 1.5 times greater than that observed for the undoped sample. - Highlights: • Magnetic and MCE of La{sub 0.7}Ca{sub 0.3}Mn{sub 1x}Zn{sub x}O{sub 3} are investigated. • Order of magnetic phase transition is dependent on the Zn doping concentration. • Although the |∆S{sub max}| decreases with increasing x, RCP increase remarkably.

  10. Magneto-optical imaging of iron-oxypnictide SmFeAsO1-xFx and SmFeAsO1-y

    International Nuclear Information System (INIS)

    Tamegai, T.; Nakajima, Y.; Tsuchiya, Y.; Iyo, A.; Miyazawa, K.; Shirage, P.M.; Kito, H.; Eisaki, H.

    2009-01-01

    We have prepared iron-oxypnictide SmFeAsO 1-x F x by ambient-pressure technique and SmFeAsO 1-y by high-pressure technique, and characterized their bulk and local magnetic properties by using SQUID magnetometer and magneto-optical imaging. While the high-pressure samples have densities close to the theoretical value, the ambient-pressure samples have several small voids. Despite these structural differences between the two kinds of samples, they both have superconducting transition temperature above 50 K. In addition, magneto-optical images for both samples show similar kinds of inhomogeneities with large current concentrated in several grains and with small intergranular current. The estimated intragranular currents for both samples are over 10 5 A/cm 2 at low temperatures and low fields.

  11. Oxygen permeability of perovskite-type BaBi1-xLaxO3

    International Nuclear Information System (INIS)

    Yaremchenko, A.A.; Kharton, V.V.; Viskup, A.P.; Naumovich, E.N.; Samokhval, V.V.

    1998-01-01

    Oxygen permeability, electrical conductivity, and thermal expansion of BaBi 1-x La x O 3-δ (x = 0, 0.2, and 0.4) perovskite-like solid solutions have been found to decrease with lanthanum content. Thermal expansion coefficients of the ceramics are (11.9--12.8) x 10 -6 K -1 . Oxygen transport through the BaBi(La)O 3-δ dense ceramic membranes within the membrane thickness range of 0.6 < d < 1.2 mm has been shown to be limited by both bulk ionic conductivity and surface exchange rate

  12. Influence of substitutional disorder on the electrical transport and the superconducting properties of Fe{sub 1+z}Te{sub 1−x−y}Se{sub x}S{sub y}

    Energy Technology Data Exchange (ETDEWEB)

    Rodríguez, M.G. [Laboratorio de Bajas Temperaturas, Departamento de Física, FCEyNUBA and IFIBA-CONICET, Buenos Aires (Argentina); Polla, G.; Ramos, C.P. [Gerencia de Investigación y Aplicaciones, CAC-CNEA, San Martín (Argentina); Acha, C., E-mail: acha@df.uba.ar [Laboratorio de Bajas Temperaturas, Departamento de Física, FCEyNUBA and IFIBA-CONICET, Buenos Aires (Argentina)

    2015-11-15

    We have carried out an investigation of the structural, magnetic, transport and superconducting properties of Fe{sub 1+z}Te{sub 1−x−y}Se{sub x}S{sub y} ceramic compounds, for z = 0 and some specific Se (0 ≤ x ≤ 0.5) and S (0 ≤ y ≤ 0.12) contents. The incorporation of Se and S to the FeTe structure produces a progressive reduction of the crystallographic parameters as well as different degrees of structural disorder associated with the differences of the ionic radius of the substituting cations. In the present study, we measure transport properties of this family of compounds and we show the direct influence of disorder in the normal and superconductor states. We notice that the structural disorder correlates with a variable range hopping conducting regime observed at temperatures T > 200 K. At lower temperatures, all the samples except the one with the highest degree of disorder show a crossover to a metallic-like regime, probably related to the transport of resilient-quasi-particles associated with the proximity of a Fermi liquid state at temperatures below the superconducting transition. Moreover, the superconducting properties are depressed only for that particular sample, in accordance to the condition that superconductivity is affected by disorder when the electronic localization length ξ{sub L} becomes smaller than the coherence length ξ{sub SC}. - Highlights: • New Fe(1 + z)Te(1−x−y)Se(x)S(y) ceramic samples were synthesized. • Structural, magnetic, transport and superconducting properties are presented. • Nonmagnetic disorder determines a VRH conduction regime near room temperature. • Superconductivity is affected by disorder.

  13. Long-term studies with the Ariel-5 asm. 1: Her X-1, Vela X-1 and Cen X-3. [periodic variations

    Science.gov (United States)

    Holt, S. S.; Kaluzienski, L. J.; Boldt, E. A.; Serlemitsos, P. J.

    1978-01-01

    Twelve hundred days of 3-6 keV X-ray data from Her X-1, Vela X-1 and Cen X-3 accumulated with the Ariel-5 all-sky monitor are interrogated. The binary periodicities of all three can be clearly observed, as can the approximately 35-d variation of Her X-1, for which we can refine the period to 34.875 plus or minus .030-d. No such longer-term periodicity less than 200-d is observed from Vela X-1. The 26.6-d low-state recurrence period for Cen X-3 previously suggested is not observed, but a 43.0-d candidate periodicity is found which may be consistent with the precession of an accretion disk in that system. The present results are illustrative of the long-term studies which can be performed on approximately 50 sources over a temporal base which will ultimately extend to at least 1800 days.

  14. Magnetic and hydrogen absorption properties of (La1-xYx) Co5-hydrides

    International Nuclear Information System (INIS)

    Fujiwara, K.; Ichinose, K.; Nagai, H.; Tsujimura, A.

    1988-01-01

    The 59 Co NMR and magnetization measurement in (La 1-x -Y x ) Co 5 H y have been performed at 77 K. The magnetizations of these compounds decrease with increasing hydrogen content (y) and are independent of Y-concentration (x). This result can be interpreted by an electron transfer effect in the direction H atom → Co atom

  15. High-pressure synthesis and structural, physical properties of CaIr1-xPtxO3 and CaIr1-xRhxO3

    Science.gov (United States)

    Hirai, S.; Bromiley, G. D.; Klemme, S.; Irifune, T.; Ohfuji, H.; Attfield, P.; Nishiyama, N.

    2010-12-01

    in terms of materials science applications. To our knowledge, this will be the first report on structural, magnetic and charge-transport properties of B-site substituted solid solutions of post-perovskite oxides with 4d/5d transition metals. High-quality polycrystalline samples of CaIr1-xPtxO3 and CaIr1-xRhxO3 have been obtained at high pressures, and structural, magnetic and charge-transport properties of the compounds will be reported. ODF analysis reveals that solutions of CaIrO3, CaPtO3 and CaRhO3 exhibit similar grain growth features to the mother compound, although growth in [0 1 0] plays a more dominant role than the growth in [0 0 1] for the solid solutions. CaIrO3 is a characteristic hard magnet suitable for applications such as magnetic recording, with TN = 108K. A new phase of CaIr1-xPtxO3 synthesized at a high P/T condition has Raman modes which resemble those of CaIrO3 perovskite, suggesting this phase has a perovskite structure.The instability of the perovskite phase of CaIr1-xPtxO3 reveals why the post-perovskite to peovskite phase transition has not been observed for CaPtO3 unlike the case for CaIrO3, CaRhO3 and CaRuO3.

  16. Observation of Cyg X-1 with the K-10-11 rocket

    International Nuclear Information System (INIS)

    Doi, Tsunenari; Matsuoka, Masaru; Miyamoto, Shigenori; Oda, Minoru; Ogawara, Yoshiaki

    1976-01-01

    The X-ray emission mechanism owing to the mass accretion to compact objects is one of cosmic X-ray sources. White dwarf, neutron star and black hole are considered as the compact objects. The mass of Cyg X-1 has been estimated to be about 10 times as large as the mass of the sun, and Cyg X-1 is only one prominent candidate for the black hole. The observation of the X-ray from Cyg C-1 provides the useful information on the physical state of the black hole. Particularly, the X-ray from Cyg X-1 showed the characteristic time variations which have not been detected in other X-ray sources. They are the intensive time variation over the duration of msec to day, the pulsation of about 1 msec breadth, and the transition between two X-ray emission states. The X-ray detector abroad the K-10-11 rocket is the proportional counter filled with 90% Xe and 10% CO 2 , and covers the 1.5-2.5 kev X-ray energy range. The total detector area is about 950 cm 2 . The observed result showed the characteristic intensive time variation and the msec pulsation. The data analysis is now in progress, and the preliminary result will be reported. (Yoshimori, M.)

  17. Effect of Cd doping on magnetocaloric effect and critical behavior analysis on perovskite Nd1-xCdxMnO3 (x = 0, 0.1, 0.2, 0.3, and 0.4) manganite polycrystals

    Science.gov (United States)

    Saravanan, C.; Thiyagarajan, R.; Manikandan, K.; Sathiskumar, M.; Kanjariya, P. V.; Bhalodia, J. A.; Arumugam, S.

    2017-12-01

    We report the doping effect of divalent cation Cd2+ at Nd-site of intermediate bandwidth manganite system NdMnO3 through the temperature- and magnetic field-dependent magnetization measurements. The parent compound shows paramagnetic-antiferromagnetic transition at 56 K, whereas Cd doped samples show the paramagnetic-ferromagnetic transition with fluctuating TC. During this transition, Nd1-xCdxMnO3 (x = 0.1 and 0.2) samples exhibit first order nature, whereas Nd1-xCdxMnO3 (x = 0.3 and 0.4) samples exhibit second order nature. It confirms a crossover from first order transition to second order transition while x = 0.2 to x = 0.3. By having first order transition, x = 0.2 sample exhibits high magnetic entropy change of 3.62 J kg-1 K-1 for the magnetic field change of 5 T out of all compositions. By having second order transitions, x = 0.4 sample exhibits a high relative cooling power of 319.71 J kg-1 for the magnetic field change of 5 T out of all the compositions. The critical behavior of second order transition of x = 0.3 and 0.4 samples has been analyzed using Arrott and Kouvel-Fisher plots. The estimated critical exponents of these samples are nearly matched with the mean free model, which can be explained by the existence of dipole-dipole interaction by the Cd doping which strengthens long range ferromagnetic interactions between the spins.

  18. Band alignment in ZnSe/Zn1-x-yCdxMnySe quantum-well structures

    International Nuclear Information System (INIS)

    Yu, W.Y.; Salib, M.S.; Petrou, A.; Jonker, B.T.; Warnock, J.

    1997-01-01

    We present a magneto-optical study of ZnSe/Zn 1-x-y Cd x Mn y Se quantum-well structures in which a suitable choice of the Cd composition leads to a system that is type I at zero magnetic field. When a magnetic field is applied perpendicular to the layers of the structure, the band edges split in such a way as to make the upper σ - (1/2, t 3/2) exciton transition type II, while the ground state σ + (-1/2, -3/2) exciton component remains type I at all field values. This alignment reduces the probability for carrier relaxation from the higher-energy exciton component and opens the possibility of hole-spin population inversion via optical pumping. copyright 1997 The American Physical Society

  19. Study of K-p→0-1/2+ and K-p→0-3/2+ reactions

    International Nuclear Information System (INIS)

    Chaurand, B.M.G.

    1976-01-01

    With 1.3x10 6 photos taken with the CERN two meters hydrogen bubble chamber, interactions of the type K - p→0 - 1/2 + (3/2 + ) at 14.3GeV/c were studied. Experimental data are given as well as the amplitudes which describe these reactions, and show how they are connected with the measurable quantities; these are determined in each of the reactions whenever it is possible (sigma sub(T), dsigma/dt, polarization of Λ and Σ + , density matrix element of Σ + (1385)). The results are compared with those obtained at other energies and with some predictions of SU 3 . Finally, it is explained how the results have contributed to the analysis of the amplitudes of the reactions 0 - 1/2 + →0 - 1/2 + (3/2 + ) [fr

  20. Influence of calcium on transport properties, band spectrum and superconductivity of YBa2Cu3O(y) and YBa(1.5)La(0.5)Cu3O(y)

    Science.gov (United States)

    Gasumyants, V. E.; Vladimirskaya, E. V.; Patrina, I. B.

    1995-01-01

    The comparative investigation of transport phenomena in Y(1-x)Ca(x)Ba2Cu3O(y) (0 is less than x is less than 0.25; 6.96 is greater than y is greater than 6.87 and 6.73 is less than x is less than 6.53); Y(1-x)Ca(x)Ba(1.5)La(0.5)Cu3O(y) (0 is less than x is less than 0.5; 7.12 is greater than y is greater than 6.96) and YBa(2-x)La(x)Cu3O(y) (0 is less than x is less than 0.5; 6.95 is less than y is less than 7.21) systems have been carried out. The temperature dependencies of resistivity and thermopower have been measured. It was found that the S(T) dependencies take some additional features with Ca content increase. The results obtained have been analyzed on the basis of the phenomenological theory of electron transport in the case of the narrow conductive band. The main parameters of the band spectrum (the band filling with electrons degree and the total effective band width) have been determined. The dependencies of these from contents of substituting elements are discussed. Analyzing the results obtained simultaneously with the tendencies in oxygen content and critical temperature change we have confirmed the conclusion that the oxygen sublattice disordering has a determinant effect on band structure parameters and superconductive properties of YBa2Cu3O(y). The results obtained suggest that Ca gives rise to some peculiarities in band spectrum of this compound.

  1. Electromagnetic mass splittings of π, a1, K, K1(1400), and K* (892)

    International Nuclear Information System (INIS)

    Gao, D.; Li, B.A.; Yan, M.

    1997-01-01

    To one-loop order and O(α EM ), the electromagnetic mass splittings of π, a 1 , K, K 1 (1400), and K * (892) are calculated in the framework of U(3) L xU(3) R chiral field theory. The logarithmic divergences emerging in the Feynman integrations of the mesonic loops are factorized by using an intrinsic parameter g of this theory. No other additional parameters or counterterms are introduced to absorb the mesonic loop divergences. When f π , m ρ , and m a are taken as inputs, the parameter g will be determined and all the physical results are finite and fixed. Dashen's theorem is satisfied in the chiral SU(3) limit of this theory and a rather large violation of the theorem is revealed at the order of m s or m K 2 . Mass ratios of light quarks have been determined. A relation for electromagnetic corrections to masses of axial-vector mesons is obtained. It could be regarded as a generalization of Dashen's theorem. Comparing with data, it is found that the nonelectromagnetic mass difference of K * is in agreement with the estimation of Schechter, Subbaraman, and Weigel. copyright 1997 The American Physical Society

  2. Architectural Processes and Physicochemical Properties of CoO/ZnO and Zn 1x Co x O/Co 1y Zn y O Nanocomposites

    KAUST Repository

    Yao, Ke Xin; Zeng, Hua Chun

    2009-01-01

    complex nanocomposite materials, especially for interdoped metal oxides. As an example, our as-prepared binary oxide composites Zn1-xCoxO/Co 1-yZnyO have shown good catalytic activity for oxidation of carbon monoxide at relatively low reaction temperatures

  3. Improvement of photoluminescence properties and thermal stability of Y{sub 2.9}Ce{sub 0.1}Al{sub 5−x}Si{sub x}O{sub 12} phosphors with Si{sub 3}N{sub 4} addition

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Fangfang [College of Electronic Information and Engineering, Hangzhou Dianzi University, Hangzhou 310018 (China); Song, Kaixin, E-mail: kxsong@hdu.edu.cn [College of Electronic Information and Engineering, Hangzhou Dianzi University, Hangzhou 310018 (China); Jiang, Jun [Ningbo Institute of Materials Technologies and Engineering, Chinese Academy of Sciences, Ningbo 315201 (China); Wu, Song; Zheng, Peng [College of Electronic Information and Engineering, Hangzhou Dianzi University, Hangzhou 310018 (China); Huang, Qingming [Instrument Analysis and Testing Center, Fuzhou University, Fuzhou 350002 (China); Xu, Junming; Qin, Huibin [College of Electronic Information and Engineering, Hangzhou Dianzi University, Hangzhou 310018 (China)

    2014-12-05

    Highlights: • Y{sub 2.9}Ce{sub 0.1}Al{sub 5−x}Si{sub x}O{sub 12} phosphors were prepared by solid-state reaction in reduced air ambience. • Si{sup 4+} could be incorporated into the host lattice of Y{sub 3}Al{sub 5}O{sub 12} through partial occupation of the Al{sup 3+} sites. • Si{sub 3}N{sub 4} addition can improve photoluminescence efficiency and thermal stability of Y{sub 3}Al{sub 5}O{sub 12}:Ce. - Abstract: A series of Si{sub 3}N{sub 4} doping Y{sub 2.9}Ce{sub 0.1}Al{sub 5−x}Si{sub x}O{sub 12−3x/2}N{sub 4x/3} phosphors were prepared by solid-state reaction in 95%N{sub 2}–5%H{sub 2} reduced air ambience. The XRD characteristics plus Rietveld refinement results shows that the as-sintered powders are unique crystal phase with the same crystal structure of Y{sub 3}Al{sub 5}O{sub 12} (PDF No. 79-1891). The N element was not detected by the analysis of X-ray photoelectron spectroscopy (XPS) and energy dispersive X-ray spectrum (EDS). The photoluminescence spectra (PL and PLE) tests show that the exciting and emitting intensity of PLE and PL gradually increase due to the increase of Si{sub 3}N{sub 4} concentration. Meanwhile, the phosphorescence decay times are prolonged from 45 ns (x = 0) to 78 ns (x = 0.3), under the monitor of 530 nm wavelength. The thermoluminescence tests (TL) confirm the thermal stability of as-phosphors with Si{sub 3}N{sub 4} addition is much better than that of the pristine Y{sub 2.9}Ce{sub 0.1}Al{sub 5}O{sub 12} phosphors.

  4. K-edge x-ray dichroism investigation of Fe1xCoxSi: Experimental evidence for spin polarization crossover

    International Nuclear Information System (INIS)

    Hearne, G.R.; Diguet, G.; Baudelet, F.; Itié, J.-P.; Manyala, N.

    2015-01-01

    Both Fe and Co K-edge x-ray magnetic circular dichroism (XMCD) have been employed as element-specific probes of the magnetic moments in the composition series of the disordered ferromagnet Fe 1x Co x Si (for x=0.2, 0.3, 0.4, 0.5). A definitive single peaked XMCD profile occurs for all compositions at both Fe and Co K-edges. The Fe 4p orbital moment, deduced from the integral of the XMCD signal, has a steep dependence on x at low doping levels and evolves to a different (weaker) dependence at x≥0.3, similar to the behavior of the magnetization in the Co composition range studied here. It is systematically higher, by at least a factor of two, than the corresponding Co orbital moment for most of the composition series. Fine structure beyond the K-edge absorption (limited range EXAFS) suggests that the local order (atomic environment) is very similar across the series, from the perspective of both the Fe and Co absorbing atom. The variation in the XMCD integral across the Co composition range has two regimes, that which occurs below x=0.3 and then evolves to different behavior at higher doping levels. This is more conspicuously present in the Fe contribution. This is rationalized as the evolution from a half-metallic ferromagnet at low Co doping to that of a strong ferromagnet at x>0.3 and as such, spin polarization crossover occurs. The Fermi level is tuned from the majority spin band for x<0.3 where a strongly polarized majority spin electron gas prevails, to a regime where minority spin carriers dominate at higher doping. The evolution of the Fe-derived spin polarized (3d) bands, indirectly probed here via the 4p states, is the primary determinant of the doping dependence of the magnetism in this alloy series. - Highlights: • Element-specific probing of the electronic structure of the Fe 1x Co x Si series. • XMCD at the level of 10 −4 at the K-edge in such low-moment systems. • Element-specific probing of magnetic contributions from both Fe and Co

  5. Relationship between interlayer hydration and photocatalytic water splitting of A'1-xNaxCa2Ta3O10.nH2O (A'=K and Li)

    International Nuclear Information System (INIS)

    Mitsuyama, Tomohiro; Tsutsumi, Akiko; Sato, Sakiko; Ikeue, Keita; Machida, Masato

    2008-01-01

    Partial replacement of alkaline metals in anhydrous KCa 2 Ta 3 O 10 and LiCa 2 Ta 3 O 10 was studied to control interlayer hydration and photocatalytic activity for water splitting under UV irradiation. A' 1-x Na x Ca 2 Ta 3 O 10 .nH 2 O (A'=K and Li) samples were synthesized by ion exchange of CsCa 2 Ta 3 O 10 in mixed molten nitrates at 400 deg. C. In K 1-x Na x Ca 2 Ta 3 O 10 .nH 2 O, two phases with the orthorhombic (C222) and tetragonal (I4/mmm) structures were formed at x≤0.7 and x≥0.5, respectively. Upon replacement by Na + having a larger enthalpy of hydration (ΔH h 0 ), the interlayer hydration occurred at x≥0.3 and the hydration number (n) was increased monotonically with an increase of x. Li 1-x Na x Ca 2 Ta 3 O 10 .nH 2 O showed a similar hydration behavior, but the phase was changed from I4/mmm (x 1-x Na x Ca 2 Ta 3 O 10 .nH 2 O exhibited the activity increasing in consistent with n, whereas Li 1-x Na x Ca 2 Ta 3 O 10 .nH 2 O exhibited the activity maximum at x=0.77, where the rates of H 2 /O 2 evolution were nearly doubled compared with those for end-member compositions (x=0 and 1). - Graphical abstract: The partial substitution of Na in the interlayer of anhydrous-layered perovskite has been found as useful structural modification toward highly active hydrated photocatalysts

  6. On the Difference Equation xn+1=xnxn-k/(xn-k+1a+bxnxn-k

    Directory of Open Access Journals (Sweden)

    Stevo Stević

    2012-01-01

    Full Text Available We show that the difference equation xn+1=xnxn-k/xn-k+1(a+bxnxn-k,n∈ℕ0, where k∈ℕ, the parameters a, b and initial values x-i, i=0,k̅ are real numbers, can be solved in closed form considerably extending the results in the literature. By using obtained formulae, we investigate asymptotic behavior of well-defined solutions of the equation.

  7. Effect of second introduced phase on magnetic and magnetotransport properties of (1-x)La0.7Sr0.3Mn0.9Co0.1O3/x% Ag (x=0%, 2%, 4%) nanocomposites

    Science.gov (United States)

    Shah, Hiral D.; Bhalodia, J. A.

    2018-05-01

    The structural, magnetic and magnetotransport properties of (1-x)La0.7Sr0.3Mn0.9Co0.1O3(LSMCO)/x% Ag (x=0%, 2%, 4%) nanocomposites were investigated to explore the role of second introduced phase. (1-x) LSMCO/x% Ag (x=0%, 2%, 4%) nanocomposites are prepared via solid-state reaction method. X-ray diffraction (XRD) and SEM analysis indicated that x% of Ag are not substituted into the main LSMCO phase and remains an additive to the second phase at grain boundaries [1]. The structural parameters and the reliability factors for all the samples were successfully determined by the Rietveld refinement. Magnetization and transport properties of (1-x)LSMCO/x% Ag nanocomposites have been reported. Resistivity of the composite samples increases with Ag content in comparison with the pure LSMCO, and suppressed with applied magnetic field in all the composite samples [2]. The metal-insulator transition (TMI) and accompanied paramagnetic-ferromagnetic transition (TC) temperatures decrease with increase in Ag content. The electrical resistivity of the experimental results is explored by theoretical model below TMI. The maximum MR was observed to be 55% in the x=4% sample at 5 K temperature under 7 T magnetic field, this value is larger than that of pure LSMCO (19% at 5 K and 7 T), which is encouraging for practical application. Summarily, the addition of Ag in LSMCO improves MR% values significantly due to the more grain boundary contribution and result in better physical properties of the parent manganite system.

  8. Raman-scattering results from Y1-xCaxSr2Cu2GaO7

    International Nuclear Information System (INIS)

    Salamon, D.; Liu, R.; Klein, M.V.; Groenke, D.A.; Poeppelmeier, K.R.; Dabrowski, B.; Han, P.D.; Payne, D.A.

    1993-01-01

    We present a Raman-scattering study of Y 1-x Ca x Sr 2 Cu 2 GaO 7 for both the x=0 parent compound and doped compositions with x=0.25 and x=0.40. Extrapolation from YBa 2 Cu 3 O 7-d and other cuprates allows us to assign many of the Raman-active phonon modes in the x=0 material, as well as identify a two-magnon scattering peak, a second-order phonon scattering peak, and a Raman continuum out to 4000 cm -1 . Despite compositional inhomogeneities, the doped superconducting samples show some of the same low-energy phonon features as the x=0 material. There is, however, a doping-dependent shift in the positions of features in the 500--700 cm -1 range, possibly due to Ca locating on Sr sites instead of Y sites. The relative intensities of the phonon peaks in the doped material are also changed from the insulator (x=0), suggesting that a resonant Raman phenomenon is occurring. The temperature-dependent spectra show what appears to be a superconducting dip in the background intensity, but the low superconducting fractions in these samples make this difficult to verify. The doped material also has a Raman continuum out to 4000 cm -1 just as in the x=0 samples, but with the two-magnon and second-order phonon scattering peaks significantly reduced in intensity. This may be a result of changes in the long-range ordering, or another manifestation of the same resonance phenomena occurring at lower energies. Single-crystal samples of the doped material Y 1-x Ca x Sr 2 Cu 2 GaO 7 are necessary for a more conclusive Raman study

  9. Tunable thermodynamic activity of LaxSr1xMnyAl1yO3–δ (0 ≤ x1, 0 ≤ y1) perovskites for solar thermochemical fuel synthesis† †Electronic supplementary information (ESI) available: Computational details, comprehensive XRD analyses, oxygen nonstoichiometry measurements and thermodynamic characterization of the perovskites. See DOI: 10.1039/c6ta06644e Click here for additional data file.

    Science.gov (United States)

    Ezbiri, M.; Takacs, M.; Theiler, D.; Steinfeld, A.

    2017-01-01

    Nonstoichiometric metal oxides with variable valence are attractive redox materials for thermochemical and electrochemical fuel processing. To guide the design of advanced redox materials for solar-driven splitting of CO2 and/or H2O to produce CO and/or H2 (syngas), we investigate the equilibrium thermodynamics of the LaxSr1xMnyAl1yO3–δ perovskite family (0 ≤ x1, 0 ≤ y1) and La0.6Ca0.4Mn0.8Al0.2O3–δ, and compare them to those of CeO2 as the baseline. Oxygen nonstoichiometry measurements from 1573 to 1773 K and from 0.206 to 180 mbar O2 show a tunable reduction extent, increasing with increasing Sr content. Maximal nonstoichiometry of 0.32 is established with La0.2Sr0.8Mn0.8Al0.2O3–δ at 1773 K and 2.37 mbar O2. As a trend, we find that oxygen capacities are most sensitive to the A-cation composition. Partial molar enthalpy, entropy and Gibbs free energy changes for oxide reduction are extracted from the experimental data using defect models for Mn4+/Mn3+ and Mn3+/Mn2+ redox couples. We find that perovskites exhibit typically decreasing enthalpy changes with increasing nonstoichiometries. This desirable characteristic is most pronounced by La0.6Sr0.4Mn0.4Al0.6O3–δ, rendering it attractive for CO2 and H2O splitting. Generally, perovskites show lower enthalpy and entropy changes than ceria, resulting in more favorable reduction but less favorable oxidation equilibria. The energy penalties due to larger temperature swings and excess oxidants are discussed in particular. Using electronic structure theory, we conclude with a practical methodology estimating thermodynamic activity to rationally design perovskites with variable stoichiometry and valence. PMID:28580143

  10. Tunability, dielectric, and piezoelectric properties of Ba{sub (1x)}Ca{sub x}Ti{sub (1y)}Zr{sub y}O{sub 3} ferroelectric thin films

    Energy Technology Data Exchange (ETDEWEB)

    Daumont, C. J. M., E-mail: christophe.daumont@univ-tours.fr; Le Mouellic, E.; Negulescu, B.; Wolfman, J. [Laboratoire GREMAN, UMR7347 CNRS, Faculté de Sciences et Techniques, Université François Rabelais, 37200 Tours (France); Simon, Q.; Payan, S.; Maglione, M. [Institute of Condensed Matter Chemistry of Bordeaux, ICMCB-CNRS, Université de Bordeaux, 33608 Pessac Cedex (France); Gardes, P.; Poveda, P. [STMicroelectronics, 10 rue Thalès de Milet, 37071 Tours Cedex (France)

    2016-03-07

    Tunable ferroelectric capacitors, which exhibit a decrease of the dielectric permittivity (ϵ) under electric field, are widely used in electronics for RF tunable applications (e.g., antenna impedance matching). Current devices use barium strontium titanate as the tunable dielectric, and the need for performance enhancement of the tunable element is the key for device improvement. We report here on libraries of Ba{sub 0.97}Ca{sub 0.03}Ti{sub 1x}Zr{sub x}O{sub 3} thin films (0 ≤ x ≤ 27%) with a thickness of about 130 nm deposited on IrO{sub 2}/SiO{sub 2}/Si substrates using combinatorial pulsed laser deposition allowing for gradients of composition on one sample. A total of 600 capacitors on a single sample were characterized in order to statistically investigate the dielectric properties. We show that the tunabilty is maximum at intermediate compositions, reaching values up to 60% for an electric field of about 400 kV cm{sup −1}. We attribute the high tunability in the intermediate compositions to the paraelectric-ferroelectric phase transition, which is brought down to room temperature by the addition of Zr. In addition, the piezoelectric coefficient is found to be decreasing with increasing Zr content.

  11. Pseudobinary glassy compositions (AsSex)1-y(AsTex)y

    International Nuclear Information System (INIS)

    El Mously, M.K.; El Dem, M.B.

    1987-09-01

    The ternery glassy composition of the general formula (AsSe x ) 1-y (AsTe x ) y can be considered as a pseudobinary system at x=1, 3/2 and 5/2 and 0 ≤ y1. The results of DTA, electrical conductivity measurements, density of such glasses as well as the X-ray diffraction of the crystallized samples have been used to confirm this point of view and to explain the presence of new phases not shown in the simple binary systems As-Se and As-Te. The possibility of transformation of the glassy network from partially polymerized state MCN (molecular cluster network) to completely polymerized state CRN (continuous random network) by mixing two structural units was also discussed. (author). 12 refs, 7 figs, 2 tabs

  12. An Investigation of the Magnetic Structure and Excitations in K2CoxFe1-xF4

    DEFF Research Database (Denmark)

    Higgins, S.A.; Couley, R.A.; Hagen, M.

    1984-01-01

    Neutron scattering techniques have been used to investigate the magnetic structure of K2CoxF1-xF4 with x=0.2 and x=0.6. The x=0.6 sample exhibits only one magnetic phase transition, at TN=92.2+or-0.1K. The x=0.2 sample has two magnetic phase transitions; below TN=66+or-1K the axial spin components...

  13. Effects of pressure and magnetic field on transport properties of Y1-xRxCo2 alloys (R=Gd, Tb, Dy, Ho and Er)

    International Nuclear Information System (INIS)

    Takaesu, Y; Nakama, T; Kinjyo, A; Yonamine, S; Hedo, M; Yagasaki, K; Uchima, K; Uwatoko, Y; Burkov, A T

    2010-01-01

    Electrical resistivity ρ and thermopower S of Y 1-x R x Co 2 (R=Gd, Tb, Dy, Ho and Er) Laves phase alloy systems were measured at temperatures from 1.5 K to 300 K in magnetic fields up to 15 T and under hydrostatic pressure up to 2 GPa. We show that there is a universal linear relation between the pressure and magnetic field derivatives of the resistivity, dρ/dP and dρ/dB, with gradient, determined by pressure derivative of the critical metamagnetic field of the cobalt 3d electron system. A similar scaling behavior was found for the thermopower dependencies on pressure and alloy composition.

  14. Preparation and physical properties of polycrystalline (Bi1-xPbx)2Sr2Ca2Cu3Oy high Tc superconductors

    International Nuclear Information System (INIS)

    Awan, M.S.; Maqsood, M.; Mirza, S.A.; Yousaf, M.; Maqsood, A.

    1995-01-01

    (Bi 1-x Pb x ) 2 Sr 2 Ca 2 Cu 3 O y (x = 0.3) high critical transition temperature (T c ) superconductors are synthesized by the solid-state reaction method in polycrystalline form. X-ray diffraction (XRD) studies, direct current (dc) electrical resistivity measurements, scanning electron microscopic (SEM) studies, critical current density measurements and zero-field alternating current (ac) susceptibility measurements are performed to investigate the physical changes, structural changes, and magnetic behavior of the superconducting samples. X-ray diffraction studies show that a high T c phase exists with orthorhombic symmetry in the specimen. According to the XRD data, the lattice parameters of the high T c phase were determined as a = 0.537(1) nm, b = 0.539(1) nm, and c = 3.70(1) nm. The compound exhibits a superconducting transition at 106 ± 1 K for zero resistance. The ac susceptibility measurements in zero field confirm the dc electrical resistivity results; hence both support the XRD results. The particle size and structural changes as a function of the cold-pressing and aging effect are also reported

  15. Synthesis, Sintering, and Electrical Properties of BaCe0.9−xZrxY0.1O3−δ

    DEFF Research Database (Denmark)

    Ricote, S.; Caboche, G.; Estournes, C.

    2008-01-01

    BaCe0.9-xZrxY0.1O3-delta powders were synthesized by a solid-state reaction. Different contents of cerium and zirconium were studied. Pellets were sintered using either conventional sintering in air at 1700 degrees C or the Spark Plasma Sintering (SPS) technique. The density of the samples sintered...

  16. Growth of Sr1-xNdxCuOy thin films by rf-magnetron sputtering and pulsed-laser deposition

    International Nuclear Information System (INIS)

    Sugii, N.; Ichikawa, M.; Kuba, K.; Sakurai, T.; Iamamoto, K.; Yamauchi, H.

    1992-01-01

    This paper reports on Sr 1- x Nd x CuO y thin films grown on SrTiO 3 substrates by rf-magnetron sputtering and pulsed-laser deposition. The sputter-deposited film with x=0 has an infinite-layer structure whose lattice constants are: a=0.390 nm and c=0.347 nm. When x is larger than 0.1, the films contain a phase of the Sr 14 Cu 24 O 41 structure. The laser-deposited films of Sr 1- x Nd x CuO y with x ≥ 0.075 were single phase of the infinite-layer structure. The lattice parameter c decreased and the lattice parameter a increased, as the Nd content, x, increased. The films with x=0.10 and 0.125 exhibited superconducting onset temperatures around 26 K. Weak Meissner signals were observed for these films at temperatures below 30 K

  17. Growth of multiferroic Gd1-xYxMnO3 single crystals by optical floating zone technique

    International Nuclear Information System (INIS)

    Sarguna, R.M.; Ganesamoorthy, S.; Sridharan, V.; Subramanian, N.

    2014-01-01

    Rare earth manganites RMnO 3 with distorted perovskite structure are excellent multiferroic materials. The discovery of magnetic spin driven ferroelectricity in orthorhombic manganites (TbMnO 3 ) has sparked a surge in research into understanding the fundamental mechanism of multiferroic behavior. These systems fall under the category of type-2 multiferroics, the change of spatially modulated magnetic moment from sinusoidal to cycloidal gives rise to electric polarization. The magnetic structure depends upon the Mn-O-Mn bond angle. GdMnO 3 shows multiferroic properties only in the presence of applied magnetic field. When a magnetic field is applied along the b-axis, GdMnO 3 enters a ferroelectric state with an electric polarisation along the c-axis. By altering the Mn-O-Mn angle it is expected that GdMnO 3 will show multiferroic property even in the absence of magnetic field like TbMnO 3 . To alter the Mn-O-Mn bond angle GdMnO 3 was substituted with Y having lower ionic radius at Gd site. The effect of Y doping at the rare-earth site in GdMnO 3 investigated on polycrystalline samples of Gd 1-x Y x MnO 3 demonstrated a magneto-electric coupling in x=0.1-0.4. Single crystals are expected to give much amplified signal in respect of ferroelectric and magnetic properties. In this work we have grown Y substituted Gd 1-x Y x MnO 3 (x = 0.2, 0.3 and 0.4) by optical floating zone technique under different gas atmosphere. Growth rate of 1-2 mm/h yielded crack free crystals. Quality of the crystals was checked using Laue diffraction. Effect of growth rate and atmosphere pressure will be presented in this talk. (author)

  18. Magnetic properties of polycrystalline PrxY1-xBa2Cu3O7-δ

    International Nuclear Information System (INIS)

    Stari, C.; Rivera, V.A.G.; Lanfredi, A.J.C.; Cardoso, C.A.; Leite, E.R.; Mombru, A.W.; Araujo-Moreira, F.M.

    2008-01-01

    In this work, we report a part of a systematic study of the influence of the synthesis routes on the properties of polycrystalline samples of Pr x Y 1-x Ba 2 Cu 3 O 7-δ . We have prepared high-quality samples of this material by following a sol-gel method, associated with heat treatment in both an inert argon and an oxygen atmospheres in order to compare their influence on the formation of the superconducting phase. Magnetic measurement (AC susceptibility) show that the superconducting transition temperature (T C ) increases in samples prepared in argon when compared to those prepared in oxygen, for the same composition and Pr fraction less than 0.5. In addition to this, preliminary results of AC and DC magnetic susceptibility show superconductivity for samples with Pr fraction higher than 0.5 (and up to 0.9) prepared under argon flux, which may indicate the existence of stable superconductivity for all compositions, including pure Pr-123

  19. Effect of Fe substitution on magnetocaloric effect in La0.7Sr0.3Mn1-xFexO3 (0.05≤x≤0.20)

    International Nuclear Information System (INIS)

    Barik, S.K.; Krishnamoorthi, C.; Mahendiran, R.

    2011-01-01

    We have studied the effect of Fe substitution on magnetic and magnetocaloric properties in La 0.7 Sr 0.3 Mn 1-x Fe x O 3 (x=0.05, 0.07, 0.10, 0.15, and 0.20) over a wide temperature range (T=10-400 K). It is shown that substitution by Fe gradually decreases the ferromagnetic Curie temperature (T C ) and saturation magnetization up to x=0.15 but a dramatic change occurs for x=0.2. The x=0.2 sample can be considered as a phase separated compound in which both short-range ordered ferromagnetic and antiferromagnetic phases coexist. The magnetic entropy change (-ΔS m ) was estimated from isothermal magnetization curves and it decreases with increase of Fe content from 4.4 J kg -1 K -1 at 343 K (x=0.05) to 1.3 J kg -1 K -1 at 105 K (x=0.2), under ΔH=5 T. The La 0.7 Sr 0.3 Mn 0.93 Fe 0.07 O 3 sample shows negligible hysteresis loss, operating temperature range over 60 K around room temperature with refrigerant capacity of 225 J kg -1 , and magnetic entropy of 4 J kg -1 K -1 which will be an interesting compound for application in room temperature refrigeration. - Research highlights: → We report magnetocaloric effect in La 0.7 Sr 0.3 Mn 1-x Fe x O 3 (x=0-0.2). → Magnetic entropy change (ΔS m ) decreases with increasing x. → A large ΔS m and refrigeration capacity are found around 300 K in x=0.07.

  20. sup 5 sup 9 Co NMR spectroscopy and relaxation in the metamagnetic system Y sub 1 sub - sub x Gd sub x Co sub 3

    CERN Document Server

    Reis, M S; García, F; Takeuchi, A Y; Guimarães, A P

    2000-01-01

    We studied the nuclear magnetic resonance (NMR) in intermetallic compounds of the series Y sub 1 sub - sub x Gd sub x Co sub 3. We found spectra exhibiting four lines, corresponding to four magnetic sites of these compounds. However, the number of lines and their widths are strongly dependent on the radiofrequency (RF) power level, a fact that may help to explain some of the discrepancies found in the NMR literature on these compounds. From the dependence of the NMR spectra with the RF power we concluded that the site labeled 18h presents the largest local magnetic anisotropy. No significant changes are observed on the value of the hyperfine fields at each site as a function of the Gd concentration x, and that is explained in terms of the statistical distribution of Gd magnetic ions in the lattice. On the contrary, the spin-lattice and spin-spin relaxation rates, 1/T sub 1 and 1/T sub 2 , measured at each line, are remarkably dependent on the concentration. 1/T sub 2 exhibits a prominent peak at x approx 0.25...

  1. New organic superconductors beta-(BDA-TTP)2X [BDA-TTP + 2,5-bis(1,3-dithian-2ylidene)-1,3,4,6-tetrathiapentalene; X(-) = SbF6(-), AsF6(-), and PF6(-)].

    Science.gov (United States)

    Yamada, J; Watanabe, M; Akutsu, H; Nakatsuji, S; Nishikawa, H; Ikemoto, I; Kikuchi, K

    2001-05-09

    The synthesis, electrochemical properties, and molecular structure of a new pi-electron donor, 2,5-bis(1,3-dithian-2-ylidene)-1,3,4,6-tetrathiapentalene (BDA-TTP), is described. In contrast to the hitherto-known tetrachalcogenafulvalene pi-donors providing organic superconductors, this donor contains only the bis-fused 1,3-dithiole-2-ylidene unit as a pi-electron system, yet produces a series of ambient-pressure superconductors beta-(BDA-TTP)2X [X = SbF6 (magnetic T(c) = 6.9 K, resistive T(c) = 7.5 K), AsF6 (magnetic T(c) = 5.9 K, resistive T(c) = 5.8 K), and PF6 (magnetic T(c) = 5.9 K)], which are isostructural. The values of the intermolecular overlap integrals calculated on the donor layers of these superconductors suggest a two-dimensional (2D) electronic structure with loose donor packing. Tight-binding band calculations also indicate that these superconductors have the 2D band dispersion relations and closed Fermi surfaces.

  2. Novel protonated and hydrated n=1 Ruddlesden-Popper phases, HxNa1-xLaTiO4.yH2O, formed by ion-exchange/intercalation reaction

    International Nuclear Information System (INIS)

    Nishimoto, Shunsuke; Matsuda, Motohide; Miyake, Michihiro

    2005-01-01

    New derivatives of layered perovskite compounds with H 3 O + ions, H + ions and water molecules in the interlayer, H x Na 1-x LaTiO 4 .yH 2 O, were successfully synthesized by an ion-exchange/intercalation reaction with dilute HCl solution, using an n=1 member of Ruddlesden-Popper phase, NaLaTiO 4 . Powder X-ray diffraction revealed that the layered structure changed from space group P4/nmm with a=3.776(1) and c=13.028(5)A to I4/mmm with a=3.7533(3) and c=28.103(4)A after the ion-exchange/intercalation reaction at pH 5. The change of space group indicates that the perovskite layers are transformed from staggered to an eclipsed configuration through the ion-exchange/intercalation reaction. Thermogravimetric analysis and high-temperature powder X-ray diffraction suggested the existence of the secondary hydrated phase by dehydrating H x Na 1-x LaTiO 4 .yH 2 O at 100 o C

  3. ESTUDIO CONFORMACIONAL EN ALGUNAS 1,3-OXAZINAS Y 1,3-BENZOXAZINAS EMPLEANDO METODOS TEORICOS.

    OpenAIRE

    HURTADO OCAMPO, SANDRA MARCELA; HURTADO OCAMPO, SANDRA MARCELA

    2007-01-01

    En la década del cincuenta, resultados experimentales entregados por Urbanski y colaboradores [1] pusieron en evidencia propiedades antituberculósicas y antitumorales en compuestos del tipo 5-nitro-R-N-1 ,3- oxazínicos. Como resultado de un proceso relati 187p.

  4. A neutron diffraction study of the superionic transition in (Ca sub 1 sub - sub x Y sub x)F sub 2 sub + sub x with x=0.06

    CERN Document Server

    Hofmann, M; Wilson, C C; McIntyre, G J

    1997-01-01

    We have investigated the high-temperature superionic transition of the anion-excess fluorite (Ca sub 1 sub - sub x Y sub x)F sub 2 sub + sub x with x=0.06 using both monochromatic and time-of-flight Laue single-crystal neutron diffraction. The measured Bragg intensities indicate that the cuboctahedral defect clusters found at ambient temperature start to break up into smaller fragments even below the superionic transition temperature, T sub c approx 1200 K. Information concerning the local defect configuration at T = 1173 K has been provided by modelling the measured distribution of the coherent elastic diffuse scattering within the (11-bar0) plane of reciprocal space. The high-temperature defects are of the 'Willis' type and strongly resemble the short-lived Frenkel clusters found in the pure fluorites such as CaF sub 2 above T sub c. (author)

  5. Cation mobility in NASICON compounds Li1-xZr2-xNbx(PO4)3 and Li1+xZr2-xScx(PO4)3

    International Nuclear Information System (INIS)

    Stenina, I.A.; Yaroslavtsev, A.B.; Aliev, A.D.; Antipov, E.V.; Velikodnyj, Yu.A.; Rebrov, A.I.

    2002-01-01

    Compounds featuring NASICON structure of the composition Li 1-x Zr 2-x Nb x (PO 4 ) 3 and Li 1+x Zr 2-x Sc x (PO 4 ) 3 were studied by the method of X-ray phase analysis and 7 Li and 31 P NMR. Structure of Li 0.8 Zr 1.8 Nb 0.2 (PO 4 ) 3 was refined on the basis of X-ray powder pattern. It is shown that cationic disordering in LiZr 2 (PO 4 ) 3 is stimulated both by cationic vacancies and interstitial atoms formation. The cationic vacancies are characterized by a higher mobility. The level of intrinsic disordering was estimated and the Frenkel constant for the compound was calculated [ru

  6. Optimization of the deposition conditions and structural characterization of Y{sub 1}Ba{sub 2}Cu{sub 3}O{sub 7-x} thin superconducting films

    Energy Technology Data Exchange (ETDEWEB)

    Chrzanowski, J.; Meng-Burany, S.; Xing, W.B. [Simon Fraser Univ., British Columbia (Canada)

    1994-12-31

    Two series of Y{sub 1}Ba{sub 2}Cu{sub 3}O{sub z} thin films deposited on (001) LaAlO{sub 3} single crystals by excimer laser ablation under two different protocols have been investigated. The research has yielded well defined deposition conditions in terms of oxygen partial pressure p(O{sub 2}) and substrate temperature of the deposition process T{sub h}, for the growth of high quality epitaxial films of YBCO. The films grown under conditions close to optimal for both j{sub c} and T{sub c} exhibited T{sub c}{ge}91 K and j{sub c}{ge}4 x 10{sup 6} A/cm{sup 2}, at 77 K. Close correlations between the structural quality of the film, the growth parameters (p(O{sub 2}), T{sub h}) and j{sub c} and T{sub c} have been found.

  7. Magnetism and electrical transport properties of La{sub 1-x-y}Pr{sub y}Ca{sub x}MnO{sub 3} (x ∼ 0.42, y ∼ 0.40) thin films: role of microstructural disorder

    Energy Technology Data Exchange (ETDEWEB)

    Agarwal, Vasudha; Sharma, Geetanjali; Siwach, P.K.; Maurya, K.K.; Singh, H.K. [Dr. K.S. Krishnan Marg, CSIR-National Physical Laboratory, New Delhi (India)

    2015-06-15

    We report the effect of substrate-induced lattice disorder on the balance between the coexisting antiferromagnetic/charge-ordered insulating (AFM/COI) and ferromagnetic metallic (FMM) phases and the dynamics of the phase transition in the strongly phase-separated single-crystalline La{sub 1-x-y}Pr{sub y}Ca{sub x}MnO{sub 3} (x ∼ 0.42, y ∼ 0.40) thin films. At lower degree of disorder, the delicate balance between AFM/COI and FMM phases gives rise to a magnetically disordered/non-equilibrium magnetic liquid, which shows a strong supercooling behaviour and colossal thermal hysteresis in temperature dependence of magnetization (M-T) and resistivity (ρ-T). At lower temperatures, the disordered liquid freezes to yield a randomly frozen glassy state. The enhanced lattice disorder quenches the non-FM phases and promotes AFM/COI-FMM phase transition, which in turn reduces the magnetic frustration and lowers the degree of supercooling. The enhanced FMM fraction also unblocks the blocked magnetic states and results in the vanishing of the pronounced minimum in the ρ-T curve observed well above the glass transition. Our results show that the impact of enhanced lattice disorder is in many ways similar to that of the extrinsic magneto-thermodynamic perturbations. (orig.)

  8. Magnetic Properties of La0.9Ag0.1(Mn1-xCoxO3 under Pressure

    Directory of Open Access Journals (Sweden)

    Mihalik M.

    2013-01-01

    Full Text Available In our paper we report on magnetic properties of La0.90Ag0.10(CoxMn1-xO3 ferromagnetic ceramics (x = 0.00 and0.03 which were studied in pressures up to 0.9 GPa. Magnetic transition at the Curie temperature TC is accompanied with metal insulator transition with a maximum at T* which is shifted to lower temperature with applied magnetic field. The Curie temperature is decreasing with substitution of Co for Mn and is ranging from 178 K to 126.5 K. Hydrostatic pressure increases TC for sample with x = 0.03 nearly linearly with the pressure coefficient dTc/dp = 5.7 K/GPa. Hysteresis loop is affected marginally; µs increases and Hc decreases with pressure.

  9. Effect of superconductivity on spin dynamics in (Y/sub 1-x/Re/sub x/)Rh4B4

    International Nuclear Information System (INIS)

    Kumagai, K.; Fradin, F.Y.

    1982-01-01

    An adiabatic field-cycle method has been used to study spin dynamics of RE ions in (Y/sub 1-x/RE/sub x/)Rh 4 B 4 . Longitudinal dipolar fluctuations of RE moments are found to be the main source of the nuclear spin-lattice relaxation time of 11 B. The variation of T 1 in the superconducting state is attributed to the reduction of the electronic spin-relaxation time, tau/sub m/, which is mainly determined by the RKKY type interaction mediated by the conduction electrons. 3 figures

  10. Magnetic field-induced elastic bending in bilayers of Tb1xDyxFe2−y and Pb(Zr1−zTiz)O3

    International Nuclear Information System (INIS)

    Jin, Tao; Qichao, Wu; Ning, Zhang

    2014-01-01

    Magnetic field-induced strain in the magnetoelectric bilayers of Tb 1x Dy x Fe 2−y and Pb(Zr 1−z Ti z )O 3 was studied. A butterfly shaped strain curve was observed on the surface of Pb(Zr 1−z Ti z )O 3 . The shape of the strain curve was found to be related to the sample thickness and the volume fraction occupied by the ferroelectrics in the bilayer. Theoretical analysis and experimental results showed that magnetoelastic bending in the bilayer composites was largely responsible for the butterfly strain curve. - Highlights: • Butterfly strain curves were observed on the PZT surface for bilayers of TDF and PZT. • The strain curve is related to the sample thickness and the volume fraction of the PZT. • A physics model depicting the field-controlled bending of the bilayers was developed. • The magnetoelastic bending was found to account for the butterfly strain curve

  11. Production and structural and magnetic characterization of a Bi1-xYxFeO3(x = 0, 0.25 and 0.30) system

    International Nuclear Information System (INIS)

    Gómez, J A Mejía; Palacio, C A; García, G I Supelano; Vargas, C A Parra

    2015-01-01

    The production and the structural and magnetic characterization of the Bi 1-x Y x FeO 3 (x= 0, 0.25 and 0.3) system is reported in this work. The system was produced through the solid-state reaction technique. The morphological characterization obtained by scanning electron microscopy technique evidences the granular behavior. The structural properties were studied by means of X-ray diffraction technique. Magnetization measurements in function of temperature of the Bi 1-x Y x FeO 3 (x= 0, 0.25 and 0.3) system were performed with the magnetometer VSM by means of the Zero Field Cooled-Field Cooled method. The results obtained from all the techniques evidence the effect of yttrium on the physical properties of BiFeO 3 . (paper)

  12. Valence and conduction band offsets at low-k a-SiO{sub x}C{sub y}:H/a-SiC{sub x}N{sub y}:H interfaces

    Energy Technology Data Exchange (ETDEWEB)

    King, Sean W., E-mail: sean.king@intel.com; Brockman, Justin; French, Marc; Jaehnig, Milt; Kuhn, Markus [Logic Technology Development, Intel Corporation, Hillsboro, Oregon 97124 (United States); French, Benjamin [Ocotillo Materials Laboratory, Intel Corporation, Chandler, Arizona 85248 (United States)

    2014-09-21

    In order to understand the fundamental electrical leakage and reliability failure mechanisms in nano-electronic low-k dielectric/metal interconnect structures, we have utilized x-ray photoelectron spectroscopy and reflection electron energy loss spectroscopy to determine the valence and conduction band offsets present at interfaces between non-porous and porous low-k a-SiO{sub x}C{sub y}:H interlayer dielectrics and a-SiC{sub x}N{sub y}:H metal capping layers. The valence band offset for such interfaces was determined to be 2.7±0.2 eV and weakly dependent on the a-SiOC:H porosity. The corresponding conduction band offset was determined to be 2.1±0.2 eV. The large band offsets indicate that intra metal layer leakage is likely dominated by defects and trap states in the a-SiOC:H and a-SiCN:H dielectrics.

  13. NH (X 3 summation -, v=1--3) formation and vibrational relaxation in electron-irradiated Ar/N2/H2 mixtures

    International Nuclear Information System (INIS)

    Dodd, J.A.; Lipson, S.J.; Flanagan, D.J.; Blumberg, W.A.M.; Person, J.C.; Green, B.D.

    1991-01-01

    Measurements of the dynamics of NH(X 3 summation - , v =1--3), created in electron-irradiated N 2 /H 2 and Ar/N 2 /H 2 mixtures, have been performed. Time-resolved Fourier spectroscopy was used to observe NH(v→v--1) vibrational fundamental band emission. Time-dependent populations were then determined by spectral fitting. Subsequent kinetic fitting of these populations using a single-quantum relaxation model and a power-law dependence of k v on v yielded the following NH(v =1--3) relaxation rate constants (units of 10 -14 cm 3 s -1 ): k v=1 (N 2 )=1.2±0.5, k v=2 (N 2 )=3.8±1.5, k v=3 (N 2 )=7.5±2.5; k v=1 (Ar)=0.2±0.1, k v=2 (Ar)=0.5±0.2, k v=3 (Ar)=0.8±0.3; k v=1 (H 2 )≤50, k v=2 (H 2 )≤100, k v=3 (H 2 )≤150. In addition, the N 2 /H 2 data provided a measurement of the nascent excited vibrational state distribution resulting from the reaction N( 2 D)+H 2 →NH(X,v)+H. The ratio NH(1):NH(2):NH(3) was found to be 1.0:0.97:0.81 (±0.28 in each value). Comparison of the observed nascent distribution with that of a statistical model suggests that the ratio NH(0):NH(1)=0.47. Using this derived distribution, we find the average product level left-angle v right-angle =1.6, and the fraction of the available product energy in vibration left-angle f v right-angle =0.44

  14. High temperature X-ray diffraction studies on HfO2-Gd2O3 system

    International Nuclear Information System (INIS)

    Panneerselvam, G.; Antony, M.P.; Ananthasivan, K.; Joseph, M.

    2016-01-01

    High temperature X-ray diffraction (HTXRD) technique is an important experimental tool for measuring thermal expansion of materials of interest. A series of solid solutions containing GdO 1.5 in HfO 2 ,Hf 1-y Gd y )O 2 (y = 0.15, 0.2, 0.3, 0.41 and 0.505) were prepared by solid state method. Structural characterization and computation of lattice parameter was carried out by using room temperature X-ray diffraction measurements. The room temperature lattice parameter estimated for (Hf 1-y Gd y )O 2 (y=0.15, 0.2, 0.3, 0.41 and 0.505) are 0.51714 nm, 0.51929 nm, 0.52359nm, 0.52789nm and 0.53241 nm, respectively. Thermal expansion coefficients and percentage linear thermal expansion of the HfO 2 -Gd 2 O 3 solid solutions containing 20 and 41 mol% GdO 1.5 were determined using HTXRD in the temperature range 298 to 1673K. The mean linear thermal expansion coefficients of the solid solutions containing 20 and 41 mol. %Gd are 11.65 x 10 -6 K -1 and 12.07 x 10 -6 K -1 , respectively. (author)

  15. Thermoelectric properties of p-type (Bi{sub 1{minus}x}Sb{sub x}){sub 2}Te{sub 3} fabricated by mechanical alloying process

    Energy Technology Data Exchange (ETDEWEB)

    Jung, B Y; Choi, J S; Oh, T S; Hyun, D B

    1997-07-01

    Thermoelectric properties of polycrystalline (Bi{sub 1{minus}x}Sb{sub x}){sub 2}Te{sub 3} (0.75 {le} x {le} 0.85), fabricated by mechanical alloying and hot pressing methods, have been investigated. Formation of (Bi{sub 0.25}Sb{sub 0.75}){sub 2}Te{sub 3} alloy powder was completed by mechanical alloying for 5 hours at ball-to-material ratio of 5:1, and processing time for (Bi{sub 1{minus}sub x}Sb{sub x}){sub 2}Te{sub 3} formation increased with Sb{sub 2}Te{sub 3} content x. When (Bi{sub 0.25}Sb{sub 0.75}){sub 2}Te{sub 3} was hot pressed at temperatures ranging from 300 C to 550 C for 30 minutes, figure-of-merit increased with hot pressing temperature and maximum value of 2.8 x 10{sup {minus}3}/K could be obtained by hot pressing at 550 C. When hot pressed at 550 C, (Bi{sub 0.2}Sb{sub 0.8}){sub 2}Te{sub 3} exhibited figure-of-merit of 2.92 x 10{sup {minus}3}/K, which could be improved to 2.97 x 10{sup {minus}3}/K with addition of 1 wt% Sb as acceptor dopant.

  16. Extrinsic and intrinsic magnetic properties of Co1-x Fex Sb3

    International Nuclear Information System (INIS)

    Amornpitoksuk, P.; Ravot, D.; Mauger, A.; Tedenac, J.C.

    2007-01-01

    We report magnetic properties of iron in Co 1-x Fe x Sb 3 for x in the range 0 3+ in the low spin d 5 configuration in presence of a strong crystal field that screens the orbital momentum. The magnetic properties give evidence that a small fraction of iron is spin-frozen in magnetite ferrimagnetic clusters, and antiferromagnetic FeO clusters. Because both types of clusters represent only very minor phases, their detection by the usual analytical means such as X-rays is not possible. The remaining part is diluted in the matrix to form a semimagnetic semiconductor characterized by a Fe-Fe nearest-neighbor exchange interaction J that is antiferromagnetic, with |J|/k B ∼19.6 degree K

  17. The dynamics of ammonium ions in K1-x(NH4)xCl mixed crystals by the neutron scattering study

    International Nuclear Information System (INIS)

    Smirnov, L.S.; Natkanets, I.; Shuvalov, L.A.; Dolbinina, V.V.

    2004-01-01

    The study of vibrational spectrum of the K 1-x (NH 4 ) x Cl mixed crystals in a dynamically disordered cubic α-phase at 10 K is carried out by means of inelastic incoherent neutron scattering on the NERA-PR time-of-flight spectrometer set at the IBR-2 reactor (JINR, Dubna). It is shown that low-energy modes of ammonium ions with the energies 19-23 and 62-63 cm -1 at 10 K are observed only within the disordered cubic α-phase and are absent in the ordered cubic δ-phase of NH 4 Cl. The energies of local translation and libration modes of ammonium ions are determined in the α- and δ-phases of the K 1-x (NH 4 ) x Cl mixed crystals

  18. Local Structure of Mn in (La1-xHox)2/3Ca1/3MnO3 Studied by X-ray Absorption Fine Structure

    International Nuclear Information System (INIS)

    Pietnoczka, A.; Bacewicz, R.; Antonowicz, J.; Zalewski, W.; Pekala, M.; Drozd, V.; Fagnard, J.F.; Vanderbemden, P.

    2010-01-01

    Results of X-ray absorption fine structure measurements in manganites (La 1-x Ho x ) 2/3 Ca 1/3 MnO 3 with 0.15 3 is doped with a divalent element such as Ca 2+ , substituting for La 3+ , holes are induced in the filled Mn d orbitals. This leads to a strong ferromagnetic coupling between Mn sites. Ca ions in La 1-x Ca x MnO 3 introduce a distortion of the crystal lattice and mixed valence Mn ions (Mn 3+ and Mn 4+ ). On the other hand, in manganites (La 1-x Ho x ) 2/3 Ca 1/3 MnO 3 the substitution of La for Ho causes a lattice distortion and induces a disorder, which reduces a magnetic interaction. The ferromagnetic transition temperature and conductivity decrease very quickly with increasing x. The magnetic and transport properties of compounds depend on the local atomic structure around Mn ions. The information on the bond lengths and Debye-Waller factor are obtained from the extended X-ray absorption fine structure (EXAFS) data analysis. The charge state of Mn is determined from the position of the absorption edge in X-ray absorption near edge structure (XANES) data. XAFS results are in good agreement with magnetic characteristics of the studied materials. (authors)

  19. Structure and magnetic properties of Gd2Co17-xCr x (1.17 ≤ x3.0) compounds

    International Nuclear Information System (INIS)

    Fuquan, B.; Tegus, O.; Dagula, W.; Brueck, E.; Klaasse, J.C.P.; Buschow, K.H.J.

    2007-01-01

    The structure and magnetic properties of Gd 2 Co 17-x Cr x (1.17 ≤ x3.0) compounds have been investigated by means of X-ray diffraction (XRD) and magnetization measurements. The powder X-ray diffraction patterns show that all samples crystallize as a single phase with the rhombohedral Th 2 Zn 17 -type structure. The lattice parameters a and the unit cell volume V increases slightly with increasing Cr content, but the c parameter varies in a less simple way with increasing Cr content. The X-ray diffraction patterns of the magnetically aligned samples show that all compounds investigated have uniaxial anisotropy. Spin reorientation phenomena occur in all of the compounds. The Curie temperature T C , the spin reorientation temperature T sr , the spontaneous magnetization M 0 and the saturation magnetization M s decrease with the increasing Cr content. The anisotropy constant K 1 and the anisotropy field B a of the compounds at room temperature reach a maximum for x = 1.76. The M 0 and M s increase with increasing temperature from 5 K to 300 K. The easy-axis anisotropy of all compounds changes to easy-plane anisotropy at low temperatures and the spin reorientation phenomena are more pronounced for low Cr concentration

  20. Structure, microstructure and magnetic properties of Sr1-xCaxCrO3 (0≤x≤1)

    International Nuclear Information System (INIS)

    Castillo-Martinez, E.; Duran, A.; Alario-Franco, M.A.

    2008-01-01

    The effect of the calcium concentration on the structural, microstructural and magnetic properties of Sr (1-x) Ca x CrO 3 with 0≤x≤1 has been studied. The compounds were prepared using high pressure and high temperature synthesis. X-ray diffraction shows that the samples evolve from the cubic Pm-3m space group for x=0-0.2 to tetragonal I4/mcm for x=0.4-0.5, then to the orthorhombic Pbnm space group for x=0.6, 0.8 and 1.0. Electron diffraction and high-resolution transmission electron microscopy confirmed the respective cells for the end compositions: a p xa p xa p (Pm-3m) for SrCrO 3 ; and the √(2)a p x√(2)a p x2a p (Pbnm) for CaCrO 3 . For intermediate compositions some extra spots appear in the electron diffraction patterns while the electron micrographs indicate the presence of microdomains. Magnetic measurements show Curie-Weiss behaviour at high temperature for all the samples. A sharp antiferromagnetic (AFM) transition at about 91.5 K appears for x=0.8-1 together with a weak ferromagnetic ordering below T N . - Graphical abstract: HRTEM image of a crystal of Sr 0.5 Ca 0.5 CrO 3 showing a random distribution of 2a p ∼7.6 A all along the crystal that lacks long range order. Inset shows the FFT of the area of the image and of a tenth of that area showing the influence of the coherence length

  1. Relaxor behavior in lead-free Ba(Ti1xScx/2Nbx/2O3 ceramics

    Directory of Open Access Journals (Sweden)

    N. Bensemma

    2014-06-01

    Full Text Available Solid solutions of (1xBaTiO3-xBaSc1/2Nb1/2O3 (BT-BSN with x = 0.025, 0.05, 0.075, 0.1 and 0.125 were prepared by a high temperature solid-state reaction technique. The effects of the Ba(Sc1/2Nb1/2O3 addition on the phase composition, dielectric properties, as well as polarization-electric field (P-E loops of the BT-BSN solid solution were investigated. The room-temperature X-ray diffraction analyses of all the ceramics revealed a perovskite phase after sintering at 1350 °C with a composition-dependent symmetry. Temperature and frequency dependence of the dielectric permittivity and losses have been explored: ceramics of compositions x ≤ 0.075 showed normal ferroelectric behavior, while ceramics with x ≥ 0.1 were of relaxor type. The degree of diffuseness and the relaxor effect increase while the transition temperature (TC or Tm decreases when both scandium and niobium are introduced in the BaTiO3 lattice. Ceramics of composition x = 0.125 exhibited interesting relaxor characteristics at 10 kHz: ΔTm = 20 K, ɛr = 12,000, and Tm = 140 K. In addition, modeled using Vogel–Fülcher relation, this same composition showed the fitting parameters: Ea = 0.0503 eV, f0 = 1.129 × 1014 Hz and TVF = 166.85 K.

  2. First principles investigation of half-metallicity and spin gapless semiconductor in CH3NH3Cr x Pb1- x I3 mixed perovskites

    Science.gov (United States)

    Huang, H. M.; Zhu, Z. W.; Zhang, C. K.; He, Z. D.; Luo, S. J.

    2018-04-01

    The structural, electronic and magnetic properties of organic-inorganic hybrid mixed perovskites CH3NH3Cr x Pb1- x I3 ( x = 0.25, 0.50, 0.75, 1.00) in cubic, tetragonal and orthorhombic phases have been investigated by first-principles calculation. The results indicate that the tetragonal CH3NH3Cr0.75Pb0.25I3 is a spin gapless semiconductor with Curie temperature of 663 K estimated using mean field approximation. All other CH3NH3Cr x Pb1- x I3 mixed perovskites are half-metallic ferromagnets together with 100% spin polarization, and their total magnetic moment are 4.00, 8.00, 12.00 and 16.00 µB per unit cell for x = 0.25, 0.50, 0.75 and 1.00, respectively. The effect of , and orientation of organic cation CH3NH3 + on the electronic properties of CH3NH3Cr0.50Pb0.50I3 was investigated. The results show that the CH3NH3 + in different orientations have a slight effect on the lattice constants, the energy gap in minority-spin states, half-metallic gap, local magnetic moment, and Curie temperature.

  3. Composition-control of magnetron-sputter-deposited (BaxSr1-x)Ti1+yO3+z thin films for voltage tunable devices

    International Nuclear Information System (INIS)

    Im, Jaemo; Auciello, O.; Baumann, P. K.; Streiffer, S. K.; Kaufman, D. Y.; Krauss, A. R.

    2000-01-01

    Precise control of composition and microstructure is critical for the production of (Ba x Sr 1-x )Ti 1+y O 3+z (BST) dielectric thin films with the large dependence of permittivity on electric field, low losses, and high electrical breakdown fields that are required for successful integration of BST into tunable high-frequency devices. Here, we present results on composition-microstructure-electrical property relationships for polycrystalline BST films produced by magnetron-sputter deposition, that are appropriate for microwave and millimeter-wave applications such as varactors and frequency triplers. Films with controlled compositions were grown from a stoichiometric Ba 0.5 Sr 0.5 TiO 3 target by control of the background processing gas pressure. It was determined that the (Ba+Sr)/Ti ratios of these BST films could be adjusted from 0.73 to 0.98 by changing the total (Ar+O 2 ) process pressure, while the O 2 /Ar ratio did not strongly affect the metal ion composition. Film crystalline structure and dielectric properties as a function of the (Ba+Sr)/Ti ratio are discussed. Optimized BST films yielded capacitors with low dielectric losses (0.0047), among the best reported for sputtered BST, while still maintaining tunabilities suitable for device applications. (c) 2000 American Institute of Physics

  4. Piezoelectric properties of nonstoichiometric Sr1-xBi2+2x/3Ta2O9 ceramics

    International Nuclear Information System (INIS)

    Jain, Rajni; Chauhan, Arun Kumar Singh; Gupta, Vinay; Sreenivas, K.

    2005-01-01

    The effect of poling on the structural, dielectric, and piezoelectric properties has been investigated for sol-gel-derived strontium bismuth tantalate (SBT) [Sr 1-x Bi 2+2x/3 Ta 2 O 9 ] ceramics with x=0.0,0.15,0.30,0.45. The dielectric and ferroelectric properties are found to improve with increase in x up to 0.3. Beyond x>0.3 the properties are found to degrade due to the limited solid solubility and the presence of a mixed phase of bismuth tantalate (BiTaO 4 ) is detected with x=0.45. Poling treatment reduces the dielectric dispersion and dielectric loss in the frequency range (0.1-100 kHz). The resonance and antiresonance frequencies increase with increase in x (x=0-0.30), and the corresponding minimum impedance decreases. The measured coupling coefficients (k p ) are small (0.0967-0.1) for x=0-0.30, and the electromechanical quality factor (Q m =915) is a maximum for the Sr 0.7 Bi 2.2 Ta 2 O 9 composition (x=0.30). The estimated piezoelectric charge coefficient (d 31 ) and piezoelectric voltage coefficient (g 31 ) are 5.2 pC/N and 5.8x10 -3 V m/N, respectively. The positive values of d 31 and g 31 and the low dielectric permittivity of SBT yield a high value for the hydrostatic coefficients, despite the low charge coefficient of d 33 =24 pC/N. The maximum values of charge coefficient (d h =34 pC/N) and voltage coefficient (g h =39x10 -3 V m/N) are obtained for Sr 0.7 Bi 2.2 Ta 2 O 9 composition, and the estimated hydrostatic figure of merit (d h g h x10 -15 =1215 m 2 /N) is high

  5. Three-Dimensional Hierarchical NixCo1-xO/NiyCo2-yP@C Hybrids on Nickel Foam for Excellent Supercapacitors.

    Science.gov (United States)

    Shao, Yubo; Zhao, Yongqing; Li, Hua; Xu, Cailing

    2016-12-28

    Active materials and special structures of the electrode have decisive influence on the electrochemical properties of supercapacitors. Herein, three-dimensional (3D) hierarchical Ni x Co 1-x O/Ni y Co 2-y P@C (denoted as NiCoOP@C) hybrids have been successfully prepared by a phosphorization treatment of hierarchical Ni x Co 1-x O@C grown on nickel foam. The resulting NiCoOP@C hybrids exhibit an outstanding specific capacitance and cycle performance because they couple the merits of the superior cycling stability of Ni x Co 1-x O, the high specific capacitance of Ni y Co 2-y P, the mechanical stability of carbon layer, and the 3D hierarchical structure. The specific capacitance of 2638 F g -1 can be obtained at the current density of 1 A g -1 , and even at the current density of 20 A g -1 , the NiCoOP@C electrode still possesses a specific capacitance of 1144 F g -1 . After 3000 cycles at 10 A g -1 , 84% of the initial specific capacitance is still remained. In addition, an asymmetric ultracapacitor (ASC) is assembled through using NiCoOP@C hybrids as anode and activated carbon as cathode. The as-prepared ASC obtains a maximum energy density of 39.4 Wh kg -1 at a power density of 394 W kg -1 and still holds 21 Wh kg -1 at 7500 W kg -1 .

  6. Lightweight Towed Howitzer Demonstrator. Phase 1 and Partial Phase 2. Volume D1. Part 1. Structural Analysis (Less Cradle and System).

    Science.gov (United States)

    1987-04-01

    X4Cro 7WAW,"G9 N k Y,1i ACCA . 2 JVM ly y,- L OA.0 v roo*Ler t-OAD. FA’ A /"Fi./A/a. (" -A,E’ CNAiv*6:CP A/ ’r/O’,L C4A$4P&4R.* -1MAGC.T?D0 VI.3 Moon...M- S 3D = .. = ==-=== Version 1.1 02/01/85 LTHD muzzle brate thermal load - steel Load Case 1: Loads Node F x FFM - My

  7. Annealing treatment effects on structure and superconductivity in Y1Ba2Cu3O/sub 9-//sub x/

    International Nuclear Information System (INIS)

    Beyers, R.; Lim, G.; Engler, E.M.

    1987-01-01

    We report the effects of heat treatment and ambient on the structure and superconducting properties of Y 1 Ba 2 Cu 3 O/sub 9-//sub x/. The structure undergoes an orthorhombic-to-tetragonal transition on heating at about 700 0 C, caused by oxygen loss and disordering of oxygen vacancies on the copper plane between the barium layers. Heat treatments that promote maximum ordering of the oxygen vacancies result in superior superconducting properties

  8. Viscosities of cesium vapor to 1,620 K and of liquid gallium to 1,800 K

    International Nuclear Information System (INIS)

    Tippelskirch, H. v.

    1976-01-01

    The viscosity of cesium at 1,620 K and 40 bar has been determined to 41 x 10 -6 (Pa x s) by the oscillating cup method. The saturated vapor density at 1,580 K could be derived from the viscosity measurements. The viscosity of liquid gallium has been determined from 370 K to 1,800 K. The experimental results have been compared with calculations based on the Enskog hard-sphere transport theory for dense fluids. (orig.) [de

  9. Lithium ionic mobility study in xLi{sub 2}CO{sub 3}-yLiI (x = 95-70, y = 5-30 wt.%) solid electrolyte by impedance spectroscopy technique

    Energy Technology Data Exchange (ETDEWEB)

    Omar, Mohd Khari; Ahmad, Azizah Hanom [Faculty of Applied Sciences, Universiti Teknologi MARA, 40450 Shah Alam, Selangor D.E. (Malaysia); Institute of Science, Universiti Teknologi MARA, 40450 Shah Alam, Selangor D.E. (Malaysia)

    2015-08-28

    A detailed systematic study on the effects of different amount (wt.%) of LiI addition on the electrical conductivity and dielectric behavior of the xLi{sub 2}CO{sub 3}-xLiI (x = 95-70, y = 5-30 wt.%) electrolyte system was carried out. The samples with different compositions were prepared and ground by mechanical milling method. The electrical and dielectric properties of the samples over a range of frequency (50Hz – 1MHz) were investigated by deploying electrical impedance spectroscopy (EIS) technique in a series of temperature set (298–373K). Normally, Li{sub 2}CO{sub 3} itself shows a very low electrical conductivity (10{sup −5} Scm{sup −1}). However, the electrical conductivity of the system was found to be increased (10{sup −3} Scm{sup −1}) as the lithium salt (LiI) were introduced to the system. The dielectric analysis displayed that the activation energy was inversely proportional to the increment of LiI (wt.%). As the electrical conductivity reached their maximum value (4.63 × 10{sup −3} Scm{sup −1}) at the 20 wt.% of LiI, the activation energy was dropped to the minimum (0.1 eV). The electrical conductivity increases with the temperature (298 – 373K) indicate that the system obeys Arrhenius law.

  10. Time effects and glassy state behaviour in superconducting Y1Ba2Cu3O7-x

    International Nuclear Information System (INIS)

    Altinkok, A.; Yetis, H.; Olutas, M.; Kilic, K.; Kilic, A.

    2007-01-01

    The quenched disorder in the moving entity is investigated in a polycrystalline bulk sample of Y 1 Ba 2 Cu 3 O 7-x (YBCO) by slow transport relaxation measurements (V-t curves) on long time scales. The time evolution of sample voltage (V-t curve) are correlated to spatial reorganization of the driving current together with increasing or decreasing of resistive and non-resistive flow channels in a multiple connected network. In addition, it is shown that the voltage decays appearing in V-t curves are characterized by an exponential time dependence which is analogous to the glassy state relaxation

  11. Phase transitions of Pb(ZrxTi1-x)O3 ceramics

    International Nuclear Information System (INIS)

    Frantti, J.; Kakihana, M.; Ivanov, S.; Eriksson, S.; Rundloef, H.; Lantto, V.; Lappalainen, J.

    2002-01-01

    Recent experimental and theoretical reports on the structure of lead zirconate titanate [Pb(Zr x Ti 1-x )O 3 (PZT)] ceramics with compositions in the vicinity of the morphotropic phase boundary are discussed. There has been ambiguity concerning the low-temperature structure of x=0.52 samples, due to the superlattice reflections which were not explained by the reported monoclinic phase Cm [B. Noheda, D. E. Cox, G. Shirane, R. Guo, B. Jones, and L. E. Cross, Phys. Rev. B 63, 014103 (2001)]. Neutron powder diffraction (NPD) and Rietveld refinement were used to identify the space group symmetries of x=0.52 and x=0.53 samples at 10 K. Both samples had two coexisting phases R3c and Cm at 10 K. At 10 K, monoclinic angles of both samples were larger than at 295 K, as was the octahedral tilt angle of the R3c phase of the x=0.53 sample. We analyzed our previous and current NPD data to study the structural changes in PZT ceramics, 0.20≤x≤0.53, as a function of x and temperature. Bond-valence calculations were carried out to test the models used in Rietveld refinements. Valences of Zr and Ti ions were larger and smaller than their nominal valences, respectively, although the anomaly decreased with increasing x. The composition-weighted-average valence of Zr and Ti ions was close to +4, and the relationship between the positions and valences of Zr and Ti ions explains the main structural features of PZT ceramics as a function of x. The valence of Pb ions was slightly below +2 and decreased with increasing x until it started to slightly increase for x≥0.50. Average oxygen valency was found to be close to -2. Also spontaneous polarization values were computed and found to be reasonable

  12. Preparation and electrical properties of Mn{sub 1.05−y}Co{sub 1.95−x−z−w}Ni{sub x}Mg{sub y}Al{sub z}Fe{sub w}O{sub 4} NTC ceramic derived from microemulsion method

    Energy Technology Data Exchange (ETDEWEB)

    Xia, Junbo [Key Laboratory of Functional Materials and Devices under Special Environments, CAS, Xinjiang Key Laboratory of Electronic Information Materials and Devices, Xinjiang Technical Institute of Physics and Chemistry, CAS, Urumqi 830011 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Zhao, Qing, E-mail: zhaoq@ms.xjb.ac.cn [Key Laboratory of Functional Materials and Devices under Special Environments, CAS, Xinjiang Key Laboratory of Electronic Information Materials and Devices, Xinjiang Technical Institute of Physics and Chemistry, CAS, Urumqi 830011 (China); Gao, Bo [Key Laboratory of Functional Materials and Devices under Special Environments, CAS, Xinjiang Key Laboratory of Electronic Information Materials and Devices, Xinjiang Technical Institute of Physics and Chemistry, CAS, Urumqi 830011 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Chang, Aimin, E-mail: changam@ms.xjb.ac.cn [Key Laboratory of Functional Materials and Devices under Special Environments, CAS, Xinjiang Key Laboratory of Electronic Information Materials and Devices, Xinjiang Technical Institute of Physics and Chemistry, CAS, Urumqi 830011 (China); Zhang, Bo; Ma, Renjun [Key Laboratory of Functional Materials and Devices under Special Environments, CAS, Xinjiang Key Laboratory of Electronic Information Materials and Devices, Xinjiang Technical Institute of Physics and Chemistry, CAS, Urumqi 830011 (China); University of Chinese Academy of Sciences, Beijing 100049 (China)

    2014-04-05

    Highlights: • The NTC thermister nano-powders Mn{sub 1.05−y}Co{sub 1.95−x−z−w}Ni{sub x}Mg{sub y}Al{sub z}Fe{sub w}O{sub 4} were prepared by microemulsion method. • The metal ions were subsided after twice sediment reaction. • The specimens show good electrical properties by doping some nontransition metals. -- Abstract: The NTC thermistor nano-powders of Mn{sub 1.05−y}Co{sub 1.95−x−z−w}Ni{sub x}Mg{sub y}Al{sub z}Fe{sub w}O{sub 4} were prepared by microemulsion method. Scanning electron microscope (SEM) image showed that the particles were well distributed. The mean particle-size was 72 nm. The structure of the precursor was investigated with Fourier infrared spectrometer (FI). The compositions of the powder and the as-sintered ceramic were evaluated by Energy Disperse Spectroscopy (EDS). X-ray diffraction (XRD) result indicated that the sintered samples were in the spinel structure. The room temperature resistivity ρ{sub 25}, material constant B{sub 25/85} and activation energies of the NTC thermistor are in the range of 1173–19,059 Ω cm, 3169–3771 k, 0.2672–0.3136 eV. The room temperature resistivity and B{sub 25/85} constant were found to increase with Al{sub 2}O{sub 3} content. The Mn{sub 0.9}Co{sub 1.2}Ni{sub 0.21}Mg{sub 0.15}Al{sub 0.09}Fe{sub 0.45}(A2) and Mn{sub 0.9}Co{sub 1.2}Ni{sub 0.27}Mg{sub 0.15}Al{sub 0.03}Fe{sub 0.45}(A3) specimens both showed a 200 °C resistance drift (ΔR/R) within 10% after aging at 910 °C for 600 h.

  13. Tunable magnetocaloric effect in Sr{sub 1-x}Ca{sub x}Mn{sub 0.5}Ti{sub 0.5}O{sub 3} perovskites

    Energy Technology Data Exchange (ETDEWEB)

    Shanmugapriya, K.; Palanivel, Balan [Pondicherry Engineering College, Department of Physics, Puducherry (India); Radheep, D.M.; Murugan, Ramaswamy [Pondicherry University, Department of Physics, Puducherry (India)

    2017-07-15

    Sr{sub 1-x}Ca{sub x}Mn{sub 0.5}Ti{sub 0.5}O{sub 3} (x = 0.25, 0.5 and 0.75) polycrystalline samples were synthesized by conventional solid-state reaction. Magnetic characterizations of Sr{sub 1-x}Ca{sub x}Mn{sub 0.5}Ti{sub 0.5}O{sub 3} revealed signature of antiferromagnetic ordering at temperatures (T{sub N}) ∝ 19, 25 and 29.5 K for x = 0.25, x = 0.5 and for x = 0.75, respectively. Sr{sub 1-x}Ca{sub x}Mn{sub 0.5}Ti{sub 0.5}O{sub 3} (x = 0.75) exhibits field-induced antiferromagnetic to ferromagnetic transition at ∝ 30 K with applied magnetic field of 4 and 5 T. Magnetocaloric change (ΔS{sub M}) increases from 3.5 to 19 J/kg K by increasing calcium concentration in the A-site. Those ΔS{sub M} values are relatively very high in these classes of antiferromagnetic perovskite systems and equal to the magnetisation values of the ferromagnetic perovskite manganites. This is the first report for the Sr{sub 1-x}Ca{sub x}Mn{sub 0.5}Ti{sub 0.5}O{sub 3} (x = 0.75) having large magnetic entropy changes induced by the low magnetic field. (orig.)

  14. Alleviation of Fermi level pinning at metal/n-Ge interface with lattice-matched Si x Ge1xy Sn y ternary alloy interlayer on Ge

    Science.gov (United States)

    Suzuki, Akihiro; Nakatsuka, Osamu; Sakashita, Mitsuo; Zaima, Shigeaki

    2018-06-01

    The impact of a silicon germanium tin (Si x Ge1xy Sn y ) ternary alloy interlayer on the Schottky barrier height (SBH) of metal/Ge contacts with various metal work functions has been investigated. Lattice matching at the Si x Ge1xy Sn y /Ge heterointerface is a key factor for controlling Fermi level pinning (FLP) at the metal/Ge interface. The Si x Ge1xy Sn y ternary alloy interlayer having a small lattice mismatch with the Ge substrate can alleviate FLP at the metal/Ge interface significantly. A Si0.11Ge0.86Sn0.03 interlayer increases the slope parameter for the work function dependence of the SBH to 0.4. An ohmic behavior with an SBH below 0.15 eV can be obtained with Zr and Al/Si0.11Ge0.86Sn0.03/n-Ge contacts at room temperature.

  15. Electrical transport in low-lead (1-x)BaTiO3xPbMg1/3Nb2/3O3 ceramics

    Institute of Scientific and Technical Information of China (English)

    J. SUCHANICZ; K. KONIECZNY; K. ŚWIERCZEK; M. LIPIŃSKI; M. KARPIERZ; D. SITKO; H. CZTERNASTEK; K. KLUCZEWSKA

    2017-01-01

    Low-lead (1-x)BaTiO3xPbMg1/3Nb2/3O3 ceramics (x = 0, 0.025, 0.05, 0.075, 0.1, and 0.15) were prepared by the conventional oxide mixed sintering process, and their optical band gap, Seebeck coefficient, ac ( σac ) and dc ( σdc ) conductivities as a function of temperature were investigated for the first time. It was found that all samples have p-type conductivity. The low-frequency (20 Hz–2 MHz) ac conductivity obeys a power law σac ~ ωs , which is characteristic for disordered materials. The frequency exponent s is a decreasing function of temperature and tends to zero at high temperature. σac is proportional to ω0.07 – ω0.31 in the low-frequency region and to ω0.51 – ω0.98 in the high-temperature region. The temperature dependence of the dc conductivity showed a change in slope around the temperature at which the phase transition appeared. Both ac and dc conductivities showed a thermally activated character and possessed linear parts with different activation energies and some irregular changes. It was found that the hopping charge carriers dominate at low temperature and small polarons and oxygen vacancies dominate at higher temperature. (1-x)BaTiO3xPbMg1/3Nb2/3O3 ceramics are expected to be promising new candidate for low-lead electronic materials.

  16. Investigating the local structure of B-site cations in (1-x)BaTiO3-xBiScO3 and (1-x)PbTiO3-xBiScO3 using X-ray absorption spectroscopy

    Science.gov (United States)

    Blanchard, Peter E. R.; Grosvenor, Andrew P.

    2018-05-01

    The structural properties of (1-x)BaTiO3-xBiScO3 and (1-x)PbTiO3-xBiScO3 were investigated using powder X-ray diffraction and X-ray absorption spectroscopy. Diffraction measurements confirmed that substituting small amounts of BiScO3 into BaTiO3 initially stabilizes a cubic phase at x = 0.2 before impurity phases begin to form at x = 0.5. BiScO3 substitution also resulted in noticeable changes in the local coordination environment of Ti4+. X-ray absorption near-edge spectroscopy (XANES) analysis showed that replacing Ti4+ with Sc3+ results in an increase in the off-centre displacement of Ti4+ cations. Surprisingly, BiScO3 substitution has no effect on the displacement of the Ti4+ cation in the (1-x)PbTiO3-xBiScO3 solid solution.

  17. U(1) x U(1) x U(1) symmetry of the Kimura 3ST model and phylogenetic branching processes

    International Nuclear Information System (INIS)

    Bashford, J D; Jarvis, P D; Sumner, J G; Steel, M A

    2004-01-01

    An analysis of the Kimura 3ST model of DNA sequence evolution is given on the basis of its continuous Lie symmetries. The rate matrix commutes with a U(1) x U(1) x U(1) phase subgroup of the group GL(4) of 4 x 4 invertible complex matrices acting on a linear space spanned by the four nucleic acid base letters. The diagonal 'branching operator' representing speciation is defined, and shown to intertwine the U(1) x U(1) x U(1) action. Using the intertwining property, a general formula for the probability density on the leaves of a binary tree under the Kimura model is derived, which is shown to be equivalent to established phylogenetic spectral transform methods. (letter to the editor)

  18. Long-term studies with the Ariel 5 ASM. I - Hercules X-1, Vela X-1, and Centaurus X-3

    Science.gov (United States)

    Holt, S. S.; Kaluzienski, L. J.; Boldt, E. A.; Serlemitsos, P. A.

    1979-01-01

    Twelve hundred days of 3-6 keV X-ray data from Her X-1, Vela X-1, and Cen X-3 accumulated with the Ariel 5 All-Sky Monitor are interrogated. The binary periodicities of all three can be clearly observed, as can the 35 day variation of Her X-1, for which we can refine the period to 34.875 plus or minus 0.030 days. No such longer-term periodicity less than 200 days is observed from Vela X-1. The 26.6 days low-state recurrence period for Cen X-3 is not observed, but a 43.0 day candidate periodicity is found which may be consistent with the precession of an accretion disk in that system. The present results are illustrative of the long-term studies which can be performed on approximately 50 sources over a temporal base which will ultimately extend to at least 1800 days.

  19. Photostimulated luminescence and defects creation processes in Ce{sup 3+}-doped epitaxial films of multicomponent Lu{sub 3x}Gd{sub x}Ga{sub y}Al{sub 5−y}O{sub 12} garnets

    Energy Technology Data Exchange (ETDEWEB)

    Babin, V. [Institute of Physics AS CR, Cukrovarnicka 10, 16253 Prague (Czech Republic); Chernenko, K. [Peter the Great Saint-Petersburg Polytechnic University, Polytekhnicheskaya 29, 195251 St. Petersburg (Russian Federation); Kučera, M. [Charles University, Faculty of Mathematics and Physics, Ke Karlovu 5, 12116 Prague (Czech Republic); Nikl, M. [Institute of Physics AS CR, Cukrovarnicka 10, 16253 Prague (Czech Republic); Zazubovich, S., E-mail: svea@ut.ee [Institute of Physics, University of Tartu, Ravila 14c, 50411 Tartu (Estonia)

    2016-11-15

    Luminescence characteristics of epitaxial films of Ce{sup 3+}-doped multicomponent garnets of the type of Lu{sub 3x}Gd{sub x}Ga{sub y}Al{sub 5−y}O{sub 12}, where x varies from 0.14 to 3 and y varies from 0 to 3.54, are investigated in the 4.2–400 K temperature range by the steady-state and time-resolved spectroscopy methods. Their dependence on the film composition is clarified. The presence in the same film of different Ce{sup 3+}-related luminescence centers is revealed, and a possible structure of these centers is discussed. The processes of the electron and hole centers creation under irradiation of the films in the Ce{sup 3+}-related absorption bands are studied by thermally stimulated luminescence method. The location of the excited 5d{sub 1} level of Ce{sup 3+} with respect to the bottom of the conduction band and the origin and thermal stability parameters of electron traps in the epitaxial films and in the single crystals of the same composition are found to be different.

  20. Phase relations in the pseudobinary systems RAO3-R2Ti2O7 (R: rare earth element and Y, A: Fe, Ga, Al, Cr and Mn) and syntheses of new compounds R(A1-xTix)O3+x/2 (2/3≤x≤3/4) at elevated temperatures in air

    Science.gov (United States)

    Brown, Francisco; Jacobo-Herrera, Ivan; Alvarez-Montaño, Victor; Kimizuka, Noboru; Kurashina, Keiji; Michiue, Yuichi; Matsuo, Yoji; Mori, Shigeo; Ikeda, Naoshi; Medrano, Felipe

    2017-07-01

    Phase relations in the pseudo-binary systems RFeO3-R2Ti2O7 (R: Lu, Ho and Dy), RGaO3-R2Ti2O7 (R: Lu and Er), LuAlO3-Lu2Ti2O7 and RAO3-R2Ti2O7 (R: Lu and Yb. A: Cr and Mn) at elevated temperatures in air were determined by means of a classic quenching method. There exist Lu(Fe1-xTix)O3+x/2, R(Ga1-xTix)O3+x/2 (R: Lu and Er) and Lu(Al1-xTix)O3+x/2 (2/3≤ x≤3/4) having the Yb(Fe1-xTix)O3+x/2-type of crystal structure (x=0.72, space group: R3m, a(Å)=17.9773 and c(Å)=16.978 as a hexagonal setting) in these pseudo binary systems. Eighteen compounds R(A1-xTix)O3+x/2 (R: Lu-Sm and Y, A: Fe, Ga and Al) were newly synthesized and their lattice constants as a hexagonal setting were measured by means of the X-ray powder diffraction method. The R occupies the octahedral site and both A and Ti does the trigonalbipyramidal one in these compounds. Relation between lattice constants for the rhombic R(A1-xTix)O3+x/2 and the monoclinic In(A1-xTix)O3+x/2 are as follows, ah≈5 x bm, ch≈3 x cm x sin β and am=31/2 x bm, where ah and ch are the lattice constants as a hexagonal setting for R(A1-xTix)O3+x/2 and am, bm, cm and β are those of the monoclinic In(A1-xTix)O3+x/2. Crystal structural relationships among α-InGaO3 (hexagonal, high pressure form, space group: P63/mmc), InGaO3 (rhombic, hypothetical), (RAO3)n(BO)m and RAO3(ZnO)m (R: Lu-Ho, Y and In, A: Fe, Ga, and Al, B: divalent cation element, m, n: natural number), the orthorhombic-and monoclinic In(A1-xTix)O3+x/2 (A: Fe, Ga, Al, Cr and Mn) and the hexagonal-and rhombic R(A1-xTix)O3+x/2 (R: Lu-Sm and Y, A: Fe, Ga and Al) are schematically presented. We concluded that the crystal structures of both the α-InGaO3 (high pressure form, hexagonal, space group: P63/mmc) and the hypothetical InGaO3 (rhombic) are the key structures for constructing the crystal structures of these compounds having the cations with CN=5.

  1. Structural, magnetic and transport properties of Pb{sub 2}Cr{sub 1+x}Mo{sub 1x}O{sub 6} (−1≤x≤1/3)

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, H.F. [Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); School of Mathematics and Physics, University of Science and Technology, Beijing 100083 (China); Cao, L.P. [Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Song, Y.J. [Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); School of Mathematics and Physics, University of Science and Technology, Beijing 100083 (China); Feng, S.M.; Shen, X. [Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Ni, X.D. [School of Mathematics and Physics, University of Science and Technology, Beijing 100083 (China); Yao, Y.; Wang, Y.G. [Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Wang, R.M. [School of Mathematics and Physics, University of Science and Technology, Beijing 100083 (China); Jin, C.Q. [Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Yu, R.C., E-mail: rcyu@aphy.iphy.ac.cn [Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100049 (China)

    2017-02-15

    Pb{sub 2}Cr{sub 1+x}Mo{sub 1-x}O{sub 6} (−1≤x≤1/3) samples were synthesized via a high pressure and high temperature route. X-ray diffraction results suggest the samples crystallize in a disordered double perovskite structure (Pm-3m). X-ray photoemission spectroscopy results confirm the presence of Mo{sup 4+} for x=−1 and Mo{sup 6+} for x=1/3. The measured magnetic and electrical properties exhibit systematic change with increasing x. - Highlights: • A series of Pb{sub 2}Cr{sub 1+x}Mo{sub 1x}O{sub 6} samples were synthesized under high pressure. • Magnetic and electrical properties of the series samples were investigated. • Valence states of Cr and Mo were determined through the analyses of XRD and XPS results. • Ground state of PbMoO{sub 3} were determined through the transport study and first-principles calculations.

  2. Synthesis and Characterization of Perovskite Type La1-xSrxAlO3-sigma(0<=X<=0.3) by Co-Precipitation Method

    International Nuclear Information System (INIS)

    Mahmoud, O.; Abderezak, G.

    2015-01-01

    This work shows the electrochemical activity of O/sub 2/ evolution reaction in KOH of perovskite type- aluminate oxide (La/sub 1-x/Sr/sub x/AlO/sub 3-sigma/ with x = 0, 0.1, 0.2, 0.3). La/sub 1-x/Sr/sub x/AlO/sub 3-sigma/ (0<x<0.3) was prepared by co-precipitation method. The white precipitates were then washed in distilled water by centrifugation, and calcined at 1000/degree C/ for 6h, the pure phase was characterized by X-ray diffraction (XRD), thermal gravimetric analysis and differential thermal (TG/DSC), Fourier transform infrared spectroscopy (FTIR), specific surface area (BET). The MEB micrographs are shown of the spherical grains and uniform agglomeration of the grains. The oxide powders were used as the films to form a support on Ni/oxides. Oxygen evolution on each oxide catalyst was signed in the cyclic voltammetry with +- 15 V range and the electrochemical impedance in the equivalent of 100 kHz. The results point out the electrode activity and stability of the x = 0.3 composition. (author)

  3. An X-ray absorption spectroscopic study of the metal site preference in Al1-xGaxFeO3

    Science.gov (United States)

    Walker, James D. S.; Grosvenor, Andrew P.

    2013-01-01

    Magnetoelectric materials have potential for being introduced into next generation technologies, especially memory devices. The AFeO3 (Pna21; A=Al, Ga) system has received attention to better understand the origins of magnetoelectric coupling. The magnetoelectric properties this system exhibits depend on the amount of anti-site disorder present, which is affected by the composition and the method of synthesis. In this study, Al1-xGaxFeO3 was synthesized by the ceramic method and studied by X-ray absorption spectroscopy. Al L2,3-, Ga K-, and Fe K-edge spectra were collected to examine how the average metal coordination number changes with composition. Examination of XANES spectra from Al1-xGaxFeO3 indicate that with increasing Ga content, Al increasingly occupies octahedral sites while Ga displays a preference for occupying the tetrahedral site. The Fe K-edge spectra indicate that more Fe is present in the tetrahedral site in AlFeO3 than in GaFeO3, implying more anti-site disorder is present in AlFeO3.

  4. Electric and magnetic properties of oxidic titanium bronzes of rare earths Lnsub(2/3+x)TiOsub(3+-y) with perovskite structure

    International Nuclear Information System (INIS)

    Bazuev, G.V.; Makarova, O.V.; Shvejkin, G.P.

    1983-01-01

    A study was made on electric and magnetic properties of oxidic titanium bronzes of rare earths and their dependence on rare earth nature and the degree of rare earth sublattice filling was followed. Data on Lnsub(2/3)TiOsub(3-y) (Ln-Ce, Nd) anion-deficient perovskites are given as well. Investigated Cesub(2/3)TiOsub(2.985) and Ndsub(2/3)TiOsub(2.875) phases as well as defectless with respect to oxygen Lnsub(2/3)TiOsub(3) phases have rhombic structure of perovskite type with ordered position of Ln 3 + cations and vacancies. Specific electric resistance and thermoelectromotive force factor were determined in vacuum at 290-1173 K for samples in the form of parallelepiped of 3x5x25 mm 3 size. Magnetic susceptibility chi was determined at 77-300 K by Faraday method using a device based on magnetic balancewith electromagnetic compensation. Relative error during chi measuring didn't exceed +-2%. Collectivized behaviour of d-electrons of Ti 3 + cations in oxidic titanium bronzes of rare earths: Lnsub(2/3+x)TiOsub(3+-y) (Ln-La, Ce, Nd; 0 < x < 1/3), conditioned by formation of narrow, partly filled π*-zone, was established on the basis of measuring specific electric resistance and magnetic susceptibility

  5. Type II band alignment in Ge1-x-ySixSny/Ge1-α-βSiαSnβ heterojunctions

    Science.gov (United States)

    Dey, Swagata; Mukhopadhyay, Bratati; Sen, Gopa; Basu, P. K.

    2018-02-01

    We have examined type II band alignment in Ge1-x-ySixSny/Ge1-α-βSiαSβ heterojunctions grown on virtual substrates in Si platform. It is found that, for different values of x, y, α and β, direct band gap type II band line up can be achieved for both tensile and compressive strains. The calculated band gap energy corresponds to the mid infrared to far infrared regions in the electromagnetic spectrum.

  6. Low-temperature magnetic susceptibility of the solid solutions (ErxY1-x)3Al5O12

    International Nuclear Information System (INIS)

    Bagdasarov, Kh.S.; Dodokin, A.P.; Sorokin, A.A.

    1988-01-01

    Measurements of magnetic susceptibility of erbium-yttrium alumogarnets in the 0.04-4.2 K temperature range are carried out. (Er x I 1-x ) 3 Al 5 O 12 monocrystals were grown by the method of vertical directed crystallization. The specimens were produced as 5 cm high cylinders 0.63 cm in diameter; the axis of the cylinders coincided with the (100) direction of the crystals. Magnetic susceptibility was measured by the Harsthorn bridge method at the frequency of 33 Hz. The analysis of measurement results shows that susceptibility of the investigated crystals at T >or approx. 2T N is well described by the Curie-Weiss law. Existence of threshold concentration of the magnetic component testifies to an essential role of exchange interactions in establishment of the magnetic order in Er 3 Al 5 O 12

  7. k-t SENSE-accelerated Myocardial Perfusion MR Imaging at 3.0 Tesla - comparison with 1.5 Tesla

    Science.gov (United States)

    Plein, Sven; Schwitter, Juerg; Suerder, Daniel; Greenwood, John P.; Boesiger, Peter; Kozerke, Sebastian

    2008-01-01

    Purpose To determine the feasibility and diagnostic accuracy of high spatial resolution myocardial perfusion MR at 3.0 Tesla using k-space and time domain undersampling with sensitivity encoding (k-t SENSE). Materials and Methods The study was reviewed and approved by the local ethic review board. k-t SENSE perfusion MR was performed at 1.5 Tesla and 3.0 Tesla (saturation recovery gradient echo pulse sequence, repetition time/echo time 3.0ms/1.0ms, flip angle 15°, 5x k-t SENSE acceleration, spatial resolution 1.3×1.3×10mm3). Fourteen volunteers were studied at rest and 37 patients during adenosine stress. In volunteers, comparison was also made with standard-resolution (2.5×2.5×10mm3) 2x SENSE perfusion MR at 3.0 Tesla. Image quality, artifact scores, signal-to-noise ratios (SNR) and contrast-enhancement ratios (CER) were derived. In patients, diagnostic accuracy of visual analysis to detect >50% diameter stenosis on quantitative coronary angiography was determined by receiver-operator-characteristics (ROC). Results In volunteers, image quality and artifact scores were similar for 3.0 Tesla and 1.5 Tesla, while SNR was higher (11.6 vs. 5.6) and CER lower (1.1 vs. 1.5, p=0.012) at 3.0 Tesla. Compared with standard-resolution perfusion MR, image quality was higher for k-t SENSE (3.6 vs. 3.1, p=0.04), endocardial dark rim artifacts were reduced (artifact thickness 1.6mm vs. 2.4mm, pTesla and 1.5 Tesla, respectively. Conclusions k-t SENSE accelerated high-resolution perfusion MR at 3.0 Tesla is feasible with similar artifacts and diagnostic accuracy as at 1.5 Tesla. Compared with standard-resolution perfusion MR, image quality is improved and artifacts are reduced. PMID:18936311

  8. Preparation and characterization of Cu{sub x}O{sub 1-y}@ZnO{sub 1-α} nanocomposites for enhanced room-temperature NO{sub 2} sensing applications

    Energy Technology Data Exchange (ETDEWEB)

    Geng, Xin [College of Mechanical Engineering, Yangzhou University, Yangzhou 225127 (China); College of Chemistry and Chemical Engineering, Yangzhou University, Yangzhou 225002 (China); Service de Science des Matériaux, Faculté Polytechnique, Université de Mons, Mons 7000 (Belgium); Zhang, Chao, E-mail: zhangc@yzu.edu.cn [College of Mechanical Engineering, Yangzhou University, Yangzhou 225127 (China); Luo, Yifan [College of Mechanical Engineering, Yangzhou University, Yangzhou 225127 (China); Debliquy, Marc [Service de Science des Matériaux, Faculté Polytechnique, Université de Mons, Mons 7000 (Belgium)

    2017-04-15

    Highlights: • Cu{sub x}O{sub 1-y}@ZnO{sub 1-(*)α} coatings with rich donor defects were successfully prepared. • Many p-n heterojunctions were formed in the as-sprayed Cu{sub x}O{sub 1-y}@ZnO{sub 1-α} coatings. • Light absorption of the coatings was extended to whole visible light region. • Cu{sub x}O{sub 1-y}@ZnO{sub 1-α} coatings showed an excellent response to NO{sub 2} at room temperature. - Abstract: In order to solve the problem that pristine ZnO show little response to NO{sub 2} gas at room temperature, some methods have been used, e.g., introducing narrow-bandgap semiconductors and donor defects into ZnO. In this work, we adopt solution precursor plasma spray to deposit Cu{sub x}O{sub 1-y}@ZnO{sub 1-α} hybrid coatings. Rapid heating and cooling as well as the reducing atmosphere provided by solution precursor plasma spray (SPPS) produce highly concentrated donor defects such as zinc interstitials and oxygen vacancies. X-ray photoelectron spectroscopy, photoluminescence spectroscopy and electron paramagnetic resonance confirmed that rich donor defects were present in the SPPS Cu{sub x}O{sub 1-y}@ZnO{sub 1-α} coatings. Field emission-scanning electron microscopy images exhibited a highly porous nanostructure, and high resolution-transmission electron microscopy showed that there were large amounts of p-n heterojunctions in the nanocomposites. The light absorption of the SPPS Cu{sub x}O{sub 1-y}@ZnO{sub 1-α} hybrids was extended up to the whole visible light region. With assistance of visible light illumination, the nanocomposites exhibited significant response to NO{sub 2} for concentrations below 1 ppm. A sensing mechanism of the Cu{sub x}O{sub 1-y}@ZnO{sub 1-α} sensors was proposed.

  9. Murine K2P5.1 Deficiency Has No Impact on Autoimmune Neuroinflammation due to Compensatory K2P3.1- and KV1.3-Dependent Mechanisms

    Directory of Open Access Journals (Sweden)

    Stefan Bittner

    2015-07-01

    Full Text Available Lymphocytes express potassium channels that regulate physiological cell functions, such as activation, proliferation and migration. Expression levels of K2P5.1 (TASK2; KCNK5 channels belonging to the family of two-pore domain potassium channels have previously been correlated to the activity of autoreactive T lymphocytes in patients with multiple sclerosis and rheumatoid arthritis. In humans, K2P5.1 channels are upregulated upon T cell stimulation and influence T cell effector functions. However, a further clinical translation of targeting K2P5.1 is currently hampered by a lack of highly selective inhibitors, making it necessary to evaluate the impact of KCNK5 in established preclinical animal disease models. We here demonstrate that K2P5.1 knockout (K2P5.1−/− mice display no significant alterations concerning T cell cytokine production, proliferation rates, surface marker molecules or signaling pathways. In an experimental model of autoimmune neuroinflammation, K2P5.1−/− mice show a comparable disease course to wild-type animals and no major changes in the peripheral immune system or CNS compartment. A compensatory upregulation of the potassium channels K2P3.1 and KV1.3 seems to counterbalance the deletion of K2P5.1. As an alternative model mimicking autoimmune neuroinflammation, experimental autoimmune encephalomyelitis in the common marmoset has been proposed, especially for testing the efficacy of new potential drugs. Initial experiments show that K2P5.1 is functionally expressed on marmoset T lymphocytes, opening up the possibility for assessing future K2P5.1-targeting drugs.

  10. Investigation of the Thermal Stability of Nd(x)Sc(y)Zr(1-x-y)O(2-δ) Materials Proposed for Inert Matrix Fuel Applications.

    Science.gov (United States)

    Hayes, John R; Grosvenor, Andrew P; Saoudi, Mouna

    2016-02-01

    Inert matrix fuels (IMF) consist of transuranic elements (i.e., Pu, Am, Np, Cm) embedded in a neutron transparent (inert) matrix and can be used to "burn up" (transmute) these elements in current or Generation IV nuclear reactors. Yttria-stabilized zirconia has been extensively studied for IMF applications, but the low thermal conductivity of this material limits its usefulness. Other elements can be used to stabilize the cubic zirconia structure, and the thermal conductivity of the fuel can be increased through the use of a lighter stabilizing element. To this end, a series of Nd(x)Sc(y)Zr(1-x-y)O(2-δ) materials has been synthesized via a co-precipitation reaction and characterized by multiple techniques (Nd was used as a surrogate for Am). The long-range and local structures of these materials were studied using powder X-ray diffraction, scanning electron microscopy, and X-ray absorption spectroscopy. Additionally, the stability of these materials over a range of temperatures has been studied by annealing the materials at 1100 and 1400 °C. It was shown that the Nd(x)Sc(y)Zr(1-x-y)O(2-δ) materials maintained a single cubic phase upon annealing at high temperatures only when both Nd and Sc were present with y ≥ 0.10 and x + y > 0.15.

  11. The Yttrium Effect on Nanoscale Structure, Mechanical Properties, and High-Temperature Oxidation Resistance of (Ti0.6Al0.4)1- x Y x N Multilayer Coatings

    Science.gov (United States)

    Wang, Jingxian; Yazdi, Mohammad Arab Pour; Lomello, Fernando; Billard, Alain; Kovács, András; Schuster, Frédéric; Guet, Claude; White, Timothy J.; Wouters, Yves; Pascal, Céline; Sanchette, Frédéric; Dong, ZhiLi

    2017-09-01

    As machine tool coating specifications become increasingly stringent, the fabrication of protective titanium aluminum nitride (Ti-Al-N) films by physical vapor deposition (PVD) is progressively more demanding. Nanostructural modification through the incorporation of metal dopants can enhance coating mechanical properties. However, dopant selection and their near-atomic-scale role in performance optimization is limited. Here, yttrium was alloyed in multilayered Ti-Al-N films to tune microstructures, microchemistries, and properties, including mechanical characteristics, adhesion, wear resistance, and resilience to oxidation. By regulating processing parameters, the multilayer period (Λ) and Y content could be adjusted, which, in turn, permitted tailoring of grain nucleation and secondary phase formation. With the composition fixed at x = 0.024 in (Ti0.6Al0.4)1- x Y x N and Λ increased from 5.5 to 24 nm, the microstructure transformed from acicular grains with 〈111〉 preferred orientation to equiaxed grains with 〈200〉 texture, while the hardness (40.8 ± 2.8 GPa to 29.7 ± 4.9 GPa) and Young's modulus (490 ± 47 GPa to 424 ± 50 GPa) concomitantly deteriorated. Alternately, when Λ = 5.5 nm and x in (Ti0.6Al0.4)1- x Y x N was raised from 0 to 0.024, the hardness was enhanced (28.7 ± 7.3 GPa to 40.8 ± 2.8 GPa) while adhesion and wear resistance were not compromised. The Ti-Al-N adopted a rock-salt type structure with Y displacing either Ti or Al and stabilizing a secondary wurtzite phase. Moreover, Y effectively retarded coating oxidation at 1073 K (800 °C) in air by inhibiting grain boundary oxygen diffusion.

  12. Mercury vacancies as divalent acceptors in Hg{sub y}Te{sub 1} {sub –} {sub y}/Cd{sub x}Hg{sub 1} {sub –} {sub x}Te structures with quantum wells

    Energy Technology Data Exchange (ETDEWEB)

    Kozlov, D. V., E-mail: dvkoz@ipmras.ru; Rumyantsev, V. V.; Morozov, S. V.; Kadykov, A. M.; Fadeev, M. A. [Russian Academy of Sciences, Institute for Physics of Microstructures (Russian Federation); Varavin, V. S.; Mikhailov, N. N.; Dvoretsky, S. A. [Russian Academy of Sciences, Rzhanov Institute of Semiconductor Physics, Siberian Branch (Russian Federation); Gavrilenko, V. I. [Russian Academy of Sciences, Institute for Physics of Microstructures (Russian Federation); Teppe, F. [Laboratoire Charles Coulomb (L2C) (France)

    2016-12-15

    A long-wavelength band caused by transitions between states related to the valence band is detected in the photoconductivity spectra of Hg{sub y}Te{sub 1y}/Cd{sub x}Hg{sub 1x}Te (CMT) structures with quantum wells. The energy states of mercury vacancies in quantum wells of CMT structures is calculated taking into account a chemical shift. It is shown that the long-wavelength band observed in the photoconductivity spectra of these structures is associated with the ionization of divalent acceptor centers which are such vacancies.

  13. PI3K-Akt-mTORC1-S6K1/2 Axis Controls Th17 Differentiation by Regulating Gfi1 Expression and Nuclear Translocation of RORγ

    Directory of Open Access Journals (Sweden)

    Yutaka Kurebayashi

    2012-04-01

    Full Text Available The PI3K-Akt-mTORC1 axis contributes to the activation, survival, and proliferation of CD4+ T cells upon stimulation through TCR and CD28. Here, we demonstrate that the suppression of this axis by deletion of p85α or PI3K/mTORC1 inhibitors as well as T cell-specific deletion of raptor, an essential component of mTORC1, impairs Th17 differentiation in vitro and in vivo in a S6K1/2-dependent fashion. Inhibition of PI3K-Akt-mTORC1-S6K1 axis impairs the downregulation of Gfi1, a negative regulator of Th17 differentiation. Furthermore, we demonstrate that S6K2, a nuclear counterpart of S6K1, is induced by the PI3K-Akt-mTORC1 axis, binds RORγ, and carries RORγ to the nucleus. These results point toward a pivotal role of PI3K-Akt-mTORC1-S6K1/2 axis in Th17 differentiation.

  14. Efficient and selective heavy metal sequestration from water by using layered sulfide K 2x Sn 4-x S 8-x (x = 0.65–1; KTS-3)

    Energy Technology Data Exchange (ETDEWEB)

    Sarma, Debajit; Islam, Saiful M.; Subrahmanyam, K. S.; Kanatzidis, Mercouri G.

    2016-09-16

    Heavy metal ions (Cd2+, Hg2+, As3+ and Pb2+) are an important contributor to the contamination of groundwater and other water bodies in and around industrial areas. Herein, we demonstrate the rapid and efficient capacity of a layered metal sulfide material, K2xSn4-xS8-x (x = 0.65-1, KTS-3) for heavy metal ion removal from water. The effect of concentration, pH, kinetics, and competitive ions such as Na+/Ca2+ on the heavy metal ion removal capacity of KTS-3 was systematically investigated. X-ray photoelectron spectroscopy (XPS), elemental analyses, and powder X-ray diffraction studies revealed that the heavy metal ion-exchange of KTS-3 is complete (quantitative replacement of all potassium ions) and topotactic. The heavy metal ion-exchange by using KTS-3 follows the Langmuir-Freundlich model with high exchange capacities, q(m) 205(17) mg g-1 for Cd2+, 372(21) mg g-1 for Hg2+ and 391(89) mg g-1 for Pb2+. KTS-3 retains excellent heavy metal ion-exchange capacity even in very high concentration (1 M) of competing ions (Na+/Ca2+) and also over a broad pH range (2-12). KTS-3 also exhibits very good ion-exchange capacity for precious Ag+ and toxic As3+ ions. The kinetics of heavy metal ion adsorption by KTS-3 are rapid (absorbs all ions within a few minutes). These properties and the environmentally friendly character of KTS-3 make it a promising candidate for sequestration of heavy metal ions from water.

  15. Magnetovolume effects of quasi-one-dimensional itinerant electron magnets (La{sub 1-x}Y{sub x})Mn{sub 4}Al{sub 8}

    Energy Technology Data Exchange (ETDEWEB)

    Muro, Y. [Graduate School of Material Science, University of Hyogo, Kamigori, Ako-gun, Hyogo 678-1297 (Japan)]. E-mail: rk04j052@stkt.u-hyogo.ac.jp; Motoyama, G. [Graduate School of Material Science, University of Hyogo, Kamigori, Ako-gun, Hyogo 678-1297 (Japan); Nakamura, H. [Graduate School of Material Science, University of Hyogo, Kamigori, Ako-gun, Hyogo 678-1297 (Japan); Kohara, T. [Graduate School of Material Science, University of Hyogo, Kamigori, Ako-gun, Hyogo 678-1297 (Japan)

    2006-05-01

    Magnetovolume effects of 3d heavy-electron compounds with linear spin chains, (La{sub 1-x}Y{sub x})Mn{sub 4}Al{sub 8} with x=<0.15 and =1, have been investigated to get information on the ground state of LaMn{sub 4}Al{sub 8} and the nature of spin fluctuations in this system. The negative thermal expansion observed for LaMn{sub 4}Al{sub 8} is suppressed by the substitution of a small amount of Y for La. Together with the field-cooled effect in the susceptibility, the magnetovolume effect suggests the development of short-range magnetic correlation in LaMn{sub 4}Al{sub 8} at low temperatures.

  16. Metal-insulator transition in SrTi1xVxO3 thin films

    International Nuclear Information System (INIS)

    Gu, Man; Wolf, Stuart A.; Lu, Jiwei

    2013-01-01

    Epitaxial SrTi 1x V x O 3 (0 ≤ x1) thin films were grown on (001)-oriented (LaAlO 3 ) 0.3 (Sr 2 AlTaO 6 ) 0.7 (LSAT) substrates using the pulsed electron-beam deposition technique. The transport study revealed a temperature driven metal-insulator transition (MIT) at 95 K for x = 0.67. The films with higher vanadium concentration (x > 0.67) were metallic corresponding to a Fermi liquid system. In the insulating phase (x < 0.67), the resistivity behavior was governed by Mott's variable range hopping mechanism. The possible mechanisms for the induced MIT are discussed, including the effects of electron correlation, lattice distortion, and Anderson localization

  17. Synthesis and structural properties of n = 1 Ruddlesden-Popper manganites Nd1-xCa1+xMnO4

    International Nuclear Information System (INIS)

    Nagai, T.; Yamazaki, A.; Kimoto, K.; Matsui, Y.

    2008-01-01

    Polycrystalline samples of n = 1 Ruddlesden-Popper manganites Nd 1-x Ca 1+x MnO 4 (0.55 ≤ x1.00) were synthesized by a solid-state reaction. X-ray diffraction (XRD) and electron diffraction (ED) measurements confirmed that the fundamental crystal structure at room temperature consists of three distorted K 2 NiF 4 -types: orthorhombic Bmab (64) phase in 0.55 ≤ x 1 /acd (142) phase in 0.85 ≤ x1.00. Furthermore, in a whole range of 0.55 ≤ x ≤ 0.75, low-temperature magnetic and ED measurements revealed charge-orbital ordering (COO) states, which are accompanied by suppression of magnetization and structural modulations with q = (1 - x)a*. The COO transition temperatures are high with a maximum of ∼330 K at x = 0.67, and then higher than those in non-distorted n = 1 Ruddlesden-Popper manganites. The observations suggest that COO states are much stabilized by the distortion in the fundamental structures

  18. Relationship between electrical and structural properties in Pr2/3+xTiO3±y

    International Nuclear Information System (INIS)

    Kirsanov, N.A.; Bazuev, G.V.

    1987-01-01

    Synthesis conditions results of X-ray diffraction investigations and electric properties of oxide titanium bronzes (OTB) of praseodymium Pr 2/3+x TiO 3±y in homogeneity region are presented. Change of crystal lattice symmetry in the region of existence of oxide titanium bronzes Pr 2/3+x TiO 3 ± y (O ≤ x1/3) was revealed. Specific electrical resistance measurements enabled to conclude that d-electrons of Ti 3+ cations were characterized by collectivized behaviour, conditioned by formation of harrow, partially occupied π*-zone

  19. Direct evidence for double-exchange coupling in Ru- substituted La0.7Pb0.3Mn 1 - x Ru x O3, 0.0 <= x <= 0.4

    Science.gov (United States)

    Sundar Manoharan, S.; Sahu, R. K.; Rao, M. L.; Elefant, D.; Schneider, C. M.

    2002-08-01

    The La0.7Pb0.3Mn 1 - x Ru x O3 (0.0 innate relationship between Mn and Ru ions by a unique double-exchange mediated transport behavior. This is exonerated by the coexistence of Tp and Tc (range 330 K 245 K for 0.0 30%, the hole carrier mass influences the transport property. X-ray absorption spectra suggest that the Tc-Tp match is due to the transport mediated by the Mn3+/Mn4+ leftrightarrow Ru4+/Ru5+ redox pair and also due to the broad low-spin Ru:4d conduction band. For x > 0.2, T < 0.5Tc obeys a modified variable-range hopping model, where kT0 propto (M/Ms)2, suggesting a random magnetic potential which localizes the charge carriers.

  20. 57Fe Moessbauer effect studies of magnetic ordering in Lasub(1-x) Srsub(x)CoO3

    International Nuclear Information System (INIS)

    Bhide, V.G.; Rajoria, D.S.

    1975-01-01

    A detailed investigation of the Lasub(1-x)Srsub(x)CoO 3 system was performed for the entire range of Sr concentrations using X-ray diffraction for structural studies, DTA for phase transition analysis, Moessbauer and magnetic susceptibility studies for magnetic properties, and electrical resistivity and Seebeck coefficient studies for electron transport properties. Among other interesting results, samples with x > 0.125 were found to show ferromagnetic ordering. (A.K.)

  1. Spatial structure determination of (√3 x3)R30 degrees and (1.5 x 1.5)R18 degrees CO on Cu(111) using angle-resolved photoemission extended fine structure

    International Nuclear Information System (INIS)

    Moler, E.J.; Kellar, S.A.; Huff, W.R.A.

    1997-01-01

    The authors report a study of the spatial structure of (√3 x3)R30 degrees (low coverage) and (1.5 x 1.5)R18 degrees (intermediate coverage) CO adsorbed on Cu(111), using the Angle-Resolved Photoemission Extended Fine Structure (ARPEFS) technique at beamline 9.3.2 at the Advanced Light Source. The CO molecule adsorbs on an atop site for both adsorption phases. Full multiple-scattering spherical-wave (MSSW) calculations were used to extract the C-Cu. bond length and the first Cu-Cu layer spacing for each adsorption phase. The authors find that the C-Cu bond length remains unchanged with increasing coverage, but the 1st Cu-Cu layer spacing contracts at the intermediate coverage. They calculate the bending mode force constant in the (1.5 x 1.5)R18 degrees phase to be K δ = 2.2 (1) x 10 -12 dyne-cm/rad from their experimentally determined bond lengths combined with previously published infra-red absorption frequencies

  2. Synthesis, structure and superconductivity in Ba1-xKxBiO3

    International Nuclear Information System (INIS)

    Hinks, D.G.

    1989-01-01

    Ba 1-x K x BiO 3 (with x = 0.4) has the highest T c (30 K) of any copperless compound. The superconducting transition temperature of this material is expected to be at the limit of conventional electron-phonon coupling. Since this material is much simpler than the copper containing high-T c superconductors (it is cubic in its superconducting state and only sp electrons are involved in the transport properties), it should be much easier to unravel the nature of the superconducting pairing mechanism in this system. Understanding this system may help explain superconductivity in the more complex copper-oxide materials. In this paper, the authors report on the development of a synthesis method which allows the preparation of stoichiometric, single-phase materials with x between 0.0 and 0.5. The structural phase diagram was determined using powder neutron diffraction as a function of both composition and temperature. Superconductivity only occurs in the cubic perovskite phase which is stable for x larger than 0.3. At a x = 0.3 composition the material undergoes a semiconductor to metal transition with a maximum value for T c . As the K content is further increased, T c is reduced

  3. Vitamin K 3 family members - Part II: Single crystal X-ray structures, temperature-induced packing polymorphism, magneto-structural correlations and probable anti-oncogenic candidature

    Science.gov (United States)

    Rane, Sandhya; Ahmed, Khursheed; Salunke-Gawali, Sunita; Zaware, Santosh B.; Srinivas, D.; Gonnade, Rajesh; Bhadbhade, Mohan

    2008-12-01

    Temperature-induced packing polymorphism is observed for vitamin K 3 (menadione, 3-methyl-1,4-naphthoquinone, 1). Form 1a crystallizes at 300 K and 1b at 277 K both in the same space group P2 1/ c. Form 1b contains one molecule per asymmetric unit, performing anisotropy in g-factor viz. g z = 2.0082, g y = 2.0055 and g x = 2.0025, whereas form 1a contains two molecules in its asymmetric unit. Vitamin K 3 family members 2, [2-hydroxy vitamin K 3] and 3, [2-hydroxy-1-oximino vitamin K 3] also perform intrinsic neutral active naphthosemiquinone valence tautomers even in dark having spin concentrations due to hydrogen bonding and aromatic stacking interactions which are compared to vitamin K 3. The significant lateral C-H⋯O and O-H⋯π bifurcated or π-π ∗ interactions are discussed for molecular associations and radical formations. X-ray structure of 3 revealed π-π ∗ stack dimers as radicals signatured in EPR as triplet with five hyperfine splits [ Ā( 14N) = 11.9 G]. The centrosymmetric biradicals in 3 show diamagnetism at high temperature but below 10 K it shows paramagnetism with μeff as 0.19 B.M. Vitamin K 3 and its family members inhibit biological activities of acid phosphatase ( APase), which are proportional to their spin concentrations. This may relate to their probable anti-oncogenic candidature in future.

  4. Structure refinement, far infrared spectroscopy, and dielectric characterization of (1-x)La(Mg1/2Ti1/2)O3-xLa2/3TiO3 solid solutions

    Science.gov (United States)

    Salak, Andrei N.; Khalyavin, Dmitry D.; Ferreira, Victor M.; Ribeiro, José L.; Vieira, Luís G.

    2006-05-01

    Dielectric properties of (1-x)La(Mg1/2Ti1/2)O3-xLa2/3TiO3 [(1-x)LMT-xLT] ceramics (0infrared (FIR) frequency ranges. The crystal structure sequence in (1-x)LMT-xLT reported by different authors has been analyzed and revised. FIR spectroscopy was used to characterize the lattice contribution to the dielectric response at microwave frequencies. The complex dielectric function was evaluated from the reflectivity data and extrapolated down to a gigahertz range. Compositional variations of the fundamental microwave dielectric parameters estimated by different methods are compared and discussed. The dependence of the quality factor on the composition in LMT-LT is interpreted in terms of the reduction of spatial phonon correlations originated from the increasing amount of La vacancies. This approach could account for the compositional behavior of the dielectric loss commonly observed in a number of microwave mixed systems.

  5. Chemical pressure induced change in multiferroicity of Bi{sub 1+2x}Gd{sub 2x/2}Fe{sub 1−2x}O{sub 3} bulk ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Pradhan, S.K. [Institute of Materials Science, Bhubaneswar 751013 Odisha (India); Center for Materials Research, Norfolk State University, Norfolk (United States); Sahu, D.R., E-mail: diptirs@yahoo.com [Institute of Materials Science, Bhubaneswar 751013 Odisha (India); Department of Natural and Applied Science, Namibia University of Science and Technology, Windhoek (Namibia); Rout, P.P.; Das, S.K. [Institute of Materials Science, Bhubaneswar 751013 Odisha (India); Pradhan, A.K. [Center for Materials Research, Norfolk State University, Norfolk (United States); Srinivasu, V.V. [Department of Physics, University of South Africa (South Africa); Roul, B.K., E-mail: ims@iopb.res.in [Institute of Materials Science, Bhubaneswar 751013 Odisha (India)

    2017-04-01

    We have optimized Gd ion substitution in BiFeO{sub 3} (BFO) and observed prominently change in structural, electrical and magnetic behavior of Bi{sub 1+2x}Gd{sub 2x/2}Fe{sub 1−2x}O{sub 3} ceramics synthesized through slow step sintering schedule. It is observed that with the increase in concentration of Gd (x=0.1), original structure of BFO is transformed from rhombohedral R3c space group to orthorhombic Pn21a space group. Surprisingly, unit cell volume is drastically contracted (35% for x=0.2) and the sintered specimen showed enhanced room temperature ferromagnetic behavior although the original BFO is normally G-type antiferromagnetic in nature at 643 K. It is expected that intrinsic chemical pressure within the bulk body built by the substitution of Gd in presence of excess bismuth greatly supported through unidirectional movement of electrical dipole moment with in each individual domain as a result of which suppression of leakage current with enhanced dielectric and ferroelectric hysteresis is observed.

  6. Determination of nucleic acids based on the quenching effect on resonance light scattering of the Y(III)-1,6-bi(1'-phenyl-3'-methyl-5'-pyrazolone-4'-)hexane-dione system.

    Science.gov (United States)

    Wu, Xia; Yang, Jing He; Sun, Shuna; Guo, Changying; Ran, Dehuan; Zheng, Jinhua

    2006-01-01

    Nucleic acids can quench resonance light scattering (RLS) intensity of the Y(III)-1,6-bi(1'-phenyl-3'-methyl-5'-pyrazolone-4'-)hexane-dione(BPMPHD) complex in the pH range 5.0-5.8. Under optimal conditions, there are linear relationships between the quenching of RLS and the concentration of nucleic acids in the range 6.3 x 10(-8)-2.1 x 10(-5) g/mL for fish sperm DNA (fsDNA), 1.2 x 10(-8)-5.0 x 10(-5) g/mL for calf thymus DNA (ctDNA) and 6.0 x 10(-8)-2.0 x 10(-5) g/mL for yeast RNA (yRNA). The detection limits (3 s) of fsDNA, ctDNA and yRNA are 0.7 ng/mL, 3.8 ng/mL and 4.2 ng/mL, respectively. Copyright (c) 2006 John Wiley & Sons, Ltd.

  7. Stoichiometry, thickness and crystallinity of MOCVD grown Hg{sub 1x-y}Cd{sub x}Mn{sub y}Te determined by nuclear techniques of analysis

    Energy Technology Data Exchange (ETDEWEB)

    Studd, W.B.; Johnston, P.N.; Bubb, I.F. [Royal Melbourne Inst. of Tech., VIC (Australia); Leech, P.W. [Applied Research and Developement, Telecom Australia, Clayton, VIC (Australia)

    1993-12-31

    The quaternary semi-conductor Hg{sub 1-x-y}Cd{sub x}Mn{sub y}Te has been grown by Metal Organic Chemical Vapour Deposition using the Interdiffused Multi-layer Process. The layers have been analysed by Ion beam (PIXE, RBS, channeling) and related analytical techniques (EDXRF, XRD, RHEED) to obtain stoichiometric and structural information. The analysis shows that all four elements are present throughout the layer and that the elemental concentrations and thickness of the layer vary considerably over the film. Channeling, XRD and RHEED have been combined to show that the layer is polycrystalline. 14 refs., 3 figs.

  8. Stoichiometry, thickness and crystallinity of MOCVD grown Hg{sub 1x-y}Cd{sub x}Mn{sub y}Te determined by nuclear techniques of analysis

    Energy Technology Data Exchange (ETDEWEB)

    Studd, W B; Johnston, P N; Bubb, I F [Royal Melbourne Inst. of Tech., VIC (Australia); Leech, P W [Applied Research and Developement, Telecom Australia, Clayton, VIC (Australia)

    1994-12-31

    The quaternary semi-conductor Hg{sub 1-x-y}Cd{sub x}Mn{sub y}Te has been grown by Metal Organic Chemical Vapour Deposition using the Interdiffused Multi-layer Process. The layers have been analysed by Ion beam (PIXE, RBS, channeling) and related analytical techniques (EDXRF, XRD, RHEED) to obtain stoichiometric and structural information. The analysis shows that all four elements are present throughout the layer and that the elemental concentrations and thickness of the layer vary considerably over the film. Channeling, XRD and RHEED have been combined to show that the layer is polycrystalline. 14 refs., 3 figs.

  9. Vibrational analysis of Fourier transform spectrum of the A3Π0–X1Σ ...

    Indian Academy of Sciences (India)

    Home; Journals; Pramana – Journal of Physics; Volume 73; Issue 5. Vibrational analysis of Fourier transform spectrum of the A 3 0 – X 1 ∑ + and B 3 1X 1 ∑ + transitions of indium monobromide. Renu Singh K N Uttam M D Saksena M N Deo. Volume 73 Issue 5 November 2009 pp 889-899 ...

  10. Spin canting and magnetic transition in NixZn1-xFe2O4 (x=0.0, 0.5 and 1.0) nanoparticles

    Science.gov (United States)

    Rani, Stuti; Raghav, Dharmendra Singh; Yadav, Prashant; Varma, G. D.

    2018-04-01

    Nanoparticles of NixZn1-xFe2O4(x=0.0, 0.5 and 1.0) have been synthesized via co-precipitation method and studied thestructural and magnetic properties. Rietveld refinement of X ray diffraction data of as synthesized samples revealthat the samples have mixed spinel structure with space group Fd-3m. The lattice parameter of the samples decreases as doping concentration of Ni ions increases. Magnetic measurements show paramagnetic to ferrimagnetic transition at room temperature on Ni doping in ZnFe2O4 nanoparticles. The magnetic measurements also show spin canting in samples possibly due to their nanocrystalline nature. The spin canting angles have been calculated with the help of Yafet-Kittel (Y-K) model. Furthermore, the Law of approach (LA) fitting of M-H curves indicates that the samples are highly anisotropicin nature. The Arrot plots of as synthesized samples also indicate the paramagnetic to ferrimagnetic transition. The correlation between the structural and observed magnetic properties of NixZn1-xFe2O4(x=0.0, 0.5 and 1.0) nanocrystals will be described and discussed in this paper.

  11. K,L X-rays production cross sections for 1H and 4He

    International Nuclear Information System (INIS)

    Heitz, C.; Costa, G.J.; Cailleret, J.; Lagarde, G.

    1982-01-01

    Experimental X-ray production cross sections are tabulated for 1 H and 4 He projectiles. In the case of K X-rays, a comparison with theoretical values is also performed in view of applications, such a PIXE analysis [fr

  12. An electron spin resonance study on the gamma-irradiation of urea, urea- d4, 1-3-dimethylurea, 1-3-diethylurea and 1,1',3,3'-tetramthylurea

    International Nuclear Information System (INIS)

    Kang, Y.S.; McManus, H.J.D.; Kevan, L.

    1994-01-01

    Urea, urea-d 4 , 1,3-dimethylurea, 1,3-diethylurea powder and 1,1',3,3'-tetramethylurea, and their solutions in D 2 O were γ-irradiated with 0.0882 kGy both at room temperature and at 77 K. The product radicals were identified with X-band electron spin resonance, based on the g-factor and hyperfine coupling constants. The radicals formed from urea and urea-d 4 were identified as nitrogen-centered and resulted from N-H bond dissociation. The radicals produced from 1,3-dimethylurea, 1,3-diethylurea and 1,1',3,3'-tetramethylurea were identified as carbon-centered and resulted from C-H bond cleavage. The electron spin resonance signals of 1,3-dimethylurea, 1,3-diethylurea and 1,1',3,3'-tetramethylurea are similar in both the powder and D 2 O solution. The radicals observed from 1,3-dimethylurea, 1,3-diethylurea and 1,1',3,3'-tetramethylurea were identified as . NH-CH 2 , . NH-CHCH 3 and . (CH 3 )(CH 2 ), respectively. (author)

  13. Low-frequency phase diagram of irradiated graphene and a periodically driven spin-1/2 X Y chain

    Science.gov (United States)

    Mukherjee, Bhaskar; Mohan, Priyanka; Sen, Diptiman; Sengupta, K.

    2018-05-01

    We study the Floquet phase diagram of two-dimensional Dirac materials such as graphene and the one-dimensional (1D) spin-1/2 X Y model in a transverse field in the presence of periodic time-varying terms in their Hamiltonians in the low drive frequency (ω ) regime where standard 1 /ω perturbative expansions fail. For graphene, such periodic time-dependent terms are generated via the application of external radiation of amplitude A0 and time period T =2 π /ω , while for the 1D X Y model, they result from a two-rate drive protocol with a time-dependent magnetic field and nearest-neighbor couplings between the spins. Using the adiabatic-impulse method, whose predictions agree almost exactly with the corresponding numerical results in the low-frequency regime, we provide several semianalytic criteria for the occurrence of changes in the topology of the phase bands (eigenstates of the evolution operator U ) of such systems. For irradiated graphene, we point out the role of the symmetries of the instantaneous Hamiltonian H (t ) and the evolution operator U behind such topology changes. Our analysis reveals that at low frequencies, topology changes of irradiated graphene phase bands may also happen at t =T /3 and2 T /3 (apart from t =T ) showing the necessity of analyzing the phase bands of the system for obtaining its phase diagrams. We chart out the phase diagrams at t =T /3 ,2 T /3 ,and T , where such topology changes occur, as a function of A0 and T using exact numerics, and compare them with the prediction of the adiabatic-impulse method. We show that several characteristics of these phase diagrams can be analytically understood from results obtained using the adiabatic-impulse method and point out the crucial contribution of the high-symmetry points in the graphene Brillouin zone to these diagrams. We study the modes that can appear at the edges of a finite-width strip of graphene and show that the change in the number of such modes agrees with the change in the

  14. Photoinduced Optical Properties Of Tl1xIn1xSixSe2 Single Crystals

    Directory of Open Access Journals (Sweden)

    Myronchuk G.L.

    2015-06-01

    Full Text Available The influence of temperature on electroconductivity and photoinduced changes of the absorption at 0.15 eV under influence of the second harmonic generation of CO2 laser for the two type of single crystals were investigated. The single crystals Tl1xIn1xSixSe2 (x=0.1 and 0.2 have been grown by the two-zone Bridgaman-Stockbarger method. The temperature studies of electroconductivity were done in cryostat with thermoregulation in the temperature 77 - 300 K, with stabilization ±0.1 K. Photoinduced treatment of the investigated single crystals were performed using the 180 ns pulses second harmonic generation of the CO2 laser operating at 5.3 μm. Experimental studies have shown that for the Tl1xIn1xSixSe2 single crystals with decreasing temperature from 300 up to 240 K and from 315 up to 270 K the conductivity is realized by thermally excited impurities with activation energies equal to about 0.24 eV and 0.22 eV for x= 0.1 and 0.2, respectively. Photoinduced absorption achieves its maximum at a power density below 100 mJ/cm2. Has been shown that the samples with x=0.2 demonstrated higher changes of the photoinduced absorption with respect to the x=0.1. With further decreasing temperature is observed monotonic decrease in the activation energy of conductivity. The origin of these effects is caused by the excitations of both the electronic as well as phonon subsystem. At some power densities the anharmonic excitations become dominant and as a consequence the photoinduced absorption dependence is saturated what were observed. Additionally, we were evaluated at given temperature the average jump length of R for localized states near Fermi level.

  15. Luminescent and scintillation properties of the Ce3+ doped Y3xLuxAl5O12:Ce single crystalline films

    International Nuclear Information System (INIS)

    Zorenko, Yu.; Gorbenko, V.; Zorenko, T.; Popielarski, P.; Mosińska, L.; Fedorov, A.

    2016-01-01

    The work is related to the investigation of scintillation and luminescent properties of single crystalline films (SCF) of solid solutions of Ce 3+ doped Y 3x Lu x Al 5 O 12 :Ce garnets with x value in the 0–3 range. We have shown a possibility of realization of high-energy shift of the Ce 3+ ion emission spectrum in these garnets up to 22 nm. We have also found that the light yield of the radioluminescence under α-particle excitation of LuAG:Ce SCF can exceed by 1.3 times the corresponding values for the YAG:Ce SCF counterpart. For investigation of the luminescent properties of Y 3x Lu x Al 5 O 12 :Ce SCF at different x values the luminescent spectroscopy of these SCFs under excitation by synchrotron radiation in the VUV range was performed. - Highlights: • Single crystalline films of Y 3x Lu x Al 5 O 12 garnets at x=0–3.0 were grown by LPE method onto YAG substrates. • Lattice constant of Y 3x Lu x Al 5 O 12 :Ce film and the film/substrate misfit changed linearly with increasing of Lu content in the x=0–3.0 range. • High-energy shift of the Ce 3+ emission up to 22 nm in Y 3x Lu x Al 5 O 12 film with increasing of Lu content in the x=0–3.0 range. • Light yield of Y 3x Lu x Al 5 O 12 :Ce film decreases in the x=0–1.8 range and increases in the x=1.8–3.0 range. • Scintillation LY of Lu 3 Al 5 O 12 :Ce film can exceed by 1.3 times the LY for YAG:Ce film counterpart.

  16. Crystallization behavior of (1 - x)Li2O.xNa2O.Al2O3.4SiO2 glasses

    International Nuclear Information System (INIS)

    Wang, Moo-Chin; Cheng, Chih-Wei; Chang, Kuo-Ming; Hsi, Chi-Shiung

    2010-01-01

    The crystallization behavior of the (1 - x)Li 2 O.xNa 2 O.Al 2 O 3 .4SiO 2 glasses has been investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), electron diffraction (ED) and energy dispersive spectroscopy (EDS). The crystalline phase was composed of β-spodumene. The isothermal crystallization kinetics of β-spodumene from the (1 - x)Li 2 O.xNa 2 O.Al 2 O 3 .4SiO 2 glasses has also been studied by a quantitative X-ray diffraction method. The activation energy of β-spodumene formation decreases from 359.2 to 317.8 kJ/mol when the Na 2 O content increases from 0 to 0.4 mol and it increases from 317.8 to 376.9 kJ/mol when the Na 2 O content increases from 0.4 to 0.6 mol. The surface nucleation and plate-like growth were dominant in the crystallization of the (1 - x)Li 2 O.xNa 2 O.Al 2 O 3 .4SiO 2 glasses.

  17. Copper NMR and hole depletion in the normal state of Y1-xPrxBa2Cu3O7

    International Nuclear Information System (INIS)

    MacLaughlin, D.E.; Reyes, A.P.; Takigawa, M.; Hammel, P.C.; Heffner, R.H.; Thompson, J.D.; Crow, J.E.

    1990-01-01

    Normal-state copper NMR spectra and spin-lattice relaxation rates 1/T 1 have been measured in the planar cuprate system YBa 2 Cu 3 O 7 . With Pr doping the Knight shift K decreases and develops a temperature dependence at both plane and chain sites. Analysis of the bulk susceptibility and NMR data indicate that pair breaking and hole depletion both take part in the suppression of the superconducting transition temperature T c . The Knight shift behavior resembles that in oxygen-deficient YBa 2 Cu 3 O 7-y , as does the temperature dependence of 1/T 1 for plane Cu sites and magnetic field perpendicular to the c axis. This agreement leads to a consistent picture of the role of antiferromagnetic fluctuations in these materials. An analysis of the data in the framework of the phenomenological theory of Millis, Monien, and Pines is given. In the end compound PrBa 2 Cu 3 O 7 the NMR signal from plane Cu sites indicates antiferromagnetic (AF) ordering at a Neel temperature ∼280 K, and in the AF state yields an internal field similar to those found in AF YBa 2 Cu 3 O 6 and La 2 CuO 4 . 32 refs., 7 figs

  18. Conductivity and electrochemical characterization of PrFe1-xNixO3-δ at high temperature

    DEFF Research Database (Denmark)

    Hashimoto, Shin-Ichi; Kammer Hansen, Kent; Poulsen, Finn Willy

    2007-01-01

    PrFe(1-x)NixO(3)- (x=0.4-0.6) compounds were synthesized and characterized by powder XRD, electrical conductivity and electrochemical impedance spectroscopy on point electrodes on a Ce0.9Gd0.1O2-delta (CGO10) electrolyte. As a reference, the electrochemical performance of LaFe(0.4)AM(0.6)O(3-delta......) was also measured. The main phase in the PrFe1-xNixO3-delta series was perovskite-type structure and belonged to the orthorhombic crystal system. The conductivities are fairly high, e.g. around 220 S cm(-1) at 873 K for the x = 0.4 compound. The electrochemical performance of the PrFe(1-x)NixO(3-delta...

  19. Metal-insulator transition in SrTi{sub 1x}V{sub x}O{sub 3} thin films

    Energy Technology Data Exchange (ETDEWEB)

    Gu, Man [Department of Physics, University of Virginia, 382 McCormick Rd., Charlottesville, Virginia 22904 (United States); Wolf, Stuart A. [Department of Physics, University of Virginia, 382 McCormick Rd., Charlottesville, Virginia 22904 (United States); Department of Materials Science and Engineering, University of Virginia, 395 McCormick Rd., Charlottesville, Virginia 22904 (United States); Lu, Jiwei [Department of Materials Science and Engineering, University of Virginia, 395 McCormick Rd., Charlottesville, Virginia 22904 (United States)

    2013-11-25

    Epitaxial SrTi{sub 1x}V{sub x}O{sub 3} (0 ≤ x1) thin films were grown on (001)-oriented (LaAlO{sub 3}){sub 0.3}(Sr{sub 2}AlTaO{sub 6}){sub 0.7} (LSAT) substrates using the pulsed electron-beam deposition technique. The transport study revealed a temperature driven metal-insulator transition (MIT) at 95 K for x = 0.67. The films with higher vanadium concentration (x > 0.67) were metallic corresponding to a Fermi liquid system. In the insulating phase (x < 0.67), the resistivity behavior was governed by Mott's variable range hopping mechanism. The possible mechanisms for the induced MIT are discussed, including the effects of electron correlation, lattice distortion, and Anderson localization.

  20. Solution-combustion synthesis of Bi1xLnxO1⋅ 5 (Ln= Y and La–Yb ...

    Indian Academy of Sciences (India)

    combustion synthesis of Bi1–LnO1.5 (Ln = Y and La–Yb) oxide ion conductors. Manjunath B Bellakki A S Prakash C Shivakumara M S Hegde A K Shukla. Ceramics and Glasses Volume 29 Issue 4 August 2006 pp 339-345 ...

  1. Electrical transport of (1-x)La{sub 0.7}Ca{sub 0.3}MnO{sub 3}+xAl{sub 2}O{sub 3} composites

    Energy Technology Data Exchange (ETDEWEB)

    Phong, P.T. [Nhatrang Pedagogic College, Khanhhoa, 1st Nguyen Chanh, Nha Trang City, Khanhhoa (Viet Nam); Institute of Material Science, Vietnamese Academy of Science and Technology, 18 Hoang Quoc Viet Road, Cau Giay District, Hanoi (Viet Nam); Khiem, N.V. [Department of Natural Sciences, Hongduc University, 307 Le Lai Street Thanh Hoa City (Viet Nam)], E-mail: nvkhiem2002@yahoo.com; Dai, N.V.; Manh, D.H.; Hong, L.V.; Phuc, N.X. [Institute of Material Science, Vietnamese Academy of Science and Technology, 18 Hoang Quoc Viet Road, Cau Giay District, Hanoi (Viet Nam)

    2009-10-15

    We report the resistivity ({rho})-temperature (T) patterns in (1-x)La{sub 0,7}Ca{sub 0,3}MnO{sub 3}+xAl{sub 2}O{sub 3} composites (0{<=}x{<=}0.05) over a temperature regime of 50-300 K. Al{sub 2}O{sub 3} addition has increased the resistivity of these composites. The Curie temperature (T{sub C}) is almost independent on the Al{sub 2}O{sub 3} content and is about 250 K for all the samples, while the metal-insulator transition temperature (T{sub MI}) decreases with increasing Al{sub 2}O{sub 3} content. Based on the phenomenological equation for conductivity under a percolation approach, which is dependent on the phase segregation of ferromagnetic metallic clusters and paramagnetic insulating regions, we fitted the experimental data ({rho}-T) from 50 to 300 K and find that the activation barrier increases as Al{sub 2}O{sub 3} content increases.

  2. Influence of baking on the photoluminescence spectra of In{sub 1-x} Ga{sub x} As{sub y} P{sub 1-y} solid solutions grown on Inp substrates

    Energy Technology Data Exchange (ETDEWEB)

    Mishurnyi, V.A.; Gorbatchev, A.Y.; Anda, F. De; Nieto N, J. [Instituto de Investigacion en Comunicacion Optica, Universidad Autonoma de San Luis Potosi, Alvaro Obregon 64, 78000 San Luis Potosi (Mexico)

    2004-07-01

    The influence of thermal treatments on the photoluminescence spectra of In{sub 1-x} Ga{sub x} As{sub y} P{sub 1-y} epitaxial layers of various compositions grown by LPE on In P substrates has been studied. To prevent the epitaxial layers from degradation, due to phosphor evaporation during the baking, their surface was covered by spin-on SiO{sub 2} layers. The photoluminescence spectra did not change for solid solutions whose compositions were near In P and InGaAs. For compositions in the middle of the lattice-matched region, the variations were very noticeable because the appearance of additional peaks in the luminescence spectra. This could be related to the decomposition of those solid solutions whose compositions lie inside a theoretically predicted miscibility gap. (Author)

  3. On the optimum processing conditions of Pb(Zr x Ti1-x )O3: revealing the mechanisms to increase the piezoelectric coefficients up to 1100 pm V-1

    Science.gov (United States)

    Zeibekis, M.; Vertsioti, G.; Stamopoulos, D.

    2016-03-01

    The ferroelectric compound family Pb(Zr x Ti1-x )O3 (PZT) is one of the most investigated and widely used piezoelectric materials. Optimization of the piezoelectric coefficients is observed for x ~ 0.52 (Pb(Zr0.52Ti0.48)O3) and is further promoted by the increase of grain size (GS). However, in some cases the piezoelectric properties of Pb(Zr0.52Ti0.48)O3 deteriorate upon processing due to the decrease of density, ρ, that is mostly ascribed to the appearance of byproduct phases. In the present study we discuss the influence of the processing conditions on the piezoelectric properties for polycrystalline Pb(Zr0.52Ti0.48)O3, specifically focusing on the sintering temperature, 1100 °C  ⩽  T sin  ⩽  1250 °C. To this end, we use atomic force microscopy (AFM), Archimedes’ method, x-ray diffraction (XRD) and a newly introduced local technique, based on a conventional optical microscope, which is further developed here to accommodate non-clamped specimens. The data obtained via this technique in the regime of relatively high electric fields evidence that the absolute piezoelectric coefficients, |d zi | (i  =  x, y) show a non-monotonic behavior with an unexpectedly high maximum value |d zi | ~ 1100 pm V-1 at T sin  =  1180 °C. These features are accompanied by a progressive increase of coercivity, reaching maximum value E C,i ~ 4.5-5.0 kV cm-1 (i  =  x, y) at T sin  =  1250 °C. To explain these findings, the |d zi | coefficients are compared with the microstructure and compositional information, coming from AFM, Archimedes’ method and XRD data. We conclude that the significantly high |d zi | values observed for samples prepared at T sin  =  1180 °C are motivated by the increase of mean GS, , while for T sin  >  1180 °C the decrease of density, ρ, ascribed to the appearance of byproduct phases, dominates and deteriorates |d zi |. These experimental results on |d zi |(T sin) are reliably

  4. Normal state magnetic behavior of (U/sub 1-x/RE/sub x/)Be13 pseudobinaries

    International Nuclear Information System (INIS)

    Zirngiebl, E.; Thompson, J.D.; Smith, J.L.; Fisk, Z.

    1987-01-01

    Any impurity doping seems to modify the low temperature properties of UBe 13 in a way rather unusual compared to normal superconductors. So far, however, little attention has been paid to the modification of the normal state properties of impurity doped UB 13 . We have investigated the normal state magnetic behavior of impurity doped (U/sub 1-x/RE/sub x/)Be 13 pseudobinaries (RE = Th, Y, La, Lu, Sc) in the temperature range between 2 K and 380 K for impurity concentrations x ≤ 0.05 to see if there are correlations with T/sub c/(x)

  5. Phase equilibrium measurements and thermodynamic modeling of aqueous solutions of polyamines CO_2 absorbents: 3-aminopropylmethylamine, 3-aminopropyldimethylamine and N,N-diethyl 1,3-propanediamine at temperatures from 273 K to 363 K

    International Nuclear Information System (INIS)

    Bouzina, Zahida; Mokbel, Ilham; Negadi, Amina; Jose, Jacques; Negadi, Latifa

    2016-01-01

    Highlights: • Experimental vapor pressures of pure MAPA, DMAPA, DEAPA and their aqueous solutions are reported. • The investigated temperatures are 273 K through 363 K. • The MAPA binary system exhibits negative deviations in G"E values. • The DMAPA and DEAPA systems exhibit negative, sinusoidal and positive deviations in G"E values. • The 3rd order Redlich–Kister, and NRTL or UNIQUAC models have been used to correlate the (P-x-y) data. - Abstract: The vapor pressures of the pure components 3-aminopropylmethylamine (MAPA), 3-aminopropyldimethylamine (DMAPA) and N,N-diethyl 1,3-propanediamine (DEAPA) along with the binary mixtures (MAPA + water), (DMAPA + water) and (DEAPA + water) were measured by means of a static apparatus at temperatures between (273 and 363) K. The data were correlated with the Antoine equation. From these data, excess Gibbs functions (G"E) were calculated for several constant temperatures, and fitted to a three parameters Redlich–Kister equation using the Barker’s method. Additionally, the NRTL and UNIQUAC models have been used for the correlation of the total pressure.

  6. Effects of Cr Substitution on Negative Thermal Expansion and Magnetic Properties of Antiperovskite Ga1-x Cr x N0.83Mn3 Compounds.

    Science.gov (United States)

    Guo, Xinge; Tong, Peng; Lin, Jianchao; Yang, Cheng; Zhang, Kui; Lin, Shuai; Song, Wenhai; Sun, Yuping

    2018-01-01

    Negative thermal expansion (NTE) and magnetic properties were investigated for antiperovskite Ga 1- x Cr x N 0.83 Mn 3 compounds. As x increases, the temperature span (Δ T ) of NTE related with Γ 5g antiferromagnetic (AFM) order is expanded and shifted to lower temperatures. At x = 0.1, NTE happens between 256 and 318 K (Δ T = 62 K) with an average linear coefficient of thermal expansion, α L = -46 ppm/K. The Δ T is expanded to 81 K (151-232 K) in x = 0.2 with α L = -22.6 ppm/K. Finally, NTE is no longer visible for x ≥ 0.3. Ferromagnetic order is introduced by Cr doping and continuously strengthened with increasing x , which may impede the AFM ordering and thus account for the broadening of NTE temperature window. Moreover, our specific heat measurement suggests the electronic density of states at the Fermi level is enhanced upon Cr doping, which favors the FM order rather than the AFM one.

  7. Preparation of nanocrystalline Ce{sub 1x}Sm{sub x}(Fe,Co){sub 11}Ti by melt spinning and mechanical alloying

    Energy Technology Data Exchange (ETDEWEB)

    Wuest, H., E-mail: holger.wuest@de.bosch.com [Robert Bosch GmbH, Postfach 10 60 50, 70049 Stuttgart (Germany); Bommer, L., E-mail: lars.bommer@de.bosch.com [Robert Bosch GmbH, Postfach 10 60 50, 70049 Stuttgart (Germany); Huber, A.M., E-mail: arne.huber@de.bosch.com [Robert Bosch GmbH, Postfach 10 60 50, 70049 Stuttgart (Germany); Goll, D., E-mail: dagmar.goll@htw-aalen.de [Aalen University, Materials Research Institute, Beethovenstr. 1, 73430 Aalen (Germany); Weissgaerber, T., E-mail: thomas.weissgaerber@ifam-dd.fraunhofer.de [Fraunhofer Institute for Manufacturing Technology and Advanced Materials (IFAM), Branch Lab Dresden, Winterbergstraße 28, 01277 Dresden (Germany); Kieback, B., E-mail: bernd.kieback@ifam-dd.fraunhofer.de [Fraunhofer Institute for Manufacturing Technology and Advanced Materials (IFAM), Branch Lab Dresden, Winterbergstraße 28, 01277 Dresden (Germany); Technische Universität Dresden, Institute for Materials Science, Helmholtzstraße 7, 01069 Dresden (Germany)

    2017-04-15

    Permanent magnetic materials based on Ce(Fe, Co){sub 12−x}Ti{sub x} with the ThMn{sub 12} structure are promising candidates for replacing NdFeB magnets. Its intrinsic magnetic properties are not far below the values of Nd{sub 2}Fe{sub 14}B, and the high amount of Fe and the fact that Ce is much more abundant and less expensive than Nd encourages the reasonable interest in these compounds. Nanocrystalline magnetic material of the composition Ce{sub 1x}Sm{sub x}Fe{sub 11−y}Co{sub y}Ti (x=0−1 and y=0; 1.95) has been produced by both melt spinning and mechanical alloying. Alloys containing only Ce as rare earth element (x=0) show coercivities below 77 kA/m, while for x=1 H{sub c,J} values up to 392 kA/m are reached. Coercivity shows rather an exponential than a linear dependence on the gradual substitution of Ce by Sm. - Highlights: • CeFe{sub 11}Ti nanocrystalline samples demonstrate values of H{sub c,J} up to 77 kA/m. • SmFe{sub 11}Ti nanocrystalline samples demonstrate values of H{sub c,J} up to 392 kA/m. • Dependence of H{sub c,J} on x in Ce{sub 1x}Sm{sub x(}Fe, Co){sub 11}Ti obeys non-linear dependence. • Optimum annealing shifts to from 800 °C for CeFe{sub 11}Ti to 900 °C for SmFe{sub 11}Ti.

  8. Magnetic properties and magnetocaloric effects in Mn1.2Fe0.8P1-xGex compounds

    International Nuclear Information System (INIS)

    Ou, Z Q; Wang, G F; Lin Song; Tegus, O; Brueck, E; Buschow, K H J

    2006-01-01

    We have studied the magnetic properties and magnetocaloric effects in the Mn 1.2 Fe 0.8 P 1-x Ge x compounds with x = 0.2, 0.22, 0.3, 0.4 and 0.5. X-ray diffraction patterns show that the Mn 1.2 Fe 0.8 P 1-x Ge x compounds crystallize in the hexagonal Fe 2 P-type crystal structure. The magnetic moments of the Mn 1.2 Fe 0.8 P 1-x Ge x compounds measured at 5 K and 5 T increase with increasing Ge content. The Curie temperature increases strongly and the magnetic entropy change has a maximum around 233 K for the compound with x = 0.22, which is about 19 and 31 J kg -1 K -1 for a field change of 2 and 5 T, respectively

  9. Synthesis and luminescence properties of Ce{sup 3+}-doped Y{sub 3}Al{sub 3.5}Ga{sub 1.5}O{sub 12} green phosphor for white LEDs

    Energy Technology Data Exchange (ETDEWEB)

    Qiang, Yaochun [Fujian Key Laboratory of Advanced Materials, Department of Materials Science and Engineering, College of Materials, Xiamen University, Xiamen 361005 (China); Yu, Yuxi, E-mail: yu_heart@xmu.edu.cn [Fujian Key Laboratory of Advanced Materials, Department of Materials Science and Engineering, College of Materials, Xiamen University, Xiamen 361005 (China); Chen, Guolong [Fujian Engineering Research Center for Solid-state Lighting, Department of Electronic Science, Xiamen University, Xiamen 361005 (China); Fang, Jiyu [Advanced Materials Processing and Analysis Center, Department of Materials Science and Engineering, University of Central Florida, Orlando, FL 32816 (United States)

    2016-04-15

    A series of Ce{sup 3+}-doped Y{sub 3}Al{sub 3.5}Ga{sub 1.5}O{sub 12} green phosphors were successfully synthesized by a solid-state reaction method. The microstructure, morphology, luminescence spectra, luminescence quantum yield (QY) and thermal stability of the phosphor were investigated. The critical concentration of Ce{sup 3+} ions in Y{sub 3−m}Al{sub 3.5}Ga{sub 1.5}O{sub 12}:mCe{sup 3+} is m=0.06. The QY of Y{sub 2.94}Al{sub 3.5}Ga{sub 1.5}O{sub 12}:0.06Ce{sup 3+} phosphor is as high as 94% under excitation at 450 nm and its luminescence intensity at 150 °C still maintains 90% of that measured at 25 °C, which are just a little worse than those of commercial Lu{sub 3}Al{sub 5}O{sub 12}:Ce{sup 3+} green phosphor but much better than those of commercial (Sr,Ba){sub 2}SiO{sub 4}:Eu{sup 2+} green phosphor. A white LED lamp was fabricated by employing Y{sub 2.94}Al{sub 3.5}Ga{sub 1.5}O{sub 12}:0.06Ce{sup 3+} as a green phosphor and commercial (Ca,Sr)AlSiN{sub 3}:Eu{sup 2+} as a red phosphor (628 nm), its Ra value, correlated color temperature (CCT), CIE1931 chromaticity coordinates and luminous efficiency is 84, 3081 K, (x=0.4369, y=0.4142) and 102 lm/W, respectively. The experimental results demonstrate that Y{sub 2.94}Al{sub 3.5}Ga{sub 1.5}O{sub 12}:0.06Ce{sup 3+} is a promising green phosphor not only can be used for high color rendering index white LEDs but also for high-power white LEDs.

  10. Study of coherent diffractive production reactions of p + C --> [Y$^{0}$K$^{+}$] + C type and observation of the new baryonic states X(2050) --> $\\Sigma$(1385)$^{0}$K$^{+}$ and X(2000) --> $\\Sigma^{0}$K$^{+}$

    CERN Document Server

    Golovkin, S V; Kozhevnikov, A A; Kubarovskii, V P; Kulyavtsev, A I; Kurshetsov, V F; Kushnirenko, A Yu; Landsberg, G L; Molchanov, V V; Mukkin, V A; Solyanik, V I; Vavilov, D V; Victorov, V A; Balats, M Ya; Dzubenko, G B; Kamenskii, A D; Kliger, G K; Kolganov, V Z; Lakaev, V S; Lomkatsi, G S; Nilov, A P; Smolyankin, V T; Vishniakov, V V

    1994-01-01

    Study of coherent diffractive production reactions of p + C --> [Y$^{0}$K$^{+}$] + C type and observation of the new baryonic states X(2050) --> $\\Sigma$(1385)$^{0}$K$^{+}$ and X(2000) --> $\\Sigma^{0}$K$^{+}$

  11. Lattice vibrations study of Ga{sub 1-x}In{sub x}As{sub y}Sb{sub 1-y} quaternary alloys with low (In, As) content grown by liquid phase epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Olvera-Herandez, J [Centro de Investigacion en Dispositivos Semiconductores (CIDS), BUAP, Puebla, Pue. 72570 (Mexico); Olvera-Cervantes, J [Centro de Investigacion en Dispositivos Semiconductores (CIDS), BUAP, Puebla, Pue. 72570 (Mexico); Rojas-Lopez, M [Centro de Investigacion en BiotecnologIa Aplicada (CIBA), IPN, Tlaxcala, Tlax. 72160 (Mexico); Navarro-Contreras, H [Instituto de Investigacion en Comunicacion Optica (IICO), UASLP, 78100, San Luis PotosI, S.L.P. (Mexico); Vidal, M A [Instituto de Investigacion en Comunicacion Optica (IICO), UASLP, 78100, San Luis PotosI, S.L.P. (Mexico); Anda, F de [Instituto de Investigacion en Comunicacion Optica (IICO), UASLP, 78100, San Luis PotosI, S.L.P. (Mexico)

    2006-01-01

    Raman scattering spectroscopy was used to measure and analyze the lattice vibrations in some quaternary Ga{sub 1-x}In{sub x}As{sub y}Sb{sub 1-y} alloys with low (In, As) contents (0.03 <x< 0.12 and 0.03 <y< 0.10). The layers were grown by liquid phase epitaxy on (001) GaSb substrates at 540{sup 0}C. High Resolution X-Ray Diffraction results showed profiles associated with a quaternary layer lattice matched to the GaSb substrate as obtained from the (004) reflection. The experimental diffractograms were simulated to estimate alloy composition, thickness and lattice mismatch of the layer. Raman scattering results show phonon frequencies associated to the TO and LO GaAs-like modes as well as GaSb + InAs-like mode, which are characteristic of this quaternary alloy. The As content dependence of the phonon frequency measured in this alloy for low (In, As) contents agree well with the modified Random-Element Isodisplacement (REI) model and also with other available experimental reports. This method can also be used to estimate alloy compositions for this kind of quaternary alloys.

  12. Directional solidification of bulk Nd1+x Ba2-x Cu3 O7±δ

    International Nuclear Information System (INIS)

    Marella, M.; Menegazzo, R.; Spatola, S.; Piraccini, N.; Scattolin, R.; Siri, A. S.; Giannini, E.

    1997-01-01

    An innovative procedure for melt-texturing Nd 1+x Ba 2-x Cu 3 O 7±δ in Ar-1 % O 2 was developed. The precursor bars were allowed to crystallize from semisolid under the strong thermal gradient created by a moving thermal shield with micro metric displacement. The advantages are in the possibility of varying the thermal profile on the sample and processing long bars. The procedure allows to obtain large domains with a satisfactory control on the stoichiometry. The problems of bar deformation and reactivity with the support were definitely solved. additional evidence of a spiral growth mechanism of the platelets stacked in the domains is shown. A.C. susceptibility measurements show T c = 95.5 K and full diamagnetism below 88 K in 0-01 mT applied field. J c value, determined from magnetization hysteresis loops by application of the standard critical state model, is: 6.5 · 10 5 A/cm 2 at 5 K and μ 0 H = 1T, revealing the strong pinning typical of textured materials

  13. Magnetocaloric effects in Mn1.35Fe0.65P1xSix compounds

    International Nuclear Information System (INIS)

    Geng Yao-Xiang; Tegus O; Bi Li-Ge

    2012-01-01

    The structural and magnetocaloric properties of Mn 1.35 Fe 0.65 P 1x Si x compounds are investigated. The Si-substituted compounds, Mn 1.35 Fe 0.65 P 1x Si x with x = 0.52, 0.54, 0.55, 0.56, and 0.57, are prepared by high-energy ball milling and the solid-state reaction. The X-ray diffraction shows that the compounds crystallize into the Fe 2 P-type hexagonal structure with space group P6-bar2m. The magnetic measurements show that the Curie temperature of the compound increases from 253 K for x = 0.52 to 296 K for x = 0.56. The isothermal magnetic-entropy change of the Mn 1.35 Fe 0.65 P 1x Si x compound decreases with the Si content increasing. The maximal value of the magnetic-entropy change is about 7.0 J/kg·K in the Mn 1.35 Fe 0.65 P 0.48 Si 0.52 compound with a field change of 1.5 T. The compound quenched in water possesses a larger magnetic entropy change and a smaller thermal hysteresis than the non-quenched samples. The thermal hysteresis of the compound is less than 3.5 K. The maximum adiabatic temperature change is about 1.4 K in the Mn 1.35 Fe 0.65 P 0.45 Si 0.55 compound with a field change of 1.48 T. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

  14. Isopiestic Investigation of the Osmotic and Activity Coefficients of {yMgCl2 + (1 - y)MgSO4}(aq) and the Osmotic Coefficients of Na2SO4.MgSO4(aq) at 298.15 K

    Energy Technology Data Exchange (ETDEWEB)

    Miladinovic, J; Ninkovic, R; Todorovic, M; Rard, J A

    2007-06-06

    Isopiestic vapor pressure measurements were made for {l_brace}yMgCl{sub 2} + (1-y)MgSO{sub 4}{r_brace}(aq) solutions with MgCl{sub 2} ionic strength fractions of y = 0, 0.1997, 0.3989, 0.5992, 0.8008, and (1) at the temperature 298.15 K, using KCl(aq) as the reference standard. These measurements for the mixtures cover the ionic strength range I = 0.9794 to 9.4318 mol {center_dot} kg{sup -1}. In addition, isopiestic measurements were made with NaCl(aq) as reference standard for mixtures of {l_brace}xNa{sub 2}SO{sub 4} + (1-x)MgSO{sub 4}{r_brace}(aq) with the molality fraction x = 0.50000 that correspond to solutions of the evaporite mineral bloedite (astrakanite), Na{sub 2}Mg(SO{sub 4}){sub 2} {center_dot} 4H{sub 2}O(cr). The total molalities, m{sub T} = m(Na{sub 2}SO{sub 4}) + m(MgSO{sub 4}), range from m{sub T} = 1.4479 to 4.4312 mol {center_dot} kg{sup -1} (I = 5.0677 to 15.509 mol {center_dot} kg{sup -1}), where the uppermost concentration is the highest oversaturation molality that could be achieved by isothermal evaporation of the solvent at 298.15 K. The parameters of an extended ion-interaction (Pitzer) model for MgCl2(aq) at 298.15 K, which were required for an analysis of the {l_brace}yMgCl{sub 2} + (1-y)MgSO{sub 4}{r_brace}(aq) mixture results, were evaluated up to I = 12.025 mol {center_dot} kg{sup -1} from published isopiestic data together with the six new osmotic coefficients obtained in this study. Osmotic coefficients of {l_brace}yMgCl{sub 2} + (1-y)MgSO{sub 4}{r_brace}(aq) solutions from the present study, along with critically-assessed values from previous studies, were used to evaluate the mixing parameters of the extended ion-interaction model.

  15. Effects of crystallization on structural and dielectric properties of thin amorphous films of (1 - x)BaTiO3-xSrTiO3 (x=0-0.5, 1.0)

    Science.gov (United States)

    Kawano, H.; Morii, K.; Nakayama, Y.

    1993-05-01

    The possibilities for fabricating solid solutions of (Ba1-x,Srx)TiO3 (x≤0.5,1.0) by crystallization of amorphous films and for improving their dielectric properties by adjusting the Sr content were investigated. Thin amorphous films were prepared from powder targets consisting of mixtures of BaTiO3 and SrTiO3 by sputtering with a neutralized Ar-ion beam. The amorphous films crystallized into (Ba1-x, Srx)TiO3 solid solutions with a cubic perovskite-type structure after annealing in air at 923 K for more than 1 h. The Debye-type dielectric relaxation was observed for the amorphous films, whereas the crystallized films showed paraelectric behavior. The relative dielectric constants were of the order of 20 for the amorphous samples, but increased greatly after crystallization to about 60-200, depending on the composition; a larger increase in the dielectric constant was observed in the higher Sr content films, in the range x≤0.5, which could be correlated with an increase in the grain size of the crystallites. The crystallization processes responsible for the difference in the grain size are discussed based on the microstructural observations.

  16. Effects of artificial holes in very large single-grain Y_1_._5Ba_2Cu_3O_7_-_y bulk superconductors

    International Nuclear Information System (INIS)

    Park, S. D.; Jun, B. H.; Kim, C. J.; Park, H. W.

    2017-01-01

    The effects of artificial holes on the trapped magnetic fields and magnetic levitation forces of very large single-grain Y_1_._5Ba_2Cu_3O_7_-_y (Y1.5) bulk superconductors were studied. Artificial holes were made for Y1.5 powder compacts by die pressing using cylindrical dies with a diameter of 30 mm or 40 m, or rectangular dies with a side length of 50 mm. The single grain Y1.5 bulk superconductors (25 mm, 33 mm in diameter and 42 mm in side length) with artificial holes were fabricated using a top-seeded melt growth (TSMG) process for the die-pressed Y1.5 powder compacts. The magnetic levitation forces at 77 K of the 25 mm single grain Y1.5 samples with one (diameters of 4.2 mm) or six artificial holes (diameters of 2.5 mm) were 10-17% higher than that of the Y1.5 sample without artificial holes. The trapped magnetic fields at 77 K of the Y1.5 samples with artificial holes were also 9.6-18% higher than that of the Y1.5 sample without artificial holes. The 33 mm and 42 mm single grain Y1.5 samples with artificial holes (2.5 mm and 4.2 mm in diameter) also showed trapped magnetic fields 10-13% higher than that of the Y1.5 samples without artificial holes in spite of the reduced superconducting volume fraction due to the presence of artificial holes. The property enhancement in the large single grain Y1.5 bulk superconductors appears to be attributed to the formation of the pore-free regions near the artificial holes and the homogeneous oxygen distribution in the large Y123 grains

  17. Electric and magnetic properties of oxidic titanium bronzes of rare earths Lnsub(2/3+x)TiOsub(3+-y) with perovskite structure

    Energy Technology Data Exchange (ETDEWEB)

    Bazuev, G V; Makarova, O V; Shvejkin, G P [AN SSSR, Sverdlovsk. Inst. Khimii

    1983-01-01

    A study was made on electric and magnetic properties of oxidic titanium bronzes of rare earths and their dependence on rare earth nature and the degree of rare earth sublattice filling was followed. Data on Lnsub(2/3)TiOsub(3-y) (Ln-Ce, Nd) anion-deficient perovskites are given as well. Investigated Cesub(2/3)TiOsub(2.985) and Ndsub(2/3)TiOsub(2.875) phases as well as defectless with respect to oxygen Lnsub(2/3)TiOsub(3) phases have rhombic structure of perovskite type with ordered position of Ln/sup 3 +/ cations and vacancies. Specific electric resistance and thermoelectromotive force factor were determined in vacuum at 290-1173 K for samples in the form of parallelepiped of 3x5x25 mm/sup 3/ size. Magnetic susceptibility chi was determined at 77-300 K by Faraday method using a device based on magnetic balance with electromagnetic compensation. Relative error during chi measuring didn't exceed +-2%. Collectivized behaviour of d-electrons of Ti/sup 3 +/ cations in oxidic titanium bronzes of rare earths: Lnsub(2/3+x)TiOsub(3+-y) (Ln-La, Ce, Nd; 0 < x < 1/3), conditioned by formation of narrow, partly filled ..pi..*-zone, was established on the basis of measuring specific electric resistance and magnetic susceptibility.

  18. Strain-dependence of the structure and ferroic properties of epitaxial Ni1xTi1yO3 thin films grown on sapphire substrates

    International Nuclear Information System (INIS)

    Varga, Tamas; Droubay, Timothy C.; Bowden, Mark E.; Stephens, Sean A.; Manandhar, Sandeep; Shutthanandan, Vaithiyalingam; Colby, Robert J.; Hu, Dehong; Shelton, William A.; Chambers, Scott A.

    2015-01-01

    Polarization-induced weak ferromagnetism has been predicted a few years back in compounds MTiO 3 (M = Fe, Mn, Ni) (Fennie, 2008). We set out to stabilize this metastable, distorted perovskite structure by growing NiTiO 3 epitaxially on sapphire Al 2 O 3 (001) substrate, and to control the polar and magnetic properties via strain. Epitaxial Ni 1x Ti 1y O 3 films of different Ni/Ti ratios and thicknesses were deposited on Al 2 O 3 substrates by pulsed laser deposition at different temperatures, and characterized using several techniques. The effect of film thickness, deposition temperature, and film stoichiometry on lattice strain, film structure, and physical properties was investigated. Our structural data from x-ray diffraction, electron microscopy, and x-ray absorption spectroscopy shows that substrate-induced strain has a marked effect on the structure and crystalline quality of the films. Physical property measurements reveal a dependence of the Néel transition and lattice polarization on strain, and highlight our ability to control the ferroic properties in NiTiO 3 thin films by film stoichiometry and thickness. - Highlights: • NiTiO 3 epitaxial thin films with LiNbO 3 -type structure by pulsed laser deposition. • Strain varied by film thickness, stoichiometry, and synthesis temperature. • Systematic study of the effect of strain on film structure and physical properties. • Manipulation of ferroic properties by strain confirmed

  19. Plasminogen fragments K 1-3 and K 5 bind to different sites in fibrin fragment DD.

    Science.gov (United States)

    Grinenko, T V; Kapustianenko, L G; Yatsenko, T A; Yusova, O I; Rybachuk, V N

    2016-01-01

    Specific plasminogen-binding sites of fibrin molecule are located in Аα148-160 regions of C-terminal domains. Plasminogen interaction with these sites initiates the activation process of proenzyme and subsequent fibrin lysis. In this study we investigated the binding of plasminogen fragments K 1-3 and K 5 with fibrin fragment DD and their effect on Glu-plasminogen interaction with DD. It was shown that the level of Glu-plasminogen binding to fibrin fragment DD is decreased by 50-60% in the presence of K 1-3 and K 5. Fragments K 1-3 and K 5 have high affinity to fibrin fragment DD (Kd is 0.02 for K 1-3 and 0.054 μМ for K 5). K 5 interaction is independent and K 1-3 is partly dependent on C-terminal lysine residues. K 1-3 interacts with complex of fragment DD-immobilized K 5 as well as K 5 with complex of fragment DD-immobilized K 1-3. The plasminogen fragments do not displace each other from binding sites located in fibrin fragment DD, but can compete for the interaction. The results indicate that fibrin fragment DD contains different binding sites for plasminogen kringle fragments K 1-3 and K 5, which can be located close to each other. The role of amino acid residues of fibrin molecule Аα148-160 region in interaction with fragments K 1-3 and K 5 is discussed.

  20. Microscopic evidence for significant ionic disorder in the Yb sup 3 sup + -chain in Yb sub 4 (As sub 1 sub - sub x P sub x) sub 3 : sup 3 sup 1 P NMR studies

    CERN Document Server

    Tanida, H; Aoki, H; Ochiai, A

    2003-01-01

    We report unambiguous microscopic evidence from sup 3 sup 1 P NMR under H sub e sub x sub t approx = 7.3 T for significant ionic disorder in the Yb sup 3 sup + chain in Yb sub 4 (As sub 1 sub - sub x P sub x) sub 3 (x=0.05 and 0.40), which have similar characteristic chi(T) and C sub p (T, H sub e sub x sub t) behavior to the antiferromagnetic quantum spin chain (AFQSC) system Yb sub 4 As sub 3. Our conclusion is based on the observations only below the charge-ordering transition at T sub 0 approx = 292 K of clear structures in the spectrum, which can be fitted well by the superpositions of almost equally spaced five Gaussian components. Since perfect ordering of Yb sup 3 sup + in the chain sites would lead to a single-line spectrum also below T sub 0 , the structures should be ascribed to significant ionic disorder in the Yb sup 3 sup + chain and resulting distribution of local configurations of Yb sup 3 sup + in the eight nearest-neighboring Yb sites around sup 3 sup 1 P. Quantitative comparisons with a sim...

  1. Energy-band alignment of (HfO2)x(Al2O3)1-x gate dielectrics deposited by atomic layer deposition on β-Ga2O3 (-201)

    Science.gov (United States)

    Yuan, Lei; Zhang, Hongpeng; Jia, Renxu; Guo, Lixin; Zhang, Yimen; Zhang, Yuming

    2018-03-01

    Energy band alignments between series band of Al-rich high-k materials (HfO2)x(Al2O3)1-x and β-Ga2O3 are investigated using X-Ray Photoelectron Spectroscopy (XPS). The results exhibit sufficient conduction band offsets (1.42-1.53 eV) in (HfO2)x(Al2O3)1-x/β-Ga2O3. In addition, it is also obtained that the value of Eg, △Ec, and △Ev for (HfO2)x(Al2O3)1-x/β-Ga2O3 change linearly with x, which can be expressed by 6.98-1.27x, 1.65-0.56x, and 0.48-0.70x, respectively. The higher dielectric constant and higher effective breakdown electric field of (HfO2)x(Al2O3)1-x compared with Al2O3, coupled with sufficient barrier height and lower gate leakage makes it a potential dielectric for high voltage β-Ga2O3 power MOSFET, and also provokes interest in further investigation of HfAlO/β-Ga2O3 interface properties.

  2. The role of dysprosium on the structural and magnetic properties of (Nd_1_−_xDy_x)_2Fe_1_4B nanoparticles

    International Nuclear Information System (INIS)

    Rahimi, Hamed; Ghasemi, Ali; Mozaffarinia, Reza; Tavoosi, Majid

    2017-01-01

    In current work, Nd2Fe14B nanoparticles was synthesized by sol-gel method. Dysprosium powders were added into Nd2Fe14B nanoparticles by mechanical alloying process in order to enhancement of coercivity. The phase analysis, structure, and magnetic properties of annealed (Nd_1_−_xDy_x)_2Fe_1_4B nanoparticles with different Dy-content (x=0.1, 0.2, 0.3, 0.4, 0.5, 0.6) were investigated by employing X-ray diffraction, X-ray photoelectron spectroscopy, energy dispersive spectroscopy, field emission scanning electron microscope, transmission electron microscope and vibrating sample magnetometer techniques. The results showed that with an increase in Dy amounts, the coercivity of particles increased from 2.9 kOe to 13.4 kOe and then decreased to 5.6 kOe. By adding an optimum amount of Dy (x=0.4), the coercivity was significantly increased from 2.9 kOe to 13.4 kOe. The average particle size of annealed (Nd_1_−_xDy_x)_2Fe_1_4B nanoparticles was below 10 nm. Magnetization reversal studies indicate that the coercivity of milled and annealed (Nd_1_−_xDy_x)_2Fe_1_4B nanoparticles is controlled by the nucleation of reversed magnetic domains. The experimental results in the angular dependence of coercivity for (Nd_1_−_xDy_x)_2Fe_1_4B permanent magnets showed that the normalized coercivity of the permanent magnets H_c(θ)/H_c(0) increases from 1 to about 1.2–1.5 with increasing θ from 0 to about π/3, for x=0.4–0.6. - Highlights: • Dy was added to Nd_2Fe_1_4B nanoparticles to improve the coercivity. • A maximum squareness ratio of 0.99 was obtained. • The average particle size decreased with an increase in Dy-content.

  3. Compositional dependence of the band-gap of Ge{sub 1−x−y}Si{sub x}Sn{sub y} alloys

    Energy Technology Data Exchange (ETDEWEB)

    Wendav, Torsten, E-mail: wendav@physik.hu-berlin.de [AG Theoretische Optik & Photonik, Humboldt Universität zu Berlin, Newtonstr. 15, 12489 Berlin (Germany); Fischer, Inga A.; Oehme, Michael; Schulze, Jörg [Institut für Halbleitertechnik, Universität Stuttgart, Pfaffenwaldring 47, 70569 Stuttgart (Germany); Montanari, Michele; Zoellner, Marvin Hartwig; Klesse, Wolfgang [IHP, Im Technologiepark 25, 15236 Frankfurt (Oder) (Germany); Capellini, Giovanni [IHP, Im Technologiepark 25, 15236 Frankfurt (Oder) (Germany); Dipartimento di Scienze, Università Roma Tre, Viale Marconi 446, 00146 Roma (Italy); Driesch, Nils von den; Buca, Dan [Peter Grünberg Institute 9 (PGI 9) and JARA-Fundamentals of Future Information Technologies, Forschungszentrum Jülich, 52428 Jülich (Germany); Busch, Kurt [AG Theoretische Optik & Photonik, Humboldt Universität zu Berlin, Newtonstr. 15, 12489 Berlin (Germany); Max-Born-Institut, Max-Born-Str. 2 A, 12489 Berlin (Germany)

    2016-06-13

    The group-IV semiconductor alloy Ge{sub 1−x−y}Si{sub x}Sn{sub y} has recently attracted great interest due to its prospective potential for use in optoelectronics, electronics, and photovoltaics. Here, we investigate molecular beam epitaxy grown Ge{sub 1−x−y}Si{sub x}Sn{sub y} alloys lattice-matched to Ge with large Si and Sn concentrations of up to 42% and 10%, respectively. The samples were characterized in detail by Rutherford backscattering/channeling spectroscopy for composition and crystal quality, x-ray diffraction for strain determination, and photoluminescence spectroscopy for the assessment of band-gap energies. Moreover, the experimentally extracted material parameters were used to determine the SiSn bowing and to make predictions about the optical transition energy.

  4. Spatial structure determination of ({radical}3 x {radical}3)R30{degrees} and (1.5 x 1.5)R18{degrees}CO on Cu(111) using angle-resolved photoemission extended fine structure

    Energy Technology Data Exchange (ETDEWEB)

    Moler, E.J.; Kellar, S.A.; Huff, W.R.A. [Lawrence Berkeley National Lab., CA (United States)] [and others

    1997-04-01

    The authors report a study of the spatial structure of ({radical}3 x {radical}3)R30{degrees} (low coverage) and (1.5 x 1.5)R18{degrees} (intermediate coverage) CO adsorbed on Cu(111), using the Angle-Resolved Photoemission Extended Fine Structure (ARPEFS) technique at beamline 9.3.2 at the Advanced Light Source. The CO molecule adsorbs on an atop site for both adsorption phases. Full multiple-scattering spherical-wave (MSSW) calculations were used to extract the C-Cu. bond length and the first Cu-Cu layer spacing for each adsorption phase. The authors find that the C-Cu bond length remains unchanged with increasing coverage, but the 1st Cu-Cu layer spacing contracts at the intermediate coverage. They calculate the bending mode force constant in the (1.5 x 1.5)R18{degrees} phase to be K{sub {delta}} = 2.2 (1) x 10{sup {minus}12} dyne-cm/rad from their experimentally determined bond lengths combined with previously published infra-red absorption frequencies.

  5. A new magnet material with ThMn{sub 12} structure: (Nd{sub 1x}Zr{sub x})(Fe{sub 1y}Co{sub y}){sub 11+z}Ti{sub 1−z}N{sub α} (α=0.6–1.3)

    Energy Technology Data Exchange (ETDEWEB)

    Suzuki, S.; Kuno, T.; Urushibata, K. [Shizuoka Institute of Science and Technology, 2200-2 Toyosawa, Fukuroi, Shizuoka 437-8555 (Japan); Kobayashi, K., E-mail: koba@ms.sist.ac.jp [Shizuoka Institute of Science and Technology, 2200-2 Toyosawa, Fukuroi, Shizuoka 437-8555 (Japan); Sakuma, N.; Washio, K.; Yano, M.; Kato, A.; Manabe, A. [Toyota Mortor Corporation, 1 Toyota-cho, Toyota 471-8572, Aichi (Japan)

    2016-03-01

    We previously reported a new compound for permanent magnets, (Nd{sub 0.7}Zr{sub 0.3})(Fe{sub 0.75}Co{sub 0.25}){sub 11.5}Ti{sub 0.5}N{sub 0.56}, which has a high saturation polarization (J{sub s}) of 1.68 T and a high magnetocrystalline anisotropy field (H{sub a}) of 2.88–4.0 MA/m. Here, we examined the effects of substituting Co and Ti at the Fe sites and Zr at the Nd sites. J{sub s} increased with Co substitution at the Fe sites, and higher Fe and Co content could be achieved by decreasing the Ti content to −Ti{sub 0.5}. The ThMn{sub 12} structure with high Fe and Co content (i.e. low Ti content) was stabilized mainly by −Zr{sub 0.3} substitution at the Nd sites. The Zr substitution resolves the local mismatch in atomic size in the structure. Specifically, the atomic radius of Zr is about 88% that of Nd, so the local structure surrounding Nd (2a site) shrinks as a result of the substitution and resolves the size mismatch in the three types of local Fe six-fold symmetric hexagons in the structure. The effect of the α-(Fe, Co) phase on J{sub s} was evaluated from the phase's volume fraction measurement of 7.7% (8.1 wt%) by electron backscatter diffraction. Nitrogenation of the starting alloy also resulted in augmentation of the c-axis magnetocrystalline anisotropy. Finally, we confirmed a high J{sub s}(−N{sub 1.3}) of 1.71T (=1.67 T, −0.04 T for the α-(Fe, Co) phase) and H{sub a} of 2.9–5.25 MA/m (H{sub a}(−N{sub 1.3})=5.25 MA/m) in the (Nd{sub 0.7}Zr{sub 0.3})(Fe{sub 0.75}Co{sub 0.25}){sub 11.5}Ti{sub 0.5}N{sub α} (α=0.60–1.30) compounds. - Highlights: • We found a new compound of composition of (Nd,Zr)(Fe,Co){sub 11.5}Ti{sub 0.5}N{sub x} (x=0.6–1.3). • The compound shows high saturation polarization of 1.67T. • The Curie temperature of compound is above 840K, and anisotropy field is nearly 6.6 T. • The basic physical properties such as inner fields of each Fe site were measured. • The reasons of stabilization of 1–12

  6. A study on the redox, spectroscopic, and photophysical characteristics of a series of octahedral hexamolybdenum(ii) clusters: [{Mo6X8}Y6]2- (X, Y = Cl, Br, or I).

    Science.gov (United States)

    Akagi, Soichiro; Fujii, Sho; Kitamura, Noboru

    2018-01-23

    We report a systematic study on the redox, spectroscopic, and photophysical properties of a series of [{Mo 6 X 8 }Y 6 ] 2- (X, Y = Cl, Br, or I. 1-9). All of the [{Mo 6 X 8 }Y 6 ] 2- clusters show intense and long-lived phosphorescence in both CH 3 CN and crystalline phases at 298 K. We found that the emission quantum yields (Φ em ) of 1-9 increase in the sequences X = Cl Br Br Br < Cl for given {Mo 6 X 8 } 4+ -core clusters. The present data demonstrate that arbitrary combinations of X and Y in [{Mo 6 X 8 }Y 6 ] 2- could tune τ em and Φ em in the ranges of 85-300 μs and 0.09-0.47, respectively. Both capping (X) and terminal ligand (Y) effects on the photophysical properties of the clusters are discussed on the basis of the energy gap (i.e., emission energy) dependence of the nonradiative decay rate constant.

  7. Synthesis, characterization and property evaluation of Y substituted TbMnO3

    International Nuclear Information System (INIS)

    Shukla, Rakesh; Mandal, B.P.; Tyagi, A.K.; Chakraborty, Keka R.; Mukadam, M.D.; Yusuf, S.M.; Kaushik, S.D.; Siruguri, V.; Lawes, G.; Naik, R.; Akila, K.

    2013-01-01

    Tb 1-x Y x MnO 3 (x = 0.0 - 0.3) compounds were synthesized by gel-combustion method in stoichiometric ratio. Phase pure compounds were obtained in orthorhombic structure (space group Pnma). Specific heat measurements revealed anomalies in between at 2K and 50K. Variable temperature neutron diffraction measurements carried out on the x = 0.1 and x = 0.2 samples at 2 K showed short range ordering of Tb moments. For the samples x = 0.1 - 0.3, neutron diffraction data at 20K showed long range antiferromagnetic ordering of Mn moments with no mark of short ranged ordering of Tb moments at these temperatures. The samples showed pyroelectric alignment of electric dipole moments. Signatures of coupling between magnetic and electrical properties were revealed in this study. (author)

  8. Photoluminescence, modulation spectroscopy and surface photovoltage characterization of quaternary Zn1-x-yCdxMgySe compounds

    International Nuclear Information System (INIS)

    Dumcenco, D.O.; Levcenco, S.V.; Huang, Y.S.; Firszt, F.; Hsu, H.P.; Tiong, K.K.

    2011-01-01

    An optical characterization of wurtzite Zn 1-x-y Cd x Mg y Se crystalline alloys grown by the modified high-pressure Bridgman method has been carried out by temperature-dependent photoluminescence (PL) and contactless electroreflectance (CER) in the temperature range of 10-300 K, and photoreflectance (PR) measurements between 300-400 K as well as surface photovoltage spectroscopy (SPS) at 300 K. Low temperature PL spectra of the investigated samples consist of an excitonic line, the 'edge emission' due to radiative recombination of shallow donor-acceptor pairs and a broad band related to recombination through deep level defects. Three excitonic features, A, B and C, in the vicinity of band edge were observed in the CER and PR spectra. The peak positions of band-edge excitonic features in the PL spectra are shifted slightly towards lower energies as compared to the lowest corresponding transition energies of A exciton determined from CER and PR data. The increase of the CER-PL shift with the increasing of Mg content in the investigated crystals is explained by the rising of compositional disorder causing the smearing of the band-edge energies. In addition, the coincidence of energy positions of features obtained from SPS measurements with excitonic transition energies E 0 A determined from CER/PR data at 300 K confirm the proper surface treatment of the samples. (authors)

  9. Giant strain with low cycling degradation in Ta-doped [Bi_1_/_2(Na_0_._8K_0_._2)_1_/_2]TiO_3 lead-free ceramics

    International Nuclear Information System (INIS)

    Liu, Xiaoming; Tan, Xiaoli

    2016-01-01

    Non-textured polycrystalline [Bi_1_/_2(Na_0_._8K_0_._2)_1_/_2](Ti_1_−_xTa_x)O_3 ceramics are fabricated and their microstructures and electrical properties are characterized. Transmission electron microscopy reveals the coexistence of the rhombohedral R3c and tetragonal P4bm phases in the form of nanometer-sized domains in [Bi_1_/_2(Na_0_._8K_0_._2)_1_/_2]TiO_3 with low Ta concentration. When the composition is x = 0.015, the electrostrain is found to be highly asymmetric under bipolar fields of ±50 kV/cm. A very large value of 0.62% is observed in this ceramic, corresponding to a large-signal piezoelectric coefficient d_3_3* of 1240 pm/V (1120 pm/V under unipolar loading). These values are greater than most previously reported lead-free polycrystalline ceramics and can even be compared with some lead-free piezoelectric single crystals. Additionally, this ceramic displays low cycling degradation; its electrostrain remains above 0.55% even after undergoing 10 000 cycles of ±50 kV/cm bipolar fields at 2 Hz. Therefore, Ta-doped [Bi_1_/_2(Na_0_._8K_0_._2)_1_/_2]TiO_3 ceramics show great potential for large displacement devices.

  10. Presenilin-1 mutations alter K+ currents in the human neuroblastoma cell line, SH-SY5Y

    DEFF Research Database (Denmark)

    Plant, Leigh D; Boyle, John P; Thomas, Natasha M

    2002-01-01

    Mutations in presenilin 1 (PS1) are the major cause of autosomal dominant Alzheimer's disease. We have measured the voltage-gated K+ current in the human neuroblastoma cell line SH-SY5Y using whole-cell patch-clamp. When cells were stably transfected to over-express PS1, no change in K+ current...

  11. Synthesis and magnetic properties of PrFe11V1-xTix and their nitrides

    International Nuclear Information System (INIS)

    Tang, S.L.; Wang, B.W.; Zhang, C.; Jin, X.M.; Zhang, S.Y.; Du, Y.W.

    1997-01-01

    We have succeeded in synthesizing PrFe 11 V 1-x Ti x (x=0.2 1) compound and their nitrides with the ThMn 12 -type structure. The phase formation and magnetic properties have been investigated by x-ray diffraction, differential thermometric analysis, and magnetic measurement. The stable temperature range of the 1-12 phase for PrFe 11 V 1-x Ti x alloys has been determined as a function of Ti content. PrFe 11 V compounds with the ThMn 12 -type structure do not exist and PrFe 11 Ti compounds with the TnMn 12 -type structure are obtained by annealing in a narrow temperature range between 1303 and 1383 K. Furthermore, 1-12 phase with the ThMn 12 -type structure can be obtained at lower temperature and wider temperature range with decreasing Ti content x (0.2≤x≤1). PrFe 11 V 1-x Ti x N y with x=0.2 1 has a T c of about 730 785 K, B a larger than 8 T and M s in the range 144 148 emu/g. These intrinsic magnetic properties are highly favorable for permanent magnet applications. As a preliminary, an intrinsic coercivity of 5.4 kOe is obtained for PrFe 11 V 0.5 Ti 0.5 N y at room temperature by using mechanical alloying technique. copyright 1997 American Institute of Physics

  12. Electron microscopy and diffraction of barium-lanthanum ferrites: Ba/sub x/La/sub 1-x/FeO/sub 3-y/

    Energy Technology Data Exchange (ETDEWEB)

    Parras, M.; Vallet-Regi, M.; Gonzalez-Calbet, J.M.; Alario-Franco, M.; Grenier, J.C.

    1988-05-01

    The system formed by Ba/sub 2/Fe/sub 2/O/sub 5/ and LaFeO/sub 3/ has been studied at the microstructural level. Four different phases, which are metrical multiples of the perovskite cubic cell, appear as a function of the Ba/La ratio. Their microstructure ranges from three-dimensional multitwinning, as in LaFeO/sub 3/, to an apparently stoichiometric line phase of Ba/sub 2/Fe/sub 2/O/sub 5/ composition with parameters a = 23.40(1) A, b = 11.71(1) A, c = 7.05(1) A, and ..beta.. = 98/sup 0/3(1)'. For 0 < x < 0.25, cubic regions appear within a LaFeO/sub 3/ matrix. When x = 0.33, a double perovskite cell is intergrown with a single one. Such a single cubic perovskite is the only phase obtained in the 0.33 < x < 0.66 range.

  13. Theoretical study on guided wave propagation in (1 - x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 (x = 0.29 and 0.33) single crystal plates

    International Nuclear Information System (INIS)

    Chen Chuanwen; Zhang Rui; Cao Wenwu

    2009-01-01

    The propagation of guided waves in free standing (1 - x)Pb(Mg 1/3 Nb 2/3 )O 3 -xPbTiO 3 [PMN-xPT] (x = 0.29 or 0.33) single crystal plates has been studied theoretically. The polar directions are in the (111) family directions of the cubic reference coordinates but the crystals are being polarized along [0 0 1] c , [0 1 1] c and [1 1 1] c of the cubic reference directions so that the effective microscopic symmetries are 4mm, mm2 and 3m, respectively. Multiple mode couplings appear in the dispersion curves for both the symmetric and the antisymmetric Lamb and shear horizontal modes. The velocities of most guided waves decrease rapidly with frequency. Then, after passing a minimum, they begin to increase with frequency and eventually saturate to the shear wave velocity v sz (or v 1 = 3507 m s -1 for [1 1 1] c polarized sample). For a [1 1 1] c polarized single domain PMN-0.33PT sample, the S 1 mode instead of the S 0 mode approaches the Rayleigh velocity v R at high frequencies.

  14. Crystal structure and magnetic properties of Y{sub 2}(Cu{sub 1x}Mg{sub x}){sub 2}O{sub 5} obtained by SHS method

    Energy Technology Data Exchange (ETDEWEB)

    Gebrel, Z., E-mail: z_gebrel@yahoo.com; Blanusa, J.; Kusigerski, V.; Spasojevic, V.; Mrakovic, A.; Perovic, M.; Alqat, A.

    2014-01-05

    Highlights: • Y{sub 2}(Cu{sub 1x}Mg{sub x}){sub 2}O{sub 5} solid solutions were synthesized for the first time by SHS method. • Ferromagnetic interactions are weakened by the induced structure changes. • Metamagnetism of the Y{sub 2}Cu{sub 2}O{sub 5} is preserved up to 15% of Mg concentration. • Significant influence of finite-size Cu–O chains is observed at low temperatures. -- Abstract: The single-phase polycrystalline samples of Y{sub 2}(Cu{sub 1x}Mg{sub x}){sub 2}O{sub 5}, x = 0.0, 0.05, 0.15 were successfully synthesized by a modified self-propagating high temperature synthesis. Effects of Mg{sup +2} substitution for Cu{sup +2} in metamagnetic Y{sub 2}Cu{sub 2}O{sub 5} on its crystal structure and magnetic properties have been analyzed by X-ray diffraction and magnetic measurements performed within 2–300 K range. Mg doping was found to introduce small distortions in the main intradimmer superexchange paths so that ferromagnetic correlations decrease with Mg concentration. More significant impact of Cu substitution was found on the low temperature magnetism due to the breaking of infinite Cu–O chains. The formation of finite size chains introduces low temperature paramagnetic contribution and reduction in Néel temperature. Overall results give a strong indication that the antiferromagnetic ordering as well as metamagnetism persists up to the 15% of the Mg concentration.

  15. On the Composition and Neutrix Composition of the Delta Function and the Function cosh^{-1}(|x|^{1/r}+1

    Directory of Open Access Journals (Sweden)

    Brian Fisher

    2017-03-01

    Full Text Available Let $F$ be a distribution in $\\mathcal{D'}$ and let $f$ be a locally summable function. The composition $F(f(x$ of $F$ and $f$ is said to exist and be equal to the distribution $h(x$ if the limit of the sequence $\\{ F_{n}(f(x\\}$ is equal to $h(x$, where $F_n(x =F(x*\\delta _n(x$ for $n=1,2, \\ldots$ and $\\{\\delta_n(x\\}$ is a certain regular sequence converging to the Dirac delta function. It is proved that the neutrix composition $ \\delta^{(s}[\\cosh^{-1} (x_+^{1/r}+1] $ exists and \\beqa \\delta^{(s}[\\cosh^{-1} (x_+^{1/r}+1] = - \\sum _{k=0} ^{M-1} \\sum_{i=0}^{kr+r} {k \\choose i}{(-1^{i+k}rc_{r,s,k} \\over (kr+rk!}\\delta ^{(k}(x, for $s =M-1,M, M+1,\\ldots$ and $r=1,2,\\ldots,$ where $$c_{r,s,k}=\\sum _{j=0}^{i} {i \\choose j}{ (-1^{kr+r-i}(2j-i^{s+1}\\over 2^{s+i+1} },$$ $M$ is the smallest integer for which $s-2r+1 < 2Mr$ and $r\\le s/(2M+2.$ Further results are also proved.

  16. Structural and conductivity study of the proton conductor BaCe(0.9−x)ZrxY0.1O(3−δ) at intermediate temperatures

    DEFF Research Database (Denmark)

    Ricote, Sandrine; Bonanos, Nikolaos; Marco de Lucas, M.C.

    2009-01-01

    The perovskite BaCe(0.9−x)ZrxY0.1O(3−δ) is prepared by solid-state reaction at 1400 °C and sintering at 1700 °C. It is characterised using X-ray diffraction, Raman spectroscopy and electrical measurements. A distortion from the cubic structure at room temperature is noticeable in the Raman spectr...

  17. Studies on electrical conduction behavior of La1-3xCaxBaxSrxMnO3 synthesized by chemical route

    International Nuclear Information System (INIS)

    Rai, A.K.; Parkash, O.; Mandal, K.D.

    2008-01-01

    In the manganite La 1-x M x MnO 3 (M=Ca,Ba,Sr) the doping concentration introduces a mixed valency (Mn 3+ , Mn 4+ ) which governs the magnetic and electrical properties of the compound. The perovskite oxides La 1-3x Ca x Ba x Sr x MnO 3 (x=0.00,0.05,0.10) were prepared by chemical method. Single-phase formation is confirmed by XRD studies. The electrical behavior of compositions with x=0.00, 0.05 and 0.10 in the system La 1-3x Ca x Ba x Sr x MnO 3 was studied in the temperature range 300-420 K. It is observed that conductivity decreases with increasing temperature as well as dopants concentration. Metallic behavior of these compositions decreases with increasing dopants concentration (x). The microstructures of these samples have been characterized using scanning electron microscopy (SEM). (copyright 2007 WILEY -VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  18. Spectroscopic properties of Er3+/Yb3+ Co-doped zinc boro-tellurite glasses for 1.5 xB5m broadband optical amplifiers

    Science.gov (United States)

    Suthanthirakumar, P.; Karthikeyan, P.; Vijayakumar, R.; Marimuthu, K.

    2015-06-01

    A new series of Er3+/Yb3+ co-doped Zinc boro-tellurite glasses with the chemical composition (40-x-y)B2O3+ 25TeO2+20ZnO+15BaO+xYb2O3+yEr2O3 (where x = 0.1, 0.5, 1 and 3; y =1 in wt %) were prepared by melt quenching technique and their spectroscopic behavior were studied through UV-Vis-NIR absorption and NIR luminescence measurements. The bonding parameters (β ¯ and δ) and Judd-Ofelt (JO) intensity parameters Ωλ (λ=2, 4 and 6) have been calculated from the band positions of the absorption spectra. A broad near-infrared emission band at 1540 nm with a full width at half maximum around 80 nm was observed from the NIR luminescence spectra by monitoring an excitation at 980 nm. The absorption cross-section and emission cross-section for the4I13/2→4I15/2 transition of the Er3+ ions were also determined using McCumber theory and the results were discussed and reported.

  19. $X_{b}$ Search and Measurement of the $Y(1)$, $(2S)$ and $Y(3S)$ Polarization

    Energy Technology Data Exchange (ETDEWEB)

    Marino, Claudia [Karlsruhe Inst. of Technology (KIT) (Germany)

    2009-10-30

    There are two studies presented in this analysis. The rst one is the measurement of the Υ(1S), Υ(2S) and Υ(3S) polarization in two orthogonal frames: the helicity and the Collins-Soper frame. The second is the search for a possible bottom counterpart of the X(3872) which would show up as a narrow resonance in the Υ(1S)π+ π- nal state.

  20. Electrical conductivity studies in (Ag3AsS3)x(As2S3)1-x superionic glasses and composites

    Science.gov (United States)

    Studenyak, I. P.; Neimet, Yu. Yu.; Kranjčec, M.; Solomon, A. M.; Orliukas, A. F.; Kežionis, A.; Kazakevičius, E.; Šalkus, T.

    2014-01-01

    Compositional, frequency, and temperature studies of impedance and electrical conductivity in (Ag3AsS3)x(As2S3)1-x superionic glasses and composites were performed. Frequency range from 10 Hz to 3 × 109 Hz and temperature interval 300-400 K were used for the measurements. Compositional dependences of electrical conductivity and activation energy are analyzed; the most substantial changes are observed with the transition from (Ag3AsS3)0.4(As2S3)0.6 glass to (Ag3AsS3)0.5(As2S3)0.5 composite. With increase of Ag3AsS3 content, the investigated materials are found to have crystalline inclusions and show the two-phase composite nature. Addition of Ag3AsS3 leads to the increase of electrical conductivity whereas the activation energy decreases.