Tellurium sulfates from reactions in oleum and sulfur trioxide: syntheses and crystal structures of TeO(SO{sub 4}), Te{sub 4}O{sub 3}(SO{sub 4}){sub 5}, and Te(S{sub 2}O{sub 7}){sub 2}

Energy Technology Data Exchange (ETDEWEB)

Logemann, Christian; Bruns, Joern; Schindler, Lisa Verena; Zimmermann, Vanessa; Wickleder, Mathias S. [Carl von Ossietzky University of Oldenburg, Institute of Chemistry (Germany)

2015-04-15

The reaction of K{sub 2}TeO{sub 4} with fuming sulfuric acid (65 % SO{sub 3}) in sealed glass ampoules at 250 C led to colorless single crystals of TeO(SO{sub 4}) [triclinic, P anti 1, Z = 8, a = 819.89(3) pm, b = 836.95(4) pm, c = 1179.12(5) pm, α = 82.820(2) , β = 70.645(2) , γ = 81.897(2) , V = 753.11(6) x 10{sup 6} pm{sup 3}]. A horseshoe type [Te{sub 4}O{sub 3}] fragment is the basic motif in the layer structure of the compound. The [Te{sub 4}O{sub 3}] moieties are linked to infinite chains by further oxide ions. Monomeric [Te{sub 4}O{sub 3}] horseshoes are found in the crystal structure of Te{sub 4}O{sub 3}(SO{sub 4}){sub 5} [trigonal, P3{sub 2}21, Z = 3, a = 859.05(2) pm, c = 2230.66(7) pm, V = 1425.61(6) x 10{sup 6} pm{sup 3}], which was obtained from TeO{sub 2} and fuming sulfuric acid (65 % SO{sub 3}) at 200 C as colorless single crystals. By switching to neat SO{sub 3} as reaction medium colorless crystals of Te(S{sub 2}O{sub 7}){sub 2} [P2{sub 1}/n, Z = 4, a = 1065.25(3) pm, b = 818.50(2) pm, c = 1206.27(3) pm, β = 102.097(1) , V = 1028.40(5) x 10{sup 6} pm{sup 3}] form when ortho-telluric acid, H{sub 6}TeO{sub 6}, is used as the tellurium source. The compound was reported previously, however, obviously with a wrong crystallographic description. In the crystal structure the tellurium atoms are coordinated by two chelating disulfate ions. Further Te-O contacts link the [Te(S{sub 2}O{sub 7}){sub 2}] units to an extended network. (Copyright copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Propriedades estruturais e térmicas de vidros teluretos 20Li2O-80TeO2 Structural and thermal properties of tellurite 20Li2O-80TeO2 glasses

Directory of Open Access Journals (Sweden)

E. Idalgo

2007-09-01

Full Text Available O presente trabalho reporta estudos sobre a cristalização em vidros teluretos 20Li2O-80TeO2 induzida a partir de tratamentos térmicos realizados sobre vidros com tamanho de partículas entre 38 µm e 75 µm. Estes estudos foram conduzidos em duas matrizes vítreas tratadas e não tratadas termicamente para aliviar as tensões após o quenching, utilizando-se de forma combinada às técnicas de difração de raios X, calorimetria diferencial de varredura e espectroscopia no infravermelho. Os resultados revelaram a presença de três fases cristalinas distintas durante o processo de cristalização e apontaram para uma hierarquia tal que as fases alfa-TeO2 e gama-TeO2 cristalizam-se antecipadamente à fase Li2Te2O5 no vidro 20Li2O-80TeO2 sujeito a tensões mecânicas induzidas durante a síntese. No vidro 20Li2O-80TeO2, livre de tensões mecânicas, não foi possível discriminar esta hierarquia de cristalização.This work report crystallization studies on tellurite 20Li2O-80TeO2 glasses induced from heat thermal annealing on glasses with particle size between 38 µm and 75 µm. These studies were conducted on two glass matrix heat thermal annealed and non-annealed to remove the stress after the quenching, by using the X-Ray diffraction analysis, Fourier transform infrared spectroscopy and differential scanning calorimetry techniques. The results shown the presence of three distinct crystalline alpha-TeO2, gamma-TeO2 and Li2Te2O5 phases during the crystallization process, suggesting a crystallization hierarchy on the glass matrix under stress, since the gamma-TeO2 and alpha-TeO2 phases crystallization occurs before the Li2Te2O5 phase. On the glass stress free, this crystallization hierarchy was not clearly determined.

e -ech-o / -ech-a na fala de Castrelo do Val

Directory of Open Access Journals (Sweden)

Aquilino Santiago Alonso Núñez

2017-01-01

Full Text Available This paper focuses on the uses of the Galician diminutive nominal suffixes -et-e / -et-a, -uc-o / -uc-a e -ech-o / -ech-a in the Castrelo do Val (Ourense, Spain dialect variety, while also surveying aspects of their use in other Galician dialects, including their occurrence in toponyms and some medieval corpora, and also in Portuguese and Spanish. This information is contrasted with data obtained from our participant observation of a particular variety of Galician while also supplying a historical perspective. The study uses a dynamic approach to word formation taking into account both words in actual use and the possibility of forming new words by means of the same suffixes. This analysis shows that the diminutive suffix -et-e is used as in the most widespread variety of Galician, whereas -uc- only has residual uses; use of -ech- is more restricted in the variety studied than in common Galician.

The EChO science case

DEFF Research Database (Denmark)

Tinetti, Giovanna; Drossart, Pierre; Eccleston, Paul

2015-01-01

in the Solar System. Observations to date have shown that our Solar System is certainly not representative of the general population of planets in our Milky Way. The key science questions that urgently need addressing are therefore: What are exoplanets made of? Why are planets as they are? How do planetary....... The mission can target super-Earths, Neptune-like, and Jupiter-like planets, in the very hot to temperate zones (planet temperatures of 300–3000 K) of F to M-type host stars. The EChO core science would be delivered by a three-tier survey. The EChO Chemical Census: This is a broad survey of a few...

Raman, FTIR, thermal and optical properties of TeO2-Nb2O5-B2O3-V2O5 quaternary glass system

Directory of Open Access Journals (Sweden)

Swapna

2017-07-01

Full Text Available A series of quaternary glass systems with the composition 79TeO2-(20−xNb2O5-xB2O3-1V2O5 was prepared using the melt quench technique. Such studies as optical absorption, Raman, FTIR spectroscopy, EPR and DSC were carried out on the glass system. The physical properties, such as density (ρ and molar volume (VM, were determined. The Urbach energy (ΔE, optical band gap (Eopt, optical basicity (Λ, refractive index (n and electron polarizability (α of the glasses were determined from optical absorption data. Spin-Hamiltonian parameters of VO2+ ions were calculated from the EPR data. With the gradual substitution of B2O3 at the expense of Nb2O5, the density and optical band gap of the glasses decreased, and the electronic polarizability increased. EPR spectra revealed that VO2+ occupies an octahedral site with tetrahedral compression. Spin-Hamiltonian parameters g|| and g⊥ increased as B2O3 content increased in the glass. The glass transition temperature (Tg also decreased as the B2O3 content in the glass increased.

Structure, glass transition temperature and spectroscopic properties of 10Li2O-xP2O5-(89-x)TeO2-1CuO (5≤x≤25 mol%) glass system.

Science.gov (United States)

Upender, G; Babu, J Chinna; Mouli, V Chandra

2012-04-01

X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), energy dispersive X-ray spectrometry (EDS), differential scanning calorimetry (DSC), infrared (IR), Raman, electron paramagnetic resonance (EPR) and optical absorption studies on 10Li2O-xP2O5-(89-x)TeO2-1CuO glasses (where x=5, 10, 15, 20 and 25 mol%) have been carried out. The amorphous nature of the glasses was confirmed using XRD and FESEM measurements. The glass transition temperature (Tg) of glass samples have been estimated from DSC traces and found that the Tg increases with increasing P2O5 content. Both the IR and Raman studies have been showed that the present glass system consists of [TeO3], [TeO4], [PO3] and [PO4] units. The spin-Hamiltonian parameters such as g∥, g⊥, and A∥ have been determined from EPR spectra and it was found that the Cu2+ ion is present in tetragonal distorted octahedral site with [Formula: see text] as the ground state. Bonding parameters and bonding symmetry of Cu2+ ions have been calculated by correlating EPR and optical data and were found to be composition dependent. Copyright © 2012 Elsevier B.V. All rights reserved.

Electrical properties of V205-ZnO-TeO2 glasses. V205-ZnO-TeO2 kei garasu no denki dendo

Energy Technology Data Exchange (ETDEWEB)

Mori, H; Igarashi, J; Sakata, H [Tokai Univ., Tokyo (Japan). Faculty of Engineering

1993-12-01

It is known that glasses contained Transition Metal Oxide (TMO) such as V2O5 show a semi-conductivity, those conductive mechanism has been understood according to the Small Polaron Hopping (SPH) theory developed by Mott and Austin. Authors investigated the glass formation regions, de-conductivity([sigma]) and the conductive mechanism for V2O5-Bi2O3-TeO2 glasses as a tellurite glass containing the TMO. It was clarified that the adiabatic SPH and the non-adiabatic SPH are satisfied for the glasses with V2O5>50 mol% and V2O5<50 mol%, respectively. In this study, the electrical properties of V2O5-ZnO-TeO2 glasses were investigated, and the SPH conductions were considered from the standpoints of the polaron band width J, carrier mobility [mu], carrier density Nc. The conductive mechanism and dependence of V2O5 density on Seebeck coefficients Q were clarified in which a formation region of V2O5 is from 30 to 60 mol%. 40 refs., 9 figs., 2 tabs.

Structure of glasses of the TeO2-MoO3 system

International Nuclear Information System (INIS)

Dimitriev, Y.; Dimitrov, V.; Bart, J.C.J.

1981-01-01

Structural models for glasses of the TeO 2 -MoO 3 system are suggested. On the basis of X-ray and infrared spectral investigations, by comparing with known crystalline structures of TeO 2 , MoO 3 and Te 2 MoO 7 9t 2 M, it is shown that the glasses from TeO 2 to Te 2 MoO 7 possess [TeO 4 ] and [MoO 5 ] groups as basic structural units. The latter are connected to form [Mo 2 O 8 ] complexes. The glasses in the MoO 3 -rich compositional range are built up of [TeO 3 ] and [MoO 6 ] polyhedra. The glass-formation tendency is discussed in relation to the role of the free electron pair and the disruption of secondary and weak primary bonds in the crystals. (author)

Low-temperature sintering and microwave dielectric properties of Al2TeO6–TeO2 ceramics

International Nuclear Information System (INIS)

Kagomiya, Isao; Kodama, Yuichiro; Shimizu, Yukihiro; Kakimoto, Ken-ichi; Ohsato, Hitoshi; Miyauchi, Yasuharu

2015-01-01

Highlights: • This is the first study of dielectric properties of Al 2 TeO 6 –TeO 2 sintered at 900 °C. • The sintering at 900 °C contributed to densification, but it causes TeO 2 evaporation. • The annealing at 750 °C was effective for the further densification. • The both ε r and Q · f in the Al 2 TeO 6 –TeO 2 were improved with the annealing. - Abstract: We propose Al 2 TeO 6 –TeO 2 ceramics as a candidate for use as low-temperature co-fired ceramics (LTCC). We investigated microwave dielectric properties and low-temperature sintering conditions for Al 2 TeO 6 –TeO 2 ceramics. The calcined Al 2 TeO 6 powders were sintered at 900 °C for 2–10 h with 30–50 wt% additive TeO 2 . X-ray powder diffraction patterns showed that the sintered samples were Al 2 TeO 6 –TeO 2 composite with no other phase. The apparent density was improved with the additive TeO 2 content of up to 45 wt%. The dielectric constant (ε r ) increased by adding TeO 2 content from 35 to 45 wt%, although the quality factor (Q · f) decreased. During sintering at 900 °C, the ε r of the Al 2 TeO 6 –TeO 2 decreased slightly, whereas the Q · f increased gradually. The observed microstructures showed that the longer sintering time makes fewer pores in Al 2 TeO 6 –TeO 2 ceramics. Sintering at 900 °C for a long time contributes to densification, but it simultaneously causes TeO 2 evaporation. To prevent TeO 2 evaporation, we investigated the effects of annealing at 750 °C after sintering at 900 °C. Apparent densities or ε r for the annealed samples were higher than those of the non-annealed samples. The Q · f improved with increasing annealing duration time, suggesting that sintering proceeded well during annealing with slower TeO 2 evaporation at 750 °C. The results show that annealing at 750 °C is effective to facilitate sintering and to control TeO 2 evaporation

Electronic conductivity in glasses of the TeO sub 2 -V sub 2 O sub 5 -MoO sub 3 system

Energy Technology Data Exchange (ETDEWEB)

Lebrun, N.; Levy, M; Souquet, J.L. (URA D1213-E.N.S.E.E.G., Saint Martin d' Heres (France). Laboratoire d' Ionique et d' Electrochimie du Solide)

1990-08-01

Conductivity and redox potential on glasses of the TeO{sub 2}-V{sub 2}O{sub 5}-MoO{sub 3} system have been measured. For temperatures between 20 to 200 pC, the electronic conductivity proceed by an activated mechanism. Variations of the pre-exponential factor interpreted by the small polaron theory indicate that only the vanadium ions are involved in the conduction mechanism. Cyclic voltamperometry measurements performed on TeO{sub 2}V{sub 2}O{sub 4}-MoO{sub 3} glasses as working electrode show that at 1 V difference between the V{sup +V}/V{sup +IV} and Mo{sup +I}/Mo{sup +V} redox potentials exists in the glassy material. This correspondend to an energy gap which may be to large to allow the electron transition from vanadium to molybdenum ions. (author). 13 refs.; 4 figs.; 1 tab.

Study of the tellurite-rich composition range in the Bi2O3-TeO2 system

International Nuclear Information System (INIS)

Ghazaryan, A.A.

2015-01-01

The TeO 2 and Bi 2 O 3 based glasses and glass ceramics are widely used for various technical needs. However, information about the phase diagram of the Bi 2 O 3 -TeO 2 system is limited, and the existing data are inconsistent. According to Demina L.A. with co-authors the Bi 2 Te 4 O 1 1 compound has a congruent melting at 662°C and forms two eutectics with neighbors. In another case, according to the Schmidt P. with co-authors, it melts incongruently at 645°C without indication of Liquidus temperature. It was the motivation for the Bi 2 Te 4 O 1 1 melting behavior investigation and the binary Bi 2 O 3 -TeO 2 system phase diagram correction in the TeO 2 rich area of compositions. As initial materials the glass and solid state sintered samples were used for these purposes. The differential thermal and X-ray analyses were used for glassy and crystallized products identification. The exothermic effect with maximum at 420°C and two endothermal effects with minimum at 635°C and 720 Degree C are clearly observed on the DTA curve of the 80 TeO 2 -20 Bi 2 O 3 (mol.percent) glass composition corresponding to the Bi 2 Te 4 O 1 1 compound. The product of Bi 2 Te 4 O 1 1 glass powder crystallization at 420°C is the Bi 2 Te 4 O 1 1 compound with melting point of 635 ± 5°C. The second endothermic effect on the DTA curve in the range of temperature 680-765°C with minimum at 720°C, is associated with dissolution of TeO 2 in the melt, formed as result of the Bi 2 Te 4 O 1 1 incongruent melting. The existence of eutectic E 1 (87 mol.percent TeO 2 ) between Bi 2 Te 4 O 1 1 and TeO 2 with a melting point of 580 ±5°C has been confirmed. Incongruent melting promotes the peritectic P 1 (81 mol.percent TeO 2 ) formation between Bi 2 Te 4 O 1 1 and eutectic E 1 (87 mol.percent TeO 2 ) with a melting point of 635±5°C. Three endothermic effects at 560 °C, 635 °C and 720°C have been observed on the DTA curve of Bi 2 Te 4 O 1 1 compound, obtained by solid state synthesis. Last

Electrical conduction of glasses in the system Fe2O3-Sb2O3-TeO2; Fe2O3-Sb2O3-TeO2 kei garasu no denki dendo

Energy Technology Data Exchange (ETDEWEB)

Qiu, Honghua; Mori, H; Sakata, H; Hirayama, T [Tokai Univ., Tokyo (Japan). Faculty of Engineering

1995-01-01

In this study, taking into consideration that TeO2 is a component of the glass network and Sb2O3 shows the redox effect in the glasses reducing its possibility of transformation of Sb{sup 3+} to Sb{sup 5+} as well as glass basicity, highly conductive tellurite based glasses have been prepared by the press-quenching method selecting the Fe2O3-Sb2O3-TeO2 system, and the electroconductive mechanism of the glasses has been examined by measuring its D.C. conductivity {sigma}. Part of the obtained information is as follows; the glass formation range of the Fe2O3-Sb2O3-TeO2 system has been 0 {le} Fe2O3 {le} 15mol%, 0 {le} Sb2O3 {le} 18mol% and 78 {le} TeO2 {le} 100mol% and about 15mol% of the additional amount of Fe2O3 has been the limit of glass formation. As the amount of Fe2O3 has increased, C{sub Fe} has also increased and with this, the linear electroconductivity of the glasses has increased from 1.86 {times} 10{sup -7}S{center_dot}cm{sup -1} to 1.62 {times} 10{sup -6}S{center_dot}cm{sup -1} and the glasses have been confirmed as the n-type semiconductor. The factor determining {sigma} of the glasses has been C{sub Fe} which has increased as the amount of Fe2O3 has increased. 34 refs., 8 figs., 2 tabs.

Shielding properties of 80TeO2–5TiO2–(15−x) WO3–xAnOm glasses using WinXCom and MCNP5 code

International Nuclear Information System (INIS)

Dong, M.G.; El-Mallawany, R.; Sayyed, M.I.; Tekin, H.O.

2017-01-01

Gamma ray shielding properties of 80TeO 2 –5TiO 2 –(15−x) WO 3 –xA n O m glasses, where A n O m is Nb 2 O 5 = 0.01, 5, Nd 2 O 3 = 3, 5 and Er 2 O 3 = 5 mol% have been achieved. Shielding parameters; mass attenuation coefficients, half value layers, and macroscopic effective removal cross section for fast neutrons have been computed by using WinXCom program and MCNP5 Monte Carlo code. In addition, by using Geometric Progression method (G-P), exposure buildup factor values were also calculated. Variations of shielding parameters are discussed for the effect of REO addition into the glasses and photon energy. - Highlights: • The shielding properties of 80TeO 2 –5TiO 2 –(15−x) WO 3 –xA n O m glasses were evaluated. • WinXCom program and MCNP simulation codes were used in the calculations. • Good agreement was noticed between the WinXCom and MCNP5 code results.

A new oxytelluride: Perovskite and CsCl intergrowth in Ba{sub 3}Yb{sub 2}O{sub 5}Te

Energy Technology Data Exchange (ETDEWEB)

Whalen, J.B., E-mail: icatchsnook@yahoo.com [The National High Magnetic Field Laboratory, Condensed Matter Science Department, 1800 E. Paul Dirac Drive, Tallahassee, FL 32310 (United States); Specialized Crystal Processing, Inc., 400 Capital Circle SE, Suite 18227, Tallahassee, FL 32301-3839 (United States); Besara, T. [The National High Magnetic Field Laboratory, Condensed Matter Science Department, 1800 E. Paul Dirac Drive, Tallahassee, FL 32310 (United States); The Florida Agricultural and Mechanical University-The Florida State University (FAMU-FSU) College of Engineering, Department of Chemical and Biomedical Engineering, 2525 Pottsdamer Street, Tallahassee, FL 32310-6046 (United States); Vasquez, R.; Herrera, F. [The Florida Agricultural and Mechanical University-The Florida State University (FAMU-FSU) College of Engineering, Department of Chemical and Biomedical Engineering, 2525 Pottsdamer Street, Tallahassee, FL 32310-6046 (United States); Sun, J. [The National High Magnetic Field Laboratory, Condensed Matter Science Department, 1800 E. Paul Dirac Drive, Tallahassee, FL 32310 (United States); The Florida Agricultural and Mechanical University-The Florida State University (FAMU-FSU) College of Engineering, Department of Chemical and Biomedical Engineering, 2525 Pottsdamer Street, Tallahassee, FL 32310-6046 (United States); Ramirez, D. [The National High Magnetic Field Laboratory, Condensed Matter Science Department, 1800 E. Paul Dirac Drive, Tallahassee, FL 32310 (United States); The Florida Agricultural and Mechanical University-The Florida State University (FAMU-FSU) College of Engineering, Department of Chemical and Biomedical Engineering, 2525 Pottsdamer Street, Tallahassee, FL 32310-6046 (United States); Specialized Crystal Processing, Inc., 400 Capital Circle SE, Suite 18227, Tallahassee, FL 32301-3839 (United States); Stillwell, R.L. [The National High Magnetic Field Laboratory, Condensed Matter Science Department, 1800 E. Paul Dirac Drive, Tallahassee, FL 32310 (United States); and others

2013-07-15

The new oxytelluride Ba{sub 3}Yb{sub 2}O{sub 5}Te was obtained from an alkaline earth flux. Ba{sub 3}Yb{sub 2}O{sub 5}Te crystallizes in the tetragonal space group P4/mmm (#123), with a=4.3615(3) Å and c=11.7596(11) Å, Z=1. The structure combines two distinct building blocks, a Ba{sub 2}Yb{sub 2}O{sub 5} perovskite-like double layer with square bipyramidal coordination of the ytterbium ions, and a CsCl-type BaTe layer. Short range magnetic order is apparent at below 5 K, with the magnetic behavior above this temperature dominated by crystal field effects. The structure may be considered as an analog to the Ruddlesden–Popper phases, where the NaCl-type layer has been replaced by the CsCl-type layer. The two-dimensional magnetic behavior is expected based on the highly anisotropic nature of the structure. - Graphical abstract: Optical images of Ba{sub 3}Yb{sub 2}O{sub 5}Te in transmission (left) and reflected (right) light, with atomic unit cell overlay. - Highlights: • Single crystal synthesis and characterization of a new phase, Ba{sub 3}Yb{sub 2}O{sub 5}Te. • The structure features the BaTe high pressure polymorph intergrowth. • Magnetic susceptibility measurements show short range 2 dimensional ordering. • Heat capacity measurements show a feature at the magnetic ordering temperature. • Optical reflectivity measurements show a {sup 2}F{sub 7/2}→{sup 2}F{sub 5/2} absorption at 976 nm.

Nb/sub 2/Te/sub 2/O/sub 9/ and Ta/sub 2/Te/sub 2/O/sub 9/: Two new mixed oxides of Te(IV)

International Nuclear Information System (INIS)

Gaitan, M.; Jerez, A.; Pico, C.; Veiga, M.L.

1987-01-01

Nb/sub 2/Te/sub 2/O/sub 9/ and Ta/sub 2/Te/sub 2/O/sub 9/ were prepared by solid state reactions between amorphous TeO/sub 3/(s) and metallic pentoxides of Nb and Ta. A crystallographic analysis carried out by X-ray diffraction showed that these compounds are isostructural (space group: P2/sub 1//C. a = 6.883 A, b = 7.853 A, c = 14.591 A, β = 103.66 for Nb/sub 2/Te/sub 2/O/sub 9/ and a = 7.10 A, b = 7.48 A, c = 14.62 A, β = 102.9 for Ta/sub 2/Te/sub 2/O/sub 9/). The IR spectra and thermal decomposition processes of both mixed oxides were studied

Shielding properties of 80TeO2-5TiO2-(15-x) WO3-xAnOm glasses using WinXCom and MCNP5 code

Science.gov (United States)

Dong, M. G.; El-Mallawany, R.; Sayyed, M. I.; Tekin, H. O.

2017-12-01

Gamma ray shielding properties of 80TeO2-5TiO2-(15-x) WO3-xAnOm glasses, where AnOm is Nb2O5 = 0.01, 5, Nd2O3 = 3, 5 and Er2O3 = 5 mol% have been achieved. Shielding parameters; mass attenuation coefficients, half value layers, and macroscopic effective removal cross section for fast neutrons have been computed by using WinXCom program and MCNP5 Monte Carlo code. In addition, by using Geometric Progression method (G-P), exposure buildup factor values were also calculated. Variations of shielding parameters are discussed for the effect of REO addition into the glasses and photon energy.

Investigations into the PbO-TeO2-B2O3 glass system

International Nuclear Information System (INIS)

Basariya, F.P.; Gugushvili, G.M.

1975-01-01

Based on the results of investigations of the system A-TeO 2 -B 2 O 3 and from the ternary phase diagram a region is determined of stable nonorganic glasses of the system PbO-TeO 2 -B 2 O 3 noncrystallizable at a temperature of 300 0 C and showing satisfactory chemical stability, as well as satisfactory isolation properties up to 300 0 C. On addition of an optimum amount of tellurium oxide one can obtain low-melting glasses with a temperature interval of 250-300 0 C. It is established that the substitution of PbO by TeO 2 or B 2 O 3 , or TeO 2 by B 2 O 3 leads to a decrease in the glass density. (author)

The dehydration of SrTeO3(H2O)--a topotactic reaction for preparation of the new metastable strontium oxotellurate(IV) phase ε-SrTeO3.

Science.gov (United States)

Stöger, Berthold; Weil, Matthias; Baran, Enrique J; González-Baró, Ana C; Malo, Sylvie; Rueff, Jean Michel; Petit, Sebastien; Lepetit, Marie Bernadette; Raveau, Bernard; Barrier, Nicolas

2011-05-28

Microcrystalline single-phase strontium oxotellurate(IV) monohydrate, SrTeO(3)(H(2)O), was obtained by microwave-assisted hydrothermal synthesis under alkaline conditions at 180 °C for 30 min. A temperature of 220 °C and longer reaction times led to single crystal growth of this material. The crystal structure of SrTeO(3)(H(2)O) was determined from single crystal X-ray diffraction data: P2(1)/c, Z = 4, a = 7.7669(5), b = 7.1739(4), c = 8.3311(5) Å, β = 107.210(1)°, V = 443.42(5) Å(3), 1403 structure factors, 63 parameters, R[F(2)>2σ(F(2))] = 0.0208, wR(F(2) all) = 0.0516, S = 1.031. SrTeO(3)(H(2)O) is isotypic with the homologous BaTeO(3)(H(2)O) and is characterised by a layered assembly parallel to (100) of edge-sharing [SrO(6)(H(2)O)] polyhedra capped on each side of the layer by trigonal-prismatic [TeO(3)] units. The cohesion of the structure is accomplished by moderate O-H···O hydrogen bonding interactions between donor water molecules and acceptor O atoms of adjacent layers. In a topochemical reaction, SrTeO(3)(H(2)O) condensates above 150 °C to the metastable phase ε-SrTeO(3) and transforms upon further heating to δ-SrTeO(3). The crystal structure of ε-SrTeO(3), the fifth known polymorph of this composition, was determined from combined electron microscopy and laboratory X-ray powder diffraction studies: P2(1)/c, Z = 4, a = 6.7759(1), b = 7.2188(1), c = 8.6773(2) Å, β = 126.4980(7)°, V = 341.20(18) Å(3), R(Fobs) = 0.0166, R(Bobs) = 0.0318, Rwp = 0.0733, Goof = 1.38. The structure of ε-SrTeO(3) shows the same basic set-up as SrTeO(3)(H(2)O), but the layered arrangement of the hydrous phase transforms into a framework structure after elimination of water. The structural studies of SrTeO(3)(H(2)O) and ε-SrTeO(3) are complemented by thermal analysis and vibrational spectroscopic measurements.

Nuclear decay scheme studies of 30-h 131Te/sup m/, 25-min 131Te/sup g/, and 55.5-min 105Cd

International Nuclear Information System (INIS)

Jackson, S.V.

1975-01-01

High-resolution Ge(Li) detectors have been used to observe γ-ray singles and coincidence spectra of 30-h 11 / 2 - , /sup 131m/Te, 25-min 3 / 2 + , and 55.5-min 5 / 2 + 105 Cd. Sources of /sup 131m/Te and /sup 131g/Te were produced by neutron irradiation of enriched 130 Te metal, and, in the case of /sup 131m/Te, were chemically purified to remove the 131 I daughter. A total of 190 and 80 γ-rays are attributed to the decays of /sup 131m/Te and /sup 131g/Te, respectively; and 174 and 77 of these transitions have been placed in a 131 I level scheme involving 52 excited states. Absolute β group intensities were determined for the transitions to 131 I levels. Spin and parity assignments were made for all observed levels. The β feeding from the 11 / 2 - /sup 131m/Te to the 7 / 2 + 131 I ground state was determined to be (5.2 +- 3.0) percent (log ft = 10.5). The isomeric transition of 11 / 2 - /sup 131m/Te to 3 / 2 + /sup 131g/Te was determined to be (22.2 +- 1.6) percent. The 6-nsec isomer in 131 I at 1797 keV has been assigned as 15 / 2 - and interpreted as a πν 1 ν 2 three quasi-particle state. Sources of 105 Cd were produced via the 106 Cd(n,2n) reaction on enriched 106 CdO using 14 MeV neutrons. A total of 274 γ-rays are attributed to the decay of 105 Cd, and 248 of these have been placed in a 105 Ag level scheme involving 50 excited states. Absolute values for the β + /EC transition intensities to 105 Ag levels were determined. The β + /EC feeding from the 5 / 2 + 105 Cd to the 7 / 2 + 25.5-keV isomeric state in 105 Ag was determined to be (51.4 +- 4.0) percent (log ft = 5.4). The experimentally determined level structures of 131 I and 105 Cd are interpreted in terms of the shell model and core excitation considerations with emphasis placed on the core coupling model and the three-particle models. (U.S.)

Optical absorption and spectroscopic properties of thulium doped (TeO{sub 2})(Nb{sub 2}O{sub 5})(TiO{sub 2}) glasses

Energy Technology Data Exchange (ETDEWEB)

Kabalci, Idris [Department of Physics Education, Education Faculty, Harran University, Sanliurfa (Turkey); Tay, Turgay [Department of Chemistry, Science Faculty, Anadolu University, Eskisehir (Turkey); Oezen, Goenuel [Department of Physics, Science and Arts Faculty, Istanbul Technical University, Istanbul (Turkey)

2011-09-15

A type of thulium doped tellurite based optical glasses was prepared through conventional melt quenching technique. In the experiments, the effect of different Tm{sup 3+} ion concentration and glass composition on optical properties of (TeO{sub 2}){sub (1-x-y)}(Nb{sub 2}O{sub 5}){sub (x)}(TiO{sub 2}){sub (y)} (x=0.05, 0.10, 0.15, and 0.20 mol) glasses have been investigated by using UV-VIS-NIR optical spectrophotometry measurements in a wavelength range 400-2000 nm. Considering absorption measurements for the 1.0mol% Tm{sup 3+} doped of (TeO{sub 2}){sub 0.9}(Nb{sub 2}O{sub 5}){sub 0.05}(TiO{sub 2}){sub 0.05} glass, {sup 1}G{sub 4}, {sup 3}F{sub 2}, {sup 3}F{sub 3}, {sup 3}F{sub 4}, {sup 3}H{sub 5}, and {sup 3}H{sub 4} absorption bands were observed from the {sup 3}H{sub 6} ground level, at 463, 660, 687, 793, 1211 and 1700 nm wavelengths, respectively. Furthermore, spontaneous emission probabilities, and the radiative lifetimes for the 4f-4f transitions of the Tm{sup 3+} ions were calculated. The spectral intensities were determined in terms of Judd-Ofelt parameters ({omega}{sub 2}, {omega}{sub 4}, {omega}{sub 6}). Luminescence analysis was realized for the different Tm{sup 3+} ion concentration (0.002, 0.005 and 0.01mol) at room temperature. The luminescence band intensity of the {sup 3}F{sub 4}{yields}{sup 3}H{sub 4} transition was measured as a function of Tm{sup 3+} ion concentration (0.002, 0.005 and 0.01mol). Furthermore, luminescence data of the thulium doped glass samples were used to determine the compositional dependence of the emission cross sections at 1470 nm (copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

X-ray diffraction study on microstructure of Li20-TeO2 glasses; Xsen kaisetsuho ni yoru Li{sub 2}O-TeO{sub 2} kei garasu no mikuro kozo kaiseki

Energy Technology Data Exchange (ETDEWEB)

Iwadate, Y; Hattori, T; Nishiyama, S; Fukushima, K; Sugawara, Y [Chiba Univ. (Japan); Noda, K. [Japan Atomic Energy Research Inst., Tokyo (Japan)] Tatsumisuna, M. [Osaka Prefectural Univ., Sakai (Japan)] Umesaki, M. [Osaka Industrial Research Inst., Osaka (Japan)

1998-07-10

Li2O-TeO2 glasses attract attention because of unique properties such as high density, high refractive index, large dielectric constants and high infrared transmittance. The short range structures of two samples of Li2O-TeO2 glasses (15:85 mol% Li2O-TeO2 and 25:75 mol% Li2O-TeO2) were investigated by X-ray diffraction technique. Interpretation of the obtained radial distribution functions was performed on the basis of the strength comparison method. The following conclusions were obtained: Two types of Te-O bond lengths of 0.18nm and 0.20nm are found in TeO4 tetragonal bipyramid. As network forming units, the TeO4 tetragonal bipyramids and TeO3 trigonal bipyramids are observed. The TeO4 tetragonal bipyramid units are transformed into the TeO3 trigonal bipyramids through the transient species of polyhedral with non-bridging oxygen atoms with increasing content of Li2O. The lone pair of Te atom does not contribute to the formation of the glass network. 17 refs., 6 figs., 2 tabs.

Evolution of MoTeO x/SiO 2 and MoBiTeO x/SiO 2 catalysts in the partial oxidation of propane to acrolein

Science.gov (United States)

He, Yiming; Wu, Ying

2010-04-01

A thorough investigation of the catalysts Mo 1Te 1O x/SiO 2 and Mo 1Bi 0.05Te 1O x/SiO 2 in the partial oxidation of propane is presented in this paper, in order to elucidate the nature and behavior of the active surface. The catalysts' structures and redox properties were investigated by means of X-ray powder diffraction, Raman spectroscopy, in situ Raman spectroscopy, X-ray photoelectron spectroscopy, and H 2-TPR techniques. The results indicate that Te-polymolybdate is the main active phase on fresh catalysts. During reaction, the catalysts underwent a progressive reduction, resulting in the reconstruction of the active surface and the formation of a MoO 3 phase. The synergistic effect between Te-polymolybdate and MoO 3 was assumed to promote catalytic performance. The different stabilities of Mo 1Te 1O x/SiO 2 and Mo 1Bi 0.05Te 1O x/SiO 2 catalysts are also discussed.

Thermal, structural and optical properties of new TeO2sbnd Sb2O3sbnd GeO2 ternary glasses

Science.gov (United States)

Pereira, C.; Barbosa, J.; Cassanjes, F. C.; Gonçalves, R. R.; Ribeiro, S. J. L.; Poirier, G.

2016-12-01

In this work the novel glass system TeO2sbnd Sb2O3sbnd GeO2 was investigated and promising glass compositions were selected for further specific studies. Glass samples in the (80-0.8x)TeO2-(20-0.2x)Sb2O3-xGeO2 molar composition were prepared by the melt-quenching method with a glass-forming domain from x = 10 to x = 90. Samples were investigated by XRD, DSC, FTIR, Raman spectroscopy and UV-visible absorption. The XRD and DSC results bring informations about the non-crystalline state and thermal properties of these materials. It has been observed that higher GeO2 contents lead to higher glass transition temperatures and thermal stabilities against crystallization. FTIR and Raman spectroscopies suggest a progressive incorporation of GeO2 in the covalent network of TeO2 with conversion of structural units TeO4 to TeO3. Absorption spectra revealed the high visible transparency of these samples and an increase of the optical band gap with GeO2 addition, in agreement with a decreasing polarizability of the glass network. Er3+ doped and Er3+/Yb3+ codoped samples were also studied with respect to their infrared emission properties and higher GeO2 contents lead to an increase in IR emission intensity at 1,5 μm as well as longer radiative lifetimes. Finally, upconversion emission in the visible were also recorded and were shown to be strongly dependent of the composition.

Synthesis and crystal structure of Fe[(Te1.5Se0.5)O5]Cl, the first iron compound with selenate(IV) and tellurate(IV) groups

Science.gov (United States)

Akhrorov, Akhmad Yu; Kuznetsova, Elena S.; Aksenov, Sergey M.; Berdonosov, Peter S.; Kuznetsov, Alexey N.; Dolgikh, Valery A.

2017-12-01

During the search for selenium analogues of FeTe2O5Cl, the new iron (III) tellurate(IV) selenate(IV) chloride with the composition Fe[(Te1.5Se0.5)O5]Cl was synthesized by chemical vapor transport (CVT) reaction and characterized by TGA-, EDX-,SCXRD-analysis, as well as IR and Raman spectroscopy. It was found that Fe[(Te1.5Se0.5)O5]Cl crystallizes in the monoclinic space group P21/c with unitcell parameters a = 5.183(3) Å, b = 15.521(9) Å, c = 7.128(5) Å and β = 107.16(1)°. The crystal structure of Fe[(Te1.5Se0.5)O5]Cl represents a new structure type and contains electroneutral heteropolyhedral layers formed by dimers of the [FeO5Cl]8- octahedra, linked via common O-O edges, and mixed [Te3SeO10]4- tetramers. Adjacent layers are stacked along the b axis and linked by weak residual bonds. The new compound is stable up to 420 °C. DFT calculations predict Fe[(Te1.5Se0.5)O5]Cl to be a wide-gap semiconductor with the band gap of ca. 2.7 eV.

Infrared Spectroscopy and Raman Scattering Studies on the Structure of Ag2O. B2O3. TeO2 Glass

International Nuclear Information System (INIS)

Thazin Myint; Soe Soe Thin; Pho Kaung; Sein Htoon

2006-06-01

Infrared spectroscopy investigation of silver - borate - tellurite glasses in the system 0.4 Ag2 O. 0.6 (x B2 O2. (1-x) TeO2) for various of x (0 < x < 1) has been performed in order to understand the glass modifying properties of the TeO2. In pure crystalline TeO2 spectra observed absorption bands at 780 cm-1 and 660 cm-1 have been ascribed to the stretching vibration of TeO bonds in the TeO4 units. In the glass 0.4 Ag2 O. 0.6 (x B2 O3. (1-x) TeO2) the bands at 700 cm-1 and 694 cm-1 are assigned to the symmetric breathing vibration of the boroxol group and the pentaborate one. The glasses show bands at 630 cm-1 which corresponds to the vibrations due to TeO4 units

Investigations on the system Te/O/Br

International Nuclear Information System (INIS)

Oppermann, H.; Kunze, G.; Wolf, E.; Titov, V.A.; Kokovin, G.A.

1978-01-01

The melting point diagram of the system TeBr 4 -TeO 2 was obtained by total pressure measurements and DTA measurements. A congruent melting composition Te 6 O 11 Br 2 exists, the melting point is 570 0 C. The enthalpy of formation and the standard entropy of the species TeOBr 2 ,g was derived from measurements of the total pressure over Te 6 O 11 Br 2 /TeBr 4 and from the transport behaviour of the TeO 2 with Br 2 . From the decomposition-pressure measurements over Te 6 O 11 Br 2 /TeO 2 follow the partial pressures. The enthalpy of formation ΔH 0 (Te 6 O 11 Br 2 ,f,298) -453.5 kcal/Mol was obtained from the enthalpy of solution. The transport-behaviour of TeO 2 with HBr, TeBr 4 and Br 2 and that of Te 6 O 11 Br 2 is clear with the thermodynamic data of TeOBr 2 . (author)

Deposition of HgTe by electrochemical atomic layer epitaxy (EC-ALE)

CSIR Research Space (South Africa)

Venkatasamy, V

2006-04-01

Full Text Available This paper describes the first instance of HgTe growth by electrochemical atomic layer epitaxy (EC-ALE). EC-ALE is the electrochemical analog of atomic layer epitaxy (ALE) and atomic layer deposition (ALD), all of which are based on the growth...

QuEChERS-HPLC-DAD method for sulphonamides in chicken breast

Directory of Open Access Journals (Sweden)

Simone Caetani Machado

2013-03-01

Full Text Available The development of a QuEChERS-HPLC-DAD method using a Lichrospher 60 RP-Select B column (250 x 4.6 mm x 5 µm at 40ºC, mobile phase constituted by phosphate buffer:acetonitrile (75:25, v/v at a initial flow rate of 0.5 mL min-1, increased by 1.2 mL min-1 and at 265 nm is presented for simultaneous determination of sulphadiazine, sulphametoxipiridazine and sulphamethoxazole in chicken breast samples. QuEchERS is inexpensive, fast and easy, and the extraction of the analytes of the matrix was successfully employed. In addition, the method presented linearity, in the range of 25, 50, 100, 150, 175, and 200 µg kg-1, precision, selectivity and sensitivity. The intraday precision (RSD % for QuEChERS method was between 3.6-10.8 (SDZ, 6.9-14.1 (SPZ and 1.9-10.9 (SMX and interday precision (RSD% was between 1.5-9.7, 1.7-4.1 and 2.1-10.2, respectively. Results of accuracy (bias were in the range of -8.6 to +11.9 %. Therefore, the validated method is clearly useful for the practical residue monitoring of the drugs evaluated in chicken samples, as all the values were within the acceptable criteria used for food safety. Of 6 samples analyzed, none of them showed contamination of the sulphonamides studied at detectable levels.O desenvolvimento de um método QuEChERS-HPLC-DAD usando uma coluna Lichrospher RP-60 Select B (250 x 4,6 mm x 5 µm a 40 ºC, fase móvel constituída por tampão de fosfato: acetonitrila (75:25, v/v a uma vazão inicial de 0,5 mL min-1, aumentando 1,2 mL min-1 e a 265 nm é apresentado para a determinação simultânea de sulfadiazina, sulfametoxipiridazina e sulfametoxazol em amostras de peito de frango. O QuEChERS é barato, rápido e fácil, e a extração dos analitos da matriz foi empregada com sucesso. Além disso, o método apresentou linearidade, na faixa de 25, 50, 100, 150, 175 e 200 µg kg-1, precisão, seletividade e sensibilidade. A precisão intradia (RSD % para o método QuEChERS foi entre 3,6-10,8 (SDZ, 6,9-14,1 (SPZ

Syntheses and structural characterization of vanado-tellurites and vanadyl-selenites: SrVTeO{sub 5}(OH), Cd{sub 2}V{sub 2}Te{sub 2}O{sub 11}, Ca{sub 3}VSe{sub 4}O{sub 13}·H{sub 2}O and Ba{sub 2}VSe{sub 3}O{sub 10}

Energy Technology Data Exchange (ETDEWEB)

Konatham, Satish; Vidyasagar, Kanamaluru, E-mail: kvsagar@iitm.ac.in

2017-05-15

Four new quaternary vanado-tellurites and vanadyl-selenites, namely, SrVTeO{sub 5}(OH)(1), Cd{sub 2}V{sub 2}Te{sub 2}O{sub 11}(2), Ca{sub 3}VSe{sub 4}O{sub 13}·H{sub 2}O(3) and Ba{sub 2}VSe{sub 3}O{sub 10}(4) have been synthesized and structurally characterized by single crystal X-ray diffraction. The oxidation state of vanadium is +5 in tellurites 1 and 2 and +4 in selenites 3 and 4. The structures of SrVTeO{sub 5}(OH)(1) and Cd{sub 2}V{sub 2}Te{sub 2}O{sub 11}(2) compounds consist of (VTeO{sub 5}(OH)){sup 2-} and (V{sub 2}Te{sub 2}O{sub 11}){sup 4-}anionic chains respectively, which are built from tetrahedral VO{sub 4} and disphenoidal TeO{sub 4} moieties. Similarly the structures of Ca{sub 3}VSe{sub 4}O{sub 13}·H{sub 2}O(3) and Ba{sub 2}VSe{sub 3}O{sub 10}(4) respectively contain (VSe{sub 2}O{sub 7}){sup 2-} and (VSe{sub 3}O{sub 10}){sup 4-} anionic chains, which are made up of octahedral VO{sub 6} and pyramidal SeO{sub 3} units. Compounds 1 and 3 have been characterized by thermogravimetric and infrared spectroscopic methods. Compounds 1 and 2 are wide band gap semiconductors. - Graphical abstract: Ca{sub 3}VSe{sub 4}O{sub 13}·H{sub 2}O and Ba{sub 2}VSe{sub 3}O{sub 10} compounds contain (VSe{sub 2}O{sub 7}){sup 2-} and (VSe{sub 3}O{sub 10}){sup 4-} chains. - Highlights: • Four new vanado-tellurites and vanadyl-selenites are synthesized. • Their structural features are different. • The vanado-tellurites are wide band gap semiconductors.

The effects of Nd2O3 concentration in the laser emission of TeO2-ZnO glasses

Science.gov (United States)

Moreira, L. M.; Anjos, V.; Bell, M. J. V.; Ramos, C. A. R.; Kassab, L. R. P.; Doualan, D. J. L.; Camy, P.; Moncorgé, R.

2016-08-01

The present work reports the modification introduced by different Nd2O3 concentration on optical properties and the laser operation of Nd3+ doped (TeO2-ZnO) bulk tellurite glass. The spectroscopic data are analyzed within the Judd Ofelt formalism framework and the results are compared to the fluorescence lifetime and emission measurements to derive values for the quantum efficiency and the stimulated emission cross section of the considered 4F3/2 → 4I11/2 infrared laser transition around 1062.5 nm. Continuous-wave laser action is achieved with this bulk tellurite glass by pumping the sample inside a standard plan-concave mirror laser cavity with different output couplers. It is possible to observe coherent emission only for the lower concentration (0.5%(wt.) of Nd2 O3). Also laser action could only be observed for this sample with threshold pump power of 73 mW associated with a laser slope efficiency of 8% for an output coupler transmission of 4% indicating that TeO2-ZnO are potential materials for laser action. The results presented in this work together with those previously reported with higher concentration (1.0% (wt) of Nd2O3) determine the adequate Nd2O3 concentration for laser action and guide the correct experimental procedure for TeO2-ZnO glasses preparation.

Crystal structure and magnetic properties of the Ba3TeCo3P2O14, Pb3TeCo3P2O14, and Pb3TeCo3V2O14 langasites

DEFF Research Database (Denmark)

Krizan, J.W.; de la Cruz, C.; Andersen, Niels Hessel

2013-01-01

We report the structural and magnetic characterizations of Ba3TeCo3P2O14, Pb3TeCo3P2O14, and Pb3TeCo3V2O14, compounds that are based on the mineral dugganite, which is isostructural to langasites. The magnetic part of the structure consists of layers of Co2+ triangles. Nuclear and magnetic...... structures were determined through a co-refinement of synchrotron and neutron powder diffraction data. In contrast to the undistorted P321 langasite structure of Ba3TeCo3P2O14, a complex structural distortion yielding a large supercell is found for both Pb3TeCo3P2O14 and Pb3TeCo3V2O14. Comparison...... of the three compounds studied along with the zinc analog Pb3TeZn3P2O14, also characterized here, suggests that the distortion is driven by Pb2+ lone pairs; as such, the Pb compounds crystallize in a pyroelectric space group, P2. Magnetic susceptibility, magnetization, and heat capacity measurements were...

CO gas sensing properties of In_4Sn_3O_1_2 and TeO_2 composite nanoparticle sensors

International Nuclear Information System (INIS)

Mirzaei, Ali; Park, Sunghoon; Sun, Gun-Joo; Kheel, Hyejoon; Lee, Chongmu

2016-01-01

Highlights: • In4Sn3O12–TeO2 composite nanoparticles were synthesized via a facile hydrothermal route. • The response of the In4Sn3O12–TeO2 composite sensor to CO was stronger than the pristine In4Sn3O12 sensor. • The response of the In4Sn3O12–TeO2 composite sensor to CO was faster than the pristine In4Sn3O12 sensor. • The improved sensing performance of the In4Sn3O12–TeO2 nanocomposite sensor is discussed in detail. • The In4Sn3O12-based nanoparticle sensors showed selectivity to CO over NH3, HCHO and H2. - Abstract: A simple hydrothermal route was used to synthesize In_4Sn_3O_1_2 nanoparticles and In_4Sn_3O_1_2–TeO_2 composite nanoparticles, with In(C_2H_3O_2)_3, SnCl_4, and TeCl_4 as the starting materials. The structure and morphology of the synthesized nanoparticles were examined by X-ray diffraction and scanning electron microscopy (SEM), respectively. The gas-sensing properties of the pure and composite nanoparticles toward CO gas were examined at different concentrations (5–100 ppm) of CO gas at different temperatures (100–300 °C). SEM observation revealed that the composite nanoparticles had a uniform shape and size. The sensor based on the In_4Sn_3O_1_2–TeO_2 composite nanoparticles showed stronger response to CO than its pure In_4Sn_3O_1_2 counterpart. The response of the In_4Sn_3O_1_2–TeO_2 composite-nanoparticle sensor to 100 ppm of CO at 200 °C was 10.21, whereas the maximum response of the In_4Sn_3O_1_2 nanoparticle sensor was 2.78 under the same conditions. Furthermore, the response time of the composite sensor was 19.73 s under these conditions, which is less than one-third of that of the In_4Sn_3O_1_2 sensor. The improved sensing performance of the In_4Sn_3O_1_2–TeO_2 nanocomposite sensor is attributed to the enhanced modulation of the potential barrier height at the In_4Sn_3O_1_2–TeO_2 interface, the stronger oxygen adsorption of p-type TeO_2, and the formation of preferential adsorption sites.

Syntheses, crystal structures, and characterization of two new Tl{sup +}-Cu{sup 2+}-Te{sup 6+} oxides: Tl{sub 4}CuTeO{sub 6} and Tl{sub 6}CuTe{sub 2}O{sub 10}

Energy Technology Data Exchange (ETDEWEB)

Yeon, Jeongho; Kim, Sang-Hwan [Department of Chemistry, University of Houston, 136 Fleming Building, Houston, TX 77204-5003 (United States); Green, Mark A. [Department of Materials Science and Engineering, University of Maryland, College Park, MD, 20742-2115 and NIST Center for Neutron Research, National Institute of Standard and Technology, 100 Bureau Drive, Gaithersburg, MD 20899-6103 (United States); Bhatti, Kanwal Preet; Leighton, C. [Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, MN 55455-0132 (United States); Shiv Halasyamani, P., E-mail: psh@uh.edu [Department of Chemistry, University of Houston, 136 Fleming Building, Houston, TX 77204-5003 (United States)

2012-12-15

Crystals and polycrystalline powders of two new oxide materials, Tl{sub 4}CuTeO{sub 6} and Tl{sub 6}CuTe{sub 2}O{sub 10}, have been synthesized by hydrothermal and solid-state methods. The materials were structurally characterized by single-crystal X-ray diffraction. Tl{sub 4}CuTeO{sub 6} and Tl{sub 6}CuTe{sub 2}O{sub 10} exhibit one dimensional anionic slabs of [CuTeO{sub 6}]{sup 4-} and [CuTe{sub 2}O{sub 10}]{sup 6-}, respectively. Common to both slabs is the occurrence of Cu{sup 2+}O{sub 4} distorted squares and Te{sup 6+}O{sub 6} octahedra. The slabs are separated by Tl{sup +} cations. For Tl{sub 4}CuTeO{sub 6}, magnetic measurements indicate a maximum at {approx}8 K in the temperature dependence of the susceptibility. Low temperature neutron diffraction data confirm no long-range magnetic ordering occurs and the susceptibility was adequately accounted for by fits to a Heisenberg alternating chain model. For Tl{sub 6}CuTe{sub 2}O{sub 10} on the other hand, magnetic measurements revealed paramagnetism with no evidence of long-range magnetic ordering. Infrared, UV-vis spectra, thermogravimetric, and differential thermal analyses are also reported. Crystal data: Tl{sub 4}CuTeO{sub 6}, Triclinic, space group P-1 (No. 2), a=5.8629(8) A, b=8.7848(11) A, c=9.2572(12) A, {alpha}=66.0460(10), {beta}=74.2010(10), {gamma}=79.254(2), V=417.70(9) A{sup 3}, and Z=2; Tl{sub 6}CuTe{sub 2}O{sub 10}, orthorhombic, space group Pnma (No. 62), a=10.8628(6) A, b=11.4962(7) A, c=10.7238(6) A, V=1339.20(13) A{sup 3}, and Z=4. - Graphical Abstract: Two new oxide materials, Tl{sub 4}CuTeO{sub 6} and Tl{sub 6}CuTe{sub 2}O{sub 10}, have been synthesized and characterized. The materials exhibit one dimensional crystal structures consisting of CuO{sub 4} and TeO{sub 6} polyhedra. Highlights: Black-Right-Pointing-Pointer Two New Tl-Te-Cu-oxides have been synthesized and structurally characterized. Black-Right-Pointing-Pointer For Tl{sub 4}CuTeO{sub 6}, magnetic measurements indicate a

Structure of TeO2 - LiNbO3 glasses

Science.gov (United States)

Shinde, A. B.; Krishna, P. S. R.; Rao, Rekha

2017-05-01

Tellurite based lithium niobate glasses with composition (100-x)TeO2-xLiNbO3 (x=0.1,0.2 & 0.3) were prepared by conventional melt quenching method. The microscopic structural investigation of these glasses is carried out by means of neutron diffraction and Raman scattering measurements. It is found that the basic structural units in these glasses are TeO4 trigonal bipyramids(TBP), TeO3 trigonal pyramids(TP) and NbO6 Octahedra depending on the composition. It is evident from Raman studies that TBPs decreases, TPs increases and NbO6 Octahedra increases with increasing x. From Neutron diffraction studies it is found that network is comprised of TBPs and TPs along with TeO3+1 structural units. Distorted NbO6 octahedral units are present and also increase with the increase in x.

Photovoltaic effect in Bi2TeO5 photorefractive crystal

International Nuclear Information System (INIS)

Oliveira, Ivan de; Capovilla, Danilo Augusto; Carvalho, Jesiel F.; Montenegro, Renata; Fabris, Zanine V.; Frejlich, Jaime

2015-01-01

We report on the presence of a strong photovoltaic effect on nominally undoped photorefractive Bi 2 TeO 5 crystals and estimated their Glass photovoltaic constant and photovoltaic field for λ = 532 nm illumination. We directly measured the photovoltaic-based photocurrent in this material under λ = 532 nm wavelength laser light illumination and compared its behavior with that of a well known photovoltaic Fe-doped Lithium Niobate crystal. We also show the photovoltaic current to strongly depend on the polarization direction of light. Holographic diffraction efficiency oscillation during recording and the behavior of fringe-locked running holograms in self-stabilized experiments are also demonstrated here as additional indirect proofs of the photovoltaic nature of this material

ECH Technology Development

Energy Technology Data Exchange (ETDEWEB)

Temkin, Richard [Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)

2014-12-24

Electron Cyclotron Heating (ECH) is needed for plasma heating, current drive, plasma stability control, and other applications in fusion energy sciences research. The program of fusion energy sciences supported by U. S. DOE, Office of Science, Fusion Energy Sciences relies on the development of ECH technology to meet the needs of several plasma devices working at the frontier of fusion energy sciences research. The largest operating ECH system in the world is at DIII-D, consisting of six 1 MW, 110 GHz gyrotrons capable of ten second pulsed operation, plus two newer gyrotrons. The ECH Technology Development research program investigated the options for upgrading the DIII-D 110 GHz ECH system. Options included extending present-day 1 MW technology to 1.3 – 1.5 MW power levels or developing an entirely new approach to achieve up to 2 MW of power per gyrotron. The research consisted of theoretical research and designs conducted by Communication and Power Industries of Palo Alto, CA working with MIT. Results of the study would be validated in a later phase by research on short pulse length gyrotrons at MIT and long pulse / cw gyrotrons in industry. This research follows a highly successful program of development that has led to the highly reliable, six megawatt ECH system at the DIII-D tokamak. Eventually, gyrotrons at the 1.5 megawatt to multi-megawatt power level will be needed for heating and current drive in large scale plasmas including ITER and DEMO.

Preparation and characterization of new glasses from the TeO2-CdO-Al2O3-SiO2 system

OpenAIRE

Zayas, Mª. E.; Espinoza-Beltrán, F. J.; Romero, Maximina; Rincón López, Jesús María

1998-01-01

A new family of glasses from the TeO2-CdO-Al2O3-SiO2 system obtained from CdS-TeO2 mixtures melted in fireclay crucibles have been prepared and characterized. The density values of these glasses are in the 3.30-3.46 gcm-3 range. The viscosity-temperature variation shows that glasses with high TeO2 content depict the typical variation of `short glasses' for a molding operation. Microstructural observations by TEM (replica method) and SEM microscopies have shown that these glasses contain very ...

Study of the optical properties of TeO2-PbO-TiO2 glass system

Directory of Open Access Journals (Sweden)

Raul F. Cuevas

1998-06-01

Full Text Available We describe the preparation and some optical properties of high refractive index TeO2-PbO-TiO2 glass system. Highly homogeneous glasses were obtained by agitating the mixture during the melting process in an alumina crucible. The characterization was done by X-ray diffraction, Raman scattering, light absorption and linear refractive index measurements. The results show a change in the glass structure as the PbO content increases: the TeO4 trigonal bipyramids characteristics of TeO2 glasses transform into TeO3 trigonal pyramids. However, the measured refractive indices are almost independent of the glass composition. We show that third-order nonlinear optical susceptibilities calculated from the measured refractive indices using Lines' theoretical model are also independent of the glass composition.

Structural, thermal and optical properties of TeO2-ZnO-CdO-BaO glasses doped with VO(2+).

Science.gov (United States)

Sreenivasulu, V; Upender, G; Chandra Mouli, V; Prasad, M

2015-09-05

The glasses with composition 64TeO2-15ZnO-(20-x)CdO-xBaO-1V2O5 (0⩽x⩽20 mol%) were prepared by conventional melt quenching technique. X-ray diffraction analysis was used to confirm the amorphous nature of the glasses. The optical absorption studies revealed that the cut-off wavelength (λα) decreases while optical band gap energy (Eopt) and Urbach energy (ΔE) values increase with an increase of BaO content. Refractive index (n) evaluated from Eopt was found to decrease with an increase of BaO content. The physical parameters such as density (ρ), molar volume (Vm), oxygen packing density (OPD), optical basicity (Λ), molar refraction (Rm), and metallization criterion (M) evaluated and discussed. FTIR and Raman spectroscopic studies showed that the glass network consists of TeO4, TeO3+1/TeO3 and ZnO4 units as basic structural units. The glass transition temperature (Tg) of glass sample, onset crystallization temperature (To) and thermal stability ΔT were determined from Differential Scanning Calorimetry (DSC). Using electron paramagnetic resonance (EPR) spectra of vanadium glasses the spin Hamiltonian parameters and dipolar hyperfine coupling parameters of VO(2+) ions were calculated. It was found that V(4+) ions in these glasses exist as VO(2+) in octahedral coordination with a tetragonal distortion and have C4V symmetry with ground state dxy. Tetragonality (Δg∥/Δg⊥) of vanadium ion sites exhibited non-linear variation with BaO content. Copyright © 2015 Elsevier B.V. All rights reserved.

Spectroscopic properties and thermal stability of Er3+ -doped TeO2-B2O3-Nb2O5-ZnO glass for potential WDM amplifier.

Science.gov (United States)

Xu, Tiefeng; Zhang, Xudong; Li, Guangpo; Dai, Shixun; Nie, Qiuhua; Shen, Xiang; Zhang, Xianghua

2007-06-01

A series of novel 70TeO2-(15-x)B2O3-xNb2O5-15ZnO-1wt.% Er2O3 (TBN x=0, 3, 6, 9, 12 and 15 mol%) tellurite glasses were prepared. The thermal stability, absorption spectra, emission spectra, and the lifetime of the (4)I(13/2) level of Er(3+) ions were measured and investigated. Three Judd-Ofelt intensity parameters Omega(t) (t=2, 4 and 6) (Omega(2)=(5.42-6.76)x10(-20)cm(2); Omega(4)=(1.37-1.73)x10(-20)cm(2); Omega(6)=(0.70-0.94)x10(-20)cm(2)) of Er(3+) ions were calculated by Judd-Ofelt theory. It is found that the Omega(6) first increases with the increase of Nb2O5 content from 0 to 6 mol% and then decreases, which is mainly affected by the number of non-bridging oxygen ions of the glass network. The high peak of stimulated emission cross-section (sigma(e)(peak)=(0.77-0.91)x10(-20)cm(2)) of Er(3+): (4)I(13/2)-->(4)I(15/2) transition were obtained according to McCumber theory and broad full width at half maximum (FWHM=65-73 nm) of the (4)I(13/2)-->(4)I(15/2) transition of Er(3+) ions were measured. The results indicate that these new TBN glasses can be used as a candidate host material for potential broadband optical amplifiers.

ECH on NSTX

International Nuclear Information System (INIS)

Bigelow, T.S.; Batchelor, D.B.; Carter, M.D.; Peng, M.; Wilson, J.R.

1997-01-01

Electron Cyclotron Heating has been proposed for plasma initiation, startup assistance and non-inductive startup on NSTX. One physics goal of NSTX will be to establish entirely non-inductive plasma operation by utilizing ECH to provide a sufficient start-up plasma to support further current drive from other heating systems. Scaling of previous ECH-only startup experiments on CDX-U and DIII-D indicate that 400 kW of ECH should be capable of driving 42 kA of pressure driven current on NSTX and possibly higher levels after optimizing the process. Due to the low NSTX magnetic field, over-dense plasmas exist during most of the discharge so conventional ECH operation is limited to the low density startup phase. To extend the useful operating range for ECH, a scheme involving mode conversion to the electron Bernstein Wave (EBW) from either O r X mode launch is being investigated for bulk heating and current drive applications at higher density. Microwave equipment, including 18 GHz klystrons and 28 GHz gyrotrons are available at ORNL and appear ideal for use on NSTX. Preliminary pre-ionization and start-up system configurations are presented here along with discussions on various operation modes

Thermochemical properties of silver tellurides including empressite (AgTe) and phase diagrams for Ag-Te and Ag-Te-O

Science.gov (United States)

Voronin, Mikhail V.; Osadchii, Evgeniy G.; Brichkina, Ekaterina A.

2017-10-01

This study compiles original experimental and literature data on the thermodynamic properties (ΔfG°, S°, ΔfH°) of silver tellurides (α-Ag2Te, β-Ag2Te, Ag1.9Te, Ag5Te3, AgTe) obtained by the method of solid-state galvanic cell with the RbAg4I5 and AgI solid electrolytes. The thermodynamic data for empressite (AgTe, pure fraction from Empress Josephine Mine, Colorado USA) have been obtained for the first time by the electrochemical experiment with the virtual reaction Ag + Te = AgTe. The Ag-Te phase diagrams in the T - x and log fTe2 (gas) - 1/ T coordinates have been refined, and the ternary Ag-Te-O diagrams with Ag-Te-TeO2 (paratellurite) composition range have been calculated.

Syntheses, crystal structures and characterizations of BaZn(SeO3)2 and BaZn(TeO3)Cl2

International Nuclear Information System (INIS)

Jiang Hailong; Feng Meiling; Mao Jianggao

2006-01-01

Two new barium zinc selenite and tellurite, namely, BaZn(SeO 3 ) 2 and BaZn(TeO 3 )Cl 2 , have been synthesized by the solid state reaction. The structure of BaZn(SeO 3 ) 2 features double chains of [Zn(SeO 3 ) 2 ] 2- anions composed of four- and eight-member rings which are alternatively along a-axis. The double chains of [Zn 2 (TeO 3 ) 2 Cl 3 ] 3- anions in BaZn(TeO 3 )Cl 2 are formed by Zn 3 Te 3 rings in which each tellurite group connects with three ZnO 3 Cl tetrahedra. BaZn(SeO 3 ) 2 and BaZn(TeO 3 )Cl 2 are wide bandgap semiconductors based on optical diffuse reflectance spectrum measurements. -- Graphical abstract: Two new barium zinc selenite and tellurite, namely, BaZn(SeO 3 ) 2 and BaZn(TeO 3 )Cl 2 , have been synthesized by solid state reaction. The structure of BaZn(SeO 3 ) 2 features 1D double chains of [Zn(SeO 3 ) 2 ] 2- anions composed of four- and eight-member rings which are alternatively along a-axis. The 1D double chains of [Zn 2 (TeO 3 ) 2 Cl 3 ] 3- anions in BaZn(TeO 3 )Cl 2 are formed by Zn 3 Te 3 rings in which each tellurite group connects with one ZnO 3 Cl and two ZnO 2 Cl 2 tetrahedra. BaZn(SeO 3 ) 2 and BaZn(TeO 3 )Cl 2 are wide bandgap semiconductors based on optical diffuse reflectance spectrum measurements

Ho3+/Yb3+ co-doped TeO2-BaF2-Y2O3 glasses for ∼1.2 μm laser applications

Science.gov (United States)

Wang, Shunbin; Li, Chengzhi; Yao, Chuanfei; Jia, Shijie; Jia, Zhixu; Qin, Guanshi; Qin, Weiping

2017-02-01

Intense ∼1.2 μm fluorescence is observed in Ho3+/Yb3+ co-doped TeO2-BaF2-Y2O3 glasses under 915 nm laser diode excitation. The 1.2 μm emission can be ascribed to the transition 5I6→5I8 of Ho3+. With the introducing of BaF2, the content of OH in the glasses drops markedly, and the 1.2 μm emission intensity increases gradually as increasing the concentration percentage of BaF2. Furthermore, microstructured fibers based on the TeO2-BaF2-Y2O3 glasses are fabricated by using a rod-in-tube method, and a relative positive gain of ∼9.42 dB at 1175.3 nm is obtained in a 5 cm long fiber.

Post-Irradiation Behaviour of I131 in TeO2

International Nuclear Information System (INIS)

Jaćimović, Lj.; Stevović, J.; Veljković, S.R.

1965-01-01

The system I 131 in TeO 2 is interesting because little is known about thermal chemical changes in this target. Radioiodine was produced by neutron irradiation of TeO 2 in the reactor. Irradiated TeO 2 was dissolved in diluted NaOH. The analysis of the iodine valency forms was made by ion exchange techniques. The thermal and radiation stability of TeO 2 was studied by using the spectrophotometric method for the determination of tellurium. Post-irradiation annealing of I 131 in TeO 2 was studied in dependence on the time and temperature of the heating. The main tendency of annealing was the reduction of radioiodine. The time dependence of this process indicates a fast change at high temperatures. The curves are more complex at lower temperatures. The annealing may appear complex because of the variety of thermal reactions of iodine intermediary. It may react with products of the following processes: tellurium recoil and corresponding hot zone, beta transition of Te 131 and TeO 2 itself. The kinetics of these changes was considered and an estimation of the processes during annealing was made. The influence of the neutron flux on the kinetics of annealing was also studied. (author) [fr

ECH on NSTX

International Nuclear Information System (INIS)

Bigelow, T.S.; Batchelor, D.B.; Carter, M.D.; Peng, M.; Wilson, J.R.

1997-01-01

Electron Cyclotron Heating has been proposed for plasma initiation, startup assistance and non-inductive startup on NSTX. One physics goal of NSTX will be to establish entirely non-inductive plasma operation by utilizing ECH to provide a sufficient start-up plasma to support further current drive from other heating systems. Scaling of previous ECH-only startup experiments on CDX-U and DIII-D indicate that 400 kW of ECH should be capable of driving 42 kA of pressure driven current on NSTX and possibly higher levels after optimizing the process. Due to the low NSTX magnetic field, over-dense plasmas exist during most of the discharge so conventional ECH operation is limited to the low density startup phase. To extend the useful operating range for ECH, a scheme involving mode conversion to the electron Bernstein Wave (EBW) from either O or X mode launch is being investigated for bulk heating and current drive applications at higher density. Microwave equipment, including 18 GHz klystrons and 28 GHz gyrotrons are available at ORNL and appear ideal for use on NSTX. Preliminary pre-ionization and start-up system configurations are presented here along with discussions on various operation modes. copyright 1997 American Institute of Physics

ECH pre-ionization and assisted startup in the fully superconducting KSTAR tokamak using second harmonic

International Nuclear Information System (INIS)

Bae, Y.S.; Joung, M.; Kim, J.H.; Hahn, S.H.; Yoon, S.W.; Yang, H.L.; Kim, W.C.; Oh, Y.K.; England, A.C.; Bak, J.S.; Jeong, J.H.; Park, S.I.; Namkung, W.; Cho, M.H.; Jackson, G.L.

2009-01-01

This letter reports on the successful demonstration of the second harmonic electron cyclotron heating (ECH)-assisted startup in the first plasma experiments recently completed in the fully superconducting Korea Superconducting Tokamak Advanced Research (KSTAR) device whose major and minor radii are 1.8 m and 0.5 m, respectively. For the second harmonic ECH-assisted startup, an 84 GHz EC wave at 0.35 MW was launched before the onset of the toroidal electric field of the Ohmic system. And it was observed that this was sufficient to achieve breakdown in the ECH pre-ionization phase, allow burn-through and sustain the plasma during the current ramp with a low loop voltage of 2.0 V and a corresponding toroidal electric field of 0.24 V m -1 at the innermost vacuum vessel wall (R = 1.3 m). This is a lower value than 0.3 Vm -1 which is the maximum electric field in ITER. Due to the limited volt-seconds and the loop voltage of the Ohmic power system, the extended pulse duration of the ECH power up to 180 ms allowed the plasma current to rise up to more than 100 kA with a ramp-up rate of 0.8 MA s -1 . (letter)

The optical properties of TeO2-Based Glasses

International Nuclear Information System (INIS)

Sahar, M.R.; Isahak, R.

1994-01-01

A series of binary glasses based on TeO2-PbCl2 has been prepared and their spectroscopy in the UV-Visible and IR regions has been investigated. It was found that the IR cut-off edge can go beyond 7μm and are largely influenced by the absorption due to Te-O-Te stretching vibrations around 638-644 cmsup -1 peaks

The optical properties of TeO2-Based Glasses

Energy Technology Data Exchange (ETDEWEB)

Sahar, M R; Isahak, R [University Technology of Malaysia, Skudai Johor (Malaysia)

1994-03-01

A series of binary glasses based on TeO2-PbCl2 has been prepared and their spectroscopy in the UV-Visible and IR regions has been investigated. It was found that the IR cut-off edge can go beyond 7{mu}m and are largely influenced by the absorption due to Te-O-Te stretching vibrations around 638-644 cmsup -1 peaks.

V sub 2 O sub 5 -based glasses as cathodes for lithium batteries

Energy Technology Data Exchange (ETDEWEB)

Levy, M; Duclot, M J; Rousseau, F [British Columbia Univ., Vancouver (Canada)

1989-05-01

The electronic conductivities of glasses in the TeO2-V2O5 and TeO2-V2O5-MoO3 systems have been determined in the 20-200 C temperature range to give simple Arrhenius relationships. Chemical and electrochemical lithium intercalations have been performed, showing that V2O5-based glasses are suitable positive electrode materials for lithium batteries. 20 refs.

Effects of Sm3+/Yb3+ co-doping and temperature on the Raman, IR spectra and structure of [TeO2-GeO2-K2O-Sm2O3/Yb2O3] glasses

International Nuclear Information System (INIS)

Shaltout, I.; Badr, Y.

2006-01-01

Effects of Sm 3+ /Yb 3+ co-doping on Raman scattering, IR absorption, temperature dependence of the Raman spectra up to 210 o C and the structure of two glass systems of the composition (80TeO 2 -10GeO 2 -8K 2 O-2Sm 2 O 3 /Yb 2 O 3 ) is discussed. It was found that the addition of Yb 3+ to the glass very strongly enhances the intensities of the antistokes' Raman bands at 155, 375, 557 and 828 cm -1 and quenches both the intensities of the stokes' vibration modes of the TeO 4 units in the range of 120-770 cm -1 and the intensities of the OH - stretching vibration modes in the range of 2600-3300 cm -1 . Sm 2 O 3 /Yb 2 O 3 rare earth co-doping has a great influence on removing and/or changing the nature of the OH - groups. The appearance and splitting of the stretching vibration modes of the OH - groups at lower frequencies (2770, 2970 cm -1 ) for the Sm +3 singly doped glass sample, compared to the band at ∼3200 cm -1 for the Sm 3+ /Yb 3+ co-doped glass sample, suggested that the OH - groups are more strongly bonded and incorporated with the glass matrix for the singly doped glass. Heating the sample up continuously weakens the hydrogen bonding of the OH - groups to the glass matrix leading to creation of NBO and breakdown of the connectivity of the OH - groups to the TeO 4 , TeO 3+1 and TeO 3 structural units. Raman bands at 286, 477, 666 and 769 cm -1 were assigned to its respective vibrations of Te 2 O 7 , TeO 4 -4 species, the (Te-O-Te) bending vibrations of the TeO 4 triagonal bipyramids (tbps), the axial symmetric stretching vibration modes (Te ax -O) s with bridging oxygen BO atoms and to the (Te-O) nbo non-bridging stretching vibration modes of the TeO 3+1 and/or TeO 3 pyramids

Photovoltaic effect in Bi{sub 2}TeO{sub 5} photorefractive crystal

Energy Technology Data Exchange (ETDEWEB)

Oliveira, Ivan de, E-mail: ivan@ft.unicamp.brg; Capovilla, Danilo Augusto [GOMNI-Faculdade de Tecnologia/UNICAMP, Limeira (Brazil); Carvalho, Jesiel F.; Montenegro, Renata; Fabris, Zanine V. [Instituto de Física/Universidade Federal de Goiás, Goiânia (Brazil); Frejlich, Jaime [Instituto de Física “Gleb Wataghin”/UNICAMP, Campinas (Brazil)

2015-10-12

We report on the presence of a strong photovoltaic effect on nominally undoped photorefractive Bi{sub 2}TeO{sub 5} crystals and estimated their Glass photovoltaic constant and photovoltaic field for λ = 532 nm illumination. We directly measured the photovoltaic-based photocurrent in this material under λ = 532 nm wavelength laser light illumination and compared its behavior with that of a well known photovoltaic Fe-doped Lithium Niobate crystal. We also show the photovoltaic current to strongly depend on the polarization direction of light. Holographic diffraction efficiency oscillation during recording and the behavior of fringe-locked running holograms in self-stabilized experiments are also demonstrated here as additional indirect proofs of the photovoltaic nature of this material.

Evolution of local structure in Ag2O-TeO2 glasses with addition of Ag2O analyzed by pulsed neutron diffraction and Raman spectroscopy

International Nuclear Information System (INIS)

Iwadate, Yasuhiko; Suzuki, Mineta; Hattori, Takeo; Fukushima, Kazuko; Nishiyama, Shin; Misawa, Masakatsu; Fukunaga, Toshiharu; Itoh, Keiji

2005-01-01

The local structure of Ag 2 O-TeO 2 glasses was studied by time-of-flight pulsed neutron diffraction (TOF-PND) and Raman spectroscopy. The results of Raman spectroscopy indicated that TeO 4 trigonal bipyramidal units (tbp) were converted to TeO 3 trigonal pyramidal units (tp) by addition of Ag 2 O to TeO 2 . Furthermore in PND, the structural parameters for each atomic pair were optimized in the Q-space, and the distances of the near neighbor Te-O correlations forming tbp units and tp units in the network were estimated with some accuracy

Phase Equilibria Study in the TeO2-Na2O-SiO2 System in Air Between 723 K (500 °C) and 1473 K (1200 °C)

Science.gov (United States)

Santoso, Imam; Taskinen, Pekka

2016-08-01

Knowledge of phase equilibria in the TeO2-Na2O-SiO2 system at elevated temperatures is important for ceramic and glass industries and for improving the operation of the smelting process of tellurium-containing materials. A review of previous investigations has indicated, however, that there are omissions in the available datasets on the liquidus temperatures of the molten TeO2-Na2O-SiO2 mixtures. The employed experimental method included equilibration of mixtures made from high purity oxides, rapid quenching of the equilibrated samples in water and followed by compositional analysis of the phases using an electron probe X-ray microanalyzer. The liquidus and phase equilibria in the TeO2-SiO2, TeO2-Na2O, and SiO2-TeO2-Na2O systems have been studied for a wide range of compositions between 723 K (500 °C) and 1473 K (1200 °C) at TeO2, SiO2, and Na2SiO3 saturations. New data have been generated in the SiO2-TeO2-Na2O system at SiO2 saturation. The liquidus compositions in the TeO2-Na2O system at TeO2 saturation have been compared with the previous data and an assessed phase diagram.

Synthesis, structural, thermal and optical properties of TeO2-Bi2O3-GeO2-Li2O glasses

Science.gov (United States)

Dimowa, Louiza; Piroeva, Iskra; Atanasova-Vladimirova, S.; Petrova, Nadia; Ganev, Valentin; Titorenkova, Rositsa; Yankov, Georgi; Petrov, Todor; Shivachev, Boris L.

2016-10-01

In this study, synthesis and characterization of novel quaternary tellurite glass system TeO2-Bi2O3-GeO2-Li2O is presented. The compositions include TeO2 and GeO2 as glass formers while different proportion of Bi2O3 and Li2O act as network modifiers. Differential thermal analysis, X-ray diffraction, scanning electron microscopy energy dispersive X-ray spectroscopy, laser ablation inductively coupled plasma mass spectrometry, UV-Vis and Raman spectroscopy are applied to study the structural, thermal and optical properties of the studied glasses. Obtained glasses possess a relatively low glass transition temperature (around 300 °C) if compared to other tellurite glasses, show good thermal transparency in the visible and near infra-red (from 2.4 to 0.4 μm) and can double the frequency of laser light from its original wavelength of 1064 nm to its second-harmonic at 532 nm (i.e. second harmonic generation).

Electric behavior of functional glasses based on TeO{sub 2}; Comportamiento electrico de vidrios funcionales con base en TeO{sub 2}

Energy Technology Data Exchange (ETDEWEB)

Terny, S.; Rubia, M. a. de la; Barolin, S.; Alonso, R. E.; Frutos, J. de; Frechero, M. A.

2014-02-01

In this paper we study the structural and electrical behavior of glass-ceramic material of general formula: xMgO (1-x) (0.5V{sub 2}O{sub 5}.0.5MoO{sub 3})2TeO{sub 2} (0{<=} x{<=}0.9) through measurements of density, molar volume, oxygen packing density (OPD), differential scanning calorimetry (DSC) and Raman spectroscopy: electric behavior was studied by impedance spectroscopy. We found that magnesium cation induces the growth of slightly crystallized areas inside the material. Those nanocrystallizations were detected to a greater extent by atomic force microscopy (AFM) and in lesser extent by X-ray diffraction (XRD). Regarding the electrical measurements, it can be established that magnesium cation does not act as good ionic conductor in this material. (Author)

The science of EChO

Science.gov (United States)

Tinetti, Giovanna; Cho, James Y.-K.; Griffith, Caitlin A.; Grasset, Olivier; Grenfell, Lee; Guillot, Tristan; Koskinen, Tommi T.; Moses, Julianne I.; Pinfield, David; Tennyson, Jonathan; Tessenyi, Marcell; Wordsworth, Robin; Aylward, Alan; van Boekel, Roy; Coradini, Angioletta; Encrenaz, Therese; Snellen, Ignas; Zapatero-Osorio, Maria R.; Bouwman, Jeroen; Coudé du Foresto, Vincent; Lopez-Morales, Mercedes; Mueller-Wodarg, Ingo; Pallé, Enric; Selsis, Franck; Sozzetti, Alessandro; Beaulieu, Jean-Philippe; Henning, Thomas; Meyer, Michael; Micela, Giuseppina; Ribas, Ignasi; Stam, Daphne; Swain, Mark; Krause, Oliver; Ollivier, Marc; Pace, Emanuele; Swinyard, Bruce; Ade, Peter A. R.; Achilleos, Nick; Adriani, Alberto; Agnor, Craig B.; Afonso, Cristina; Allende Prieto, Carlos; Bakos, Gaspar; Barber, Robert J.; Barlow, Michael; Bernath, Peter; Bézard, Bruno; Bordé, Pascal; Brown, Linda R.; Cassan, Arnaud; Cavarroc, Céline; Ciaravella, Angela; Cockell, Charles; Coustenis, Athéna; Danielski, Camilla; Decin, Leen; De Kok, Remco; Demangeon, Olivier; Deroo, Pieter; Doel, Peter; Drossart, Pierre; Fletcher, Leigh N.; Focardi, Matteo; Forget, Francois; Fossey, Steve; Fouqué, Pascal; Frith, James; Galand, Marina; Gaulme, Patrick; González Hernández, Jonay I.; Grassi, Davide; Griffin, Matt J.; Grözinger, Ulrich; Guedel, Manuel; Guio, Pactrick; Hainaut, Olivier; Hargreaves, Robert; Hauschildt, Peter H.; Heng, Kevin; Heyrovsky, David; Hueso, Ricardo; Irwin, Pat; Kaltenegger, Lisa; Kervella, Patrick; Kipping, David; Kovacs, Geza; La Barbera, Antonino; Lammer, Helmut; Lellouch, Emmanuel; Leto, Giuseppe; Lopez Morales, Mercedes; Valverde, Lopez Miguel A.; Lopez-Puertas, Manuel; Lovi, Christophe; Maggio, Antonio; Maillard, Jean-Pierre; Prado, Jesus Maldonado; Marquette, Jean-Baptiste; Martin-Torres, Francisco J.; Maxted, Pierre; Miller, Steve; Molinari, Sergio; Montes, David; Moro-Martin, Amaya; Mousis, Olivier; Tuong, Napoléon Nguyen; Nelson, Richard; Orton, Glenn S.; Pantin, Eric; Pascale, Enzo; Pezzuto, Stefano; Poretti, Ennio; Prinja, Raman; Prisinzano, Loredana; Réess, Jean-Michel; Reiners, Ansgar; Samuel, Benjamin; Sanz Forcada, Jorge; Sasselov, Dimitar; Savini, Giorgio; Sicardy, Bruno; Smith, Alan; Stixrude, Lars; Strazzulla, Giovanni; Vasisht, Gautam; Vinatier, Sandrine; Viti, Serena; Waldmann, Ingo; White, Glenn J.; Widemann, Thomas; Yelle, Roger; Yung, Yuk; Yurchenko, Sergey

2011-11-01

The science of extra-solar planets is one of the most rapidly changing areas of astrophysics and since 1995 the number of planets known has increased by almost two orders of magnitude. A combination of ground-based surveys and dedicated space missions has resulted in 560-plus planets being detected, and over 1200 that await confirmation. NASA's Kepler mission has opened up the possibility of discovering Earth-like planets in the habitable zone around some of the 100,000 stars it is surveying during its 3 to 4-year lifetime. The new ESA's Gaia mission is expected to discover thousands of new planets around stars within 200 parsecs of the Sun. The key challenge now is moving on from discovery, important though that remains, to characterisation: what are these planets actually like, and why are they as they are? In the past ten years, we have learned how to obtain the first spectra of exoplanets using transit transmission and emission spectroscopy. With the high stability of Spitzer, Hubble, and large ground-based telescopes the spectra of bright close-in massive planets can be obtained and species like water vapour, methane, carbon monoxide and dioxide have been detected. With transit science came the first tangible remote sensing of these planetary bodies and so one can start to extrapolate from what has been learnt from Solar System probes to what one might plan to learn about their faraway siblings. As we learn more about the atmospheres, surfaces and near-surfaces of these remote bodies, we will begin to build up a clearer picture of their construction, history and suitability for life. The Exoplanet Characterisation Observatory, EChO, will be the first dedicated mission to investigate the physics and chemistry of Exoplanetary Atmospheres. By characterising spectroscopically more bodies in different environments we will take detailed planetology out of the Solar System and into the Galaxy as a whole. EChO has now been selected by the European Space Agency to be

Heat Treatment Effect on Eu3+ Doped TeO2-BaO-Bi2O3 Glass Systems with Ag Nanoparticles

Directory of Open Access Journals (Sweden)

Tomasz Lewandowski

2017-01-01

Full Text Available Glass systems of 73TeO2-4BaO-3Bi2O3-2Eu2O3-xAg (in molar ratio where x = 0, 1, 2, and 3 compositions have been successfully synthesized. Silver nanoparticles were obtained with the employment of heat treatment (HT procedure executed at 350°C. Glass transition temperatures of different compositions have been determined through DSC measurements. XRD results presented characteristic amorphous halo indicating lack of long range order in the samples. FTIR structural studies revealed that glass matrix is mainly composed of TeO3 and TeO4 species and is stable after different applied heat treatment times. X-ray photoelectron spectroscopy (XPS measurements confirmed that in selected samples part of Ag ions changed oxidation state to form Ag0 species. TEM measurements revealed nanoparticles of size in the range of 20–40 nm. UV-vis absorption results demonstrated characteristic transitions of Eu3+ ions. Additionally, UV-vis spectra of samples heat-treated for 6, 12, 24, and 48 hours presented bands related to silver nanoparticles. Photoluminescence (PL studies have been performed with excitation wavelength of λexc=395 nm. Obtained spectra exhibited peaks due to 5D0-7FJ (where J=2,3,4 and 5D1-7FJ (where J=1,2,3 transitions of Eu3+. Moreover, luminescence measurement indicated enhancement of rare earth ions emissions in several of the annealed samples. Increase of emission intensity of about 35% has been observed.

Thermal, optical and structural properties of glasses within the TeO{sub 2}-TiO{sub 2}-ZnO system

Energy Technology Data Exchange (ETDEWEB)

Ghribi, N. [CNRS-Université de Limoges, Science des Procédés Céramiques et de Traitements de Surface, UMR7315 CNRS, Centre Européen de la Céramique, 12 rue Atlantis, 87068 Limoges Cedex (France); Sciences des Matériaux et de l’Environnement Laboratory, Sfax University, Route de Soukra km 4, 3038 Sfax (Tunisia); Dutreilh-Colas, M.; Duclère, J.-R. [CNRS-Université de Limoges, Science des Procédés Céramiques et de Traitements de Surface, UMR7315 CNRS, Centre Européen de la Céramique, 12 rue Atlantis, 87068 Limoges Cedex (France); Hayakawa, T. [Field of Advanced Energy Conversion, Department of Frontier Materials, Nagoya Institute of Technology, Gokiso, Showa, Nagoya 466-8555 (Japan); Carreaud, J. [CNRS-Université de Limoges, Science des Procédés Céramiques et de Traitements de Surface, UMR7315 CNRS, Centre Européen de la Céramique, 12 rue Atlantis, 87068 Limoges Cedex (France); Karray, R.; Kabadou, A. [Sciences des Matériaux et de l’Environnement Laboratory, Sfax University, Route de Soukra km 4, 3038 Sfax (Tunisia); and others

2015-02-15

Highlights: • This paper reports on original results on new tellurium oxide-based glasses which are actually very promising glasses in the field of nonlinear optics. • We present for the first time the determination of a new glassy system and the structure of the glasses has been investigated using Raman spectroscopy which is actually the most adapted method in laboratory to study the local structure of tellurite glasses, a detail linear and non-linear optical study is also presented. - Abstract: A glass-forming domain was evidenced and studied within the TeO{sub 2}-TiO{sub 2}-ZnO system. Density, glass transition temperature (T{sub g}) and onset crystallization temperature (T{sub 0}) were measured and interpreted as a function of the zinc oxide mole fraction for relevant glasses. It was concluded that the zinc oxide favors the thermal stability of glasses. On the other hand, the impact of TiO{sub 2} addition is even more pronounced on the enhancement of the thermal stability. The optical transmission was recorded for series of glasses in the UV-Visible-NIR range. Refractive index and optical band gap were extracted from these measurements and studied as a function of the ZnO content. Linear refractive indices and optical band gap were found to decrease and increase respectively, with increasing ZnO content. The third-order non-linear susceptibility Re (χ{sup 3}), measured for two series of glasses (TiO{sub 2} content was fixed either to 5 or 10 mol%), was found to progressively decrease when the ZnO concentration increases. The impact of ZnO modifier on the glass structure was discussed based on Raman spectroscopy data. We evidenced that TiO{sub 2} does not change drastically the glass network, whereas ZnO leads in a first step to the breaking of the Te-O-Te bridges, inducing network depolymerization. A further addition in ZnO leads to the formation of new Te-O-Zn and Zn-O-Zn linkages.

2.3 µm laser potential of TeO2 based glasses

Science.gov (United States)

Denker, B. I.; Dorofeev, V. V.; Galagan, B. I.; Motorin, S. E.; Sverchkov, S. E.

2017-09-01

Tm3+ doped TeO2-based well-dehydrated glasses were synthesized and investigated. The analysis of their spectral and relaxation properties have showed that these glasses can be a suitable host for bulk and fiber lasers emitting at ~2.3 µm wavelength (3H4-3H5 Tm3+ transition). Laser action in the bulk glass sample was demonstrated.

Dispersion and guidance characteristics of microstructured 68TeO2 - 22WO3 - 8La2O3 - 2Bi2O3 glass fibres for supercontinuum generation

International Nuclear Information System (INIS)

Yatsenko, Yu P; Nazaryants, V O; Kosolapov, A F; Astapovich, M S; Plotnichenko, V G; Dianov, Evgenii M; Moiseev, A N; Churbanov, M F; Dorofeev, V V; Chilyasov, A V; Snopatin, G E

2010-01-01

We report the preparation of a high-purity optical-quality four-component glass of composition 68TeO 2 - 22WO 3 - 8La 2 O 3 - 2Bi 2 O 3 , containing (2.7±0.5)x10 -5 mol % OH groups. Its refractive index has been determined in the range 0.9 - 5.45 μm using interference refractometry. The data are used to assess the dispersion and guidance characteristics of microstructured optical fibres potentially attractive for supercontinuum generation in the range 1 - 5 μm (optical fibres)

Electric behavior of functional glasses based on TeO2

International Nuclear Information System (INIS)

Terny, S.; Rubia, M. a. de la; Barolin, S.; Alonso, R. E.; Frutos, J. de; Frechero, M. A.

2014-01-01

In this paper we study the structural and electrical behavior of glass-ceramic material of general formula: xMgO (1-x) (0.5V 2 O 5 .0.5MoO 3 )2TeO 2 (0≤ x≤0.9) through measurements of density, molar volume, oxygen packing density (OPD), differential scanning calorimetry (DSC) and Raman spectroscopy: electric behavior was studied by impedance spectroscopy. We found that magnesium cation induces the growth of slightly crystallized areas inside the material. Those nanocrystallizations were detected to a greater extent by atomic force microscopy (AFM) and in lesser extent by X-ray diffraction (XRD). Regarding the electrical measurements, it can be established that magnesium cation does not act as good ionic conductor in this material. (Author)

DSC, Raman and impedance spectroscopy studies on the xB2O3 - (90 - x)TeO2 - 10TiO2 (where x = 0 to 50 mol%) glass system

Science.gov (United States)

Sripada, Suresh; Rani, D. Esther Kalpana; Upender, G.; Pavani, P. Gayathri

2013-03-01

Titanium boro tellurite glasses in the xB2O3 -(90- x) TeO2 - 10TiO2 (where x = 0 to 50 mol%) system were prepared by using the conventional melt-quenching technique. Glass transition temperatures were measured with differential scanning calorimetry (DSC) and found to be in the range of 300-370 °C. The Raman spectra showed a cleavage of the continuous TeO4 (tbp) network by breaking of the Te-O-Te linkages. The relative transition of TeO4 - groups to TeO3 - groups is accompanied by a change in the oxygen coordination of the boron from 3 to 4 (BO3 - to BO4 -). The impedance plots Z″( ω) versus Z'( ω) for all the glass samples were recorded and found to exhibit a single circle. The AC conductivity of all glass samples was studied in the frequency range from 100 Hz to 1 MHz and in the temperature range from room temperature (RT) to 375 °C. The AC conductivity decreased by about one order in magnitude with increasing B2O3 content. The conductivity was found to be on the order of 10-4.5 to 10-6 (Ωcm)-1 at 375 °C and 1 MHz for 10 mol% and 50 mol% B2O3 contents, respectively. The relaxation behavior in these glass samples is discussed based on the complex modulus and impedance data.

YCu(TeO32(NO3(H2O3: a novel layered tellurite

Directory of Open Access Journals (Sweden)

Stuart J. Mills

2016-08-01

Full Text Available A new hydrated yttrium copper tellurite nitrate, yttrium(III copper(II bis[trioxidotellurate(IV] nitrate trihydrate, has been synthesized hydrothermally in a Teflon-lined autoclave and structurally determined using synchrotron radiation. The new phase is the first example containing yttrium, copper and tellurium in one structure. Its crystal structure is unique, with relatively strongly bound layers extending parallel to (020, defined by YO8, CuO4 and TeO3 polyhedra, while the NO3− anions and one third of the water molecules lie between those layers. The structural unit consists of [Cu2(TeO34]4− loop-branched chains of {Cu...Te...Cu...Te} squares running parallel to [001], which are linked further into layers only through Y(O,H2O8 polyhedra. Weak `secondary' Te bonds and O—H...O hydrogen-bonding interactions, involving water molecules and layer O atoms, link the layers and interlayer species. IR spectroscopic data are also presented.

Plan for the sawtooth control by the ECH in KSTAR

International Nuclear Information System (INIS)

Jeong, J.H.; Bae, Y.S.; Joung, M.

2013-01-01

The sawtooth control in tokamak is very important because the long period sawtooth is able to trigger TM/NTMs which are significantly reducing the operational performance of plasma and even lead disruptions. The different sawtooth period behaviors by ECH and NBI with different injection conditions are observed in KSTAR during the 2012 campaign. The period of sawtooth is shortened by on-axis X2 110 GHz ECCD in NB-heated plasmas, and the stabilization of the sawtooth is also observed by off-axis X2 110 GHz ECCD. This means that the sawtooth period can be controlled in an accurate way by various EC beam injection conditions in KSTAR and to lengthen it as well. Two new recent sawtooth control methods are of interest and under the plan in KSTAR experiments: sawtooth locking and sawtooth pacing which is a well-known technique to control the sawtooth period behavior by periodic forcing by electron cyclotron waves nearby q=1 surface. The locking range can be investigated with a variable deposition location and the modulated RF power with a certain period and duty cycle in an open-loop control. And then, using the best parameters to lengthen in a controlled-way the sawtooth period, the relations between the sawtooth period and triggering of TM/NTM will be obtained at different beta values. For these experiments, the real-time control development of EC beam power modulation is under plan to control the sawtooth periods to a desired value. This requires the arbitrary power modulation of EC beam synchronized with external waveform generator which can be set the various modulation frequencies. This paper presents the sawtooth characteristics in present KSTAR operation scenario and the plan of the real-time sawtooth control. Also, the upgrade plan of the fast EC power modulation is presented including the present status of KSTAR ECH systems. (author)

Effect of TeO2 on the elastic moduli of sodium borate glasses

International Nuclear Information System (INIS)

Saddeek, Y.B.; Abd El Latif, Lamia

2004-01-01

Sodium borate glass containing tellurite as Te x Na 2-2x B 4-4x O 7-5x with x=0, 0.05, 0.15, 0.25 and 0.35 have been prepared by rapid quenching. Ultrasonic velocity (both longitudinal and shear) measurements have been made using a transducer operated at the fundamental frequency of 4 MHz at room temperature. The density was measured by the conventional Archimedes method. The elastic moduli, the Debye temperature, Poisson's ratio, and the parameters derived from the Makishima-Mackenzie model and the bond compression model have been obtained as a function of TeO 2 content. The monotonic decrease in the velocities and the elastic moduli, and the increase in the ring diameter and the ratio K bc /K e as a function of TeO 2 modifier content reveals the loose packing structure, which is attributed to the increase in the molar volume and the reduction in the vibrations of the borate lattice. The observed results confirm that the addition of TeO 2 changes the rigid character of Na 2 B 4 O 7 to a matrix of ionic behaviour bonds (NBOs). This is due to the creation of more and more discontinuities and defects in the glasses, thus breaking down the borax structure

Optical properties of ternary TeO2-B2O3-ZnO Glass system

International Nuclear Information System (INIS)

Nurfarhana Ayuni Joha; Halimah, M.K.; Talib, Z.A.; Sidek, H.A.A.; Daud, W.M.; Zaidan, A.W.; Khamirul, A.M.

2009-01-01

Full text: A series of ternary tellurite based glasses [ (TeO 2 ) 70 (B 2 0 3 ) 30 ] 100-x [ZnO] x glasses with different compositions of ZnO (x= 5 to 30 wt.% in steps of 5 wt.%) have been synthesized by melt quenching method. The role of ZnO to the glasses structure was studied by IR spectroscopy. FTIR spectra revealed broad, weak and strong absorption bands in the investigated range of wavenumber from 280 - 4000 cm -1 which associated with their corresponding bond modes of vibration and the glass structure. The indirect optical band gap and the direct optical band gap are in the range 2.08-3.12 and 1.54-2.36 eV, respectively. An increase in the values of energy band gap E g may come down to the reason that the non-bridging oxygen ion content decreases with increasing ZnO content and shifting the band edge to higher energies. The optical band gap and Urbach energies were calculated from the absorption spectra measured between 190 and 900 nm at room temperature. The refractive index, n of the glasses change from 1.84 - 2.00 while the molar refractivities decrease from 13.06 to 12.00 with the increase of ZnO in mol %. (author)

Evaluation of TeO2 content on the optical and spectroscopic properties of Yb3 +-doped calcium borotellurite glasses

Science.gov (United States)

Lima, A. M. O.; Gomes, J. F.; Hegeto, F. L.; Medina, A. N.; Steimacher, A.; Barboza, M. J.

2018-03-01

This paper reports the synthesis and the characterization of Yb3 +-doped calcium borotellurite (CaBTeX) glasses with composition 10CaF2-(29.5 - 0.4x)CaO-(60 - 0.6x)B2O3-xTeO2-0.5Yb2O3 (x = 10, 16, 22, 31 and 54 mol%). The results of XRD confirm the amorphous character of all the samples. The density, molar volume, refractive index and electronic polarizability values show an increase with TeO2 content. Otherwise, the optical band gap energy shows a decrease with the increase of TeO2 content. The replacement of CaO and B2O3 by TeO2 changes the glass structure, which decreases the excited Yb3 +/cm3 and, consequently, the luminescence intensity. The temperature dependence of luminescence was studied for all the samples up to 420 K. The fluorescence lifetime does not change significantly due to TeO2 addition. In addition, absorption and emission cross section were calculated and present high values as compared to other tellurite and phosphate glasses.

Kinetic study and application of analytical techniques in the obtention of TeO2 for the production of 131 I

International Nuclear Information System (INIS)

Plata D, G.

2006-01-01

The objectives of this investigation work were: A) To synthesize TeO 2 starting from the reaction among the Te and HNO 3 with a superior yield to 90% b) To determine the good temperature of obtaining of the TeO 2 at laboratory level, c) To determine those constant of reaction kinetics, for each one of the tests carried out to different temperatures, and the activation energy of the reaction, d) To characterize the produced TeO 2 , e) To check the viability of using the obtained TeO 2 as raw matter in the production of 131 I in order to contribute to the technological development of our country inside the radioisotope production area. The production process of TeO 2 consists primarily of seven phases: 1) Preparing and assembly of the production equipment of TeO 2 , 2) Oxidation reaction of tellurium, 3) Drying and elimination of sludges of TeO 2 , 4) Sintering of TeO 2 , 5) Characterization of the TeO 2 by means of analytical techniques, 6) Irradiation of the TeO 2 , 7) Quality control. The present document has five chapters, which allow the reader to follow the development of this work to achieve the objectives and to contrast with the hypothesis of the work. (Author)

Optical Properties of Ternary TeO2-B2O3-ZnO Glass System

Energy Technology Data Exchange (ETDEWEB)

Ayuni, J N; Halimah, M K; Talib, Z A; Sidek, H A A; Daud, W M; Zaidan, A W; Khamirul, A M, E-mail: nfarhanayuni@gmail.com, E-mail: halimah@science.upm.edu.my [Department of Physics, Faculty of Science, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor (Malaysia)

2011-02-15

A series of ternary tellurite based glasses [(TeO2)70 (B203)30]100-x [ZnO]x glasses with different compositions of ZnO (x= 5 to 30 wt.% in steps of 5 wt.%) have been synthesized by melt quenching method. The role of ZnO to the glasses structure was studied by IR spectroscopy. FTIR spectra revealed broad, weak and strong absorption bands in the investigated range of wavenumber from 280-4000 cm-1 which associated with their corresponding bond modes of vibration and the glass structure. The indirect optical band gap and the direct optical band gap are in the range 2.08-3.12 and 1.54-2.36 eV, respectively. A decrease in the values of energy band gap Eg may come down to the reason that the non-bridging oxygen ion content increases with increasing ZnO content and shifting the band edge to lower energies. The optical band gap and Urbach energies were calculated from the absorption spectra measured between 190 and 900 nm at room temperature. The refractive index, n of the glasses change from 1.84-2.00 while the molar refractivities decrease from 13.06 to 12.00 with the increase of ZnO in mol%.

Optical Properties of Ternary TeO2-B2O3-ZnO Glass System

International Nuclear Information System (INIS)

Ayuni, J N; Halimah, M K; Talib, Z A; Sidek, H A A; Daud, W M; Zaidan, A W; Khamirul, A M

2011-01-01

A series of ternary tellurite based glasses [(TeO2)70 (B203)30]100-x [ZnO]x glasses with different compositions of ZnO (x= 5 to 30 wt.% in steps of 5 wt.%) have been synthesized by melt quenching method. The role of ZnO to the glasses structure was studied by IR spectroscopy. FTIR spectra revealed broad, weak and strong absorption bands in the investigated range of wavenumber from 280-4000 cm-1 which associated with their corresponding bond modes of vibration and the glass structure. The indirect optical band gap and the direct optical band gap are in the range 2.08-3.12 and 1.54-2.36 eV, respectively. A decrease in the values of energy band gap Eg may come down to the reason that the non-bridging oxygen ion content increases with increasing ZnO content and shifting the band edge to lower energies. The optical band gap and Urbach energies were calculated from the absorption spectra measured between 190 and 900 nm at room temperature. The refractive index, n of the glasses change from 1.84-2.00 while the molar refractivities decrease from 13.06 to 12.00 with the increase of ZnO in mol%.

Nd3+-doped TeO2-Bi2O3-ZnO transparent glass ceramics for laser application at 1.06 μm

Science.gov (United States)

Hu, Xiaolin; Luo, Zhiwei; Liu, Taoyong; Lu, Anxian

2017-04-01

The high crystallinity transparent glass ceramics based on Nd3+-doped 70TeO2-15Bi2O3-15ZnO (TBZ) compositions were successfully prepared by two-step heat treatment process. The effects of Nd2O3 content on the thermal, structural, mechanical, and optical properties of TBZ glass ceramics were studied. The incorporation of Nd2O3 enhanced the crystallization tendency in the matrix glass composition. The crystal phase and morphology of Bi2Te4O11 in the glass ceramics were confirmed by X-ray diffraction and field emission scanning electron microscopy. Due to precipitate more crystal phase, the hardness values increased from 3.21 to 3.66 GPa. Eight absorption peaks were observed from 400 to 900 nm and three emission bands appeared in the range of 850-1400 nm. With the increasing of Nd2O3 content from 0.5 to 2.5 wt%, the intensity of absorption peaks enhanced and the emission intensity increased up to 1.0 wt% and then fell down for further dopant concentration. The fluorescence decay lifetime decreased rapidly starting from 1.5 wt% Nd2O3 content due to the obvious energy migration among Nd3+. According to the extreme strong emission band around 1062 nm and the optimum Nd2O3 content (1.0 wt%), N10 glass ceramic was considered as a potential material for 1.06 μm laser applications.

Improvements in 130Te double beta decay search with cryogenic TeO2 array detectors

International Nuclear Information System (INIS)

Alessandrello, A.; Brofferio, C.; Bucci, C.; Caspani, P.; Cremonesi, O.; Fiorini, E.; Giuliani, A.; Nucciotti, A.; Pavan, M.; Pessina, G.; Previtali, E.; Zanotti, L.

1996-01-01

Single crystal TeO 2 bolometers have been used since 5 years ago to search for neutrinoless DBD of 130 Te. During the last year, our group has been studying and preparing the first array of 4 crystals, 340 g each, opening this technique to new frontiers in rare events' physics. The results and perspectives of this second generation cryogenic detectors are here reported and discussed, with particular emphasis on the peculiarities which make them feasible for a consistent upgrading of our previous result in DBD search. (orig.)

Kinetic study and application of analytical techniques in the obtention of TeO{sub 2} for the production of {sup 131} I; Estudio cinetico y aplicacion de tecnicas analiticas en la obtencion de TeO{sub 2} para la produccion de {sup 131} I

Energy Technology Data Exchange (ETDEWEB)

Plata D, G

2006-07-01

The objectives of this investigation work were: A) To synthesize TeO{sub 2} starting from the reaction among the Te and HNO{sub 3} with a superior yield to 90% b) To determine the good temperature of obtaining of the TeO{sub 2} at laboratory level, c) To determine those constant of reaction kinetics, for each one of the tests carried out to different temperatures, and the activation energy of the reaction, d) To characterize the produced TeO{sub 2}, e) To check the viability of using the obtained TeO{sub 2} as raw matter in the production of {sup 131} I in order to contribute to the technological development of our country inside the radioisotope production area. The production process of TeO{sub 2} consists primarily of seven phases: 1) Preparing and assembly of the production equipment of TeO{sub 2}, 2) Oxidation reaction of tellurium, 3) Drying and elimination of sludges of TeO{sub 2}, 4) Sintering of TeO{sub 2}, 5) Characterization of the TeO{sub 2} by means of analytical techniques, 6) Irradiation of the TeO{sub 2}, 7) Quality control. The present document has five chapters, which allow the reader to follow the development of this work to achieve the objectives and to contrast with the hypothesis of the work. (Author)

Screened coulomb hybrid DFT study on electronic structure and optical properties of anionic and cationic Te-doped anatase TiO2

KAUST Repository

Harb, Moussab

2013-06-27

The origin of the enhanced visible-light optical absorption in Te-doped bulk anatase TiO2 is investigated in the framework of DFT and DFPT within HSE06 in order to ensure accurate electronic structure and optical transition predictions. Various oxidation states of Te species are considered based on their structural location in bulk TiO2. In fact, TiO (2-x)Tex (with isolated Te2- species at Te-Te distance of 8.28 Å), TiO2Tex (with isolated TeO 2- species at Te-Te distance of 8.28 Å), TiO2Te 2x (with two concomitant TeO2- species at Te-Te distance of 4.11 Å), and Ti(1-2x)O2Te2x (with two neighboring Te4+ species at nearest-neighbor Te-Te distance of 3.05 Å) show improved optical absorption responses in the visible range similarly as it is experimentally observed in Te-doped TiO2 powders. The optical absorption edges of TiO(2-x)Tex, TiO 2Tex, and TiO2Te2x are found to be red-shifted by 400 nm compared with undoped TiO2 whereas that of Ti(1-2x)O2Te2x is red-shifted by 150 nm. On the basis of calculated valence and conduction band edge positions of Te-doped TiO2, only TiO(2-x)Tex and Ti (1-2x)O2Te2x show suitable potentials for overall water splitting under visible-light irradiation. The electronic structure analysis revealed narrower band gaps of 1.12 and 1.17 eV with respect to undoped TiO2, respectively, resulting from the appearance of new occupied electronic states in the gap of TiO2. A delocalized nature of the gap states is found to be much more pronounced in TiO (2-x)Tex than that with Ti(1-2x)O 2Te2x due to the important contribution of numerous O 2p orbitals together with Te 5p orbitals. © 2013 American Chemical Society.

Single-step synthesis of In{sub 2}O{sub 3} nanowires decorated with TeO{sub 2} nanobeads and their acetone-sensing properties

Energy Technology Data Exchange (ETDEWEB)

Park, Sunghoon; Kheel, Hyejoon; Sun, Gun-Joo; Lee, Chongmu [Inha University, Department of Materials Science and Engineering, Incheon (Korea, Republic of); Park, Sang Eon [Inha University, Department of Chemistry, Incheon (Korea, Republic of)

2016-04-15

In{sub 2}O{sub 3} nanowires decorated with TeO{sub 2} nanobeads were synthesized by a facile single-step thermal evaporation process, and their acetone-gas-sensing properties were examined. The diameters and lengths of the In{sub 2}O{sub 3} nanowires ranged from 10 to 20 nm and up to 100 μm, respectively, whereas the diameters of the TeO{sub 2} beads ranged from 50 to 200 nm. The TeO{sub 2}-decorated In{sub 2}O{sub 3} nanowire sensor showed stronger response to acetone gas than the pristine In{sub 2}O{sub 3} nanowire sensor. The pristine and TeO{sub 2}-decorated In{sub 2}O{sub 3} nanowires exhibited sensitivity of ∝10.13 and ∝24.87, respectively, to 200 ppm acetone at 300 C. The decorated nanowire sensor also showed much more rapid response and recovery than the latter. Both sensors showed the strongest response to acetone gas at 300 C, respectively. The mechanism and origin of the enhanced acetone-gas-sensing performance of the TeO{sub 2}-decorated In{sub 2}O{sub 3} nanowire sensor compared to the pristine In{sub 2}O{sub 3} nanowire sensor were discussed in detail. The enhanced sensing performance of the TeO{sub 2}-decorated In{sub 2}O{sub 3} nanowire is mainly due to the modulation of the potential barrier height at the TeO{sub 2}-In{sub 2}O{sub 3} interface, high catalytic activity of TeO{sub 2,} and creation of active adsorption sites by incorporation of TeO{sub 2}. (orig.)

2 MW 110 GHz ECH heating system for DIII-D

International Nuclear Information System (INIS)

Moeller, C.; Prater, R.; Callis, R.; Remsen, D.; Doane, J.; Cary, W.; Phelps, R.; Tupper, M.

1990-09-01

A 2 MW 110 GHz ECH system using Varian 0.5 MW gyrotrons is under construction for use on the DIII-D tokamak by late 1991. Most of the components are being design and fabricated at General Atomics, including the gyrotron tanks, superconducting magnets, and transmission line. These components are intended for operation with 10 second pulses and, in the future, with 1 MW gyrotrons. 6 refs., 5 figs

Investigation of thermal stability and spectroscopic properties in Er3+/Yb3+-codoped TeO2-Li2O-B2O3-GeO2 glasses.

Science.gov (United States)

Nie, Qiu-Hua; Gao, Yuan; Xu, Tie-Feng; Shen, Xiang

2005-06-01

The new Er3+/Yb3+ co-doped 70TeO2-5Li2O-(25-x)B2O3-xGeO2 (x = 0, 5, 10, 15 fand 20 mol.%) glasses were prepared. The thermal stability, absorption spectra, emission spectra and lifetime of the 4I(13/2) level of Er3+ ions were measured and studied. The FT-IR spectra were carried out in order to investigate the structure of local arrangements in glasses. It is found that the thermal stability, absorption cross-section of Yb3+, emission intensity and lifetime of the 4I(13/2) level of Er3+ increase with increasing GeO2 content in the glass composition, while the fluorescence width at half maximum (FWHM) at 1.5 um of Er3+ is about 70 nm. The obtained data suggest that this system glass can be used as a candidate host material for potential broadband optical amplifiers.

Conduction and reversible memory phenomena in Au-nanoparticles-incorporated TeO{sub 2}–ZnO films

Energy Technology Data Exchange (ETDEWEB)

Bontempo, L., E-mail: bontempo@usp.br [Laboratório de Sistemas Integráveis, Escola Politécnica da Universidade de São Paulo, Av. Prof. Luciano Gualberto, 158, Travessa 3, 05508-900 São Paulo, SP (Brazil); Laboratório de Materiais Fotônicos e Optoeletrônicos, Faculdade de Tecnologia de São Paulo, Praça Cel. Fernando Prestes, 30, 01124-060 São Paulo, SP (Brazil); Santos Filho, S.G. dos, E-mail: sgsantos@usp.br [Laboratório de Sistemas Integráveis, Escola Politécnica da Universidade de São Paulo, Av. Prof. Luciano Gualberto, 158, Travessa 3, 05508-900 São Paulo, SP (Brazil); Kassab, L.R.P., E-mail: kassablm@osite.com.br [Laboratório de Materiais Fotônicos e Optoeletrônicos, Faculdade de Tecnologia de São Paulo, Praça Cel. Fernando Prestes, 30, 01124-060 São Paulo, SP (Brazil)

2016-07-29

A reversible memory behavior in TeO{sub 2}–ZnO thin films containing Au nanoparticles prepared using the sputtering technique has been observed. The current–voltage characteristics of the films, having Al and Si as electrodes, showed a switching behavior starting from an initial state of low conductivity to a high conductivity one. As a result, an abrupt increase of current (10{sup −7} to 10{sup −3} A) was observed for 6.5 V (100 nm thickness). Au nanoparticles provide a larger electron storage capability, and do not favor the transport through the insulator; they present a higher trapped charge concentration, which reduces the leakage current to lower levels. The influence of the Au nanoparticle diameter and volumetric concentration to reach the abrupt current transition and the value of the transition voltage was studied. These parameters were found to play an important role on reversible memory phenomena as they determine the facility/difficulty to fill and saturate the traps (Au nanoparticles) with electrons. - Highlights: • TeO{sub 2}–ZnO thin films with Au nanoparticles grown by magnetron co-sputtering for memory devices • Nucleation of gold nanoparticles by annealing process • Electrical properties of TeO{sub 2}–ZnO thin films with and without gold nanoparticles • Reversible memory phenomenum in Au-nanoparticles-incorporated TeO{sub 2}–ZnO thin films.

Optical spectroscopy of Sm(3+) doped Na2O-ZnO-La2O3-TeO2 glasses.

Science.gov (United States)

Sobczyk, Marcin

2015-10-05

Telluride glasses with the composition xSm2O3-(7-x)La2O3-3Na2O-25ZnO-65TeO2 (where x=0.1, 1, 2, 5 and 7 mol%) were obtained by the melt quenching technique. Electronic absorption and fluorescence spectra as well as fluorescence dynamics of the Sm(3+)-doped title glasses are presented and analysed in detail. A Judd-Ofelt intensity analysis of the absorption spectrum at 300 K has been applied for determination of Ωλ parameters (Ω2=3.10, Ω4=3.80, Ω6=1.61×10(-20) cm(2)) which in turn have been used for calculations of the radiative transition probabilities (AT), the natural (radiative) lifetimes (τR) of the (4)G5/2 level of Sm(3+), the fluorescence branching ratios (β) and the emission cross-sections (σem). The τR value of the (4)G5/2 level amount to 1546 μs and is slightly higher than the measured decay time of 1306 μs. With the increasing of Sm2O3 concentration from 0.1 to 7.0 mol% the experimental lifetime of the fluorescent level decreases from 1306 to 41 μs. An analysis of the non-radiative decay was based on the cross-relaxation mechanisms. The optical achieved results indicate that the investigated glasses are potentially applicable as an orange and/or red laser host. Copyright © 2015 Elsevier B.V. All rights reserved.

Design and construction of the equipment and obtention process of TeO2 for the 131 I production

International Nuclear Information System (INIS)

Alanis M, J.

2000-09-01

This project was carried out in the National Institute of Nuclear Research, Nuclear Center of Mexico (ININ), with the name 'A New Method to Obtain 131 I by Neutron Irradiation of TeO 2 and it Dry Distillation'. This work establishes the optimal parameters to produce 131 I by neutron irradiation and foundry of TeO 2 sinterized. The TeO 2 of high purity was produced adding HNO 3 to the metallic tellurium (Merck 8100) and heating several samples to different temperatures until dryness in presence of an air current. The optimal conditions of temperature and reaction velocity were obtained, as well as of drying and sintering, to obtain TeO 2 crystals with high purity able to retain the 131 I produced by the radioactive decay. After drying and purified by the heating, the TeO 2 was sinterized, applying a next temperature to it melting point by few minutes, enough to create cavities in the middle of it crystalline structure, where the 131 I in gas form produced by the decay of the 131 Te it is retained, one time that the TeO 2 is bombarded with thermal neutrons in the nuclear reactor. Then, the reactions 130 Te(n, γ) 131 Te m (t 1/2 = 30 h) and 130 Te(n, γ) 131 Te (t 1/2 = 24.8 m) with an optimal irradiation time of 2.5 h. (Author)

Synthesis, structure, and characterization of two new bismuth(III) selenite/tellurite nitrates: [(Bi3O2)(SeO3)2](NO3) and [Bi(TeO3)](NO3)

Science.gov (United States)

Meng, Chang-Yu; Wei, Ming-Fang; Geng, Lei; Hu, Pei-Qing; Yu, Meng-Xia; Cheng, Wen-Dan

2016-07-01

Two new bismuth(III) selenite/tellurite nitrates, [(Bi3O2)(SeO3)2](NO3) and [Bi(TeO3)](NO3), have been synthesized by conventional facile hydrothermal method at middle temperature 200 °C and characterized by single-crystal X-ray diffraction, powder diffraction, UV-vis-NIR optical absorption spectrum, infrared spectrum and thermal analylsis. Both [(Bi3O2)(SeO3)2](NO3) and [Bi(TeO3)](NO3) crystallize in the monoclinic centronsymmetric space group P21/c with a=9.9403(4) Å, b=9.6857(4) Å, c=10.6864(5) Å, β=93.1150(10)° for [(Bi3O2)(SeO3)2](NO3) and a=8.1489(3) Å, b=9.0663(4) Å, c=7.4729(3) Å, β=114.899(2)° for Bi(TeO3)(NO3), respectively. The two compounds, whose structures are composed of three different asymmetric building units, exhibit two different types of structures. The structure of [(Bi3O2)(SeO3)2](NO3) features a three-dimensional (3D) bismuth(III) selenite cationic tunnel structure [(Bi3O2)(SeO3)2] 3∞ with NO3- anion group filling in the 1D tunnel along b axis. The structure of [Bi(TeO3)](NO3) features 2D bismuth(III) tellurite [Bi(TeO3)2]2∞ layers separated by NO3- anion groups. The results of optical diffuse-reflectance spectrum measurements and electronic structure calculations based on density functional theory methods show that the two compounds are wide band-gap semiconductors.

Phase change behaviors of Zn-doped Ge2Sb2Te5 films

International Nuclear Information System (INIS)

Wang Guoxiang; Nie Qiuhua; Shen Xiang; Fu Jing; Xu Tiefeng; Dai Shixun; Wang, R. P.; Wu Liangcai

2012-01-01

Zn-doped Ge 2 Sb 2 Te 5 phase-change materials have been investigated for phase change memory applications. Zn 15.16 (Ge 2 Sb 2 Te 5 ) 84.84 phase change film exhibits a higher crystallization temperature (∼258 °C), wider band gap (∼0.78 eV), better data retention of 10 years at 167.5 °C, higher crystalline resistance, and faster crystallization speed compared with the conventional Ge 2 Sb 2 Te 5 . The proper Zn atom added into Ge 2 Sb 2 Te 5 serves as a center for suppression of the face-centered-cubic (fcc) phase to hexagonal close-packed (hcp) phase transition, and fcc phase has high thermal stability partially due to the bond recombination among Zn, Sb, and Te atoms.

Design and construction of the equipment and obtention process of TeO{sub 2} for the {sup 131} I production; Diseno y construccion del equipo y proceso de obtencion de TeO{sub 2} para la produccion de {sup 131} I

Energy Technology Data Exchange (ETDEWEB)

Alanis M, J. [ININ, Departamento de Materiales Radiactivos, 52045 Ocoyoacac, Estado de Mexico (Mexico)

2000-09-15

This project was carried out in the National Institute of Nuclear Research, Nuclear Center of Mexico (ININ), with the name 'A New Method to Obtain {sup 131}I by Neutron Irradiation of TeO{sub 2} and it Dry Distillation'. This work establishes the optimal parameters to produce {sup 131}I by neutron irradiation and foundry of TeO{sub 2} sinterized. The TeO{sub 2} of high purity was produced adding HNO{sub 3} to the metallic tellurium (Merck 8100) and heating several samples to different temperatures until dryness in presence of an air current. The optimal conditions of temperature and reaction velocity were obtained, as well as of drying and sintering, to obtain TeO{sub 2} crystals with high purity able to retain the {sup 131}I produced by the radioactive decay. After drying and purified by the heating, the TeO{sub 2} was sinterized, applying a next temperature to it melting point by few minutes, enough to create cavities in the middle of it crystalline structure, where the {sup 131}I in gas form produced by the decay of the {sup 131}Te it is retained, one time that the TeO{sub 2} is bombarded with thermal neutrons in the nuclear reactor. Then, the reactions {sup 130}Te(n, {gamma}){sup 131}Te{sup m} (t{sub 1/2} = 30 h) and {sup 130}Te(n, {gamma}){sup 131}Te (t{sub 1/2} = 24.8 m) with an optimal irradiation time of 2.5 h. (Author)

Design and construction of a prototype to obtain TeO2

International Nuclear Information System (INIS)

Roque H, I.

1997-01-01

At the National Institute of Nuclear Research is developed the process to produce the radioisotope Iodine 131 which is employed in medicine with therapeutical purposes. The raw material to produce iodine 131 is tellurium dioxide (TeO 2 ). TeO 2 is intended to be produced from a prototype being this aim of this thesis named D esign and construction of a prototype to obtain TeO 2 . The TeO 2 obtained must have specific physicochemical characteristics, being necessary an special design of a prototype which will guarantee the quality of tellurium dioxide obtention. Design and building the final prototype project, was developed in to three stages. At the first stage, the TeO 2 was obtained at the laboratory, this allows to know the basic reaction characteristics. The second stage purpose, was to work with an former prototype which allowed to produce 100 g of tellurium dioxide. In the last stage a depurated chemical process parameters was made and the prototype was refined in regard to its mechanical design, giving us as result the final prototype. With this final prototype, the production reaches 2 Kg/week of tellurium dioxide with the best physicochemical properties which is to be employed as raw material in order to produce iodine 131. (Author)

PbTe mechanosynthesis from PbO and Te

International Nuclear Information System (INIS)

Rojas-Chavez, Hugo; Diaz-de la Torre, Sebastian; Jaramillo-Vigueras, David; Plascencia, Gabriel

2009-01-01

Experimental results concerning the mechanosynthesis (MSY), of PbTe from the PbO-Te powder system, at room temperature an atmospheric conditions are reported. XRD results for samples milled for and after 5.4 ks only show PbTe diffraction peaks; neither Te nor PbO or any other solid phase were detected. Particle size and morphology, was followed by SEM observations. Phase evolution and quantification was monitored by Rietveld refinements of the X-ray diffraction data. It was found that the use of lead oxide as a component of the mechanosynthesis system reduces milling time with respect to the Pb-Te metallic system with mechanical alloying.

Admittance of MIS-Structures Based on HgCdTe with a Double-Layer CdTe/Al2O3 Insulator

Science.gov (United States)

Dzyadukh, S. M.; Voitsekhovskii, A. V.; Nesmelov, S. N.; Sidorov, G. Yu.; Varavin, V. S.; Vasil'ev, V. V.; Dvoretsky, S. A.; Mikhailov, N. N.; Yakushev, M. V.

2018-03-01

Admittance of MIS structures based on n( p)- Hg1-xCdxTe (at x from 0.22 to 0.40) with SiO2/Si3N4, Al2O3, and CdTe/Al2O3 insulators is studied experimentally at 77 K. Growth of an intermediate CdTe layer during epitaxy results in the almost complete disappearance of the hysteresis of electrophysical characteristics of MIS structures based on graded-gap n-HgCdTe for a small range of the voltage variation. For a wide range of the voltage variation, the hysteresis of the capacitance-voltage characteristics appears for MIS structures based on n-HgCdTe with the CdTe/Al2O3 insulator. However, the hysteresis mechanism differs from that in case of a single-layer Al2O3 insulator. For MIS structures based on p-HgCdTe, introduction of an additional CdTe layer does not lead to a significant decrease of the hysteresis phenomena, which may be due to the degradation of the interface properties when mercury leaves the film as a result of low-temperature annealing changing the conductivity type of the semiconductor.

An integrated payload design for the Exoplanet Characterisation Observatory (EChO)

DEFF Research Database (Denmark)

Swinyard, Bruce; Tinetti, Giovanna; Tennyson, Jonathan

2012-01-01

by ESA in the context of a medium class mission within the Cosmic Vision programme for launch post 2020. The payload suite is required to provide simultaneous coverage from the visible to the mid-infrared and must be highly stable and effectively operate as a single instrument. In this paper we describe......The Exoplanet Characterisation Observatory (EChO) is a space mission dedicated to undertaking spectroscopy of transiting exoplanets over the widest wavelength range possible. It is based around a highly stable space platform with a 1.2 m class telescope. The mission is currently being studied...

Thermomechanical Properties of Sb2O3-TeO2-V2O5 Glassy Systems: Thermal Stability, Glass Forming Tendency and Vickers Hardness

Science.gov (United States)

Souri, Dariush; Torkashvand, Ziba

2017-04-01

Three-component 40TeO2-(60- x)V2O5- xSb2O3 glasses with 0 ≤ x ≤ 10 (in mol.%) were obtained by the rapid melt-quenching method. These glasses were studied with respect to some mechanical properties with the goal of obtaining information about their structure. The Vickers hardness test was employed to obtain Vickers micro-hardness ( H V) at two different loads, which was within the range of 13.187-17.557 GPa for a typical 0.1 HV (0.9807 N) load. In addition, theoretical micro-hardness ( H) was investigated and compared with experimental H V, showing the elevating trend with increase of Sb2O3 content, as for H V. Furthermore, differential scanning calorimetry (DSC) was employed within the range of 150-500°C at heating rates of φ = 3 K/min, 6 K/min, 9 K/min, 10 K/min, and 13 K/min. In this work, thermal stability ( T s = T cr - T x) and glass forming tendency ( K gl) were measured and reported for these glasses to determine the relationship between the chemical composition and the thermal stability, in order to interpret the structure of glass. Generally, from the ascertained outputs [analysis of mechanical data, titration study, the values of reduced fraction of vanadium ions ( C V) and oxygen molar volume ( V_{{O}}^{*} )], it was found that the micro-hardness had an increasing trend with increasing the Sb2O3 content. Among the studied glasses, the sample with x = 8 had a higher average micro-hardness value, the highest average thermal stability and glass forming tendency with respect to the other samples, which makes it a useful material (owning very good resistance against thermal attacks) for device manufacturing.

Effect of Ga2O3 Nanoparticles Dispersion on Microstructure and Thermoelectric Properties of p-Type BiSbTe Based Alloys

Directory of Open Access Journals (Sweden)

Kim E.-B.

2017-06-01

Full Text Available In this study, p-type Bi0.5Sb1.5Te3 based nanocomposites with addition of different weight percentages of Ga2O3 nanoparticles are fabricated by mechanical milling and spark plasma sintering. The fracture surfaces of all Bi0.5Sb1.5Te3 nanocomposites exhibited similar grain distribution on the entire fracture surface. The Vickers hardness is improved for the Bi0.5Sb1.5Te3 nanocomposites with 6 wt% added Ga2O3 due to exhibiting fine microstructure, and dispersion strengthening mechanism. The Seebeck coefficient of Bi0.5Sb1.5Te3 nanocomposites are significantly improved owing to the decrease in carrier concentration. The electrical conductivity is decreased rapidly upon the addition of Ga2O3 nanoparticle due to increasing carrier scattering at newly formed interfaces. The peak power factor of 3.24 W/mK2 is achieved for the base Bi0.5Sb1.5Te3 sintered bulk. The Bi0.5Sb1.5Te3 nanocomposites show low power factor than base sample due to low electrical conductivity.

Ba{sub 2}Cu{sub 2}Te{sub 2}P{sub 2}O{sub 13}: A new telluro-phosphate with S=1/2 Heisenberg chain

Energy Technology Data Exchange (ETDEWEB)

Xia, Mingjun [Beijing Center for Crystal Research and Development, Key Laboratory of Functional Crystals and Laser Technology, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190 (China); Shen, Shipeng; Lu, Jun; Sun, Young [Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Li, R.K., E-mail: rkli@mail.ipc.ac.cn [Beijing Center for Crystal Research and Development, Key Laboratory of Functional Crystals and Laser Technology, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190 (China)

2015-10-15

A new telluro-phosphate compound Ba{sub 2}Cu{sub 2}Te{sub 2}P{sub 2}O{sub 13} with S=1/2 Heisenberg chain has been successfully synthesized by solid state reaction and grown by flux method. Single crystal X-ray diffraction reveals that Ba{sub 2}Cu{sub 2}Te{sub 2}P{sub 2}O{sub 13} crystallizes into a monoclinic space group C2/c and cell parameters of a=17.647(3) Å, b=7.255(2) Å, c=9.191(2) Å and β=100.16 (3)°. In the structure of Ba{sub 2}Cu{sub 2}Te{sub 2}P{sub 2}O{sub 13}, one dimensional [CuTePO{sub 7}]{sup 3−} chains are formed by tetrahedral PO{sub 4} and trigonal bi-pyramidal TeO{sub 4} joining square planar CuO{sub 4} groups. Those [CuTePO{sub 7}]{sup 3−} chains are inter-connected by sharing one oxygen atom from the TeO{sub 4} group to form two dimensional layers. Magnetic susceptibility and specific heat measurements confirm that the title compound is a model one dimensional Heisenberg antiferromagnetic chain system. - Graphical abstract: Ba{sub 2}Cu{sub 2}Te{sub 2}P{sub 2}O{sub 13}, containing (CuTePO{sub 7}){sup 3−} chains formed by PO{sub 4} and TeO{sub 4} joining CuO{sub 4} groups, shows typical 1D Heisenberg antiferromagnetic chain model behavior as confirmed by magnetic measurements. - Highlights: • New telluro-phosphate Ba{sub 2}Cu{sub 2}Te{sub 2}P{sub 2}O{sub 13} has been grown. • It features layered structure composed of [CuTePO{sub 7}]{sup 3−} chains and TeO{sub 4} groups. • It shows the Heisenberg antiferromagnetic chain behavior. • It is transparent in the range of 1000–2500 nm with a UV absorption edge of 393 nm.

Theoretical studies on a TeO2/ZnO/diamond-layered structure for zero TCD SAW devices

Science.gov (United States)

Dewan, Namrata; Sreenivas, K.; Gupta, Vinay

2008-08-01

High-frequency surface acoustic wave (SAW) devices based on diamond substrate are useful because of their very high SAW velocity. In the present work, SAW propagation characteristics, such as phase velocity, coupling coefficient and temperature coefficient of delay (TCD) of a TeO2/ZnO/diamond-layered structure, are examined using theoretical calculations. The ZnO/diamond bi-layer structure is found to exhibit a high positive TCD value. A zero TCD device structure is obtained after integration with a TeO2 over layer having a negative TCD value. Introduction of a non-piezoelectric TeO2 over layer on the bi-layer structure (ZnO/diamond) increases the coupling coefficient. A relatively low thickness of TeO2 thin film (~(1.6-3.1) × 10-3λ) is required to achieve temperature-stable SAW devices based on diamond.

Theoretical and experimental investigations of the properties of Ge2Sb2Te5 and indium-doped Ge2Sb2Te5 phase change material

Science.gov (United States)

Singh, Gurinder; Kaura, Aman; Mukul, Monika; Singh, Janpreet; Tripathi, S. K.

2014-06-01

We have carried out comprehensive computational and experimental study on the face-centered cubic Ge2Sb2Te5 (GST) and indium (In)-doped GST phase change materials. Structural calculations, total density of states and crystal orbital Hamilton population have been calculated using first-principle calculation. 5 at.% doping of In weakens the Ge-Te, Sb-Te and Te-Te bond lengths. In element substitutes Sb to form In-Te-like structure in the GST system. In-Te has a weaker bond strength compared with the Sb-Te bond. However, both GST and doped alloy remain in rock salt structure. It is more favorable to replace Sb with In than with any other atomic position. X-ray diffraction (XRD) analysis has been carried out on thin film of In-doped GST phase change materials. XRD graph reveals that In-doped phase change materials have rock salt structure with the formation of In2Te3 crystallites in the material. Temperature dependence of impedance spectra has been calculated for thin films of GST and doped material. Thickness of the as-deposited films is calculated from Swanepoel method. Absorption coefficient (α) has been calculated for amorphous and crystalline thin films of the alloys. The optical gap (indirect band gap) energy of the amorphous and crystalline thin films has also been calculated by the equation α hν = β (hν - E_{{g }} )2 . Optical contrast (C) of pure and doped phase change materials have also been calculated. Sufficient optical contrast has been found for pure and doped phase change materials.

Theoretical and experimental investigations of the properties of Ge2Sb2Te5 and indium-doped Ge2Sb2Te5 phase change material

International Nuclear Information System (INIS)

Singh, Gurinder; Kaura, Aman; Mukul, Monika; Singh, Janpreet; Tripathi, S.K.

2014-01-01

We have carried out comprehensive computational and experimental study on the face-centered cubic Ge 2 Sb 2 Te 5 (GST) and indium (In)-doped GST phase change materials. Structural calculations, total density of states and crystal orbital Hamilton population have been calculated using first-principle calculation. 5 at.% doping of In weakens the Ge-Te, Sb-Te and Te-Te bond lengths. In element substitutes Sb to form In-Te-like structure in the GST system. In-Te has a weaker bond strength compared with the Sb-Te bond. However, both GST and doped alloy remain in rock salt structure. It is more favorable to replace Sb with In than with any other atomic position. X-ray diffraction (XRD) analysis has been carried out on thin film of In-doped GST phase change materials. XRD graph reveals that In-doped phase change materials have rock salt structure with the formation of In 2 Te 3 crystallites in the material. Temperature dependence of impedance spectra has been calculated for thin films of GST and doped material. Thickness of the as-deposited films is calculated from Swanepoel method. Absorption coefficient (α) has been calculated for amorphous and crystalline thin films of the alloys. The optical gap (indirect band gap) energy of the amorphous and crystalline thin films has also been calculated by the equation αhν = β(hν - E g ) 2 . Optical contrast (C) of pure and doped phase change materials have also been calculated. Sufficient optical contrast has been found for pure and doped phase change materials. (orig.)

Investigation of radiation shielding properties for MeO-PbCl2-TeO2 (MeO = Bi2O3, MoO3, Sb2O3, WO3, ZnO) glasses

Science.gov (United States)

Sayyed, M. I.; Çelikbilek Ersundu, M.; Ersundu, A. E.; Lakshminarayana, G.; Kostka, P.

2018-03-01

In this work, glasses in the MeO-PbCl2-TeO2 (MeO = Bi2O3, MoO3, Sb2O3, WO3, ZnO) system, which show a great potential for optoelectronic applications, were used to evaluate their resistance under high energy ionizing radiations. The basic shielding quantities for determining the penetration of radiation in glass, such as mass attenuation coefficient (μ/ρ), half value layer (HVL), mean free path (MFP) and exposure buildup factor (EBF) values were investigated within the energy range 0.015 MeV ‒ 15 MeV using XCOM program and variation of shielding parameters were compared with different glass systems and ordinary concrete. From the derived results, it was determined that MeO-PbCl2-TeO2 (MeO = Bi2O3, MoO3, Sb2O3, WO3, ZnO) glasses show great potentiality to be used under high energy radiations. Among the studied glass compositions, Bi2O3 and WO3 containing glasses were found to possess superior gamma-ray shielding effectiveness.

Effect of O- and Mn-doping on superconductivity in FeTe{sub 0.5}Se{sub 0.5} superconductor

Energy Technology Data Exchange (ETDEWEB)

Thakur, Gohil S.; Haque, Zeba; Ganguli, Ashok K. [Department of Chemistry, Indian Institute of Technology, New Delhi (India); Neha, Prakriti; Patnaik, Satyabrata [School of Physical Science, Jawaharlal Nehru University, New Delhi (India); Gupta, Laxmi C. [Department of Chemistry, Indian Institute of Technology, New Delhi (India); Visiting project scientist at the:Solid State and Nanomaterials Research Laboratory, Department of Chemistry, IIT Delhi (India)

2014-05-15

The effect of oxygen substitution at the selenium site and manganese substitution at the iron site in FeTe{sub 0.5}Se{sub 0.5} superconductor was investigated. It was found that upon partial O substitution, T{sub c} marginally decreases as seen in both resistivity and magnetization experiments. T{sub c} decreases even by a small amount of oxygen concentration (as low as 1 %). This observation is in contrast against an earlier work on Fe(Te/Se) samples,1 wherein T{sub c} as well as superconducting volume fraction were reported to increase in the samples annealed in air. Mn-doping leads to a decrease in T{sub c} in FeTe{sub 0.5}Se{sub 0.5}, which one would expect considering pair-breaking due to Mn{sup 2+}-ions. (Copyright copyright 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Development of 1 MW gyrotron and progress of ECH system for the GAMMA 10 tandem mirror in Tsukuba

International Nuclear Information System (INIS)

Imai, T.; Kariya, T.; Minami, R.; Shidara, H.; Endo, Y.; Harigae, M.; Nakamura, M.; Sakagoshi, Y.; Murofushi, N.; Ichimura, M.; Nakashima, Y.; Yoshikawa, M.; Yamaguchi, Y.; Sakamoto, Keishi; Kubo, S.; Shimozuma, T.; Mutoh, T.; Takahashi, H.; Mitsunaka, Y.

2008-10-01

High power gyrotrons with TE 4,2 cavity at 28 GHz and with TE 18,6 cavity and a diamond window at 77 GHz have been developed for GAMMA 10 and LHD in the joint program of NIFS and University of Tsukuba. The maximum outputs of 570 kW at 28 GHz and 1.1 MW at 77 GHz were obtained corresponding to each design. The operations of more than 750 kW for 5 sec. and 810 kW for 3.5 sec. were achieved in the developing tubes at 77 GHz, which is the first high power-long pulse result of the 77 GHz tube. The experimental simulation of the effect of the stray RF in the 28 GHz tube indicates the stray RF is the one of the major causes limiting gyrotron performance. The output of more than 1 MW with 40% oscillation efficiency is expected from the design of the next 28 GHz gyrotron for GAMMA 10. Installation of the polarizer in the transmission line enhanced the performance of the ECH system in GAMMA 10, that is the first result which clearly showed ∼100% X mode excitation is a key to design the efficient fundamental ECH system of strong field side injection in mirror devices. (author)

Theoretical studies on a TeO2/ZnO/diamond-layered structure for zero TCD SAW devices

International Nuclear Information System (INIS)

Dewan, Namrata; Sreenivas, K; Gupta, Vinay

2008-01-01

High-frequency surface acoustic wave (SAW) devices based on diamond substrate are useful because of their very high SAW velocity. In the present work, SAW propagation characteristics, such as phase velocity, coupling coefficient and temperature coefficient of delay (TCD) of a TeO 2 /ZnO/diamond-layered structure, are examined using theoretical calculations. The ZnO/diamond bi-layer structure is found to exhibit a high positive TCD value. A zero TCD device structure is obtained after integration with a TeO 2 over layer having a negative TCD value. Introduction of a non-piezoelectric TeO 2 over layer on the bi-layer structure (ZnO/diamond) increases the coupling coefficient. A relatively low thickness of TeO 2 thin film (∼(1.6–3.1) × 10 −3 λ) is required to achieve temperature-stable SAW devices based on diamond

The stimulatory adenosine receptor ADORA2B regulates serotonin (5-HT synthesis and release in oxygen-depleted EC cells in inflammatory bowel disease.

Directory of Open Access Journals (Sweden)

Rikard Dammen

Full Text Available We recently demonstrated that hypoxia, a key feature of IBD, increases enterochromaffin (EC cell 5-HT secretion, which is also physiologically regulated by the ADORA2B mechanoreceptor. Since hypoxia is associated with increased extracellular adenosine, we wanted to examine whether this nucleotide amplifies HIF-1α-mediated 5-HT secretion.The effects of hypoxia were studied on IBD mucosa, isolated IBD-EC cells, isolated normal EC cells and the EC cell tumor derived cell line KRJ-1. Hypoxia (0.5% O2 was compared to NECA (adenosine agonist, MRS1754 (ADORA2B receptor antagonist and SCH442146 (ADORA2A antagonist on HIF signaling and 5-HT secretion. Antisense approaches were used to mechanistically evaluate EC cells in vitro. PCR and western blot were used to analyze transcript and protein levels of HIF-1α signaling and neuroendocrine cell function. An animal model of colitis was evaluated to confirm hypoxia:adenosine signaling in vivo.HIF-1α is upregulated in IBD mucosa and IBD-EC cells, the majority (~90% of which express an activated phenotype in situ. Hypoxia stimulated 5-HT release maximally at 30 mins, an effect amplified by NECA and selectively inhibited by MRS1754, through phosphorylation of TPH-1 and activation of VMAT-1. Transient transfection with Renilla luciferase under hypoxia transcriptional response element (HRE control identified that ADORA2B activated HIF-1α signaling under hypoxic conditions. Additional signaling pathways associated with hypoxia:adenosine included MAP kinase and CREB. Antisense approaches mechanistically confirmed that ADORA2B signaling was linked to these pathways and 5-HT release under hypoxic conditions. Hypoxia:adenosine activation which could be reversed by 5'-ASA treatment was confirmed in a TNBS-model.Hypoxia induced 5-HT synthesis and secretion is amplified by ADORA2B signaling via MAPK/CREB and TPH-1 activation. Targeting ADORA2s may decrease EC cell 5-HT production and secretion in IBD.

Structural chemistry and magnetic properties of the perovskite SrLa{sub 2}Ni{sub 2}TeO{sub 9}

Energy Technology Data Exchange (ETDEWEB)

Paria Sena, Robert; Hadermann, Joke [EMAT, University of Antwerp, Groenenborgerlaan 171, 2020 Antwerp (Belgium); Chin, Chun-Mann; Hunter, Emily C. [Inorganic Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QR (United Kingdom); Battle, Peter D., E-mail: peter.battle@chem.ox.ac.uk [Inorganic Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QR (United Kingdom)

2016-11-15

A polycrystalline sample of SrLa{sub 2}Ni{sub 2}TeO{sub 9} has been synthesized using a standard ceramic method and characterized by neutron diffraction, magnetometry and electron microscopy. The compound adopts a monoclinic, perovskite-like structure with space group P2{sub 1}/n and unit cell parameters a=5.6008(1), b=5.5872(1), c=7.9018(2) Å, β=90.021(6)° at room temperature. The two crystallographically-distinct B sites are occupied by Ni{sup 2+} and Te{sup 6+} in ratios of 83:17 and 50:50. Both ac and dc magnetometry suggest that the compound is a spin glass below 35 K but the neutron diffraction data show that some regions of the sample are antiferromagnetic. Electron microscopy revealed twinning on a nanoscale and local variations in composition. These defects are thought to be responsible for the presence of two distinct types of antiferromagnetic ordering. - Highlights: • Coexistence of spin-glass and ordered phases. • Local inhomogeneity despite long-range inhomogeneity. • Contrasting magnetic properties of SrLa{sub 2}Ni{sub 2}TeO{sub 9} and La{sub 3}Ni{sub 2}SbO{sub 9}.

Emission analysis of RE3+ (RE = Sm, Dy):B2O3-TeO2-Li2O-AlF3 glasses.

Science.gov (United States)

Raju, C Nageswara; Sailaja, S; Kumari, S Pavan; Dhoble, S J; Kumar, V Ramesh; Ramanaiah, M V; Reddy, B Sudhakar

2013-01-01

This article reports on the optical properties of 0.5% mol of Sm(3+), Dy(3+) ion-doped B2O3-TeO2-Li2O-AlF3 (LiAlFBT) glasses. The glass samples were characterized by optical absorption and emission spectra. Judd-Ofelt theory was applied to analyze the optical absorption spectra and calculate the intensity parameters and radiative properties of the emission transitions. The emission spectra of Sm(3+) and Dy(3+):LiAlFBT glasses showed a bright reddish-orange emission at 598 nm ((4)G5/2 → (6)H7/2) and an intense yellow emission at 574 nm ((4)F9/2 → (6)H13/2), respectively. Full width at half maximum (FWHM), stimulated emission cross section, gain bandwidth and optical gain values were also calculated to extend the applications of the Sm(3+) and Dy(3+):LiAlFBT glasses. Copyright © 2012 John Wiley & Sons, Ltd.

Impact of D2O/H2O Solvent Exchange on the Emission of HgTe and CdTe Quantum Dots: Polaron and Energy Transfer Effects.

Science.gov (United States)

Wen, Qiannan; Kershaw, Stephen V; Kalytchuk, Sergii; Zhovtiuk, Olga; Reckmeier, Claas; Vasilevskiy, Mikhail I; Rogach, Andrey L

2016-04-26

We have studied light emission kinetics and analyzed carrier recombination channels in HgTe quantum dots that were initially grown in H2O. When the solvent is replaced by D2O, the nonradiative recombination rate changes highlight the role of the vibrational degrees of freedom in the medium surrounding the dots, including both solvent and ligands. The contributing energy loss mechanisms have been evaluated by developing quantitative models for the nonradiative recombination via (i) polaron states formed by strong coupling of ligand vibration modes to a surface trap state (nonresonant channel) and (ii) resonant energy transfer to vibration modes in the solvent. We conclude that channel (i) is more important than (ii) for HgTe dots in either solution. When some of these modes are removed from the relevant spectral range by the H2O to D2O replacement, the polaron effect becomes weaker and the nonradiative lifetime increases. Comparisons with CdTe quantum dots (QDs) served as a reference where the resonant energy loss (ii) a priori was not a factor, also confirmed by our experiments. The solvent exchange (H2O to D2O), however, is found to slightly increase the overall quantum yield of CdTe samples, probably by increasing the fraction of bright dots in the ensemble. The fundamental study reported here can serve as the foundation for the design and optimization principles of narrow bandgap quantum dots aimed at applications in long wavelength colloidal materials for infrared light emitting diodes and photodetectors.

Quarternair CuGaSeTe and CuGa0.5In 0.5Te2 Thin Films Fabrication Using Flash Evaporation

Directory of Open Access Journals (Sweden)

A Harsono Soepardjo

2010-10-01

Full Text Available Quarternair materials CuGaSeTe and CuGa0.5In 0.5Te2 are the basic materials to solar cell fabrication. These materials have high absorption coefficients around 103 - 105 cm-1 and band gap energy in the range of 1-5 eV. In this research, the films were made by flash evaporation method using quarternair powder materials of CuGaSeTe and CuGa0.5In 0.5Te2 to adhere in a glass substrate. After the films were obtained, the properties of these films will be characterized optically and electrically. The lattice parameter of the films and the crystalline film structure were obtained using X-Ray Diffraction (XRD spectroscopy. The XRD results show that the quarternair CuGaSeTe and CuGa0.5In 0.5Te2 films have a chalcopyrite structure. The absorption coefficient and the  band gap energy of the films were calculated using transmittance and reflectance patterns that measured using UV-VIS Difractometer. The films composition can be detected by using the Energy Dispersive Spectroscopy (EDS, while the films resistivity, mobility and the majority carrier of the films were obtained from Hall Effect experiments.

Comportamiento eléctrico de vidrios funcionales con base en TeO2

Directory of Open Access Journals (Sweden)

Terny, S.

2014-02-01

Full Text Available In this paper we study the structural and electrical behavior of glass-ceramic material of general formula: xMgO (1-x (0.5V2O5.0.5MoO32TeO2 (0≤x≤0.9 through measurements of density, molar volume, oxygen packing density (OPD, differential scanning calorimetry (DSC and Raman spectroscopy: electric behavior was studied by impedance spectroscopy. We found that magnesium cation induces the growth of slightly crystallized areas inside the material. Those nanocrystallizations were detected to a greater extent by atomic force microscopy (AFM and in lesser extent by X-ray diffraction (XRD. Regarding the electrical measurements, it can be established that magnesium cation does not act as good ionic conductor in this material.En este trabajo estudiamos la estructura de un material vítreo cuya fórmula general es: xMgO(1-x(0.5V2O5.0.5MoO32TeO2 (0≤x≤0.9, mediante medidas de densidad, volumen molar, empaquetamiento denso de oxigeno (OPD, calorimetría diferencial de barrido (DSC y espectroscopia Raman; el comportamiento eléctrico se estudió por medio de espectroscopia de impedancia. Encontramos que el catión magnesio induce el crecimiento de zonas levemente cristalizadas dentro del material. Dichas nanocristalizaciones pudieron ser detectadas en mayor medida por microscopia de fuerzas atómicas (AFM y en menor medida se pudo observar en los patrones de difracción de Rayos X (DRX. Con respecto a las propiedades eléctricas, se puede establecer que el catión magnesio no actúa como buen conductor iónico en este material.

Uncertainty in CH4 and N2O emission estimates from a managed fen meadow using EC measurements

International Nuclear Information System (INIS)

Kroon, P.S.; Hensen, A.; Van 't Veen, W.H.; Vermeulen, A.T.; Jonker, H.

2009-02-01

The overall uncertainty in annual flux estimates derived from chamber measurements may be as high as 50% due to the temporal and spatial variability in the fluxes. As even a large number of chamber plots still cover typically less than 1% of the total field area, the field-scale integrated emission necessarily remains a matter of speculation. High frequency micrometeorological methods are a good option for obtaining integrated estimates on a hectare scale with a continuous coverage in time. Instrumentation is now becoming available that meets the requirements for CH4 and N2O eddy covariance (EC) measurements. A system consisting of a quantum cascade laser (QCL) spectrometer and a sonic anemometer has recently been proven to be suitable for performing EC measurements. This study analyses the EC flux measurements of CH4 and N2O and its corrections, like calibration, Webb-correction, and corrections for high and low frequency losses, and assesses the magnitude of the uncertainties associated with the precision of the measurement instruments, measurement set-up and the methodology. The uncertainty of one single EC flux measurement, a daily, monthly and 3-monthly average EC flux is estimated. In addition, the cumulative emission of C-CH4 and N-N2O and their uncertainties are determined over several fertilizing events at a dairy farm site in the Netherlands. These fertilizing events are selected from the continuously EC flux measurements from August 2006 to September 2008. The EC flux uncertainties are compared by the overall uncertainty in annual flux estimates derived from chamber measurements. It will be shown that EC flux measurements can decrease the overall uncertainty in annual flux estimates

Uncertainty in CH4 and N2O emission estimates from a managed fen meadow using EC measurements

Energy Technology Data Exchange (ETDEWEB)

Kroon, P.S.; Hensen, A.; Van ' t Veen, W.H.; Vermeulen, A.T. [ECN Biomass, Coal and Environment, Petten (Netherlands); Jonker, H. [Delft University of Technology, Delft (Netherlands)

2009-02-15

The overall uncertainty in annual flux estimates derived from chamber measurements may be as high as 50% due to the temporal and spatial variability in the fluxes. As even a large number of chamber plots still cover typically less than 1% of the total field area, the field-scale integrated emission necessarily remains a matter of speculation. High frequency micrometeorological methods are a good option for obtaining integrated estimates on a hectare scale with a continuous coverage in time. Instrumentation is now becoming available that meets the requirements for CH4 and N2O eddy covariance (EC) measurements. A system consisting of a quantum cascade laser (QCL) spectrometer and a sonic anemometer has recently been proven to be suitable for performing EC measurements. This study analyses the EC flux measurements of CH4 and N2O and its corrections, like calibration, Webb-correction, and corrections for high and low frequency losses, and assesses the magnitude of the uncertainties associated with the precision of the measurement instruments, measurement set-up and the methodology. The uncertainty of one single EC flux measurement, a daily, monthly and 3-monthly average EC flux is estimated. In addition, the cumulative emission of C-CH4 and N-N2O and their uncertainties are determined over several fertilizing events at a dairy farm site in the Netherlands. These fertilizing events are selected from the continuously EC flux measurements from August 2006 to September 2008. The EC flux uncertainties are compared by the overall uncertainty in annual flux estimates derived from chamber measurements. It will be shown that EC flux measurements can decrease the overall uncertainty in annual flux estimates.

Nonlinear optical properties of TeO$_2$ crystalline phases from first principles

OpenAIRE

Berkaine, Nabil; Orhan, Emmanuelle; Masson, Olivier; Thomas, Philippe; Junquera, Javier

2010-01-01

We have computed second and third nonlinear optical susceptibilities of two crystalline bulk tellurium oxide polymorphs: $\\alpha$-TeO$_{2}$ (the most stable crystalline bulk phase) and $\\gamma$-TeO$_{2}$ (the crystalline phase that ressembles the more to the glass phase. Third order nonlinear susceptibilities of the crystalline phases are two orders of magnitude larger than $\\alpha$-SiO$_{2}$ cristoballite, thus extending the experimental observations on glasses to the case of crystalline com...

Influence of valence state of copper ions on structural and spectroscopic properties of multi-component PbO-Al2O3-TeO2-GeO2-SiO2 glass ceramic system- a possible material for memory switching devices

Science.gov (United States)

Tirupataiah, Ch.; Narendrudu, T.; Suresh, S.; Srinivasa Rao, P.; Vinaya Teja, P. M.; Sambasiva Rao, M. V.; Chinna Ram, G.; Krishna Rao, D.

2017-11-01

Multi-component glass ceramics with composition 29PbO-5Al2O3-1TeO2 -10GeO2- (55-x) SiO2 doped with different concentrations of CuO (0 ≤ x ≤ 1.0 mol %) were synthesized by melt quenching technique and subsequent heat treatment. These glass ceramics were characterized by X-ray diffraction, scanning electron microscope, differential thermal analysis, optical absorption, electron paramagnetic resonance, Fourier transform infrared and Raman studies. The absorption spectra of these glass ceramics exhibited a broad absorption band in the range 650-950 nm which is ascribed to 2B1g → 2B2g octahedral transition of Cu2+ ions. A feeble band around 364 nm is also identified in the samples doped with CuO up to 0.6 mol% as being due to charge transfer between the two oxidation states Cu2+ and Cu+ of copper ions. The EPR spectrum recorded at room temperature exhibited a strong resonance signal at g⊥ = 2.072 and a shallow quadruplet at about gǁ = 2.401. FTIR and Raman spectra of the titled samples provide significant information about various structural units viz., silicate, germanate, PbO4, PbO6, AlO6, TeO4 and TeO3 that are present in these ceramic matrix. Analysis of the spectroscopic investigations reveals that with an increase in the concentration of CuO up to 0.6 mol% copper ions do exist in Cu2+ and Cu+ states and they act as modifiers and net work formers respectively. Therefore, glass ceramic sample contains 0.6 mol% of CuO is favorable for memory switching action.

CdTe/TiO{sub 2} nanocomposite material for photogenerated cathodic protection of 304 stainless steel

Energy Technology Data Exchange (ETDEWEB)

Wang, Xiu-tong, E-mail: xiutongwang@gmail.com [Institutes of Oceanology, Chinese Academy of Sciences, Qingdao 266071 China (China); Wei, Qin-yi, E-mail: weiqiny200@163.com [Institutes of Oceanology, Chinese Academy of Sciences, Qingdao 266071 China (China); University of Chinese Academy of Sciences, 19 (Jia) Yuquan Road, Beijing 100049 (China); Zhang, Liang, E-mail: zzll20081988@126.com [CNOOC Information Technology co., Ltd. Beijing Branch, Beijing 100029 China (China); Sun, Hao-fen, E-mail: fyqfyx@163.com [School of Environmental and Municipal Engineering Qingdao, Qingdao Technological University, Qingdao 266033 China (China); Li, Hong, E-mail: lhqdio1987@163.com [Institutes of Oceanology, Chinese Academy of Sciences, Qingdao 266071 China (China); Zhang, Qiao-xia, E-mail: qiaoxiazhang1989@163.com [Institutes of Oceanology, Chinese Academy of Sciences, Qingdao 266071 China (China)

2016-06-15

Graphical abstract: - Highlights: • The photoelectric properties of TiO{sub 2} could greatly improve by doping with CdTe. • The cathodic protection property of the CdTe/TiO{sub 2} was superior to that of pure TiO{sub 2}. • The protective action of the CdTe/TiO{sub 2} for 304SS could be maintained in the dark. - Abstract: TiO{sub 2} nanotubes were fabricated by the anodization method, and CdTe was deposited on them via electrochemical deposition method. The optimal performance of the CdTe/TiO{sub 2} composites was achieved via changing the acidity of the electrolyte. Scanning electron microscopy, energy dispersive spectroscopy and X-ray diffraction were used to investigate the surface morphology, elemental analysis and phase characteristics of the composite materials. Some electrochemical tests, such as open-circuit potential, current variation versus time were carried out to investigate the photogenerated cathodic protection of 304 stainless steel by CdTe/TiO{sub 2}. The results indicated that the cathodic protection performance of the CdTe/TiO{sub 2} composite was superior to that of pure TiO{sub 2} in the wavelength of visible light. The CdTe/TiO{sub 2} composite exhibited optimal photogenerated cathodic protection properties under visible light for the corrosion potential of 304 stainless steel shifted negatively to −850 mV when the concentration of HCl in the deposition electrolyte was 1 mol/L.

Effects of dopants on the amorphous-to-fcc transition in Ge{sub 2}Sb{sub 2}Te{sub 5} thin films

Energy Technology Data Exchange (ETDEWEB)

Privitera, S. [R and D Department, Micro, Power, Analog (MPA) Group, STMicroelectronics, MP8, Stradale Primosole 50, 95121 Catania (Italy)]. E-mail: stefania.privitera@st.com; Rimini, E. [Istituto di Microelettronica e Microsistemi (IMM), Consiglio Nazionale delle Ricerche (CNR), Stradale Primosole 50, 95121 Catania (Italy); Bongiorno, C. [Istituto di Microelettronica e Microsistemi (IMM), Consiglio Nazionale delle Ricerche (CNR), Stradale Primosole 50, 95121 Catania (Italy); Pirovano, A. [FTM, Advanced R and D, NVMTD, STMicroelectronics, Via Olivetti 2, 20041, Agrate Brianza (Italy); Bez, R. [FTM, Advanced R and D, NVMTD, STMicroelectronics, Via Olivetti 2, 20041, Agrate Brianza (Italy)

2007-04-15

The amorphous-to-crystal transition has been studied through in situ resistance measurements in Ge{sub 2}Sb{sub 2}Te{sub 5} thin films doped by ion implantation with nitrogen, oxygen or fluorine at different concentrations. Enhancement of the thermal stability has been observed in O and N amorphous doped Ge{sub 2}Sb{sub 2}Te{sub 5}. Larger effects have been found in the case of nitrogen doping. On the contrary, doping with Fluorine produced a decrease in the crystallization temperature. The electrical properties have been related to the structural phase change through in situ transmission electron microscopy analysis. The comparison between undoped and doped Ge{sub 2}Sb{sub 2}Te{sub 5} shows that the introduction of oxygen or nitrogen modifies in a different way the kinetics of the amorphous-to-fcc transition and gives new insight on the effects of doping with light elements in GeSbTe alloys.

Optical properties of CuCdTeO thin films sputtered from CdTe-CuO composite targets

Energy Technology Data Exchange (ETDEWEB)

Mendoza-Galván, A., E-mail: amendoza@qro.cinvestav.mx [Cinvestav-IPN, Unidad Querétaro, Libramiento Norponiente 2000, 76230 Querétaro (Mexico); Laboratory of Applied Optics, Department of Physics, Chemistry and Biology, Linköping University, SE-581 83 Linköping (Sweden); Arreola-Jardón, G. [Cinvestav-IPN, Unidad Querétaro, Libramiento Norponiente 2000, 76230 Querétaro (Mexico); Karlsson, L.H.; Persson, P.O.Å. [Thin Film Physics Division, Department of Physics, Chemistry and Biology, Linköping University, SE-581 83 Linköping (Sweden); Jiménez-Sandoval, S. [Cinvestav-IPN, Unidad Querétaro, Libramiento Norponiente 2000, 76230 Querétaro (Mexico)

2014-11-28

The effective complex dielectric function (ε) of Cu and O containing CdTe thin films is reported in the spectral range of 0.05 to 6 eV. The films were fabricated by rf sputtering from targets comprised by a mixture of CdTe and CuO powders with nominal Cu and O concentrations in the range of 2–10 at.%. Low concentration levels improved the crystalline quality of the films. Spectroscopic ellipsometry and transmittance measurements were used to determine ε. The critical point energies E{sub 1}, E{sub 1} + Δ{sub 1}, and E{sub 2} of CdTe are red-shifted with the incorporation of Cu and O. Also, an absorption band is developed in the infrared range which is associated with a mixture of CdTe and low resistivity phases Cu{sub 2−x}Te according to an effective medium analysis. The elemental distribution of the films was mapped by energy dispersive X-ray spectroscopy using scanning transmission electron microscopy. - Highlights: • Incorporation of 2 to 10 at.% of Cu and O atoms in CdTe films • Improved crystalline quality with 2 and 3 at.% of Cu and O • Complex dielectric function of Cu and O containing CdTe thin films • Effective medium modeling of below band-gap absorption.

Improvement of thermoelectric properties induced by uniquely ordered lattice field in Bi2Se0.5Te2.5 pillar array

International Nuclear Information System (INIS)

Tan, Ming; Hao, Yanming; Wang, Gangzhi

2014-01-01

In this study, it was found that uniquely ordered lattice field favors transport of carriers but hinder that of phonons. The n-Bi 2 Se 0.5 Te 2.5 pillar array film was successfully achieved by a simple ion beam assisted deposition technique. This oriented pillar array structure is clear with pillar diameter of about 30 nm, exhibiting a uniquely ordered lattice field. The properties of the ordered Bi 2 Se 0.5 Te 2.5 pillar array were greatly enhanced in comparison with those of the ordinary film. The Bi 2 Se 0.5 Te 2.5 pillar array with a thermoelectric dimensionless figure-of-merit ZT=1.28 was obtained at room temperature. The in-plane transport mechanisms of the ordered pillar array and the ordinary structures, lattice field model, are proposed and investigated. The specially ordered lattice field is the main reason for the properties enhancement observed in the Bi 2 Se 0.5 Te 2.5 film. Introduction of such ordered lattice field into TE films is therefore a very promising approach. - Graphical abstract: In this study, it was found that uniquely ordered lattice field favors transport of carriers but hinder that of phonons. The Bi 2 Se 0.5 Te 2.5 pillar array film with a thermoelectric dimensionless figure-of-merit ZT=1.28 was obtained at room temperature. The in-plane transport mechanisms of the ordered pillar array and the ordinary structures, the lattice field model, are proposed and investigated. The specially ordered lattice field is the main reason for the properties enhancement observed in the Bi 2 Se 0.5 Te 2.5 pillar array. Introduction of such uniquely ordered lattice field into TE films is therefore a very promising approach. In (a) TEM and (b) HRTEM images of the ordered Bi 2 Se 0.5 Te 2.5 column array. - Highlights: • Uniquely ordered Bi 2 Se 0.5 Te 2.5 pillar array was achieved by an IBAD method. • The pillar array with an ordered lattice field exhibits attractive TE property. • The transport mechanism of such ordered pillar array is proposed and

Raman spectra of TeO2-PbCl2 glasses

Czech Academy of Sciences Publication Activity Database

Ležal, Dimitrij; Bludská, Jana; Horák, J.; Sklenář, A.; Karamazov, S.; Vlček, M.

2002-01-01

Roč. 43, č. 6 (2002), s. 296-299 ISSN 0031-9090 Institutional research plan: CEZ:AV0Z4032918 Keywords : tellurite glasses * TeO2glass * model Subject RIV: CA - Inorganic Chemistry Impact factor: 0.691, year: 2002

New quaternary oxides with both families of second-order Jahn–Teller (SOJT) distortive cations: Solid-state synthesis, structure determination, and characterization of YNbTe{sub 2}O{sub 8} and YNbSe{sub 2}O{sub 8}

Energy Technology Data Exchange (ETDEWEB)

Kim, Yeong Hun [Department of Chemistry, Chung-Ang University, 84 Heukseok-ro, Dongjak-gu, Seoul 156-756 (Korea, Republic of); Jeon, Beom-Yong; You, Tae-Soo [Department of Chemistry, Chungbuk National University, Cheongju, Chungbuk 361-763 (Korea, Republic of); Ok, Kang Min, E-mail: kmok@cau.ac.kr [Department of Chemistry, Chung-Ang University, 84 Heukseok-ro, Dongjak-gu, Seoul 156-756 (Korea, Republic of)

2015-07-15

Graphical abstract: Ball-and-stick representation of YNbTe{sub 2}O{sub 8} composed of polyhedra of SOJT distortive cations, i.e., NbO{sub 6} and TeO{sub 3}, in the ac-plane. - Highlights: • Two novel tellurite and selenite (YNbQ{sub 2}O{sub 8}; Q = Te and Se) are synthesized. • YNbQ{sub 2}O{sub 8} possess both families of second-order Jahn–Teller distortive cations. • The distortive environments and bonding nature are supported by electronic structure calculations. - Abstract: Two novel quaternary mixed metal tellurite and selenite, YNbTe{sub 2}O{sub 8} and YNbSe{sub 2}O{sub 8}, respectively, have been synthesized through standard solid-state reactions using Y{sub 2}O{sub 3}, Nb{sub 2}O{sub 5}, TeO{sub 2} or SeO{sub 2} as reagents. Single crystal X-ray and powder neutron diffraction analyses have been utilized to determine the structures of the reported materials. YNbTe{sub 2}O{sub 8} and YNbSe{sub 2}O{sub 8} are isostructural to each other and crystallize in the monoclinic centrosymmetric space group, C2/m (No. 12). Due to the two families of constituent second-order Jahn–Teller (SOJT) distortive cations, i.e., Nb{sup 5+} and Te{sup 4+}/Se{sup 4+}, local asymmetric environments occur from the three-dimensional frameworks. Intra-octahedral distortions along the local C{sub 4} direction and asymmetric trigonal pyramidal coordination moieties generated by stereoactive lone pairs are observed from the NbO{sub 6} octahedra and TeO{sub 3} (or SeO{sub 3}) polyhedra, respectively. Thermogravimetric analysis, infrared and UV–vis diffuse reflectance spectroscopies, elemental analysis, out-of-center distortions, dipole moment calculations, and electronic structure calculations for the reported materials are presented.

Nd{sup 3+}-doped TeO{sub 2}-Bi{sub 2}O{sub 3}-ZnO transparent glass ceramics for laser application at 1.06 μm

Energy Technology Data Exchange (ETDEWEB)

Hu, Xiaolin; Luo, Zhiwei; Liu, Taoyong; Lu, Anxian [Central South of University, School of Materials Science and Engineering, Changsha (China)

2017-04-15

The high crystallinity transparent glass ceramics based on Nd{sup 3+}-doped 70TeO{sub 2}-15Bi{sub 2}O{sub 3}-15ZnO (TBZ) compositions were successfully prepared by two-step heat treatment process. The effects of Nd{sub 2}O{sub 3} content on the thermal, structural, mechanical, and optical properties of TBZ glass ceramics were studied. The incorporation of Nd{sub 2}O{sub 3} enhanced the crystallization tendency in the matrix glass composition. The crystal phase and morphology of Bi{sub 2}Te{sub 4}O{sub 11} in the glass ceramics were confirmed by X-ray diffraction and field emission scanning electron microscopy. Due to precipitate more crystal phase, the hardness values increased from 3.21 to 3.66 GPa. Eight absorption peaks were observed from 400 to 900 nm and three emission bands appeared in the range of 850-1400 nm. With the increasing of Nd{sub 2}O{sub 3} content from 0.5 to 2.5 wt%, the intensity of absorption peaks enhanced and the emission intensity increased up to 1.0 wt% and then fell down for further dopant concentration. The fluorescence decay lifetime decreased rapidly starting from 1.5 wt% Nd{sub 2}O{sub 3} content due to the obvious energy migration among Nd{sup 3+}. According to the extreme strong emission band around 1062 nm and the optimum Nd{sub 2}O{sub 3} content (1.0 wt%), N10 glass ceramic was considered as a potential material for 1.06 μm laser applications. (orig.)

Quantum mechanical study of pre-dissociation enhancement of linear and nonlinear polarizabilities of (TeO2)(n) oligomers as a key to understanding the remarkable dielectric properties of TeO2 glasses.

Science.gov (United States)

Smirnov, Mikhail; Mirgorodsky, Andrei; Masson, Olivier; Thomas, Philippe

2012-09-20

The effects of intermolecular interactions of TeO(2) molecules in the (TeO(2))(n) oligomers on the polarizability (α) and second hyperpolarizability (γ) are investigated by the use of a density functional method. A significant intermolecular distance dependence of both quantities is observed. The huge dissociation-induced polarizability enhancement is analyzed in terms of the molecular orbital evolution. It is shown that the obtained results can provide a new look at the microscopic origin of the extraordinary dielectric properties of TeO(2) glass.

Growth and Characterization of Magnetoelectric Fe2TeO6 Thin Films

Science.gov (United States)

Wang, Junlei; Colon Santana, Juan; Wu, Ning; Dowben, Peter; Binek, Christian

2013-03-01

Voltage-controlled spintronics is of vital importance in information technology where power consumption and Joule heating restrict progress through scaling. Motivated by spintronic concepts and specifically by device applications utilizing electrically controlled interface or boundary magnetization (BM) in magnetic thin film heterostructures, we report on growth, structural, magnetic and magnetoelectric (ME) characterization of the antiferromagnet Fe2TeO6. Magnetometry of synthesized Fe2TeO6 powder, in combination with ME susceptibility data reveals 3D Heisenberg criticality in striking similarity to the archetypical ME chromia. X-ray diffraction shows (110) texture of the PLD grown films. Measurements of the magnetic susceptibility of the latter confirm in-plane magnetic anisotropy. X-ray photoemission spectroscopy indicates a Te-O terminated (110) surface. We interpret it in terms of surface reconstruction. Measurements of X-ray magnetic circular dichroism combined with photoemission electron microscopy support the presence of electrically controllable BM in the PLD-grown Fe2TeO6 thin film. We acknowledge financial support by NSF-MRSEC & Nanoelectronics Research Initiative.

Fabrication and photocatalytic activity of high-efficiency visible-light-responsive photocatalyst ZnTe/TiO2 nanotube arrays

International Nuclear Information System (INIS)

Liu Yutang; Zhang Xilin; Liu Ronghua; Yang Renbin; Liu Chengbin; Cai Qingyun

2011-01-01

A new ZnTe modified TiO 2 nanotube (NT) array catalyst was prepared by pulse potential electrodeposition of ZnTe nanoparticles (NPs) onto TiO 2 NT arrays, and its application for photocatalytic degradation of anthracene-9-carboxylic acid (9-AnCOOH) was investigated. The even distribution of ZnTe NPs was well-proportionately grown on the top surface of the TiO 2 NT while without clogging the tube entrances. Compared with the unmodified TiO 2 NT, the ZnTe modified TiO 2 NT (ZnTe/TiO 2 NT) showed significantly enhanced photocatalytic activity towards 9-AnCOOH under simulated solar light. After 70 min of irradiation, 9-AnCOOH was degraded with the removal ratio of 45% on the bare TiO 2 NT, much lower than 80%, 90%, and 100% on the ZnTe/TiO 2 NT with the ZnTe NPs prepared under the pulsed 'on' potentials of -0.8, -1.0, and -2.0 V, respectively. The increased photodegradation efficiency mainly results from the improved photocurrent density as results of enhanced visible-light absorption and decreased hole-electron recombination due to the presence of narrow-band-gap p-type semiconductor ZnTe. -- Graphical abstract: Surface-view SEM images of ZnTe/TiO 2 NT prepared under -2.0 V, and the inset is the corresponding enlarged drawings. Display Omitted Research highlights: → A new method to deposit chalcogenides of transition metals on the TiO 2 nanotubes. → The even distribution of ZnTe nanoparticles was well-proportionedly grown onto TiO 2 NT arrays. → ZnTe/TiO 2 NT showed remarkably increased photocurrent density. → ZnTe/TiO 2 NT showed good photocatalytic performance. → The prepared new catalyst has a promising application in practical systems.

Observation of Hg-diffusion in CdTe using heavy ion (40MeV-O5+) backscattering

International Nuclear Information System (INIS)

Otake, H.; Takita, K.; Murakami, K.; Masuda, K.; Kudo, H.; Seki, S.

1984-01-01

Diffusion of Hg in the near-surface region of CdTe crystals was observed by means of 40MeV-O 5+ ion backscattering. CdTe crystals immersed in Hg were kept in furnace at 280 -- 340 0 C for 2 -- 240hours. The backscattering spectra of these crystals were measured. The concentration of the diffused Hg atoms in the surface reached to 4 x 10 20 cm -3 , and Hg distribution was observed up to 1.4 μm from surface. Temperature dependence of the diffusion coefficients was determined as D = 5 x 10 3 exp (-2.0 +- 0.3eV/kT) cm 2 /sec. Hg-diffusion was not observed in the case of CdTe kept in Hg with a small amount of Cd. These facts suggest that Hg diffusion is controlled by the diffusion of Cd-vacancy. A method of observing the Hg-atoms profile in the near-surface region of the semiconductor was established. (author)

Cd3(MoO4)(TeO3)2: A Polar 3D Compound Containing d10-d0 SCALP-Effect Cations.

Science.gov (United States)

Feng, Yuquan; Fan, Huitao; Zhong, Zhiguo; Wang, Hongwei; Qiu, Dongfang

2016-11-21

The new polar 3D cadmium molybdotellurite Cd 3 (MoO 4 )(TeO 3 ) 2 was obtained by means of a high-temperature solid-state method. Cd 3 (MoO 4 )(TeO 3 ) 2 is a monoclinic crystal system, and it exhibits the polar space group P2 1 (No. 4). The structure of Cd 3 (MoO 4 )(TeO 3 ) 2 can be viewed as a complicated 3D architecture that is composed of distorted CdO n (n = 6, 7) polyhedra, TeO 3 trigonal pyramids, and MoO 4 polyhedra. The compound features the first 3D NCS cadmium molybdotellurite with 1D 4- and 6-MR channels and a polar structure originating from the TeO 3 groups, MoO 4 groups, and displacements of d 10 Cd 2+ cations. The results were further confirmed by calculations of the net polarization. The UV-vis spectrum and thermal properties indicate that Cd 3 (MoO 4 )(TeO 3 ) 2 exhibits a broad transparent region and excellent thermal stability. SHG tests of Cd 3 (MoO 4 )(TeO 3 ) 2 revealed that its response is approximately the same as that of KH 2 PO 4 at the same grain size between 105 and 150 μm and that it is phase-matchable.

Visible light driven multifunctional photocatalysis in TeO2-based semiconductor glass ceramics

Science.gov (United States)

Kushwaha, Himmat Singh; Thomas, Paramanandam; Vaish, Rahul

2017-01-01

Photocatalytic xCaCu3Ti4O12-(100-x)TeO2 (x=0.25 mol% to 3 mol%), glass nanocomposites were fabricated and investigated for wastewater treatment, self-cleaning surfaces, and photocatalytic hydrogen evolution. Visible light active crystals of Cu-doped TiO2 and TiTe3O8 were grown by optimized crystallization of as-quenched glasses. The visible light photocatalytic activity of glass samples was investigated for estrogenic pharmaceutical pollutants, and the degradation rate was obtained as 168.56 min-1 m-2. A higher photocatalytic H2 production rate was observed (135 μmole h-1 g-1) for the crystallized CaCu3Ti4O12-TeO2 (x=3. 0) glass plate under visible light. The self-cleaning performance was observed using contact angle measurements for water under dark and light conditions. These visible light active glass ceramics are a cost effective sustainable solution for water treatment and self-cleaning applications.

Structural and thermal properties of tellurite 20Li2O-80TeO2 glasses

OpenAIRE

Idalgo, E. [UNESP; Araújo, E. B. [UNESP

2007-01-01

O presente trabalho reporta estudos sobre a cristalização em vidros teluretos 20Li2O-80TeO2 induzida a partir de tratamentos térmicos realizados sobre vidros com tamanho de partículas entre 38 µm e 75 µm. Estes estudos foram conduzidos em duas matrizes vítreas tratadas e não tratadas termicamente para aliviar as tensões após o quenching, utilizando-se de forma combinada às técnicas de difração de raios X, calorimetria diferencial de varredura e espectroscopia no infravermelho. Os resultados r...

Study of gamma radiation shielding properties of ZnO-TeO_2 glasses

International Nuclear Information System (INIS)

Issa, Shama A.M.; Sayyed, M.I.; Kurudirek, Murat

2017-01-01

Mass attenuation coefficient (μm), half value layer (HVL) and mean free path (MFP) for xZnO-(100-x)TeO_2, where x=10, 15, 20, 25, 30, 35 and 40 mol%, have been measured for 0.662, 1.173 and 1.33 MeV photons emitted from "1"3"7Cs and "6"0Co using a 3 x 3 inch NaI (Tl) detector. Some relevant parameters such as effective atomic numbers (Z_e_f_f) and electron densities (Nel) of glass samples have been also calculated in the photon energy range of 0.015-15 MeV. Moreover, gamma-ray energy absorption buildup factor (EABF) and exposure buildup factor (EBF) were estimated using a five-parameter Geometric Progression (GP) fitting approximation, for penetration depths up to 40 MFP and in the energy range 0.015-15 MeV. The measured mass attenuation coefficients were found to agree satisfactorily with the theoretical values obtained through WinXcom. Effective atomic numbers (Z_e_f_f) and electron densities (N_e_l) were found to be the highest for 40ZnO-60TeO_2 glass in the energy range 0.04-0.2 MeV. The 10ZnO-90TeO_2 glass sample has lower values of gamma-ray EBFs in the intermediate energy region. The reported new data on radiation shielding characteristics of zinc tellurite glasses should be beneficial from the point of proper gamma shield designs when intended to be used as radiation shields. (author)

Facile fabrication of core–shell ZnO/Bi{sub 0.5}Sb{sub 1.5}Te{sub 3} nanorods: Enhanced photoluminescence through electron charge

Energy Technology Data Exchange (ETDEWEB)

Shen, Shengfei; Gao, Hongli [School of Materials Science & Engineering, Beihang University, Beijing 100191 (China); Deng, Yuan, E-mail: dengyuan@buaa.edu.cn [School of Materials Science & Engineering, Beihang University, Beijing 100191 (China); Wang, Yao [School of Materials Science & Engineering, Beihang University, Beijing 100191 (China); Qu, Shengchun, E-mail: qsc@semi.ac.cn [Key Laboratory of Semiconductor Materials Science, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083 (China)

2016-01-15

Graphical abstract: - Highlights: • The Bi{sub 0.5}Sb{sub 1.5}Te{sub 3}/ZnO core–shells prepared by combining a facile hydrothermal growth and magnetron sputtering approach. • The light absorption and photoluminescence emission of the ZnO and the Bi{sub 0.5}Sb{sub 1.5}Te{sub 3}/ZnO core–shells are investigated. • The core–shell structure reveals a simultaneous novelty enhancement of the photoluminescence emission in the UV and visible range. • The mechanism for the PL simultaneous enhancement is described. - Abstract: Surface decoration techniques are emerging as promising strategy to improve the optical properties of the ZnO based materials. The core–shell ZnO/Bi{sub 0.5}Sb{sub 1.5}Te{sub 3} nanorods were grown on a FTO substrate through a facile hydrothermal and magnetron sputtering combined approach. The microstructure of the core–shell nanorod arrays were investigated by the X-ray diffraction (XRD), a field emission Scanning electron microscopy (SEM) and high resolution transmission electron microscope (HTEM). The optical properties of the core–shell nanorod arrays were investigated through the diffuse reflectance absorption spectra and photoluminescence emission. The visible light absorption and especially the photoluminescence emission of the ZnO nanorods are enhanced markedly with the Bi{sub 0.5}Sb{sub 1.5}Te{sub 3} grains coating the ZnO nanorods through the electron charge.

Application of ECH to the Study of Transport in ITER Baseline Scenario-like Discharges in DIII-D

Directory of Open Access Journals (Sweden)

Pinsker R.I.

2015-01-01

Full Text Available Recent DIII-D experiments in the ITER Baseline Scenario (IBS have shown strong increases in fluctuations and correlated reduction of confinement associated with entering the electron-heating-dominated regime with strong electron cyclotron heating (ECH. The addition of 3.2 MW of 110 GHz EC power deposited at ρ∼0.42 to IBS discharges with ∼3 MW of neutral beam injection causes large increases in low-k and medium-k turbulent density fluctuations observed with Doppler backscatter (DBS, beam emission spectroscopy (BES and phase-contrast imaging (PCI diagnostics, correlated with decreases in the energy, particle, and momentum confinement times. Power balance calculations show the electron heat diffusivity χe increases significantly in the mid-radius region 0.4<ρ<0.8, which is roughly the same region where the DBS and BES diagnostics show the increases in turbulent density fluctuations. Confinement of angular momentum is also reduced during ECH. Studies with the TGYRO transport solver show that the model of turbulent transport embodied in the TGLF code quantitatively reproduces the measured transport in both the neutral beam (NB-only and in the NB plus EC cases. A simple model of the decrease in toroidal rotation with EC power is set forth, which exhibits a bifurcation in the rotational state of the discharge.

Investigations on the electrodeposition behaviors of Bi0.5Sb1.5Te3 thin film from nitric acid baths

International Nuclear Information System (INIS)

Li Feihui; Huang Qinghua; Wang Wei

2009-01-01

The electrochemical reduction process of Bi 3+ , HTeO 2 + , Sb III and their mixtures in nitric acid medium was investigated by means of cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) measurements. The reduction products electrodeposited at various potentials were examined using X-ray diffraction (XRD) and energy dispersive spectroscopy (EDS). The results show that cathodic process in the nitric acid solution containing Bi 3+ , HTeO 2 + and Sb III involves the following reduction reactions in different polarizing potential ranges: In low polarizing potential ranges, Te 0 is formed firstly on the electrode surface through the electrochemical reduction of HTeO 2 + ; with the negative shift of the cathodic polarizing potential, the reduction reaction of Bi 3+ with Te 0 to form Bi 2 Te 3 takes place; when the cathodic polarizing potential is negative enough, Bi 3+ and Sb III react with Te 0 to form Bi 0.5 Sb 1.5 Te 3 . The results indicate that Bi 0.5 Sb 1.5 Te 3 films can be fabricated by controlling the electrodepositing potential in a proper high potential ranges.

Post-Irradiation Behaviour of I{sup 131} in TeO{sub 2}; Comportement de {sup 131}I Dans TeO{sub 2} Apres Irradiation; 041f 041e 0412 0415 0414 0415 041d 0418 0415 0419 041e 0414 0410 -131 0412 TeO{sub 2} 0433 041f 041e 0421 041b 0415 041e 0411 041b 0423 0427 0415 041d 0418 042f ; Comportamiento del {sup 131}I en TeO{sub 2} Despues de su Irradiacion

Energy Technology Data Exchange (ETDEWEB)

Jacimovic, Lj.; Stevovic, J.; Veljkovic, S. R. [Boris Kidric Institute of Nuclear Sciences, Belgrade, Yugoslavia (Serbia)

1965-04-15

The system I{sup 131} in TeO{sub 2} is interesting because little is known about thermal chemical changes in this target. Radioiodine was produced by neutron irradiation of TeO{sub 2} in the reactor. Irradiated TeO{sub 2} was dissolved in diluted NaOH. The analysis of the iodine valency forms was made by ion exchange techniques. The thermal and radiation stability of TeO{sub 2} was studied by using the spectrophotometric method for the determination of tellurium. Post-irradiation annealing of I{sup 131} in TeO{sub 2} was studied in dependence on the time and temperature of the heating. The main tendency of annealing was the reduction of radioiodine. The time dependence of this process indicates a fast change at high temperatures. The curves are more complex at lower temperatures. The annealing may appear complex because of the variety of thermal reactions of iodine intermediary. It may react with products of the following processes: tellurium recoil and corresponding hot zone, beta transition of Te{sup 131} and TeO{sub 2} itself. The kinetics of these changes was considered and an estimation of the processes during annealing was made. The influence of the neutron flux on the kinetics of annealing was also studied. (author) [French] Le cas de 131I dans TeO{sub 2} presente un interet en raison du peu de connaissances dont on dispose sur les modifications chimico-thermiques dans cette cible. Les auteurs ont obtenu le radioiode par exposition de TeO{sub 2} aux neutrons en pile, puis dissous TeO{sub 2} irradie dans NaOH dilue. Ils ont fait l'analyse des divers etats de valence de l'iode par des procedes d'echange d'ions. Ils ont etudie la stabilite thermique et la radiostabilite de TeO{sub 2} en recourant a la methode spectrophotometrique pour la determination du tellure. Ils ont etudie le recuit de 131I dans TeO{sub 2} apres irradiation en fonction du temps et de la temperature de chauffage. La tendance du recuit a ete surtout une tendance a la reduction du radioiode

The electronic spectra of FeH and TeO2

International Nuclear Information System (INIS)

Hullah, D.F.

1999-01-01

A thesis submitted for the degree of Doctor of Philosophy at the University of Oxford. Daniel Fearnley Hullah, Jesus College, Trinity Term 1999. This thesis is presented in two parts. The subject of Part One is the recording and analysis of part of the electronic spectrum of the iron monohydride, FeH, at visible wavelengths with Doppler-limited resolution. The subject of Part Two is the recording and analysis of the electronic spectrum of tellurium dioxide, TeO 2 , at near ultra-violet wavelengths under free jet expansion conditions. PART ONE: The fourth sub-bands of the e 6 Π-c 6 Σ + and e 6 Π-a 6 Δ transitions of FeH were recorded using both direct laser induced fluorescence and dispersed laser induced fluorescence. A total of sixteen lines were assigned to the e 6 Π 1/2 -c 6 Σ + -1/2 transition and fourteen lines were assigned to the e 6 Π 1/2 -a 6 Δ 3/2 transition. This allowed the e 6 Π 1/2 spin-orbit component to be characterised for J levels from 1/2 to 7/2 and the a 6 Δ 3/2 spin-orbit component to be characterised for J levels from 3/2 to 9/2. The first sub-band of the e 6 Π-a 6 Δ transition was extended following analysis of the high temperature spectrum of McCormack and O'Connor (recorded in 1976). Dispersed fluorescence spectra of the first four sub-bands of the e 6 Π-a 6 Δ transition were recorded. Following analysis, transitions at ∼ 600 nm were recorded using direct laser induced fluorescence. These were assigned to transitions from the first three spin-orbit components of a new sextet electronic state, b 6 Π (e 6 Π-b 6 Π), one spin orbit component of a new quartet state, C 4 Φ 7/2 , (e 6 Π 5/2 -C 4 Φ 7/2 ), and the previously observed X 4 Δ 7/2 υ = 2 state (e 6 Π 7/2 -X 4 Δ 7/2 υ = 2). PART TWO: The electronic spectrum of TeO 2 was recorded between 345 and 406 nm using a pulsed dye laser. TeO 2 (g) was produced by heating TeO 2(s) to 850 deg. C and entraining the vapour in argon and expanding the gases in a continuous free

Artificial intelligence for the EChO mission planning tool

Science.gov (United States)

Garcia-Piquer, Alvaro; Ribas, Ignasi; Colomé, Josep

2015-12-01

The Exoplanet Characterisation Observatory (EChO) has as its main goal the measurement of atmospheres of transiting planets. This requires the observation of two types of events: primary and secondary eclipses. In order to yield measurements of sufficient Signal-to-Noise Ratio to fulfil the mission objectives, the events of each exoplanet have to be observed several times. In addition, several criteria have to be considered to carry out each observation, such as the exoplanet visibility, its event duration, and no overlapping with other tasks. It is expected that a suitable mission plan increases the efficiency of telescope operation, which will represent an important benefit in terms of scientific return and operational costs. Nevertheless, to obtain a long term mission plan becomes unaffordable for human planners due to the complexity of computing the huge number of possible combinations for finding an optimum solution. In this contribution we present a long term mission planning tool based on Genetic Algorithms, which are focused on solving optimization problems such as the planning of several tasks. Specifically, the proposed tool finds a solution that highly optimizes the defined objectives, which are based on the maximization of the time spent on scientific observations and the scientific return (e.g., the coverage of the mission survey). The results obtained on the large experimental set up support that the proposed scheduler technology is robust and can function in a variety of scenarios, offering a competitive performance which does not depend on the collection of exoplanets to be observed. Specifically, the results show that, with the proposed tool, EChO uses 94% of the available time of the mission, so the amount of downtime is small, and it completes 98% of the targets.

Electrical and Thermal Conductivity and Conduction Mechanism of Ge2Sb2Te5 Alloy

Science.gov (United States)

Lan, Rui; Endo, Rie; Kuwahara, Masashi; Kobayashi, Yoshinao; Susa, Masahiro

2018-06-01

Ge2Sb2Te5 alloy has drawn much attention due to its application in phase-change random-access memory and potential as a thermoelectric material. Electrical and thermal conductivity are important material properties in both applications. The aim of this work is to investigate the temperature dependence of the electrical and thermal conductivity of Ge2Sb2Te5 alloy and discuss the thermal conduction mechanism. The electrical resistivity and thermal conductivity of Ge2Sb2Te5 alloy were measured from room temperature to 823 K by four-terminal and hot-strip method, respectively. With increasing temperature, the electrical resistivity increased while the thermal conductivity first decreased up to about 600 K then increased. The electronic component of the thermal conductivity was calculated from the Wiedemann-Franz law using the resistivity results. At room temperature, Ge2Sb2Te5 alloy has large electronic thermal conductivity and low lattice thermal conductivity. Bipolar diffusion contributes more to the thermal conductivity with increasing temperature. The special crystallographic structure of Ge2Sb2Te5 alloy accounts for the thermal conduction mechanism.

Electrical and Thermal Conductivity and Conduction Mechanism of Ge2Sb2Te5 Alloy

Science.gov (United States)

Lan, Rui; Endo, Rie; Kuwahara, Masashi; Kobayashi, Yoshinao; Susa, Masahiro

2017-11-01

Ge2Sb2Te5 alloy has drawn much attention due to its application in phase-change random-access memory and potential as a thermoelectric material. Electrical and thermal conductivity are important material properties in both applications. The aim of this work is to investigate the temperature dependence of the electrical and thermal conductivity of Ge2Sb2Te5 alloy and discuss the thermal conduction mechanism. The electrical resistivity and thermal conductivity of Ge2Sb2Te5 alloy were measured from room temperature to 823 K by four-terminal and hot-strip method, respectively. With increasing temperature, the electrical resistivity increased while the thermal conductivity first decreased up to about 600 K then increased. The electronic component of the thermal conductivity was calculated from the Wiedemann-Franz law using the resistivity results. At room temperature, Ge2Sb2Te5 alloy has large electronic thermal conductivity and low lattice thermal conductivity. Bipolar diffusion contributes more to the thermal conductivity with increasing temperature. The special crystallographic structure of Ge2Sb2Te5 alloy accounts for the thermal conduction mechanism.

Improved electron density through hetero-junction binary sensitized TiO2/ CdTe / D719 system as photoanode for dye sensitized solar cell

Science.gov (United States)

Pandey, A. K.; Ahmad, Muhammad Shakeel; Alizadeh, Mahdi; Rahim, Nasrudin Abd

2018-07-01

The combined effect of dual sensitization and hetero-junction symmetry has been investigated on the performance of TiO2 based dye sensitized solar cell. CdTe nanoparticles have been introduced in TiO2 matrix to function as sensitizer as well as act as hetero-junction between D719 dye and TiO2 nanoarchitecture. Four concentrations of CdTe i.e. 0.5 wt%, 2 wt%, 5 wt% and 8 wt% have been investigated. Morphological and compositional studies have been conducted using scanning electron microscope (SEM) and X-ray diffraction (XRD) respectively. Light absorption characteristics have been investigated by employing Uv-vis spectroscopy and the overall performance has been studied using solar simulator and electrochemical impedance spectroscopy (EIS). Performance has been found to be increased with the addition of CdTe due to high electron density and reduction in recombination reactions. An increase of 41.73% in incident photo conversion efficiency (IPCE) and 75.57% in short circuit current density (Jsc) have been recorded for the specimens containing 5 wt% CdTe compared to bare TiO2 based DSSCs. Further addition of CdTe leads to reduction in overall performance of DSSCs.

Preparation and observation of an artifact-free Ge2Sb2Te5 TEM specimen by the small angle cleavage technique

International Nuclear Information System (INIS)

Kim, M.S.; Kim, H.G.

2006-01-01

The amorphous Ge 2 Sb 2 Te 5 thin film for the application to the non-volatile memory device was prepared by the pulsed laser deposition on a SiO2/Si substrate. The amorphous Ge 2 Sb 2 Te 5 which has the T C around 150 deg. C is readily crystallized when exposed to a comparable heat such as the Ar beam irradiation during the conventional ion milling process. Retaining its amorphous initial phase is important in order to precisely observe and understand the crystallization behaviour whether it be the sample for a pure materialistic research or applied into the device. To avoid such deterioration of the film's amorphous nature, the complete mechanical TEM specimen preparation which is called the small angle cleavage technique (SACT) was adopted to show thermally undisturbed, an artifact-free amorphous Ge 2 Sb 2 Te 5 TEM specimen. The two distinctive amorphous and crystalline phases has been observed by the HRTEM study

Study of Synergetic Effect of X2 and X3 EC Wave in KSTAR

Directory of Open Access Journals (Sweden)

Bae Y.S.

2015-01-01

Full Text Available An experimental study of the X-mode absorption at the second and the third harmonic frequencies has been performed in KSTAR tokamak. The X2 EC frequency is 110 GHz and the X3 EC frequency is 170 GHz at the nominal KSTAR operating toroidal magnetic field. From the 1-D model of the synergetic effect, the X3 cold resonance should lie at low field side with the X2 cold resonance at the high field side to meet the condition which both X2 and X3 EC waves interact with the same resonant electron at the same radial position. However, 170 GHz X3 cold resonance lies at the high field side with distance of 54 mm from the X2 cold resonance position in KSTAR. This paper presents the study of the synergetic effect of X3 absorption by the X2 ECCD with a scheme of two beam target positions at the same flux surface by scanning the poloidal and toroidal beam injection angles to enhance X3 absorption even in the low temperature plasma in KSTAR. For this study, the3D relativistic ray/tracing and Fokker-Planck codes C3PO/LUKE is used for the quantitative prediction of its synergetic effect. The C3PO/LUKE codes are appropriate for X2 and X3 synergy calculations as the distribution function can be calculated with either one or both waves affecting the absorption rate of each other. This paper also introduces the future ECH system upgrade plan.

1887 nm lasing in Tm3+-doped TeO2-BaF2-Y2O3 glass microstructured fibers

Science.gov (United States)

Wang, Shunbin; Yao, Chuanfei; Jia, Zhixu; Qin, Guanshi; Qin, Weiping

2017-04-01

In this paper, we demonstrate ∼2 μm lasing in Tm3+-doped fluorotellurite microstructured fibers. The Tm3+-doped fibers are based on TeO2-BaF2-Y2O3 glasses and fabricated by using a rod-in-tube method. Under the pump of a 1570 nm Er3+-doped fiber laser, lasing at 1887 nm is obtained in a ∼42.5 cm long Tm3+-doped fiber with a threshold pump power of 94 mW. As the pump power increases to 780 mW, the obtained maximum unsaturated power reaches up to ∼408 mW with a slop efficiency of ∼58.1%. This result indicates that the Tm3+-doped fluorotellurite fibers are promising gain media for ∼2 μm fiber lasers.

Fabrication of transparent TiO2 nanotube-based photoanodes for CdS/CdTe quantum co-sensitized solar cells

Science.gov (United States)

Gualdrón-Reyes, A. F.; Cárdenas-Arenas, A.; Martínez, C. A.; Kouznetsov, V. V.; Meléndez, A. M.

2017-01-01

In order to fabricate a solar cell, ordered TiO2 nanotube (TNT) arrays were prepared by double anodization. TNT arrays with variable lengths were obtained by changing the duration of the anodizing process of up to 3h. TNT membranes were transferred to indium tin oxide substrates and attached with a B-TiO2 sol. TNT photoanode with the best photoelectrochemical performance was sensitized with CdS by SILAR method. On other hand, CdTe quantum dots prepared via colloidal synthesis were deposited on TNT photoanodes for 2h, 4h and 6h. In addition, TNT/CdS was loaded with CdTe quantum dots for 4 h. Morphology and chemical modification of TiO2 were characterized by FESEM and XPS, while their photoelectrochemical performance was measured by open-circuit photopotential and photovoltammetry under visible light. TiO2 nanotubes grown during 2.5h showed the highest photocurrent due to presence of Ti3+ donor states by N and F co-doping, increasing the number of photogenerated electrons transported to back collector. TNT/CdS/CdTe photoanode reach the highest conversion efficiency under AM 1.5G simulated solar illumination.

Structural, morphological and optical investigations on electron-beam irradiated PbF2-TeO2-B2O3-Eu2O3 glasses

Science.gov (United States)

Wagh, Akshatha; Petwal, Vikash; Dwivedi, Jishnu; Upadhyaya, V.; Raviprakash, Y.; Kamath, Sudha D.

2016-09-01

Combined structural, optical and morphological studies were carried out on Eu2O3 doped PbF2-TeO2-B2O3 glass samples, before and after being subjected to electron beam of energy 7.5 MeV. XRD confirmed the amorphous nature of the glasses even after 150 kGy electron beam irradiation. Densities of the irradiated samples showed slightly greater values when compared to their respective values before irradiation, which proved the increase in the compaction of the network. The intensities of the three prominent bands; B-O-B linkages, BO4 units and BO3 units of FT-IR spectra, of the titled glasses, showed slight decrease after electron beam irradiation. The decrement in the values of energy band gap and shift in cut-off wavelength towards red edge, proved the formation of color centers in the glass network after irradiation. The change in Hunter L values, through color measurement was a proof for the Farbe/color/absorption centers created in the glass sites after irradiation.

Effects of SiO2 encapsulation and laser processing on single CdTe/ZnTe quantum dots grown on Si (001) substrates

International Nuclear Information System (INIS)

Lee, Hong Seok; Rastelli, Armando; Schmidt, Oliver G.; Kim, Tae Whan; Lee, In Won

2011-01-01

Micro-photoluminescence (μ-PL) measurements are carried out to investigate the effects of SiO 2 encapsulation and laser processing of single CdTe/ZnTe quantum dots (QDs) grown on Si (001) substrates by using molecular beam epitaxy and atomic layer epitaxy. After laser processing, the μ-PL peak shift for the 200-nm SiO 2 capped single QD is larger than that of the as-grown sample. The large μ-PL peak shift in the 200-nm SiO 2 capped sample is related to the compressive stress induced by the ZnTe cap layer during laser processing. These results indicate that SiO 2 encapsulation and laser processing represent effective methods for achieving local wavelength tuning in single QDs.

Synthesis, structure, and characterization of two new bismuth(III) selenite/tellurite nitrates: [(Bi{sub 3}O{sub 2})(SeO{sub 3}){sub 2}](NO{sub 3}) and [Bi(TeO{sub 3})](NO{sub 3})

Energy Technology Data Exchange (ETDEWEB)

Meng, Chang-Yu; Wei, Ming-Fang [Department of Chemistry and Materials, Yulin Normal University,Yulin, Guangxi 537000 (China); Geng, Lei, E-mail: lgeng.cn@gmail.com [Department of Materials Science and Engineering, Huaibei Normal University, Huaibei, Anhui 235000 (China); Hu, Pei-Qing; Yu, Meng-Xia [Department of Chemistry and Materials, Yulin Normal University,Yulin, Guangxi 537000 (China); Cheng, Wen-Dan [State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002 (China)

2016-07-15

Two new bismuth(III) selenite/tellurite nitrates, [(Bi{sub 3}O{sub 2})(SeO{sub 3}){sub 2}](NO{sub 3}) and [Bi(TeO{sub 3})](NO{sub 3}), have been synthesized by conventional facile hydrothermal method at middle temperature 200 °C and characterized by single-crystal X-ray diffraction, powder diffraction, UV–vis–NIR optical absorption spectrum, infrared spectrum and thermal analylsis. Both [(Bi{sub 3}O{sub 2})(SeO{sub 3}){sub 2}](NO{sub 3}) and [Bi(TeO3)](NO3) crystallize in the monoclinic centronsymmetric space group P2{sub 1}/c with a=9.9403(4) Å, b=9.6857(4) Å, c=10.6864(5) Å, β=93.1150(10)° for [(Bi{sub 3}O{sub 2})(SeO{sub 3}){sub 2}](NO{sub 3}) and a=8.1489(3) Å, b=9.0663(4) Å, c=7.4729(3) Å, β=114.899(2)° for Bi(TeO3)(NO3), respectively. The two compounds, whose structures are composed of three different asymmetric building units, exhibit two different types of structures. The structure of [(Bi{sub 3}O{sub 2})(SeO{sub 3}){sub 2}](NO{sub 3}) features a three-dimensional (3D) bismuth(III) selenite cationic tunnel structure [(Bi{sub 3}O{sub 2})(SeO{sub 3}){sub 2}] {sup 3}{sub ∞} with NO{sub 3}{sup −} anion group filling in the 1D tunnel along b axis. The structure of [Bi(TeO{sub 3})](NO{sub 3}) features 2D bismuth(III) tellurite [Bi(TeO{sub 3}){sub 2}]{sup 2}{sub ∞} layers separated by NO{sub 3}{sup −} anion groups. The results of optical diffuse-reflectance spectrum measurements and electronic structure calculations based on density functional theory methods show that the two compounds are wide band-gap semiconductors. - Graphical abstract: Two novel bismuth{sup III} selenite/tellurite nitrates [(Bi{sub 3}O{sub 2})(SeO{sub 3}){sub 2}](NO{sub 3}) with 3D tunnel structure and [Bi(TeO{sub 3})](NO{sub 3}) with 2D layer structure have been firstly synthesized and characterized. Display Omitted - Highlights: • Two novel bismuth{sup III} nitrates [(Bi{sub 3}O{sub 2})(SeO{sub 3}){sub 2}](NO{sub 3}) and [Bi(TeO{sub 3})](NO{sub 3}) were firstly

On Ba2Ge2Te5, a new telluridogermanate(III) with chain structure

International Nuclear Information System (INIS)

Brinkmann, C.; Eisenmann, B.; Schaefer, H.

1984-01-01

The new compound Ba 2 Ge 2 Te 5 crystallizes in the orthorhombic system (space group: Pna2 1 (No. 33)). The lattice constants are given. In the structure distorted Ge 2 Te 6 -trigonal prisms are connected by common corners to infinite chains. (author)

Infrared investigation of the phonon spectrum in the frustrated spin cluster compound FeTe{sub 2}O{sub 5}Cl

Energy Technology Data Exchange (ETDEWEB)

Pfuner, F; Degiorgi, L [Laboratorium fuer Festkoerperphysik, ETH Zuerich, CH-8093 Zuerich (Switzerland); Berger, H; Forro, L [Institut de Physique de la Matiere Complexe (IPMC), EPF Lausanne, CH-1015 Lausanne (Switzerland)

2009-09-16

We present our optical investigations on the frustrated spin cluster compound FeTe{sub 2}O{sub 5}Cl, which develops a long-range antiferromagnetic order below 10 K. We measure the optical reflectivity from the far-infrared to the ultraviolet with polarized light. We focus our attention on the lattice dynamics by discussing the infrared-active modes. Our findings reveal a polarization dependence of the vibrational modes but which do not seem to be affected by structural anomalies linked to the magnetically ordered state at low temperatures.

Background suppression in TeO2 bolometers with Neganov-Luke amplified cryogenic light detectors

International Nuclear Information System (INIS)

Willers, Michael

2015-01-01

Cryogenic detectors based on non-scintillating TeO 2 crystals are used in the search for the neutrinoless double beta decay, presently one of the most important fields of research in neutrino and astroparticle physics. Within this work, the application of Neganov-Luke amplified cryogenic light detectors for the background suppression in TeO 2 crystals is investigated. Alpha-induced background events can be discriminated from signal-like electron/gamma events via the detection of Cherenkov radiation produced by highly energetic electrons within the TeO 2 crystal. Using Neganov-Luke light detectors, it could be shown for the first time that a highly efficient event-by-event discrimination between alpha and electron/gamma-induced events can be achieved.

Upconversion in rare earth ions doped TeO2-ZnO glass

International Nuclear Information System (INIS)

Mohanty, Deepak Kumar; Rai, Vineet Kumar

2012-01-01

The Er 3+ /Yb 3+ doped/codoped TeO 2 -ZnO glasses have been fabricated by conventional melt and quenching technique. The absorption spectra of the doped/codoped glasses have been performed. The visible upconversion emissions of both doped and codoped glasses have been observed using 808 nm diode laser excitation. The process involved in upconversion emissions has been discussed in detail. (author)

Enhancement effect of CdTe quantum dots-IgG bioconjugates on chemiluminescence of luminol-H2O2 system

International Nuclear Information System (INIS)

Kanwal, Shamsa; Traore, Zoumana; Zhao Chunfang; Su Xingguang

2010-01-01

In this paper we developed an entirely new and highly sensitive luminol-H 2 O 2 flow injection chemiluminescence system using the enhancement effect of CdTe quantum dots-IgG bioconjugates. Immunoglobulin G (IgG) as a kind of bio-molecule was conjugated to different sized CdTe semiconductor quantum dots (QDs). Using PL spectra and CL intensity profiles, it was found that chemiluminescence resonance energy transfer (CRET) was possibly occurring between CdTe-IgG bioconjugate and luminol. Under optimum conditions, increase of IgG concentration in CdTe-IgG bioconjugate resulted enhancing effect on CL intensity of luminol-H 2 O 2 system. Moreover quenching effects on CL intensity by addition of different proteases can construct turn off biosensor for these proteases with low detection limits and wide linear range. Furthermore, the effects of various organic and inorganic species on CdTe-IgG bioconjugates enhanced luminol-H 2 O 2 CL system were also studied in this paper.

Low-potential sensitive H2O2 detection based on composite micro tubular Te adsorbed on platinum electrode.

Science.gov (United States)

Guascito, M R; Chirizzi, D; Malitesta, C; Mazzotta, E; M Siciliano; Siciliano, T; Tepore, A; Turco, A

2011-04-15

In this work a new original amperometric sensor for H(2)O(2) detection based on a Pt electrode modified with Te-microtubes was developed. Te-microtubes, synthesized by the simple thermal evaporation of Te powder, have a tubular structure with a hexagonal cross-section and are open ended. Modified electrode was prepared by direct drop casting of the mixture of Te-microtubes dispersed in ethanol on Pt surface. The spectroscopic characterization of synthesized Te-microtubes and Pt/Te-microtubes modified electrodes was performed by scanning electron microscopy (SEM), energy-dispersive X-rays microanalysis (EDX), X-ray diffraction analysis (XRD) and X-ray photoelectron spectroscopy (XPS). Moreover a complete electrochemical characterization of the new composite material Pt/Te-microtubes was performed by cyclic voltammetry (CV) and cronoamperometry (CA) in phosphate buffer solution (PBS) at pH 7. Electrochemical experiments showed that the presence of Te-microtubes on modified electrode was responsible for an increment of both cathodic and anodic currents in presence of H(2)O(2) with respect to bare Pt. Specifically, data collected from amperometric experiments at -150 mV vs. SCE in batch and -200 mV vs. SCE in flow injection analysis (FIA) experiments show a remarkable increment of the cathodic current. The electrochemical performances of tested sensors make them suitable for the quantitative determination of H(2)O(2) substrate both in batch and in FIA. Copyright © 2011 Elsevier B.V. All rights reserved.

Thermal analyses, spectral characterization and structural interpretation of Nd3+/Er3+ ions co-doped TeO2-ZnCl2 glasses system

Science.gov (United States)

Ahmed, Kasim F.; Ibrahim, Saeed O.; Sahar, Md. R.; Mawlud, Saman Q.; Khizir, Hersh A.

2017-09-01

The Nd3+/Er3+ ions co-doped in the system of zinc-tellurite with the composition of (70-2x)TeO2-30ZnCl2-xNd2O3-xEr2O3 concentration from 1.0 to 3.0 mol% (x=1, 2 and 3) glasses were prepared by using conventional melt-quenching technique. The amorphous nature of the glass been confirmed by using X-RAY Diffraction Spectroscopy. Thermal characteristic were determined using a DTA. The obtained results discussed in terms of the glass structure. The glass structure studied by means of FTIR. Seven significant vibrational peaks around 471, 687, 742, 768, 1632, 2833 and 3378 cm-1 which correspond to the structural bonding of the glass are observed in a range of 400-4000cm-1. The peaks observed are consistent with the stretching and bending vibrations of the Te-O, TeO4 trigonal bipyramids, TeO3 trigonal pyramids, Te-O-Te and OH linkages respectively.

Measurements of defect structures by positron annihilation lifetime spectroscopy of the tellurite glass TeO2-P2O5-ZnO-LiNbO3 doped with ions of rare earth elements: Er3+, Nd3+ and Gd3+

Science.gov (United States)

Golis, E.; Yousef, El. S.; Reben, M.; Kotynia, K.; Filipecki, J.

2015-12-01

The objective of the study was the structural analysis of the TeO2-P2O5-ZnO-LiNbO3 tellurite glasses doped with ions of the rare-earth elements: Er3+, Nd3+ and Gd3+ based on the PALS (Positron Annihilation Lifetime Spectroscopy) method of measuring positron lifetimes. Values of positron lifetimes and the corresponding intensities may be connected with the sizes and number of structural defects, such as vacancies, mono-vacancies, dislocations or pores, the sizes of which range from a few angstroms to a few dozen nanometres. Experimental positron lifetime spectrum revealed existence of two positron lifetime components τ1 and τ2. Their interpretation was based on two-state positron trapping model where the physical parameters are the annihilation velocity and positron trapping rate.

Investigations on the Local Structures and the Spin Hamiltonian Parameters for Cu2+ in (90-x)TeO2-10GeO2-xWO3 Glasses

Science.gov (United States)

Feng, Chun-Rong; Jian, Jun; Chen, Xiao-Hong; Du, Quan; Wang, Ling

2017-12-01

The local structures and the spin Hamiltonian parameters (SHPs) for Cu2+ in (90-x)TeO2-10GeO2-xWO3 glasses are theoretically investigated at various WO3 concentrations (x=7.5, 15, 22.5 and 30 mol%). Subject to the Jahn-Teller effect, the [CuO6]10- groups are found to experience the small or moderate tetragonal elongation distortions (characterised by the relative tetragonal elongation ratios ρ≈0.35-3.09%) in C4 axis. With only three adjusted coefficients a, b and ω, the relevant model parameters (Dq, k and ρ) are described by the Fourier type and linear functions, respectively, and the measured concentration dependences of the d-d transition bands and SHPs are reproduced. The maximum of g∥ and the minimum of |A∥| at x=15 mol% are illustrated from the abrupt decrease of the copper-oxygen electron cloud admixtures or covalency and the obvious decline of the copper 3d-3s (4s) orbital admixtures due to the decreasing electron cloud density around oxygen ligands spontaneously bonding with Cu2+ and Te4+ (W6+), respectively.

Selected highlights of ECH/ECCD physics studies in the TCV tokamak

Directory of Open Access Journals (Sweden)

Goodman T.P.

2015-01-01

Full Text Available The Tokamak a Configuration Variable, TCV, has used Electron Cyclotron Heating and Current Drive as its only auxiliary heating system for nearly two decades. In addition to basic plasma heating and current profiling, ECH and ECCD under either feedforward or real-time (feedback control allows control of plasma parameters and MHD behaviour to aid in physics studies and measurements. This paper describes four such studies in which EC control has proved crucial – increased resolution Thomson Scattering measurements in the plasma edge, time-resolved plasma rotation modification during the sawtooth cycle, robust neoclassical tearing mode (NTM suppression, and double pass transmission measurements of EC waves for scattering and polarization studies. The relative merits of feedforward and feedback methods for recent TCV experiments are discussed.

Influence of substrate type on transport properties of superconducting FeSe0.5Te0.5 thin films

International Nuclear Information System (INIS)

Yuan, Feifei; Shi, Zhixiang; Iida, Kazumasa; Langer, Marco; Hänisch, Jens; Hühne, Ruben; Schultz, Ludwig; Ichinose, Ataru; Tsukada, Ichiro; Sala, Alberto; Putti, Marina

2015-01-01

FeSe 0.5 Te 0.5 thin films were grown by pulsed laser deposition on CaF 2 , LaAlO 3 and MgO substrates and structurally and electro-magnetically characterized in order to study the influence of the substrate on their transport properties. The in-plane lattice mismatch between FeSe 0.5 Te 0.5 bulk and the substrate shows no influence on the lattice parameters of the films, whereas the type of substrate affects the crystalline quality of the films and, therefore, the superconducting properties. The film on MgO showed an extra peak in the angular dependence of critical current density J c (θ) at θ = 180° (H||c), which arises from c-axis defects as confirmed by transmission electron microscopy. In contrast, no J c (θ) peaks for H||c were observed in films on CaF 2 and LaAlO 3 . J c (θ) can be scaled successfully for both films without c-axis correlated defects by the anisotropic Ginzburg–Landau approach with appropriate anisotropy ratio γ J . The scaling parameter γ J is decreasing with decreasing temperature, which is different from what we observed in FeSe 0.5 Te 0.5 films on Fe-buffered MgO substrates. (paper)

Effect of Se substitution on the phase change properties of Ge2Sb2Te5

Science.gov (United States)

Shekhawat, Roopali; Rangappa, Ramanna; Gopal, E. S. R.; Ramesh, K.

2018-05-01

Ge2Sb2Te5 popularly known as GST is being explored for non-volatile phase change random access memory(PCRAM) applications. Under high electric field, thin films of amorphous GST undergo a phase change from amorphous to crystalline with a high contrast in electrical resistivity (about 103). The phase change is between amorphous and metastable NaCl structure occurs at about 150°C and not to the stable hexagonal phase which occurs at a high temperature (> 250 °C). In GST, about 50 % of Te substituted by Se (Ge2Sb2Te2.5Se2.5) is found to increase the contrast in electrical resistivity by 7 orders of magnitude (about 4 orders of magnitude higher than GST). The phase transition in Se added GST also found to be between amorphous and the stable hexagonal structure. The threshold voltage at which the Ge2Sb2Te2.5Se2.5 switches to the high conducting state increases to 9V as compared to 2V in GST. Interestingly, the threshold current decrease to 1mA as compared to 1.8mA in GST indicating the Se substitution reduces the power needed for switching between the low and high conducting states. The reduction in power needed for phase change, high contrast in electrical resistivity with high thermal stability makes Ge2Sb2Te2.5Se2.5 as a better candidate for PCRAM.

Scandium doped Ge2Sb2Te5 for high-speed and low-power-consumption phase change memory

Science.gov (United States)

Wang, Yong; Zheng, Yonghui; Liu, Guangyu; Li, Tao; Guo, Tianqi; Cheng, Yan; Lv, Shilong; Song, Sannian; Ren, Kun; Song, Zhitang

2018-03-01

To bridge the gap of access time between memories and storage systems, the concept of storage class memory has been put forward based on emerging nonvolatile memory technologies. For all the nonvolatile memory candidates, the unpleasant tradeoff between operation speed and retention seems to be inevitable. To promote both the write speed and the retention of phase change memory (PCM), Sc doped Ge2Sb2Te5 (SGST) has been proposed as the storage medium. Octahedral Sc-Te motifs, acting as crystallization precursors to shorten the nucleation incubation period, are the possible reason for the high write speed of 6 ns in PCM cells, five-times faster than that of Ge2Sb2Te5 (GST) cells. Meanwhile, an enhanced 10-year data retention of 119 °C has been achieved. Benefiting from both the increased crystalline resistance and the inhibited formation of the hexagonal phase, the SGST cell has a 77% reduction in power consumption compared to the GST cell. Adhesion of the SGST/SiO2 interface has been strengthened, attributed to the reduced stress by forming smaller grains during crystallization, guaranteeing the reliability of the device. These improvements have made the SGST material a promising candidate for PCM application.

Upconversion properties of Er3+/Yb3+ co-doped TeO2-TiO2-K2O glasses.

Science.gov (United States)

Su, Fangning; Deng, Zaide

2006-01-01

The Er3+/Yb3+ co-doped TeO2-TiO2-K2O glasses were prepared by conventional melting procedures, and their upconversion spectra were performed. The dependence of luminescence intensity on the ratio of Yb3+/Er3+ was studied, and the relationship between green upconversion luminescence intensity and Er3+ concentration is discussed in detail. The 546 nm green upconversion luminescence intensity is optimised in the studied glasses either when the Yb3+/Er3+ ratio is 25/1 and Er3+ concentration is 0.1 mol%, or when the Yb3+/Er3+ ratio is 10/1 and Er3+ concentration is 0.15 mol%. These glasses could be one of the potential candidates for LD pumping microchip solid-state lasers.

Electron cyclotron heating (ECH) of tokamak plasmas

International Nuclear Information System (INIS)

Hoshino, Katsumichi

1990-01-01

Electron cyclotron heating (ECH) is one of the intense methods of plasma heating, and which utilizes the collisionless electron-cyclotron-resonance-interaction between the launched electromagnetic waves (called electron cyclotron waves) and electrons which are one of the constituents of the high temperature plasmas. Another constituent, namely the ions which are subject to nuclear fusion, are heated indirectly but strongly and instantly (in about 0.1 s) by the collisions with the ECH-heated electrons in the fusion plasmas. The recent progress on the development of high-power and high-frequency millimeter-wave-source enabled the ECH experiments in the middle size tokamaks such as JFT-2M (Japan), Doublet III (USA), T-10 (USSR) etc., and ECH has been demonstrated to be the sure and intense plasma heating method. The ECH attracts much attention for its remarkable capabilities; to produce plasmas (pre-ionization), to heat plasmas, to drive plasma current for the plasma confinement, and recently especially by the localization and the spatial controllability of its heating zone, which is beneficial for the fine controls of the profiles of plasma parameters (temperature, current density etc.), for the control of the magnetohydrodynamic instabilities, or for the optimization/improvement of the plasma confinement characteristics. Here, the present status of the ECH studies on tokamak plasmas are reviewed. (author)

Effect of polarizable lone pair cations on the second-harmonic generation (SHG) properties of noncentrosymmetric (NCS) Bi(2-x)Y(x)TeO₅ (x = 0-0.2).

Science.gov (United States)

Jo, Hongil; Kim, Yeong Hun; Lee, Dong Woo; Ok, Kang Min

2014-08-14

Y(3+)-doped noncentrosymmetric (NCS) bismuth tellurite materials, Bi(2-x)Y(x)TeO5 (x = 0, 0.1, and 0.2), have been synthesized through standard solid-state reactions and structurally characterized by powder neutron diffraction. The reported NCS materials crystallize in the orthorhombic space group Abm2 (no. 39), and exhibit pseudo-three-dimensional frameworks that are composed of BiO3, BiO5, and TeO3 polyhedra. Detailed diffraction studies show that the cell volume of Bi(2-x)Y(x)TeO5 decreases with an increasing amount of Y(3+)on the Bi(3+) sites. However, no ordering between Bi(3+) and Y(3+) was observed in the Bi(2-x)Y(x)TeO5. Powder second-harmonic generation (SHG) measurements, using 1064 nm radiation, reveal that Bi2TeO5, Bi(1.9)Y(0.1)TeO5, and Bi(1.8)Y(0.2)TeO5 exhibit SHG efficiencies of approximately 300, 200, and 60 times that of α-SiO2, respectively. The reduction in SHG for Y(3+)-doped materials is consistent with the lack of net moment originating from polyhedra with a polarizable Bi(3+) cation.

Heating, current drive and MHD control using ECH in TCV

International Nuclear Information System (INIS)

Goodman, T.

2001-01-01

The 6 beam 2nd harmonic X-mode (X2), 3MW, ECH/ECCD system of the TCV tokamak allows a fine tailoring of the deposition profiles in the plasma. The sensitivity of the sawtooth period to the deposition location is used to increase the equilibria reconstruction and ray-tracing accuracy. Off-axis ECH, followed by on-axis counter-ECCD produces improved central confinement regimes in which τ Ee exceeds RLW scaling by a factor of 3.5. The PRETOR transport code (incorporating an RLW local transport model but constrained by the experimental density profiles) predicts an extreme sensitivity of τ Ee to the deposition location of the counter-ECCD. This is confirmed by experiments. Sawtooth simulations using PRETOR, including the effects of current drive with inputs from the TORAY ray-tracing code, are in good agreement with experimental results. These results are an initial benchmark for the package of analysis codes, LIUQE/TORAY/PRETOR used during ECH/ECCD experiments on TCV. (author)

Optical transitions of Er3+/Yb3+ codoped TeO2-WO3-Bi2O3 glass.

Science.gov (United States)

Shen, Xiang; Nie, Qiuhua; Xu, Tiefeng; Gao, Yuan

2005-10-01

Optical absorption and emission properties of the Er3+/Yb3+ codoped TeO2-WO3-Bi2O3 (TWB) glass has been investigated. The transition probabilities, excited state lifetimes, and the branching ratios have been predicted for Er3+ based on the Judd-Ofelt theory. The broad 1.5 microm fluorescence was observed under 970 nm excitation, and its full width at half maximum (FWHM) is 77 nm. The emission cross-section is calculated using the McCumber theory, and the peak emission cross-section is 1.03 x 10(-21) cm2 at 1.531 microm. This value is much larger than those of the silicate and phosphate glasses. Efficient green and weak red upconversion luminescence from Er3+ centers in the glass sample was observed at room temperature, and the upconversion excitation processes have been analyzed.

Temperature stable LiNbO3 surface acoustic wave device with diode sputtered amorphous TeO2 over-layer

International Nuclear Information System (INIS)

Dewan, Namrata; Tomar, Monika; Gupta, Vinay; Sreenivas, K.

2005-01-01

Amorphous TeO 2 thin film, sputtered in the O 2 +Ar(25%+75%) gas environment using a metallic tellurium target, has been identified as an attractive negative temperature coefficient of delay (TCD) material that can yield a temperature stable device when combined with a surface acoustic wave (SAW) device based on positive TCD material such as LiNbO 3 . The influence of amorphous TeO 2 over-layer on the SAW propagation characteristics (velocity and temperature coefficient of delay) of the SAW filters (36 and 70 MHz) based on 128 deg. rotated Y-cut X-propagating lithium niobate (128 deg. Y-X LiNbO 3 ) single crystal has been studied. It is found that 0.042 λ thick TeO 2 over-layer on a prefabricated SAW device operating at 36 MHz centre frequency, reduces the TCD of the device from 76 ppm deg. C -1 to almost zero (∼1.4 ppm deg. C -1 ) without deteriorating its efficiency and could be considered as a suitable alternative for temperature stable devices in comparison to conventional SiO 2 over-layer

Passivation Effect of Atomic Layer Deposition of Al2O3 Film on HgCdTe Infrared Detectors

Science.gov (United States)

Zhang, Peng; Ye, Zhen-Hua; Sun, Chang-Hong; Chen, Yi-Yu; Zhang, Tian-Ning; Chen, Xin; Lin, Chun; Ding, Ring-Jun; He, Li

2016-09-01

The passivation effect of atomic layer deposition of (ALD) Al2O3 film on a HgCdTe infrared detector was investigated in this work. The passivation effect of Al2O3 film was evaluated by measuring the minority carrier lifetime, capacitance versus voltage ( C- V) characteristics of metal-insulator-semiconductor devices, and resistance versus voltage ( R- V) characteristics of variable-area photodiodes. The minority carrier lifetime, C- V characteristics, and R- V characteristics of HgCdTe devices passivated by ALD Al2O3 film was comparable to those of HgCdTe devices passivated by e-beam evaporation of ZnS/CdTe film. However, the baking stability of devices passivated by Al2O3 film is inferior to that of devices passivated by ZnS/CdTe film. In future work, by optimizing the ALD Al2O3 film growing process and annealing conditions, it may be feasible to achieve both excellent electrical properties and good baking stability.

X- and O-mode ECH breakdown and startup in TCA

International Nuclear Information System (INIS)

Whaley, D.R.; Goodman, T.P.; Pochelon, A.; Behn, R.; Cardinali, A.; Duval, B.P.; Joye, B.; Tran, M.Q.

1992-02-01

We have performed a comparative study of X- and O-mode high field side launch for ECH breakdown and startup of tokamak plasmas. We observe that X-mode power is not absorbed at the cyclotron resonance but uniquely at the upper hybrid resonance, displaced to the lower field side of the cyclotron resonance. O-mode power, however, is absorbed at the cyclotron resonance as well. We also observe that the displacement of the upper hybrid resonance to the low field side with O-mode launch is significantly smaller than with X-mode launch due to the lower densities produced at the same microwave power level. The result is a more central and less localized breakdown with O-mode launch. The breakdown characteristics of X- and O-mode launch are seen to affect the position of the initial plasma current centroid in the poloidal cross section. We observe a strong correlation between the initial current ramp and the initial plasma current position which is most likely due to the dependence of the plasma inductance, toroidal electric field, and field-line connection lengths on the plasma major radius. X-mode startup occurs further to the low field side where current ramp rates are observed to be poor. (author) 18 figs., 23 refs

Synthesis and Optical Characterization of Nd3+ doped TeO2-PbO-Li2O

Directory of Open Access Journals (Sweden)

M. Rahim Sahar

2012-02-01

Full Text Available Glass based on Nd3+-doped TeO2-PbO-Li2O has successfully been made by melt quenching technique and their thermal parameters have been determined using Differential Thermal Analyzer (DTA. The glass is then nucleated and/or growth by controlled heat treatment at slightly below the crystallization temperature. The X-ray diffraction (XRD technique is used to estimate the nano-crystallite size. Meanwhile, the optical characterization has been determined using the Photoluminescence Spectroscopy. It is found out that the crystallite size is about 20 nm and very much depending on the heat-treatment time. Meanwhile, the intensity of the luminescence spectra is very much depending on the concentration of the dopant.   Keyword: tellurium glasses, melt quenching technique, optical characterization

CORRIGENDUM First principles study of crystalline and amorphous Ge2Sb2Te5 and the effects of stoichiometric defects First principles study of crystalline and amorphous Ge2Sb2Te5 and the effects of stoichiometric defects

Science.gov (United States)

Caravati, S.; Bernasconi, M.; Kühne, T. D.; Krack, M.; Parrinello, M.

2010-10-01

The distributions of coordination numbers reported in the insets of figure 7 actually refer to a bonding cutoff of 3.2 Å for all pairs of atoms. The distributions of coordination numbers referred to in the paper with bonding cutoff equal to 3.2 Å for all pairs but Sb-Te for which the bonding cutoff was set to the outer edge of the pair correlation function of c-GST (3.4 Å at 300 K) are given below for the three compounds. figure 1 Figure 7. Distribution of coordination numbers of different species obtained by integration of the partial pair correlation functions for (from left to right) Ge2Sb2Te5, Ge2Sb1.8Te5 and Ge2.2Sb2Te5.

Physical and optical studies of BaO-TeO2-TiO2-B2O3 glasses containing Cu2+ transition metal ion

Science.gov (United States)

Srinivas, B.; Kumar, R. Vijaya; Hameed, Abdul; Sagar, D. Karuna; Chary, M. Narasimha; Shareefuddin, Md.

2018-05-01

Glasses with the composition xBaO-(30-x) TeO2-10TiO2-59B2O3-1CuO (where x = 10, 15, 20 and 25 mole %) were prepared by melt quenching technique. The XRD studies were made on these glass samples at room temperature. The amorphous nature of the glass samples was confirmed from the XRD patterns. The physical parameters such as density (ρ), molar volume (Vm), average boron-boron separation (dB-B) and oxygen packing density (OPD) were calculated. The change in density and molar volume has been investigated in terms of the variation of BaO in the glass composition. The optical absorption spectra have been recorded at room temperature. The values of optical band gap have been estimated from the ASF and Tauc's methods. Both Tauc's and ASF methods have been showing progressively increasing indirect optical band gap values with the increase of BaO concentrations.

Structural phase transitions in the ordered double perovskite Sr2MnTeO6

International Nuclear Information System (INIS)

Ortega-San Martin, L; Chapman, J P; Hernandez-Bocanegra, E; Insausti, M; Arriortua, M I; Rojo, T

2004-01-01

The crystal structure of the ordered double perovskite Sr 2 MnTeO 6 has been refined at ambient temperature from high resolution neutron and x-ray powder diffraction data in the monoclinic space group P 12 1 /n 1 with a 5.7009(1) A, b = 5.6770(1) A, c = 8.0334(1) A and β = 90.085(1) deg. This represents a combination of in-phase (+) and out-of-phase (-) rotations of virtually undistorted MnO 6 and TeO 6 octahedra in the (-+) sense about the axes of the ideal cubic perovskite. High temperature x-ray powder diffraction shows three structural phase transitions at approximately 250, 550 and 675 deg. C, each corresponding to the disappearance of rotations about one of these axes. The first transition was analysed by differential scanning calorimetry and showed a thermal hysteresis with an enthalpy of 0.55 J g -1 . We propose the (P12 1 /n1 → I12/m1 → I4/m → Fm3barm) sequence of structural transitions which has not been previously reported for a double perovskite oxide

Nanoscale nuclei in phase change materials: Origin of different crystallization mechanisms of Ge2Sb2Te5 and AgInSbTe

International Nuclear Information System (INIS)

Lee, Bong-Sub; Bogle, Stephanie N.; Darmawikarta, Kristof; Abelson, John R.; Shelby, Robert M.; Retter, Charles T.; Burr, Geoffrey W.; Raoux, Simone; Bishop, Stephen G.

2014-01-01

Phase change memory devices are based on the rapid and reversible amorphous-to-crystalline transformations of phase change materials, such as Ge 2 Sb 2 Te 5 and AgInSbTe. Since the maximum switching speed of these devices is typically limited by crystallization speed, understanding the crystallization process is of crucial importance. While Ge 2 Sb 2 Te 5 and AgInSbTe show very different crystallization mechanisms from their melt-quenched states, the nanostructural origin of this difference has not been clearly demonstrated. Here, we show that an amorphous state includes different sizes and number of nanoscale nuclei, after thermal treatment such as melt-quenching or furnace annealing is performed. We employ fluctuation transmission electron microscopy to detect nanoscale nuclei embedded in amorphous materials, and use a pump-probe laser technique and atomic force microscopy to study the kinetics of nucleation and growth. We confirm that melt-quenched amorphous Ge 2 Sb 2 Te 5 includes considerably larger and more quenched-in nuclei than its as-deposited state, while melt-quenched AgInSbTe does not, and explain this contrast by the different ratio between quenching time and nucleation time in these materials. In addition to providing insights to the crystallization process in these technologically important devices, this study presents experimental illustrations of temperature-dependence of nucleation rate and growth speed, which was predicted by theory of phase transformation but rarely demonstrated

Studies on solid solutions based on layered honeycomb-ordered phases P2-Na{sub 2}M{sub 2}TeO{sub 6} (M=Co, Ni, Zn)

Energy Technology Data Exchange (ETDEWEB)

Berthelot, Romain; Schmidt, Whitney; Sleight, A.W. [Department of Chemistry, Oregon State University, Corvallis, OR 97331 (United States); Subramanian, M.A., E-mail: mas.subramanian@oregonstate.edu [Department of Chemistry, Oregon State University, Corvallis, OR 97331 (United States)

2012-12-15

Three complete solid solutions between the layered phases P2-Na{sub 2}M{sub 2}TeO{sub 6} (M=Co, Ni, Zn) have been prepared by conventional solid state method and investigated through X-ray diffraction, magnetism and optical measurements. All compositions are characterized by a M{sup 2+}/X{sup 6+} honeycomb ordering within the slabs and crystallize in a hexagonal unit cell. However, a structural transition based on a different stacking is observed as nickel (space group P6{sub 3}/mcm) is substituted by zinc or cobalt (space group P6{sub 3}22). All compositions exhibit a paramagnetic Curie-Weiss behavior at high temperatures; and the magnetic moment values confirm the presence of Ni{sup 2+} and/or Co{sup 2+} cations. The low-temperature antiferromagnetic order of Na{sub 2}Ni{sub 2}TeO{sub 6} and Na{sub 2}Co{sub 2}TeO{sub 6} is suppressed by zinc substitution. The color of the obtained compositions varies from pink, to light green and white when M=Co, Ni, Zn, respectively. - Graphical abstract: The comparison between the structure of Na{sub 2}Ni{sub 2}TeO{sub 6} (left) and Na{sub 2}M{sub 2}TeO{sub 6} (M=Co, Zn) (right) evidences the stacking difference with distinct atom sequences along the hexagonal c-axis. Highlights: Black-Right-Pointing-Pointer Solid solutions between lamellar phases Na{sub 2}M{sub 2}TeO{sub 6} (M=Co, Ni, Zn) are investigated. Black-Right-Pointing-Pointer A M{sup 2+}/X{sup 6+} honeycomb ordering characterized all the compositions. Black-Right-Pointing-Pointer A structural transition is shown when Ni is replaced by Co or Zn. Black-Right-Pointing-Pointer The low-temperature AFM ordering of Na{sub 2}Ni{sub 2}TeO{sub 6} and Na{sub 2}Co{sub 2}TeO{sub 6} is suppressed by zinc substitution. Black-Right-Pointing-Pointer Color changes from pink to light green and white when M=Co, Ni, Zn, respectively.

Ho3+-doped AlF3-TeO2-based glass fibers for 2.1 µm laser applications

Science.gov (United States)

Wang, S. B.; Jia, Z. X.; Yao, C. F.; Ohishi, Y.; Qin, G. S.; Qin, W. P.

2017-05-01

Ho3+-doped AlF3-TeO2-based glass fibers based on AlF3-BaF2-CaF2-YF3-SrF2-MgF2-TeO2 glasses are fabricated by using a rod-in-tube method. The glass rod including a core and a thick cladding layer is prepared by using a suction method, where the thick cladding layer is used to protect the core from the effect of surface crystallization during the fiber drawing. By inserting the glass rod into a glass tube, the glass fibers with relatively low loss (~2.3 dB m-1 @ 1560 nm) are prepared. By using a 38 cm long Ho3+-doped AlF3-TeO2-based glass fiber as the gain medium and a 1965 nm fiber laser as the pump source, 2065 nm lasing is obtained for a threshold pump power of ~220 mW. With further increasing the pump power to ~325 mW, the unsaturated output power of the 2065 nm laser is about 82 mW and the corresponding slope efficiency is up to 68.8%. The effects of the gain fiber length on the lasing threshold, the slope efficiency, and the operating wavelength are also investigated. Our experimental results show that Ho3+-doped AlF3-TeO2-based glass fibers are promising gain media for 2.1 µm laser applications.

Epitaxial growth and optical investigations of ZnTeO alloys

International Nuclear Information System (INIS)

Nabetani, Y.; Okuno, T.; Aoki, K.; Kato, T.; Matsumoto, T.; Hirai, T.

2006-01-01

We have grown zincblende-structured ZnTeO alloy semiconductors on GaAs substrates by molecular beam epitaxy using RF-excited O. O concentrations measured by secondary ion mass spectroscopy were found to increase with the increase of O 2 flow rate supplied during the growth, while the change of lattice constant measured by X-ray diffraction does not follow Vegard's law. It is considered that the O atoms are incorporated not only into group-VI sites but also as interstitials. Formation of other compounds such as ZnTeO 3 , Zn 2 Te 3 O 8 , and TeO 2 was not detected. Optical reflectance spectroscopy revealed the increase of the band-gap energy with O concentration that can be interpreted as the repulsive interaction between the energy states originated in the localized states of O and the conduction-band edge of host ZnTe. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (Abstract Copyright [2006], Wiley Periodicals, Inc.)

Jensenite, Cu3 Te (super 6+) O6 .2H2O, a new mineral species from the Centennial Eureka Mine, Tintic District, Juab County, Utah

Science.gov (United States)

Roberts, Andrew C.; Grice, Joel D.; Groat, Lee A.; Criddle, Alan J.; Gault, Robert A.; Erd, Richard C.; Moffatt, Elizabeth A.

1996-01-01

Sigma 2.94) Te (super 6+) (sub 1.01) O (sub 5.97) .2.03H 2 O, based on O = 8. The mineral name honors Martin C. Jensen, Reno, Nevada, who discovered the mineral.

Surface-biofunctionalized multicore/shell CdTe@SiO2 composite particles for immunofluorescence assay

Science.gov (United States)

Jing, Lihong; Li, Yilin; Ding, Ke; Qiao, Ruirui; Rogach, Andrey L.; Gao, Mingyuan

2011-12-01

Strongly fluorescent multicore/shell structured CdTe@SiO2 composite particles of ~ 50 nm were synthesized via the reverse microemulsion method by using CdTe quantum dots co-stabilized by thioglycolic acid and thioglycerol. The optical stability of the CdTe@SiO2 composite particles in a wide pH range, under prolonged UV irradiation in pure water, or in different types of physiological buffers was systematically investigated. Towards immunofluorescence assay, both poly(ethylene glycol) (PEG) and carboxyl residues were simultaneously grafted on the surface of the silanol-terminated CdTe@SiO2 composite particles upon further reactions with silane reagents bearing a PEG segment and carboxyl group, respectively, in order to suppress the nonspecific interactions of the silica particles with proteins and meanwhile introduce reactive moieties to the fluorescent particles. Agarose gel electrophoresis, dynamic light scattering and conventional optical spectroscopy were combined to investigate the effectiveness of the surface modifications. Via the surface carboxyl residue, various antibodies were covalently conjugated to the fluorescent particles and the resultant fluorescent probes were used in detecting cancer cells through both direct fluorescent antibody and indirect fluorescent antibody assays, respectively.

Chemical bonding characteristics of Ge2Sb2Te5 for thin films

International Nuclear Information System (INIS)

Shin, Min-Jung; Choi, Doo-Jin; Kang, Myung-Jin; Choi, Se-Young; Jang, In-Woo; Lee, Kye-Nam; Park, Young-Jin

2004-01-01

The chalcogenide-based phase change memory has been suggested as an alternative non-volatile memory device at the 180 nm technology node. These materials appear to have a reversible phase change between amorphous and crystalline phases. A sputtered Ge 2 Sb 2 Te 5 film is deposited on a (100) Si substrate. In order to investigate the crystallization tendency at a certain temperature, we use X-ray diffraction and X-ray photoelectron spectroscopy. The film morphology is observed by using atomic forces microscopy. Grain growth and a phase transition from cubic to hexagonal occurs when the films are heated from 170 .deg. C and 380 .deg. C, and Ge-Te and Te-Sb bonds increased with annealing.

Controlling Lateral Fano Interference Optical Force with Au-Ge2Sb2Te5 Hybrid Nanostructure

DEFF Research Database (Denmark)

Cao, Tun; Bao, Jiaxin; Mao, Libang

2016-01-01

is revealed through optical singularity in the Poynting vector. A thermal-electric simulation is adopted to investigate the temporal change of the Ge2Sb2Te5 film's temperature, which demonstrates the possibility of transiting the Ge2Sb2Te5 state by electrical heating. Our mechanism by tailoring the DQ...... in flexible nanomechanical control and may provide a new means of biomedical sensing and nano -optical conveyor belts....

Recent Progress on ECH Technology for ITER

Science.gov (United States)

Sirigiri, Jagadishwar

2005-10-01

The Electron Cyclotron Heating and Current Drive (ECH&CD) system for ITER is a critical ITER system that must be available for use on Day 1 of the ITER experimental program. The applications of the system include plasma start-up, plasma heating and suppression of Neoclassical Tearing Modes (NTMs). These applications are accomplished using 27 one megawatt continuous wave gyrotrons: 24 at a frequency of 170 GHz and 3 at a frequency of 120 GHz. There are DC power supplies for the gyrotrons, a transmission line system, one launcher at the equatorial plane and three upper port launchers. The US will play a major role in delivering parts of the ECH&CD system to ITER. The present state-of-the-art includes major advances in all areas of ECH technology. In the US, a major effort is underway to supply gyrotrons of up to 1.5 MW power level at 110 GHz to General Atomics for use in heating the DIII-D tokamak. This presentation will include a brief review of the state-of-the-art, worldwide, in ECH technology. The requirements for the ITER ECH&CD system will then be reviewed. ITER calls for gyrotrons capable of operating from a 50 kV power supply, after potential depression, with a minimum of 50% overall efficiency. This is a very significant challenge and some approaches to meeting this goal will be presented. Recent experimental results at MIT showing improved efficiency of high frequency, 1.5 MW gyrotrons will be described. These results will be incorporated into the planned development of gyrotrons for ITER. The ITER ECH&CD system will also be a challenge to the transmission lines, which must operate at high average power at up to 1000 seconds and with high efficiency. The technology challenges and efforts in the US and other ITER parties to solve these problems will be reviewed. *In collaboration with E. Choi, C. Marchewka, I. Mastovosky, M. A. Shapiro and R. J. Temkin. This work is supported by the Office of Fusion Energy Sciences of the U. S. Department of Energy.

New vanadium tellurites: Syntheses, structures, optical properties of noncentrosymmetric VTeO{sub 4}(OH), centrosymmetric Ba{sub 2}V{sub 4}O{sub 8}(Te{sub 3}O{sub 10})

Energy Technology Data Exchange (ETDEWEB)

Liang, Ming-Li [College of Chemistry, Fuzhou University, Fuzhou, Fujian 350108 (China); State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou 350002 (China); Marsh, Matthew [Department of Chemistry and Biochemistry, Florida State University, Tallahassee, FL 32306 (United States); Shang, Xian-Xing [College of Chemistry, Fuzhou University, Fuzhou, Fujian 350108 (China); State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou 350002 (China); Mao, Jiang-Gao [State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou 350002 (China); Albrecht-Schmitt, Thomas E. [Department of Chemistry and Biochemistry, Florida State University, Tallahassee, FL 32306 (United States); Kong, Fang, E-mail: kongfang@fjirsm.ac.cn [State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou 350002 (China); Department of Chemistry and Biochemistry, Florida State University, Tallahassee, FL 32306 (United States)

2017-05-15

Two new vanadium tellurites, VTeO{sub 4}(OH) (1) and Ba{sub 2}V{sub 4}O{sub 8}(Te{sub 3}O{sub 10}) (2), have been synthesized successfully with the use of hydrothermal reactions. The crystal structures of the two compounds were determined by single-crystal X-ray diffraction. Compound 1 crystallizes in the polar space group Pca2{sub 1} (No. 29) while compound 2 crystallizes in the centrosymmetric space group C2/c (No. 15). The topography of compound 1 reveals a two-dimensional, layered structure comprised of VO{sub 6} octahedral chains and TeO{sub 3}(OH) zig-zag chains. Compound 2, on the contrary, features a three-dimensional [V{sub 4}O{sub 8}(Te{sub 3}O{sub 10})]{sup 4-} anionic framework with Ba{sup 2+} ions filled into the 10-member ring helical tunnels. The [V{sub 4}O{sub 8}(Te{sub 3}O{sub 10})]{sup 4-} anionic network is the first 3D vanadium tellurite framework to be discovered in the alkaline-earth vanadium tellurite system. Powder second harmonic generation (SHG) measurements indicate that compound 1 shows a weak SHG response of about 0.3×KDP (KH{sub 2}PO{sub 4}) under 1064 nm laser radiation. Infrared spectroscopy, elemental analysis, thermal analysis, and dipole moment calculations have also been carried out. - Graphical abstract: VTeO{sub 4}(OH) (1) crystallizes in the noncentrosymmetric space group Pca2{sub 1} (No. 29) while Ba{sub 2}V{sub 4}O{sub 8}(Te{sub 3}O{sub 10}) (2) crystallizes in the centrosymmetric space group C2/c (No. 15). - Highlights: • VTeO{sub 4}(OH) (1) and Ba{sub 2}V{sub 4}O{sub 8}(Te{sub 3}O{sub 10}) (2) have been synthesized successfully with the use of hydrothermal reactions. • VTeO{sub 4}(OH) (1) crystallizes in the noncentrosymmetric space group Pca2{sub 1} and displays a weak SHG response. • VTeO{sub 4}(OH) (1) represents only the fourth SHG-active material found in vanadium tellurite systems. • Ba{sub 2}V{sub 4}O{sub 8}(Te{sub 3}O{sub 10}) (2) exhibits a novel three-dimensional [V{sub 4}O{sub 8}(Te{sub 3}O{sub 10

Molecular dynamics investigation of Na+ in Na2Ni2TeO6

International Nuclear Information System (INIS)

Sau, Kartik; Kumar, P. Padma

2014-01-01

An inter-atomic potential for Na 2 Ni 2 TeO 6 in the Parrinello- Rahman-Vashishta (PRV) model is parameterized empirically. The potential reproduces variety of structural and transport properties of that material in good agreement with recent experimental results. The study provides fresh insights on the migration channels and mechanism of Na + in the system

Preparation and optical properties of TeO2-BaO-ZnO-ZnF2 fluoro-tellurite glass for mid-infrared fiber Raman laser applications

Science.gov (United States)

Li, Jie; Xiao, Xusheng; Gu, Shaoxuan; Xu, Yantao; Zhou, Zhiguang; Guo, Haitao

2017-04-01

A serial of novel fluoro-tellurite glasses with compositions of 60TeO2-20BaO-(20-x)ZnO-xZnF2 (x = 0, 2, 4, 5 and 6 mol%) were prepared. The compositional dependences of glass structural evaluation, Raman gain coefficient, UV-Vis transmission spectrum, IR transmission spectrum, linear refractive index and third-order nonlinearity were analyzed. The results showed that the addition of 6 mol% ZnF2 can further improve the Raman gain coefficient to as well as 52 × 10-11 cm/W and effectively decrease around 73% and 57% absorption coefficients respectively caused by free Osbnd H groups (@3.3 μm) and hydrogen-bonded Osbnd H groups (@4.5 μm) in glass. Addition of ZnF2 does not change the UV-Vis absorption edge, optical band gap energy and infrared region cut-off edge almost, while the linear refraction index and ultrafast third-nonlinearity show unmonotonic changes. These novel fluoro-tellurite glasses may be suitable candidates for using in mid-infrared Raman fiber laser and/or amplifier.

Ba/sub 2/Ge/sub 2/Te/sub 5/, a new telluridogermanate(III) with chain structure

Energy Technology Data Exchange (ETDEWEB)

Brinkmann, C; Eisenmann, B; Schaefer, H [Technische Hochschule Darmstadt (Germany, F.R.). Fachbereich Anorganische Chemie und Kernchemie

1984-10-01

The new compound Ba/sub 2/Ge/sub 2/Te/sub 5/ crystallizes in the orthorhombic system (space group: Pna2/sub 1/ (No. 33)). The lattice constants are given. In the structure distorted Ge/sub 2/Te/sub 6/-trigonal prisms are connected by common corners to infinite chains.

Interpretation of the vacancy-ordering controlled growth morphology of Hg5In2Te8 precipitates in Hg3In2Te6 single crystals by TEM observation and crystallographic calculation

International Nuclear Information System (INIS)

Sun, Jie; Fu, Li; Liu, Hongwei; Ringer, S.P.; Liu, Zongwen

2015-01-01

Graphical abstract: The growth morphology and detailed crystallography of Hg 5 In 2 Te 8 precipitates in Hg 3 In 2 Te 6 matrix to has been interpreted by means of transmission electron microscopy and invariant element deformation model. Three crystallographic equivalent variants of Hg 5 In 2 Te 8 precipitates in Hg 3 In 2 Te 6 matrix were found to have different growth directions and habit planes. Such growth morphology is fully attributed to the lattice shrinkage induced by vacancy ordering under high temperature in Hg 5 In 2 Te 8 . Through near coincident site lattice and invariant strain calculation, the morphology and crystallographic features of the precipitate has been successfully interpreted. - Highlights: • The growth morphology of Hg 5 In 2 Te 8 precipitates in Hg 3 In 2 Te 6 was observed by TEM. • Near-CSL calculation show 0.7577% lattice shrinkage of Hg 5 In 2 Te 8 at high temperature. • All the involved factors have inverse relationship with the move speed of interface. • The calculated crystallography features of Hg 5 In 2 Te 8 agree well with the TEM results. - Abstract: Generally, the crystal growth morphology in liquid or vapor was controlled by chemical potential, while that in solid solute was restricted by 3D strain matching between matrix and secondary phase. It is already known that the growth and evolution of the morphology of secondary phase during the solid phase transformation are highly determined by the variation of interface energy induced by lattice mismatch. In this work, the growth morphology and crystallography of Hg 5 In 2 Te 8 precipitates in Hg 3 In 2 Te 6 matrix were investigated by means of transmission electron microscopy (TEM). It was found that the growth of Hg 5 In 2 Te 8 precipitates displayed an unusual growth morphology which contain three crystallographically equivalent variants with different growth directions in Hg 3 In 2 Te 6 matrix, suggesting a slight lattice constant variation of Hg 5 In 2 Te 8 precipitate

CdTeO3 Deposited Mesoporous NiO Photocathode for a Solar Cell

Directory of Open Access Journals (Sweden)

Chuan Zhao

2014-01-01

Full Text Available Semiconductor sensitized NiO photocathodes have been fabricated by successive ionic layer adsorption and reaction (SILAR method depositing CdTeO3 quantum dots onto mesoscopic NiO films. A solar cell using CdTeO3 deposited NiO mesoporous photocathode has been fabricated. It yields a photovoltage of 103.7 mV and a short-circuit current density of 0.364 mA/cm2. The incident photon to current conversion efficiency (IPCE value is found to be 12% for the newly designed NiO/CdTeO3 solar cell. It shows that the p-type NiO/CdTeO3 structure could be successfully utilized to fabricate p-type solar cell.

Controlling DIII-D QH-Mode Particle and Electron Thermal Transport with ECH

Science.gov (United States)

Ernst, D. R.; Burrell, K. H.; Rhodes, T. L.; Guttenfelder, W.; McKee, G. R.; Grierson, B. A.; Holland, C.; Dimits, A.; Petty, C. C.; Schmitz, L.; Wang, G.; Zeng, L.; Doyle, E. J.; Austin, M. E.

2014-10-01

Quiescent H-mode core particle transport and density peaking are locally controlled by modulated electron cyclotron heating (ECH) at ρ ~ 0 . 2 . Gyrokinetic simulations show density gradient driven trapped electron modes (TEMs) are only unstable in the inner core, where the density profile flattens in response to ECH. Thus α-heating could reduce density peaking, providing burn control. Density fluctuations from Doppler backscattering intensify at TEM wavenumbers kθρs ~ 0 . 8 during ECH, while new quasi-coherent modes are observed with adjacent toroidal mode numbers consistent with TEMs. Separately, ECH at two-deposition locations (r / a ~ ρ = 0 . 5 & 0.7) varied the electron temperature gradient. A jump in ``heat pulse'' diffusivity during the scan indicates a critical gradient was crossed. Work supported by the US DOE under DE-FC02-08ER54966, DE-FC02-04ER54698, DE-FG02-08ER54984, DE-AC02-09CH11466, DE-FG02-89ER53296, DE-FC02-11ER55104, DE-AC52-07NA27344 & DE-FG03-97ER54415.

CdTe and graphene co-sensitized TiO2 nanotube array photoanodes for protection of 304SS under visible light

International Nuclear Information System (INIS)

Li, Hong; Wang, Xiutong; Hou, Baorong; Zhang, Liang

2015-01-01

CdTe/graphene/TiO 2 films that served as photoanodes for cathodic protection application were prepared by an electrochemical deposition method. The deposition of graphene and CdTe nanoparticles (NPs) on the surface of the TiO 2 nanotubes was confirmed by scanning electron microscope and transmission electron microscopy. The composites exhibited high light absorption in both the UV and visible light region. The results indicated that TiO 2 nanotube photoelectrodes sensitized by 20-cycle graphene and 30-cycle CdTe NPs exhibited effective photocathodic protection properties for 304 stainless steel (304SS) under the visible-light illumination, with an photopotential of −750 mV versus saturated calomel electrode and a current density of 560 μA cm −2 . Due to the efficient photogenerated charge separation, the three-component CdTe/graphene/TiO 2 showed stronger photoresponse than pure TiO 2 under visible-light illumination. In summary, the CdTe/graphene could improve the photocathodic protection properties of TiO 2 films. (paper)

A novel double perovskite tellurate Eu3+-doped Sr2MgTeO6 red-emitting phosphor with high thermal stability

Science.gov (United States)

Liang, Jingyun; Zhao, Shancang; Yuan, Xuexia; Li, Zengmei

2018-05-01

A series of novel double perovskite tellurate red-emitting phosphors Sr2MgTeO6:xEu3+ (x = 0.05-0.40) were successfully synthesized by a high-temperature solid-state reaction method. The phase structure, photoluminescence properties and thermal stability of the phosphor were investigated in detail. The phosphor shows dominant emission peak at 614 nm belonging to the 5D0 → 7F2 electric dipole transition under 465 nm excitation. The luminescence intensity keeps increasing with increasing the content of Eu3+ to 25 mol%, and the critical transfer distance of Eu3+ was calculated to be 12 Å. The quenching temperature for Sr2MgTeO6:0.25Eu3+ was estimated to be above 500 K. This spectral feature reveals high color purity and excellent chromaticity coordinate characteristics. Therefore, Eu3+-doped Sr2MgTeO6 phosphors are potential red phosphors for blue chip-based white light-emitting diode and display devices.

Examination of adhesion layer of TeO2 film with indented platinum substrate after radiation loading by 13 MeV deuterons

International Nuclear Information System (INIS)

Garapatskij, A.A.; Troyan, P.E.

2011-01-01

In this work the influence of a corrugated surface of a Pt substrate on the quality of thermal contact of an adhesion layer with a material of different compositions of TeO 2 and Al 2 O 3 when bombing a target by a 20 µA, 13.7 MeV deuteron beam has been studied. Before the irradiation a Raman spectrum of the TeO 2 +4%Al 2 O 3 material had a fuzzy contour, what corresponds to a polycrystalline composition or glass, but after the irradiation the spectrum has distinct Raman peaks which relate to the α-phase. In Raman spectrums for TeO 2 , containing α-phase peaks, essential changes were not observed after the irradiation. However, the glassy structure was formed in the target’s central part. Studies have shown good thermal contact of TeO 2 with the surface of a Pt substrate, processed by the offered technique. It allows to manage without addition of Al 2 O 3 and to carry out the target irradiation without loss of TeO 2 . (authors)

Ba ₃ (Cr _0.97(1) Te _0.03(1) ) ₂ TeO ₉ : in Search of Jahn–Teller Distorted Cr(II) Oxide

Energy Technology Data Exchange (ETDEWEB)

Li, Man-Rong; Deng, Zheng; Lapidus, Saul H.; Stephens, Peter W.; Segre, Carlo U.; Croft, Mark; Paria Sena, Robert; Hadermann, Joke; Walker, David; Greenblatt, Martha

2016-10-17

A novel 6H - type hexagonal perovskite Ba 3 (Cr 0.97(1) Te 0.03 (1 ) ) 2 TeO 9 was prepared at high pressure (6 GPa) and temperature ( 1 773 K). Both transmission electron microscopy and synchrotron powder x - ray diffraction data demonstrate that Ba 3 (Cr 0.97(1) Te 0.03(1) ) 2 TeO 9 crystallize s in P6 3 / mmc with face - shared (Cr 0.97(1) Te 0.03(1) )O 6 octahedral pairs interconnected with TeO 6 octahedra via corner - sharing. Structure analysis shows a mixed Cr 2+ /Cr 3+ valence state with ~ 10% Cr 2+ . The existence of Cr 2+ in Ba 3 (Cr 2+ 0.10(1) Cr 3+ 0.87(1) Te 6+ 0.03 ) 2 TeO 9 is further evidenced by x - ray absorption near edge spectr oscopy . Magnetic properties measurements show a paramagnetic response down to 4 K and a small glassy - state curvature at low temperature. In this work, the o ctahedral Cr 2+ O 6 component is stabilized in an oxide material for the first time ; the expected Jahn - Teller distortion of high - spin ( d 4 ) Cr 2+ is not found , which is attributed to the small proportion of Cr 2+ (~ 10%) and the face - sharing arrangement of CrO 6 octahedral pairs, that structu rally dis favor axial distortion.

Atividade de três drogas antivirais sobre os herpesvírus bovino tipos 1, 2 e 5 em cultivo celular Activity of three antiviral drugs against bovine herpesviruses 1, 2 and 5 in cell culture

Directory of Open Access Journals (Sweden)

Renata Dezengrini

2010-10-01

Full Text Available A atividade de três fármacos antivirais (Aciclovir [ACV], Ganciclovir [GCV] e Foscarnet [PFA] foi testada in vitro frente aos herpesvírus bovino tipos 1 (BoHV-1, 2 (BoHV-2 e 5 (BoHV-5. Para isso, utilizou-se o teste de reducao de placas virais em cultivo celular, testando-se diferentes concentracoes dos farmacos frente a 100 doses infectantes para 50% dos cultivos celulares (DICC50 dos respectivos virus. Pelo teste de MTT (3-(4,5-Dimethylthiazol- 2-yl-2,5-diphenyltetrazolium bromide, verificou-se que concentracoes inferiores a 200ƒÊg/mL dos tres antivirais resultaram em indices de viabilidade de celulas MDBK e Hep2 superiores a 80%. Com base na concentracao citotoxica para 50% das celulas (CC50 e na concentracao dos farmacos efetiva para inibir em 50% o numero de placas virais (EC50, calculou-se o indice de seletividade (IS dos antivirais para os tres herpesvirus. Assim, o ACV demonstrou ser moderadamente ativo frente ao BoHV-1 (EC50: 112,9ƒÊg/mL e IS: 4,5, ao BoHV-2 (EC50: 114,2 ƒÊg/mL e IS: 4,5 e BoHV-5 (EC50: 96,9ƒÊg/mL e IS: 5,3. O GCV apresentou atividade moderada frente ao BoHV-2 (EC50: 33,5ƒÊg/mL e IS: 16,6 e, em menor grau, contra o BoHV-5 (EC50: 123,2ƒÊg/mL e IS: 4,5, sendo ineficaz frente ao BoHV-1 (EC50: 335,8ƒÊg/mL e IS: 1,7. O PFA apresentou atividade antiviral mais pronunciada, sendo o unico farmaco que, na concentracao de 100ƒÊg/mL, inibiu completamente a producao de placas pelos tres virus testados. O PFA foi o mais efetivo in vitro frente ao BoHV-1 (EC50: 29,5ƒÊg/mL e IS: 42,2, ao BoHV-2 (EC50: 45,2ƒÊg/mL e IS: 27,6 e ao BoHV-5 (EC50: 7,8ƒÊg/mL e IS: 160,6. Portanto, os resultados obtidos indicam que o PFA pode se constituir em um candidato para terapia experimental de infeccoes pelos herpesvirus de bovinos in vivo.The activity of three anti-herpetic drugs (Acyclovir [ACV], Gancyclovir [GCV] and Foscarnet [PFA] was tested against bovine herpesvirus 1 (BoHV-1, 2 (BoHV-2 and 5 (BoHV-5 in vitro using the

Optical properties and crystallization kinetics of (TeO{sub 2})(ZnO)(TiO{sub 2}) glasses

Energy Technology Data Exchange (ETDEWEB)

Kabalci, Idris [Department of Physics Education, Education Faculty, Harran University, Sanliurfa (Turkey); Koerpe, Nese Oeztuerk [Department of Materials Science, Eskisehir, Osmangazi University, Eskisehir (Turkey); Duran, Tugba; Oezdemir, Mustafa [Department of Physics, Science and Arts Faculty, Marmara University, Istanbul (Turkey)

2011-09-15

Ternary tellurite based glasses in the (TeO{sub 2})(ZnO)(TiO{sub 2}) system were prepared and its optical properties and crystallization kinetics investigated by using UV-VIS spectrophotometer and differential thermal analyzer (DTA). All the glasses were transparent from visible to near infrared region for different ZnO glass compositions (x=0.05, 0.10, 0.20, and 0.30 mol). In the experiment, optical band gap and Urbach energies were estimated from the optical absorption spectra between 400 and 800 nm wavelength region. The observed results confirm that the addition of ZnO glass composition from 0.05 to 0.30 mol increases the optical band gap energy from 2.94 to 3.0 eV. In addition, glass transition (T{sub g}), crystallization (T{sub p}) and melting temperature (T{sub m}) were determined by using the DTA plots. Finally, DTA results obtained with a heating rate of 20 C/min show that the peak crystallization temperature increases from 463 to 533 C as the ZnO content increases from 0.05 to 0.30 mol (copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

A study on the temperature dependence of the threshold switching characteristics of Ge2Sb2Te5

Science.gov (United States)

Lee, Suyoun; Jeong, Doo Seok; Jeong, Jeung-hyun; Zhe, Wu; Park, Young-Wook; Ahn, Hyung-Woo; Cheong, Byung-ki

2010-01-01

We investigated the temperature dependence of the threshold switching characteristics of a memory-type chalcogenide material, Ge2Sb2Te5. We found that the threshold voltage (Vth) decreased linearly with temperature, implying the existence of a critical conductivity of Ge2Sb2Te5 for its threshold switching. In addition, we investigated the effect of bias voltage and temperature on the delay time (tdel) of the threshold switching of Ge2Sb2Te5 and described the measured relationship by an analytic expression which we derived based on a physical model where thermally activated hopping is a dominant transport mechanism in the material.

Explorations of new phases in the Ga(III)/In(III)-Mo(VI)-Se(IV)/Te(IV)-O systems.

Science.gov (United States)

Kong, Fang; Hu, Chun-Li; Hu, Ting; Zhou, Yong; Mao, Jiang-Gao

2009-07-07

Systematic explorations of new phases in the Ga(III)/In(III)-Mo(VI)-Se(IV)/Te(IV)-O systems by hydrothermal syntheses or solid-state reactions at high-temperature led to four new quaternary compounds, namely, Ga(2)MoQ(2)O(10) (Q = Se, Te), In(2)Mo(2)Se(2)O(13)(H(2)O) and In(2)MoTe(2)O(10). Ga(2)MoQ(2)O(10) (Q = Se, Te) are isostructural and their structures feature a 3D network of gallium selenite/tellurite with 12-member ring tunnels along b-axis, the distorted MoO(6) octahedra are attached on the wall of the above tunnels. The structure of In(2)Mo(2)Se(2)O(13)(H(2)O) features a new pillared-layered architecture composed of 2D indium(III) selenite layers that are interconnected by Mo(2)O(10) dimers, forming 8-membered ring tunnels along the b-axis. The structure of In(2)MoTe(2)O(10) features a 2D indium oxide layer formed by corner- and edge-sharing InO(6) and InO(7) polyhedra with MoO(4) tetrahedra and TeO(n) (n = 4, 5) polyhedra hanging on both sides of the layer, there are weak interlayer Te-O bonds of 2.512 A. Results of optical diffuse reflectance spectrum measurements indicate that all four compounds are insulators, which are in agreement with results of band structure calculations based on DFT methods.

Second Harmonic 110 GHz ECH-assisted Start-up in KSTAR

Directory of Open Access Journals (Sweden)

Han S. H.

2012-09-01

Full Text Available In KSTAR device, a 110 GHz ECH system has been a useful heating device for a stable plasma start-up because a pure ohmic discharge scenario with a limited loop voltage of about 4 V was sometimes not successful for burn-through and plasma current ramp-up due to inconsistent wall conditioning and density control. Even though a pure ohmic discharge also was successful, the application of X2-mode ECH could reduce the flux consumption of poloidal field coils, leading to long pulse discharges. The ECH power was injected at the time of the field null formation after the onset of the toroidal electric field in which the electron temperature significantly increased up to 100 eV so that burn-through is overcome. The ECH heating enabled the formation of close flux surfaces earlier, leading to the reliable plasma current ramp-up, but, it caused outward plasma movement and failure of the plasma control, resulting in loss of the discharge. Moreover, impurities from the plasma facing components caused by not fully absorbed ECH power had a detrimental effect on the H-mode transition. In ECH-assisted start-up in the ramp-up phase, ECH power was mainly used for central electron heating, leading to reduction of the flux consumption of the central coils by increasing the electron temperature along with a density increase in the ramp-up phase. When X2-mode ECH power of 350 kW was injected at the mid-plane with a toroidal angle of 10 degree for 1 sec after the onset of the loop voltage, the flux consumption was reduced by about 30% in comparison with the pure ohmic discharges.

Determination of the oxidation mechanism to Cd Te obtained by rf reactive magnetron sputtering in a plasma of Ar-N{sub 2}O; Determinacion del mecanismo de oxigenacion del CdTe obtenido por rf sputtering reactivo con magnetron en un plasma de Ar-N{sub 2}O

Energy Technology Data Exchange (ETDEWEB)

Caballero B, F.; Zapata N, A.; Bartolo P, P.; Castro R, R.; Zapata T, M.; Cauich, W.; Pena, J.L. [Departamento de Fisica Aplicada, Centro deInvestigacion y de Estudios Avanzados, Instituto Politecnico Nacional, Unidad Merida, Apartado postal 73, Cordemex, 97310 Merida, Yucatan (Mexico)

1998-12-31

In this work we did studies to determinate the oxidation site and incorporation mechanism of oxygen to Cd Te, when preparing Cd Te:O thin films by r f reactive magnetron sputtering, using a Cd Te target and a controlled plasma of Ar-N{sub 2}O. We study the influence in the oxygen content in films due to the variation of N{sub 2}O partial pressure, plasma power and substrate position. We monitored the process in situ by mass spectrometry to determinate the variation of present compounds when varying the N{sub 2}O partial pressure and plasma power. Thin films composition was determined by Auger electron spectroscopy and their structure by X-ray diffraction. We demonstrate that oxygen incorporation has place mainly in the substrate, forming an amorphous Cd Te:O film. We found that exists Cd Te oxidation without using nitrous oxide, may be due to residual atmosphere. We demonstrate that Cd Te oxidation depends on nitrous oxide partial pressure and plasma power. We found that deposition rate of Cd Te:O thin films depend on nitrous oxide interaction with Cd Te in the target and on the chamber walls. We propose a reaction mechanism to explain the oxygen incorporation to Cd Te. (Author)

Photoluminescence of polycrystalline CuIn 0.5 Ga 0.5 Te 2 thin films grown by flash evaporation

KAUST Repository

Yandjah, L.; Bechiri, L.; Benabdeslem, M.; Benslim, N.; Amara, A.; Portier, X.; Bououdina, M.; Ziani, Ahmed

2018-01-01

Polycrystalline CuIn0.5Ga0.5Te2 films were deposited by flash evaporation from ingot prepared by reacting, in stoichiometric proportions, high purity Cu, In, Ga and Te elements in vacuum sealed quartz . The as-obtained films were characterized by X

Luminescence properties of Nd{sup 3+}-doped Y{sub 2}Te{sub 4}O{sub 11} microcrystalline powder

Energy Technology Data Exchange (ETDEWEB)

Sobczyk, Marcin, E-mail: marcin.sobczyk@chem.uni.wroc.pl; Szymański, Damian

2017-03-15

In this paper, some spectroscopic properties of Y{sub 2}Te{sub 4}O{sub 11} microcrystalline powders, doped with Nd{sup 3+} ions are presented. The samples were successfully synthesized by the solid state reaction method. Absorption (300 K) and fluorescence (at 77 and 300 K) spectra as well as the fluorescence decay curves (300 K) of the {sup 4}F{sub 3/2} state are presented and analyzed. The phenomenological Ω{sub λ} (λ=2, 4, 6) Judd-Ofelt parameters were evaluated in order to determine radiative probabilities (A), branching ratios (β), the radiative lifetime (τ{sub R}) of the {sup 4}F{sub 3/2} level and the stimulated emission cross-section (σ{sub em}) for the {sup 4}F{sub 3/2} → {sup 4}I{sub J/2} (J=9 and 11) transitions of the Nd{sup 3+} ion. The fluorescence decay curves were single exponential for 0.01–5.0 at% of Nd{sup 3+} and became evidently non-exponential for higher Nd{sup 3+} ion concentration. With increasing activator concentration from 0.01 to 10.0 at%, the experimental lifetime of the emitting level decreases from 95 to 33 μs. The non-exponential fluorescence decay curve has been fitted by the Yokota-Tanimoto model, indicating that the energy migration process via a diffusion limited relaxation, plays a important role in the depopulation of the {sup 4}F{sub 3/2} level of Nd{sup 3+} ions doped in the Y{sub 2}Te{sub 4}O{sub 11} microcrystalline powder. The calculated absorption value (1.135×10{sup –19} cm{sup 2} at 807.5 nm) of the {sup 4}I{sub 9/2} → {sup 4}F{sub 5/2} transition as well as the value of the stimulated emission cross-section (1.196×10{sup –19} cm{sup 2} at 1063.5 nm) for that of {sup 4}F{sub 3/2} → {sup 4}I{sub 11/2} were compared with the corresponding values of other laser hosts. For the first time a very high σ{sub em} value of the {sup 4}F{sub 3/2} → {sup 4}I{sub 11/2} transition for TeO{sub 2}-based compounds, has been observed. From the presented spectroscopic properties follows that the Nd{sup 3+}:Y{sub 2

Holographic recording and characterization of photorefractive Bi{sub 2}TeO{sub 5} crystals at 633 nm wavelength light

Energy Technology Data Exchange (ETDEWEB)

Oliveira, Ivan de, E-mail: ivan@ft.unicamp.br [Grupo de Óptica e Modelagem Numérica (GOMNI)-Faculdade de Tecnologia/UNICAMP, Limeira-SP (Brazil); Carvalho, Jesiel F., E-mail: carvalho@if.ufg.br; Fabris, Zanine V. [Instituto de Física/Universidade Federal de Goiás, Goiânia-GO (Brazil); Frejlich, Jaime, E-mail: frejlich@ifi.unicamp.br [Instituto de Física “Gleb Wataghin”/UNICAMP, Campinas-SP (Brazil)

2014-04-28

We report on the holographic recording on photorefractive Bi{sub 2}TeO{sub 5} crystals using λ=633 nm wavelength light. We studied the behavior of this material under the action of this low photonic energy light and found out the presence of a fast and a slow hologram, both of photorefractive nature and exhibiting rather high diffraction efficiencies. The faster and the slower holograms are based on the excitation and diffusion of oppositely charged carriers (likely electrons and holes). Relevant parameters for the photoactive centers responsible for both kind of holograms were characterized using purely holographic techniques. No evidences of non-photosensitive ionic charge carriers being involved in the recording process at room temperature nor self-fixing effects were found.

Collective flow in 2.76 and 5.02 A TeV Pb + Pb collisions

Energy Technology Data Exchange (ETDEWEB)

Zhao, Wenbin; Xu, Hao-jie [Peking University, Department of Physics and State Key Laboratory of Nuclear Physics and Technology, Beijing (China); Song, Huichao [Peking University, Department of Physics and State Key Laboratory of Nuclear Physics and Technology, Beijing (China); Collaborative Innovation Center of Quantum Matter, Beijing (China); Peking University, Center for High Energy Physics, Beijing (China)

2017-09-15

In this paper, we study and predict flow observables in 2.76 and 5.02 A TeV Pb + Pb collisions, using the iEBE-VISHNU hybrid model with TRENTo and AMPT initial conditions and with different forms of the QGP transport coefficients. With properly chosen and tuned parameter sets, our model calculations can nicely describe various flow observables in 2.76 A TeV Pb + Pb collisions, as well as the measured flow harmonics of all charged hadrons in 5.02 A TeV Pb + Pb collisions. We also predict other flow observables, including v{sub n}(p{sub T}) of identified particles, event-by-event v{sub n} distributions, event-plane correlations, (normalized) symmetric cumulants, non-linear response coefficients and p{sub T}-dependent factorization ratios, in 5.02 A TeV Pb + Pb collisions. We find many of these observables to remain approximately the same values as the ones in 2.76 A TeV Pb + Pb collisions. Our theoretical studies and predictions could shed light to the experimental investigations in the near future. (orig.)

Broadband ˜2μm emission in Tm3+/Ho3+ co-doped TeO2-WO3-La2O3 glass

Science.gov (United States)

Li, Kefeng; Wang, Guonian; Zhang, Junjie; Hu, Lili

2010-10-01

In this work, we report the infrared emission properties of Tm 3+/Ho 3+ co-doped TeO 2-WO 3-La 2O 3 (TWL) glass under 808 nm laser excitation. A broad and flat emission from 1600 to 2200 nm corresponding to the Tm 3+ ( 3F 4→ 3H 6) and Ho 3+ ( 5I 7→ 5I 8) emissions is observed. The full width at half maximum (FWHM) of this broadband increases up to a value of ˜370 nm with an optimal [Tm 3+]/[Ho 3+] concentration ratio. The energy transfer processes of Tm 3+↔Ho 3+ are analyzed and the results show that energy transfer between Tm 3+ and Ho 3+ plays an important role in the luminescence mechanism. The OH - influence on the broadband emission is also discussed. These results indicate that Tm 3+-Ho 3+ co-doped TWL glass could be a promising material for widely tunable laser or broadband amplifier applications.

Mass transport in Ti0.5Sb2Te3 phase-change nanobridge

International Nuclear Information System (INIS)

Ji, Xinglong; Wu, Liangcai; Lv, Shilong; Rao, Feng; Zhu, Min; Song, Zhitang; Zhou, Xilin; Feng, Songlin

2014-01-01

Investigation of atomic migration behavior in nanoscale phase-change material is very valuable for phase-change memory applications. In this work, Ti 0.5 Sb 2 Te 3 -based phase-change nanobridges were fabricated and mass transport by atomic migration was studied. A 3-D finite-element simulation on the electrothermal field was introduced to describe the electrothermal environment in the phase-change region. During the nanosecond operation, an obvious compositional distribution resulting from atomic migration was observed in the Ti 0.5 Sb 2 Te 3 phase-change nanobridge. Based on the mass continuity equation, a physical model for mass transport is proposed to illustrate that the density variation during the amorphous-to-crystalline structural transformation is the main reason for the atomic migration in nanoscale Ti 0.5 Sb 2 Te 3 phase-change material

High-accuracy and high-sensitivity spectroscopic measurement of dinitrogen pentoxide (N2O5) in an atmospheric simulation chamber using a quantum cascade laser.

Science.gov (United States)

Yi, Hongming; Wu, Tao; Lauraguais, Amélie; Semenov, Vladimir; Coeur, Cecile; Cassez, Andy; Fertein, Eric; Gao, Xiaoming; Chen, Weidong

2017-12-04

A spectroscopic instrument based on a mid-infrared external cavity quantum cascade laser (EC-QCL) was developed for high-accuracy measurements of dinitrogen pentoxide (N 2 O 5 ) at the ppbv-level. A specific concentration retrieval algorithm was developed to remove, from the broadband absorption spectrum of N 2 O 5 , both etalon fringes resulting from the EC-QCL intrinsic structure and spectral interference lines of H 2 O vapour absorption, which led to a significant improvement in measurement accuracy and detection sensitivity (by a factor of 10), compared to using a traditional algorithm for gas concentration retrieval. The developed EC-QCL-based N 2 O 5 sensing platform was evaluated by real-time tracking N 2 O 5 concentration in its most important nocturnal tropospheric chemical reaction of NO 3 + NO 2 ↔ N 2 O 5 in an atmospheric simulation chamber. Based on an optical absorption path-length of L eff = 70 m, a minimum detection limit of 15 ppbv was achieved with a 25 s integration time and it was down to 3 ppbv in 400 s. The equilibrium rate constant K eq involved in the above chemical reaction was determined with direct concentration measurements using the developed EC-QCL sensing platform, which was in good agreement with the theoretical value deduced from a referenced empirical formula under well controlled experimental conditions. The present work demonstrates the potential and the unique advantage of the use of a modern external cavity quantum cascade laser for applications in direct quantitative measurement of broadband absorption of key molecular species involved in chemical kinetic and climate-change related tropospheric chemistry.

Investigations on the local structures and the spin Hamiltonian parameters for Cu{sup 2+} in (90-x)TeO{sub 2}-10GeO{sub 2}-xWO{sub 3} glasses

Energy Technology Data Exchange (ETDEWEB)

Feng, Chun-Rong [Xihua Univ., Chengdu (China). School of Science; Jian, Jun [Xihua Univ., Chengdu (China). Dept. of Applied Physics; Chen, Xiao-Hong; Du, Quan; Wang, Ling [Xihua Univ., Chengdu (China). School of Science and Research Center for Advanced Computation

2018-04-01

The local structures and the spin Hamiltonian parameters (SHPs) for Cu{sup 2+} in (90-x)TeO{sub 2}-10GeO{sub 2}-xWO{sub 3} glasses are theoretically investigated at various WO{sub 3} concentrations (x=7.5, 15, 22.5 and 30 mol%). Subject to the Jahn-Teller effect, the [CuO{sub 6}]{sup 10-} groups are found to experience the small or moderate tetragonal elongation distortions (characterised by the relative tetragonal elongation ratios ρ ∼ 0.35-3.09%) in C{sub 4} axis. With only three adjusted coefficients a, b and ω, the relevant model parameters (Dq, k and ρ) are described by the Fourier type and linear functions, respectively, and the measured concentration dependences of the d-d transition bands and SHPs are reproduced. The maximum of g {sub parallel} and the minimum of vertical stroke A {sub parallel} vertical stroke at x=15 mol% are illustrated from the abrupt decrease of the copper-oxygen electron cloud admixtures or covalency and the obvious decline of the copper 3d-3s (4s) orbital admixtures due to the decreasing electron cloud density around oxygen ligands spontaneously bonding with Cu{sup 2+} and Te{sup 4+} (W{sup 6+}), respectively.

Application of core–shell-structured CdTe-SiO2 quantum dots synthesized via a facile solution method for improving latent fingerprint detection

International Nuclear Information System (INIS)

Gao Feng; Han Jiaxing; Lv Caifeng; Wang Qin; Zhang Jun; Li Qun; Bao Liru; Li Xin

2012-01-01

Fingerprint detection is important in criminal investigation. This paper reports a facile powder brushing technique for improving latent fingerprint detection using core–shell-structured CdTe-SiO 2 quantum dots (QDs) as fluorescent labeling marks. Core–shell-structured CdTe-SiO 2 QDs are prepared via a simple solution-based approach using NH 2 NH 2 ·H 2 O as pH adjustor and stabilizer, and their application for improving latent fingerprint detection is explored. The obtained CdTe-SiO 2 QDs show spherical shapes with well-defined core–shell structures encapsulating different amounts of QDs depending on the type of the pH adjustor and stabilizer. Moreover, the fluorescence of CdTe-SiO 2 QDs is largely enhanced by surface modification of the SiO 2 shell. The CdTe-SiO 2 QDs overcome the oxidation problem of pure CdTe QDs in air, thus affording better variability with strong adhesive ability, better resolution, and bright emission colors for practical application in latent fingerprint detection. In comparison with the conventional fluorescence powders, silver powders, and others, the effectiveness of CdTe-SiO 2 QD powders for detection of latent fingerprints present on a large variety of object surfaces is greatly improved. The synthesis method for CdTe-SiO 2 QDs is simple, cheap, and easy for large-scale production, and thus offers many advantages in the practical application of fingerprint detection.

Thermal stability of atomic layer deposition Al2O3 film on HgCdTe

Science.gov (United States)

Zhang, P.; Sun, C. H.; Zhang, Y.; Chen, X.; He, K.; Chen, Y. Y.; Ye, Z. H.

2015-06-01

Thermal stability of Atomic Layer Deposition Al2O3 film on HgCdTe was investigated by Al2O3 film post-deposition annealing treatment and Metal-Insulator-Semiconductor device low-temperature baking treatment. The effectiveness of Al2O3 film was evaluated by measuring the minority carrier lifetime and capacitance versus voltage characteristics. After annealing treatment, the minority carrier lifetime of the HgCdTe sample presented a slight decrease. Furthermore, the fixed charge density and the slow charge density decreased significantly in the annealed MIS device. After baking treatment, the fixed charge density and the slow charge density of the unannealed and annealed MIS devices decreased and increased, respectively.

Crystal structure of 2-phenyl-2λ4,3-ditelluratetracyclo[5.5.2.04,13.010,14]tetradeca-1(12,4,6,10,13-pentaen-2-ylium trifluoromethanesulfonate

Directory of Open Access Journals (Sweden)

Louise M. Diamond

2014-09-01

Full Text Available In the title compound, C18H13Te2+·CF3O3S−, the TeII atom of the cation and one O atom of the trifluoromethanesulfonate counter-ion form a close-to-linear Te—Te—O system, with a Te—Te—O angle of 172.3 (1° and a Te—O distance of 2.816 (5 Å, which may suggest the presence of a three-centre–four-electron (3c–4e bond. Secondary Te...O interactions [3.003 (4 and 3.016 (4 Å], involving the second TeII atom of the binuclear molecule, are also noted, resulting in a supramolecular layer in the bc plane.

Si{sub 2}Sb{sub 2}Te{sub 5} phase change material studied by an atomic force microscope nano-tip

Energy Technology Data Exchange (ETDEWEB)

Liu Yanbo; Min Guoquan; Zhang Jing; Zhou Weimin; Wan Yongzhong; Zhang Jianping; Li Xiaoli [Laboratory of Nano-Technology, Shanghai Nanotechnology Promotion Center, Shanghai 200237 (China); Zhang Ting; Niu Xiaoming; Song Zhitang; Feng Songlin, E-mail: liuyanbo@snpc.org.c, E-mail: tzhang@mail.sim.ac.c [State Key Laboratory of Functional Materials for Informatics, Laboratory of Nanotechnology, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050 (China)

2009-06-01

The Si{sub 2}Sb{sub 2}Te{sub 5} phase change material has been studied by applying a nano-tip (30 nm in diameter) on an atomic force microscopy system. Memory switching from a high resistance state to a low resistance state has been achieved, with a resistance change of about 1000 times. In a typical I-V curve, the current increases significantly after the voltage exceeds approx4.3 V. The phase transformation of a Si{sub 2}Sb{sub 2}Te{sub 5} film was studied in situ by means of in situ X-ray diffraction and temperature dependent resistance measurements. The thermal stability of Si{sub 2}Sb{sub 2}Te{sub 5} and Ge{sub 2}Sb{sub 2}Te{sub 5} was characterized and compared as well.

Chalcogenidosilicates: Ba/sub 2/SiTe/sub 4/ and Ba/sub 2/SiSe/sub 4/

Energy Technology Data Exchange (ETDEWEB)

Brinkmann, C; Eisenmann, B; Schaefer, H [Technische Hochschule Darmstadt (Germany, F.R.). Fachbereich Anorganische Chemie und Kernchemie

1985-05-01

The new compounds Ba/sub 2/SiSe/sub 4/ and Ba/sub 2/SiTe/sub 4/ crystallize in the monoclinic system, space group: P2/sub 1//m (No. 11) with the lattice constants Ba/sub 2/SiSe/sub 4/: a = 918.4(5) pm, b = 703.3(3) pm, c = 687.2(3) pm, ..beta.. = 109.2(1)/sup 0/, Ba/sub 2/SiTe/sub 4/: a = 965.0(5) pm, b = 762.6(3) pm, c = 746.6(3) pm, ..beta.. = 108.9(1)/sup 0/. Both compounds are isotypic to the Sr/sub 2/GeS/sub 4/ structure. Ba/sub 2/SiTe/sub 4/ is the first o-telluridosilicate with discrete SiTe/sub 4//sup 4 -/ anions.

Thermal and galvanomagnetic properties of monocrystals CuInGa{sub 2}Te{sub 5}

Energy Technology Data Exchange (ETDEWEB)

Abilov, Ch. I., E-mail: cabilov@yahoo.com; Hasanova, M. Sh., E-mail: mhsh28@mail.ru; Huseynova, N. T. [Azerbaijan Technical University, Baku (Azerbaijan); Zeynalov, S. A. [Azerbaijan Institute of Teachers, Baku (Azerbaijan)

2016-03-25

By the methods of the physic-chemical analysis, determination of density and by measurement of micro hardness the character of chemical interaction in the In{sub 2}Te{sub 3}-Cu{sub 2}Ga{sub 4}Te{sub 7} system has been investigated and its faze diagram has been plotted. It is established that the system is quasibinary, of eutectic type. In the system the chemical combination of CuGa{sub 2}InTe{sub 5} composition melting congruently at 855°C is generated. There have been revealed solid solutions boundary of which based on In{sub 2}Te{sub 3} reach 5mol% at room temperatures. Temperature dependences of electric conductivity, the coefficient of thermo-emf, general heat conductivity, the Hall mobility of charge carriers.The mechanisms of electron-phonon diffusion in crystals of its compound have been revealed.

Ge nitride formation in N-doped amorphous Ge2Sb2Te5

International Nuclear Information System (INIS)

Jung, M.-C.; Lee, Y. M.; Kim, H.-D.; Kim, M. G.; Shin, H. J.; Kim, K. H.; Song, S. A.; Jeong, H. S.; Ko, C. H.; Han, M.

2007-01-01

The chemical state of N in N-doped amorphous Ge 2 Sb 2 Te 5 (a-GST) samples with 0-14.3 N at. % doping concentrations was investigated by high-resolution x-ray photoelectron spectroscopy (HRXPS) and Ge K-edge x-ray absorption spectroscopy (XAS). HRXPS showed negligible change in the Te 4d and Sb 4d core-level spectra. In the Ge 3d core-level spectra, a Ge nitride (GeN x ) peak developed at the binding energy of 30.2 eV and increased in intensity as the N-doping concentration increased. Generation of GeN x was confirmed by the Ge K-edge absorption spectra. These results indicate that the N atoms bonded with the Ge atoms to form GeN x , rather than bonding with the Te or Sb atoms. It has been suggested that the formation of Ge nitride results in increased resistance and phase-change temperature

Critical V2O5/TeO2 Ratio Inducing Abrupt Property Changes in Vanadium Tellurite Glasses.

Science.gov (United States)

Kjeldsen, Jonas; Rodrigues, Ana C M; Mossin, Susanne; Yue, Yuanzheng

2014-12-26

Transition metal containing glasses have unique electrical properties and are therefore often used for electrochemical applications, such as in batteries. Among oxide glasses, vanadium tellurite glasses exhibit the highest electronic conductivity and thus the high potential for applications. In this work, we investigate how the dynamic and physical properties vary with composition in the vanadium tellurite system. The results show that there exists a critical V(2)O(5) concentration of 45 mol %, above which the local structure is subjected to a drastic change with increasing V(2)O(5), leading to abrupt changes in both hardness and liquid fragility. Electronic conductivity does not follow the expected correlation to the valence state of the vanadium as predicted by the Mott-Austin equation but shows a linear correlation to the mean distance between vanadium ions. These findings could contribute to designing optimum vanadium tellurite compositions for electrochemical devices. The work gives insight into the mechanism of electron conduction in the vanadium tellurite systems.

Synthesis of ZnTe nanowires onto TiO2 nanotubular arrays by pulse-reverse electrodeposition

International Nuclear Information System (INIS)

Gandhi, T.; Raja, K.S.; Misra, M.

2009-01-01

Growth of ZnTe nanowires using a pulse-reverse electrodeposition technique from a non-aqueous solution is reported. ZnTe nanowires were grown on to an ordered nanotubular TiO 2 template in a propylene carbonate solution at 130 o C inside a controlled atmosphere glove box. The pulse-reverse electro deposition process consisted of a cathodic pulse at - 0.62 V and an anodic pulse at 0.75 V Vs Zn 2+ /Zn. Stoichiometry growth of crystalline ZnTe nanowires was observed in the as-deposited condition. The anodic pulse cycle of the pulse-reverse electrodeposition process presumably introduced zinc vacancies as deep level acceptors at an energy level of E v + 0.47 eV. The resultant ZnTe nanowires showed p-type semiconductivity with a resistivity of 7.8 x 10 4 Ω cm and a charge carrier density of 1.67 x 10 14 cm -3 . Annihilation of the defects occurred upon thermal annealing that resulted in marginal decrease in the defect density.

Synthesis and structural investigation of new Co1-xNixTeO4 (x = 0, 0.2, 0.5, 0.8 and 1) compounds

Science.gov (United States)

Patel, Akhilesh K.; Singh, Harishchandra; Suresh, K. G.

2018-05-01

The new polycrystalline compounds Co1-xNixTeO4 (x = 0, 0.2, 0.5, 0.8 and 1) were prepared by sol-gel method and their structural properties have been studied. Structural investigation through Rietveld method shows monoclinic structure with space group P21/c for all compounds. All compounds polyhedral structure found to be in octahedral form with cations (M) at the center and six oxygen atoms at corner of octahedral structure. The lattice parameters variation with Ni substitution are found to be decreasing with Ni substitution.

Thermoelectric properties of c-GeSb{sub 0.75}Te{sub 0.5} to h-GeSbTe{sub 0.5} thin films through annealing treatment effects

Energy Technology Data Exchange (ETDEWEB)

Vora-ud, Athorn, E-mail: athornvora-ud@snru.ac.th [Program of Physics, Faculty of Science and Technology, Sakon Nakhon Rajabhat University, Mueang District, Sakon Nakhon 47000 (Thailand); Thermoelectrics Research Center, Research and Development Institution, Sakon Nakhon Rajabhat University, Mueang District, Sakon Nakhon 47000 (Thailand); Horprathum, Mati, E-mail: mati.horprathum@nectec.or.th [National Electronics and Computer Technology Center, National Science and Technology Development Agency, Pathumthani 12120 (Thailand); Eiamchai, Pitak [National Electronics and Computer Technology Center, National Science and Technology Development Agency, Pathumthani 12120 (Thailand); Muthitamongkol, Pennapa; Chayasombat, Bralee; Thanachayanont, Chanchana [National Metal and Materials Technology Center, National Science and Technology Development Agency, Pathumthani 12120 (Thailand); Pankiew, Apirak [National Electronics and Computer Technology Center, National Science and Technology Development Agency, Pathumthani 12120 (Thailand); Klamchuen, Annop [National Nanotechnology Center, National Science and Technology Development Agency, Pathumthani 12120 (Thailand); Naenkieng, Daengdech; Plirdpring, Theerayuth; Harnwunggmoung, Adul [Thermoelectric and Nanotechnology Research Center, Faculty of Science and Technology, Rajamangala University of Technology Suvarnabhumi, Huntra Phranakhon, Si Ayutthaya 13000 (Thailand); Charoenphakdee, Anek [NANO-Thermoelectrics Research Center, Division of Applied Physics, Faculty of Sciences and Liberal Arts, Rajamangala University of Technology Isan, Mueng Nakorn Ratchasima 30000 Thailand (Thailand); Somkhunthot, Weerasak [Program of Physics, Faculty of Science and Technology, Loei Rajabhat University, Muang District, Loei 42000 (Thailand); and others

2015-11-15

Germanium–Antimony–Tellurium (Ge–Sb–Te) thin films were deposited on silicon wafers with 1-μm silicon dioxide (SiO{sub 2}/Si) by pulsed dc magnetron sputtering from a 99.99% GeSbTe target of 1:1:1 ratio at ambient temperature. The samples were annealed at 573, 623, 673, and 723 K for 3600 s in a vacuum state. The effects of the annealing treatment on phase identification, atomic composition, morphology and film thickness, carrier concentration, mobility, and Seebeck coefficient of the Ge–Sb–Te samples have been investigated by grazing-incidence X-ray diffraction, auger electron spectroscopy, field-emission scanning electron microscopy, Hall-effect measurements, and steady state method, respectively. The results demonstrated that the as-deposited Ge–Sb–Te sample was amorphous. Atomic composition of as-deposited and annealed films at 573 K and 623 K were GeSb{sub 0.75}Te{sub 0.5} while annealed films at 673 K and 723 K were GeSbTe{sub 0.5} due to Sb-rich GeSb{sub 0.75}Te{sub 0.5}. The samples annealed at 573 K and 623 K showed the crystal phases of cubic structure (c-GeSb{sub 0.75}Te{sub 0.5}) into hexagonal structure (h-GeSbTe{sub 0.5}) after annealing at 673 K and 723 K. The study demonstrated the insulating condition from the as-deposited GeSbTe film, and the changes towards the thermoelectric properties from the annealing treatments. The GeSbTe films annealed at 673 K yielded excellent thermoelectric properties with the electrical resistivity, Seebeck coefficient, and power factor at approximately 1.45 × 10{sup −5} Ωm, 71.07 μV K{sup −1}, and 3.48 × 10{sup −4} W m{sup −1} K{sup −2}, respectively. - Highlights: • GeSbTe thin films were successfully sputtered for thermoelectric properties. • GeSbTe films were examined among physical, electrical and thermoelectric properties. • Thermoelectric properties were discussed based on composition of the films.

Temperature-dependent luminescence and temperature-stimulated NIR-to-VIS up-conversion in Nd3+-doped La2O3-Na2O-ZnO-TeO2 glasses

Science.gov (United States)

Sobczyk, Marcin

2013-04-01

Telluride glasses of the composition xNd2O3-(7-x)La2O3-3Na2O-25ZnO-65TeO2, where (0≤x≤7) were prepared by the melt quench technique. Some physical and optical properties of the glasses were evaluated. The thermal behavior i.e. glass transition and crystallization temperatures were studied by using TGA-DTA technique. Optical properties of Nd3+-doped telluride glasses were investigated between 298 and 700 K. Basing on the obtained values of J-O parameter values (×10-20 cm2: Ω2=4.49±0.84, Ω4=5.03±0.61, Ω6=4.31±0.73), the radiative transition probabilities (AT), radiative lifetimes (τR), fluorescence branching ratios (β) and emission cross-sections (σem) were calculated for the 4F3/2→4IJ/2 (where J=9, 11 and 13) transitions of Nd3+ ions. The τR value of the 4F3/2 level amount to 164 μs and is slightly higher than the measured decay time of 162 μs. With the increasing of Nd2O3 concentration from 0.5 to 7.0 mol% the experimental lifetime of the fluorescent level decreases from 162 to 5.6 μs. The estimated quantum efficiency amount to 100%, based on a comparison of τR and the experimental decay time of a slightly doped Nd3+ telluride glass. An analysis of the non-radiative decay was based on the cross-relaxation mechanisms. The 4F3/2→4I9/2 and 4F5/2→4I9/2 transitions were analyzed with respect to the fluorescence intensity ratio (FIR) and were found to be temperature dependent. Infrared-to-visible up-conversion emissions with a maximum at 603.0 and 635.3 nm were observed at high temperatures using the 804 nm excitation and are due to the 4G5/2→4I9/2 and 4G5/2→4I11/2 transitions of Nd3+ ions, respectively. The near quadratic dependence of fluorescence on excitation laser power confirms that two photons contribute to up-conversion of the orange emissions. The temperature-stimulated up-conversion excitation processes have been analyzed in detail. The optical results indicate that the investigated glasses are potentially applicable as a 1063 nm

Change in local atomic and chemical bonding structures of Ge2Sb2Te5 alloys by isothermal heat treatment

International Nuclear Information System (INIS)

Lim, Woo-Sik; Cho, Sung-June; Lee, Hyun-Yong

2008-01-01

In this work, we report evaluation of the atomic-scale phase transformation characteristics in one of the most comprehensively utilized phase change materials today, Ge 2 Sb 2 Te 5 thin film. The phase transformation of Ge 2 Sb 2 Te 5 thin film from amorphous to hexagonal structure via fcc structure was confirmed by XRD measurements. The approximate values of optical energy gap are 0.72 and 0.50 eV, with slopes (B 1/2 ) in the extended absorption region of 5.3 x 10 5 and 10 x 10 5 cm -1 ·eV -1 for the amorphous and fcc-crystalline structures, respectively. In addition, X-ray photoelectron spectroscopy analysis revealed strengthening of the Te-Te bond as well as weakening of the Ge-Te bond during the amorphous-to-crystalline transition. This trend was also observed in extended X-ray absorption fine structure analysis where the Ge metallic bond lengths in the amorphous, fcc, and hexagonal structures were 0.262, 0.280, and 0.290 nm

Enhanced photocatalytic activity of Te-doped Bi{sub 2}MoO{sub 6} under visible light irradiation: Effective separation of photogenerated carriers resulted from inhomogeneous lattice distortion and improved electron capturing ability

Energy Technology Data Exchange (ETDEWEB)

Chen, Shuguang, E-mail: csustcsg@yahoo.com; Li, Yuhan; Wu, Zixu; Wu, Baoxin; Li, Haibin; Li, Fujin

2017-05-15

Te-doped Bi{sub 2}MoO{sub 6} photocatalyst was hydrothermally synthesized, and nonmetal atoms Te were homogeneously incorporated into Bi{sub 2}MoO{sub 6} lattice with the substitution of Te{sup 4+} to Mo{sup 6+}. With increasing Te-doping concentration in Bi{sub 2}MoO{sub 6}, no detectable band-gap narrowing but more and more severe inhomogeneous lattice distortions were determined. The activity of Bi{sub 2}MoO{sub 6} photocatalyst was evaluated through methylene blue degradation under visible light irradiation (λ>410 nm) and was greatly enhanced by Te-doping. When Te-doped Bi{sub 2}MoO{sub 6} was synthesized at Te/Mo molar ratio of 7.5%, a maximum first-order rate constant of methylene blue degradation was obtained. The inhomogeneous lattice distortion generated an internal dipole moment, and the holes generated with the substitution of Te{sup 4+} to Mo{sup 6+} acted as the capturing centers of photogenerated electrons, thus the effective separation of photogenerated carriers was facilitated to result in a relatively high concentration of holes on the surface of Te-doped Bi{sub 2}MoO{sub 6} to be favorable for the efficient methylene blue degradation. - Graphical abstract: With the substitution of Te{sup 4+} to Mo{sup 6+}, effective separation of photogenerated carriers resulted from inhomogeneous lattice distortion and improved electron capturing ability is achieved to be responsible for enhanced photocatalytic activity of Te-doped Bi{sub 2}MoO{sub 6}. - Highlights: • Nonmetal Te is incorporated into Bi{sub 2}MoO{sub 6} with the substitution of Te{sup 4+} to Mo{sup 6+}. • Revealing inhomogeneous lattice distortion and improved electron capturing ability. • Effective separation of photogenerated carriers in Te-doped Bi{sub 2}MoO{sub 6} is achieved. • The mechanism of methylene blue degradation over Te-doped Bi{sub 2}MoO{sub 6} is proposed.

Structural studies of WO3-TeO2 glasses by high-Q-neutron diffraction and Raman spectroscopy

International Nuclear Information System (INIS)

Khanna, A.; Kaur, A.; Krishna, P.S.R.; Shinde, A.B.

2013-01-01

Glasses from the system: xWO 3 -(100-x)TeO 2 (x=15, 20 and 25 mol %) were prepared by melt quenching technique and characterized by density, UV-visible absorption spectroscopy, Differential Scanning Calorimetry (DSC), Raman spectroscopy and high-Q neutron diffraction measurements. Glass density and glass transition temperature increased with increase in WO 3 concentration, Raman spectroscopy indicated the conversion of TeO 4 units into TeO 3 units with increase in WO 3 content. The increase in glass transition temperature with the incorporation of WO 3 was attributed to the increase in average bond strength of the glass network since the bond dissociation energy of W-O bonds (672 kJ/mol) is significantly higher than that of Te-O bonds (376 kJ/mol). UV-visible studies found a very strong optical absorption band due to W 6+ ions, just below the absorption edge. High-Q neutron diffraction measurements were performed on glasses and radial distribution function analyses revealed changes in W-O and Te-O correlations in the glass network. The findings about changes in glass structure from neutron diffraction studies were consistent with structural information obtained from Raman spectroscopy and structure-property correlations were made. (author)

Enhanced thermoelectric figure-of-merit in Bi-Sb-Te nanocomposites with homogenously dispersed oxide ceramic ZrO2 nanoparticles

Science.gov (United States)

Madavali, B.; Kim, H. S.; Lee, K. H.; Hong, S. J.

2017-06-01

In this research, p-type BiSbTe/ZrO2 nanocomposite powders were fabricated by high-energy ball milling. Different weight percentages of ZrO2 (2, 4, and 6 wt. %) nanoparticles were incorporated into the bulk (BiSbTe) matrix by consolidation of as-synthesized nanocomposites (NCs) powder by spark plasma sintering at 673 K. The phase and existence of ZrO2 nano-inclusions was confirmed by X-ray diffraction and transmission electron microscopy-selected area electron diffraction analysis. The Seebeck coefficient of the BiSbTe/ZrO2 NCs was significantly improved (˜36% for 4 wt. % added NCs) by a decrease in the carrier concentration and energy filtering effect, whereas the thermal conductivity was much reduced via strong scattering of carriers/phonons. The peak thermoelectric figure-of-merit (1.34 ± 0.06) was obtained for BiSbTe into which 2 wt. % ZrO2 was dispersed, which was approximately 20% greater than that of the undispersed sample. The hardness of the nanocomposites was significantly improved (˜27%) due to grain-boundary hardening and a dispersion strengthening mechanism.

110GHz ECH on DIII-D

International Nuclear Information System (INIS)

Cary, W.P.; Allen, J.C.; Callis, R.W.; Doane, J.L.; Harris, T.E.; Moetler, C.P.; Neren, A.; Prater, P.; Rensen, D.

1992-01-01

This paper reports on a new high power electron cyclotron heating (ECH) system which has been introduced on DIII-D. This system is designed to operate at 110 GHz with a total output power of 2 MW. The system consists of four Varian VGT-8011 gyrotrons (output power of 500 kW), and their associated support equipment. All components have been designed for up to a 10 second pulse duration. The 110 GHz system is intended to further progress in rf current drive experiments on DIII-D when used in conjunction with the existing 60 GHz ECH (1. 6 MW) , and the 30-60 MHz ICH (2MW) systems. H-mode physics, plasma stabilization experiments and transport studies are also to be conducted at 110 GHz

Variation of energy absorption and exposure buildup factors with incident photon energy and penetration depth for boro-tellurite (B2O3-TeO2) glasses

Science.gov (United States)

Sayyed, M. I.; Elhouichet, H.

2017-01-01

The gamma ray energy absorption (EABF) and exposure buildup factors (EBF) of (100-x)TeO2-xB2O3 glass systems (where x=5, 10, 15, 20, 22.5 and 25 mol%) have been calculated in the energy region 0.015-15 MeV up to a penetration depth of 40 mfp (mean free path). The five parameters (G-P) fitting method has been used to estimate both EABF and EBF values. Variations of EABF and EBF with incident photon energy and penetration depth have been studied. It was found that EABF and EBF values were higher in the intermediate energy region, for all the glass systems. Furthermore, boro-tellurite glass with 5 mol% B2O3, was found to present the lowest EABF and EBF values, hence it is superior gamma-ray shielding material. The results indicate that the boro-tellurite glasses can be used as radiation shielding materials.

Obtention, sintering and operational tests of the obtention prototype TeO2 for the production of 131 I

International Nuclear Information System (INIS)

Alanis M, J.

1997-12-01

The demand that exists in Mexico of developing production techniques of applicable radiopharmaceuticals in nuclear medicine, it forces to the National Institute of Nuclear Research to develop the obtaining process of 131 I by dry via starting from TeO 2 . The obtaining process of 131 I, it begins with the synthesis of the TeO 2 like matter prevails, starting from the oxidation of Te-elementary one, inside HNO 3 . Later on the TeO 2 , passes to the sintering process in ingots form, in that way it is encapsulated in aluminum, to be irradiated under optimal parameters of irradiation in the nuclear reactor. The irradiated TeO 2 , it passes to the stage of distillation of 131 I, in a distillation equipment of 131 I by dry via starting from TeO 2 . The process equipment consists mainly of three parts: a) the system of distillation control, built of steel, aluminum, bronze and brass, among other, b) distillation system, built of glass pyrex and of quartz, in this system is where the chemical and nuclear reactions take place for the obtaining of 131 I and c) electric system, is the one in charge of the electric energy supply for the process oven, ventilation system and vacuum system. The results of experimental tests, check the effectiveness of the production process of 131 I in the ININ in routine form (industrial), however it is indispensable to optimize the physical, chemical and nuclear parameters that intervene in each stage of the process with the purpose to obtaining the maximum yield, purity, quality and radiological control and economic production costs. (Author)

Large optical second-order nonlinearity of poled WO3-TeO2 glass.

Science.gov (United States)

Tanaka, K; Narazaki, A; Hirao, K

2000-02-15

Second-harmonic generation, one of the second-order nonlinear optical properties of thermally and electrically poled WO>(3)-TeO>(2) glasses, has been examined. We poled glass samples with two thicknesses (0.60 and 0.86 mm) at various temperatures to explore the effects of external electric field strength and poling temperature on second-order nonlinearity. The dependence of second-harmonic intensity on the poling temperature is maximum at a specific poling temperature. A second-order nonlinear susceptibility of 2.1 pm/V was attained for the 0.60-mm-thick glass poled at 250 degrees C. This value is fairly large compared with those for poled silica and tellurite glasses reported thus far. We speculate that the large third-order nonlinear susceptibility of WO>(3)- TeO>(2) glasses gives rise to the large second-order nonlinearity by means of a X((2)) = 3X((3)) E(dc) process.

EBT-S ECH transmission systems

International Nuclear Information System (INIS)

White, T.

1983-01-01

Over the past 18 months the EBT-S 28-GHz 200 kW cw mixed mode ECH system efficiency has increased from 70 to 80% by the substitution of 90 0 smooth radius W/G bends for the earlier miter bends, by eliminating several mode absorbers necessary for miter bend operation, and by optimizing the microwave coupling through the quasi-optical toroidal distribution manifold. Along with reduced system losses, these improvements have allowed the gyrotron sources to operate in a wider parameter range with high dc to rf conversion efficiency than previously attainable. Other components that have been developed besides radiused bends include T/sub i/O 2 mode absorbers, power splitters, bellows, and several types of high field mixed mode launchers. Details on these components will be presented as time allows

Structural chemistry and magnetic properties of the perovskite Sr{sub 3}Fe{sub 2}TeO{sub 9}

Energy Technology Data Exchange (ETDEWEB)

Tang, Yawei; Hunter, Emily C. [Inorganic Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QR (United Kingdom); Battle, Peter D., E-mail: peter.battle@chem.ox.ac.uk [Inorganic Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QR (United Kingdom); Sena, Robert Paria; Hadermann, Joke [EMAT, University of Antwerp, Groenenborgerlaan 171, 2020 Antwerp (Belgium); Avdeev, Maxim [Bragg Institute, Australian Nuclear Science and Technology Organisation, Lucas Heights, NSW 2234 (Australia); Cadogan, J.M. [School of Physical, Environmental and Mathematical Sciences, UNSW Canberra at the Australian Defence Force Academy, Canberra BC 2610 (Australia)

2016-10-15

A polycrystalline sample of perovskite-like Sr{sub 3}Fe{sub 2}TeO{sub 9} has been prepared in a solid-state reaction and studied by a combination of electron microscopy, Mössbauer spectroscopy, magnetometry, X-ray diffraction and neutron diffraction. The majority of the reaction product is shown to be a trigonal phase with a 2:1 ordered arrangement of Fe{sup 3+} and Te{sup 6+} cations. However, the sample is prone to nano-twinning and tetragonal domains with a different pattern of cation ordering exist within many crystallites. Antiferromagnetic ordering exists in the trigonal phase at 300 K and Sr{sub 3}Fe{sub 2}TeO{sub 9} is thus the first example of a perovskite with 2:1 trigonal cation ordering to show long-range magnetic order. At 300 K the antiferromagnetic phase coexists with two paramagnetic phases which show spin-glass behaviour below ~80 K. - Graphical abstract: Sr{sub 3}Fe{sub 2}TeO{sub 9} has a 2:1 ordered arrangement of Fe{sup 3+} and Te{sup 6+} cations over the octahedral sites of a perovskite structure and is antiferromagnetic at room temperature. - Highlights: • 2:1 Cation ordering in a trigonal perovskite. • Magnetically ordered trigonal perovskite. • Intergrowth of nanodomains in perovskite microstructure.

Thermoelectric properties of In{sub 0.2}Co{sub 4}Sb{sub 12} skutterudites with embedded PbTe or ZnO nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Chubilleau, C.; Lenoir, B.; Candolfi, C.; Masschelein, P. [Université de Lorraine, CNRS, UMR 7198, Institut Jean Lamour, Parc de Saurupt, 54011 Nancy (France); Dauscher, A., E-mail: anne.dauscher@univ-lorraine.fr [Université de Lorraine, CNRS, UMR 7198, Institut Jean Lamour, Parc de Saurupt, 54011 Nancy (France); Guilmeau, E. [Laboratoire CRISMAT, UMR 6508, 6 boulevard Maréchal Juin, 14050 Caen Cedex (France); Godart, C. [ICMPE-CMTR, CNRS-UMR 7182, 2-8 rue H. Dunant, 94320 Thiais (France)

2014-03-15

Highlights: • Fabrication of nanostructured skutterudites ZnO or PbTe/In{sub 0.2}Co{sub 4}Sb{sub 12.} • Thermal conductivity modeling accounts for experimental results. • Greater lattice thermal conductivity decrease in In{sub 0.2}Co{sub 4}Sb{sub 12} than in CoSb{sub 3}. • A max ZT of 1.05 is obtained at 700 K in a 2 wt% ZnO-containing sample. -- Abstract: Transport properties of the skutterudite compound In{sub 0.2}Co{sub 4}Sb{sub 12} containing ZnO or PbTe nano-sized particles (2–12 wt%) were investigated by means of electrical resistivity, thermopower and thermal conductivity between 5 and 800 K. The composite powders were prepared by freeze-drying the nanoparticles with micron-sized In{sub 0.2}Co{sub 4}Sb{sub 12} powders. Densification was achieved by spark plasma sintering. All composites were characterized by X-ray powder diffraction and scanning electron microscopy. All the transport coefficients show similar temperature dependences suggesting little influence of the nature, semiconducting or insulating, of the nanoparticles. Both the electrical and the thermal conductivities decrease with increasing the PbTe or ZnO content. The impact of ZnO and PbTe on the thermal conductivity was modelled based on the Debye model taking into account a relaxation time constant reflecting phonon scattering by spherical nanoparticles. A maximum dimensionless figure of merit ZT of 1.05 at 700 K was achieved in a sample containing 2 wt% ZnO, a value quite similar to that of the reference In{sub 0.2}Co{sub 4}Sb{sub 12} compound.

Obtention, sintering and operational tests of the obtention prototype TeO{sub 2} for the production of {sup 131} I; Obtencion, sinterizado y pruebas operacionales del prototipo de obtencion TeO{sub 2} para la produccion de {sup 131} I

Energy Technology Data Exchange (ETDEWEB)

Alanis M, J [ININ, 52045 Ocoyoacac, Estado de Mexico (Mexico)

1997-12-15

The demand that exists in Mexico of developing production techniques of applicable radiopharmaceuticals in nuclear medicine, it forces to the National Institute of Nuclear Research to develop the obtaining process of {sup 131} I by dry via starting from TeO{sub 2}. The obtaining process of {sup 131} I, it begins with the synthesis of the TeO{sub 2} like matter prevails, starting from the oxidation of Te-elementary one, inside HNO{sub 3}. Later on the TeO{sub 2}, passes to the sintering process in ingots form, in that way it is encapsulated in aluminum, to be irradiated under optimal parameters of irradiation in the nuclear reactor. The irradiated TeO{sub 2}, it passes to the stage of distillation of {sup 131} I, in a distillation equipment of {sup 131} I by dry via starting from TeO{sub 2}. The process equipment consists mainly of three parts: a) the system of distillation control, built of steel, aluminum, bronze and brass, among other, b) distillation system, built of glass pyrex and of quartz, in this system is where the chemical and nuclear reactions take place for the obtaining of {sup 131} I and c) electric system, is the one in charge of the electric energy supply for the process oven, ventilation system and vacuum system. The results of experimental tests, check the effectiveness of the production process of {sup 131} I in the ININ in routine form (industrial), however it is indispensable to optimize the physical, chemical and nuclear parameters that intervene in each stage of the process with the purpose to obtaining the maximum yield, purity, quality and radiological control and economic production costs. (Author)

Influence of Si and N additions on structure and phase stability of Ge(2)Sb(2)Te(5) thin films.

Science.gov (United States)

Kölpin, Helmut; Music, Denis; Laptyeva, Galyna; Ghadimi, Reza; Merget, Florian; Richter, Silvia; Mykhaylonka, Ruslàn; Mayer, Joachim; Schneider, Jochen M

2009-10-28

The influence of Si and N in Ge(2)Sb(2)Te(5) (space group [Formula: see text]) on structure and phase stability thereof was studied experimentally by thin film growth and characterization as well as theoretically by ab initio calculations. It was found that Si and N most probably accumulate in the amorphous matrix embedding Ge(2)Sb(2)Te(5) grains. The incorporation of Si and N in these samples causes an increase of the crystallization temperature and the formation of finer grains. N is more efficient in increasing the crystallization temperature and in reducing the grain size than Si which can be understood based on the bonding analysis. The incorporation of both Si and N in Ge(2)Sb(2)Te(5) is energetically unfavourable, leading to finer grains and larger crystallization temperatures. While in the case of Si additions no significant changes in bonding are observed, N additions appear to enable the formation of strong Te-N bonds in the amorphous matrix, which are shown to be almost twice as strong as the strongest bonds in unalloyed Ge(2)Sb(2)Te(5).

Influence of Si and N additions on structure and phase stability of Ge2Sb2Te5 thin films

International Nuclear Information System (INIS)

Koelpin, Helmut; Music, Denis; Mykhaylonka, Ruslan; Schneider, Jochen M; Laptyeva, Galyna; Ghadimi, Reza; Richter, Silvia; Mayer, Joachim; Merget, Florian

2009-01-01

The influence of Si and N in Ge 2 Sb 2 Te 5 (space group Fm3-barm) on structure and phase stability thereof was studied experimentally by thin film growth and characterization as well as theoretically by ab initio calculations. It was found that Si and N most probably accumulate in the amorphous matrix embedding Ge 2 Sb 2 Te 5 grains. The incorporation of Si and N in these samples causes an increase of the crystallization temperature and the formation of finer grains. N is more efficient in increasing the crystallization temperature and in reducing the grain size than Si which can be understood based on the bonding analysis. The incorporation of both Si and N in Ge 2 Sb 2 Te 5 is energetically unfavourable, leading to finer grains and larger crystallization temperatures. While in the case of Si additions no significant changes in bonding are observed, N additions appear to enable the formation of strong Te-N bonds in the amorphous matrix, which are shown to be almost twice as strong as the strongest bonds in unalloyed Ge 2 Sb 2 Te 5 .

Terahertz conductivity measurement of FeSe0.5Te0.5 and Co-doped BaFe2As2 thin films

International Nuclear Information System (INIS)

Nakamura, D.; Akiike, T.; Takahashi, H.; Nabeshima, F.; Imai, Y.; Maeda, A.; Katase, T.; Hiramatsu, H.; Hosono, H.; Komiya, S.; Tsukada, I.

2011-01-01

We investigated the THz conductivity of FeSe 0.5 Te 0.5 and Ba (Fe 2-x Co x )As 2 thin films. We estimated the superconducting gap energy values. We found anomolous conductivity spectrum in the antiferromagnetic phase. The terahertz (THz) conductivity of FeSe 0.5 Te 0.5 ('11'-type) and Co-doped BaFe 2 As 2 ('122'-type) thin films are investigated. For '11'-type, the frequency dependence of the complex conductivity can be understood as that of BCS-type superconductor near the superconducting gap energy, and we estimated the superconducting gap energy to be 0.6 meV. For '122'-type, we estimated the superconducting gap energy to be 2.8 meV, which is considered to be the superconducting gap opened at the electron-type Fermi surface near the M point.

Enriched TeO2 bolometers with active particle discrimination: Towards the CUPID experiment

Directory of Open Access Journals (Sweden)

D.R. Artusa

2017-04-01

Full Text Available We present the performances of two 92% enriched 130TeO2 crystals operated as thermal bolometers in view of a next generation experiment to search for neutrinoless double beta decay of 130Te. The crystals, 435 g each, show an energy resolution, evaluated at the 2615 keV γ-line of 208Tl, of 6.5 and 4.3 keV FWHM. The only observable internal radioactive contamination arises from 238U (15 and 8 μBq/kg, respectively. The internal activity of the most problematic nuclei for neutrinoless double beta decay, 226Ra and 228Th, are both evaluated as <3.1 μBq/kg for one crystal and <2.3 μBq/kg for the second. Thanks to the readout of the weak Cherenkov light emitted by β/γ particles by means of Neganov–Luke bolometric light detectors we were able to perform an event-by-event identification of β/γ events with a 95% acceptance level, while establishing a rejection factor of 98.21% and 99.99% for α particles.

Single crystal growth and structure refinements of CsMxTe2-xO6 (M = Al, Ga, Ge, In) pyrochlores

International Nuclear Information System (INIS)

Siritanon, Theeranun; Sleight, A.W.; Subramanian, M.A.

2011-01-01

Graphical abstract: Single crystals of CsM x Te 2-x O 6 pyrochlores with M = Al, Ga, Ge, and In have been grown and structure refinements indicate deviations from ideal stoichiometry presumably related to mixed valency of tellurium. Highlights: → Single crystals of CsM x Te 2-x O 6 pyrochlores with M = Al, Ga, Ge, and In have been grown. → Structure refinements from single crystal X-ray diffraction data confirm e structure. → Deviations from ideal stoichiometry suggest mixed valency of tellurium and hence conductivity. -- Abstract: Single crystals of CsM x Te 2-x O 6 pyrochlores with M = Al, Ga, Ge, and In have been grown from a TeO 2 flux. Structure refinements from single crystal X-ray diffraction data are reported. These results are used to discuss deviations from ideal stoichiometry that result in electronic conductivity presumably related to mixed valency of tellurium.

Structural aspects of B2O3-substituted (PbO)0.5(SiO2)0.5 glasses

International Nuclear Information System (INIS)

Sudarsan, V.; Kulshreshtha, S.K.; Shrikhande, V.K.; Kothiyal, G.P.

2002-01-01

Lead borosilicate glasses having general formulae (PbO) 0.5-x (SiO 2 ) 0.5 (B 2 O 3 ) x with 0.0≤x≤0.4 and (PbO) 0.5 (SiO 2 ) 0.5-y (B 2 O 3 ) y with 0.0≤y≤0.5 have been prepared by a conventional melt-quench method and characterized by 29 Si, 11 B magic angle spinning (MAS) NMR techniques and infrared spectroscopy, as regards their structural features. From 29 Si NMR results, it has been inferred that with increasing concentration of boron oxide, (PbO) 0.5-x (SiO 2 ) 0.5 (B 2 O 3 )x glasses exhibit a systematic increase in the number of Q 4 structural units of Si at the expense of Q 2 structural units, along with the formation of Si-O-B linkages. On the other hand, for (PbO) 0.5 (SiO 2 ) 0.5-y (B 2 O 3 ) y glasses, there is no direct interaction between SiO 2 and B 2 O 3 in the glass network, as revealed by the 29 Si MAS NMR studies. Boron exists in both trigonal and tetrahedral configurations for these two series of glasses and for the (PbO) 0.5 (SiO 2 ) 0.5-y (B 2 O 3 ) y series of glasses; the relative concentration of these two structural units remains almost constant with increasing B 2 O 3 concentration. In contrast, for (PbO) 0.5-x (SiO 2 ) 0.5 (B 2 O 3 ) x glasses, there is a slight increase in the number of BO 3 structural units above x = 0.2, as there is a competition between SiO 2 and B 2 O 3 for interaction with Pb 2+ , thereby leading to the formation of BO 3 structural units. For both series of glasses, the thermal expansion coefficient is found to decrease with increasing B 2 O 3 concentration, the effect being more pronounced for the (PbO) 0.5-x (SiO 2 ) 0.5 (B 2 O 3 ) x series of glasses due to the increased concentration of Q 4 structural units of silicon and better cross-linking as a result of the formation of Si-O-B-type linkages. (author)

Electric transport properties of the pentatelluride materials HfTe{sub 5} and ZrTe{sub 5}