Growth of BaTiO3-PVDF composite thick films by using aerosol deposition

Science.gov (United States)

Cho, Sung Hwan; Yoon, Young Joon

2016-01-01

Barium titanate (BaTiO3)-polyvinylidene fluoride (PVDF) composite thick films were grown by using aerosol deposition at room temperature with BaTiO3 and PVDF powders. To produce a uniform composition in ceramic and polymer composite films, which show a substantial difference in specific gravity, we used PVDF-coated BaTiO3 powders as the starting materials. An examination of the microstructure confirmed that the BaTiO3 were well distributed in the PVDF matrix in the form of a 0 - 3 compound. The crystallite size in the BaTiO3-PVDF composite thick films was 5 ˜ 50 times higher than that in pure BaTiO3 thick films. PVDF plays a role in suppressing the fragmentation of BaTiO3 powder during the aerosol deposition process and in controlling the relative permittivity.

Syntheses of nanocrystalline BaTiO3 and their optical properties

Science.gov (United States)

Yu, J.; Chu, J.; Zhang, M.

Stoichiometric and titanium-excess nanocrystalline barium titanates were synthesized using a hydrothermal process at various hydrothermal temperatures and with further heat treatment at 500 °C and 900 °C. Owing to the different process conditions, the excess titanium exists in different states and configurations within the nanocrystalline BaTiO3 matrix; this was demonstrated by X-ray diffraction, Raman scattering, and photoluminescence. In these nanocrystalline BaTiO3, the 590, 571, 543 and 694 nm light emission bands were observed; mechanisms leading to such emissions were also discussed.

Niobium-doped strontium titanates as SOFC anodes

DEFF Research Database (Denmark)

Blennow Tullmar, Peter; Kammer Hansen, Kent; Wallenberg, L. Reine

2008-01-01

been synthesized with a recently developed modified glycine-nitrate process. The synthesized powders have been calcined and sintered in air or in 9% H(2) / N(2) between 800 - 1400 degrees C. After calcination the samples were single phase Nb-doped strontium titanate with grain sizes of less than 100 nm...... in diameter on average. The phase purity, defect structure, and microstructure of the materials have been analyzed with SEM, XRD, and TGA. The electrical conductivity of the Nb-doped titanate decreased with increasing temperature and showed a phonon scattering conduction mechanism with sigma > 120 S...... ability of the Nb-doped titanates to be used as a part of a SOFC anode. However, the catalytic activity of the materials was not sufficient and it needs to be improved if titanate based materials are to be realized as constituents in SOFC anodes....

Two steps hydrothermal growth and characterisations of BaTiO3 films composed of nanowires

Science.gov (United States)

Zawawi, Che Zaheerah Najeehah Che Mohd; Salleh, Shahril; Oon Jew, Lee; Tufail Chaudhary, Kashif; Helmi, Mohamad; Safwan Aziz, Muhammad; Haider, Zuhaib; Ali, Jalil

2018-05-01

Barium titanate (BaTiO3) films composed of nanowires have gained considerable research interest due to their lead-free composition and strong energy conversion efficiency. BaTiO3 films can be developed with a simple two steps hydrothermal reactions, which are low cost effective. In this research, BaTiO3 films were fabricated on titanium foil through two steps hydrothermal method namely, the growth of TiO2 and followed by BaTiO3 films. The structural evolutions and the dielectric properties of the films were investigated as well. The structural evolutions of titanium dioxide (TiO2) and BaTiO3 nanowires were characterized using X-ray diffraction and scanning electron microscopy. First step of hydrothermal reaction, TiO2 nanowires were prepared in varied temperatures of 160 °C, 200 °C and 250 °C respectively. Second step of hydrothermal reaction was performed to produce a layer of BaTiO3 films.

Influence of Impurities on the Luminescence of Er3+ Doped BaTiO3 Nanophosphors

Directory of Open Access Journals (Sweden)

G. D. Webler

2014-01-01

Full Text Available The influence of the presence of barium carbonate (BaCO3 phase on the luminescence properties of barium titanate nanocrystals (BaTiO3 powders was investigated. Structural and optical characterizations of erbium (Er3+ doped BaTiO3 synthesized by the sol-emulsion-gel were performed. Using Fourier transform infrared spectroscopy and X-ray powder diffraction, we identified the presence of impurities related to BaCO3 and quantified its fraction. It was observed that the presence of BaCO3 phase, even at low levels, depletes significantly the infrared-to-visible upconverted luminescence efficiency of the produced nanopowders.

Morphology controlled ultrafine BaTiO3 based PVDF-HFP ...

Indian Academy of Sciences (India)

21

... for real applications. Kew Words: Polygonal, Barium Titanate, Hydrothermal, Dielectric and Sensor. 1. 2 ... structure and can be tuned further by substituting various dopants (Sr, Ca and Zr). .... Modified BaTiO3 induces less displacement of Ti and O ions along c- axis and .... sputter coated on both sides with gold. The films ...

Electronic structure of barium strontium titanate by soft-x-ray absorption spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Uehara, Y. [Mitsubishi Electric Co., Hyogo (Japan); Underwood, J.H.; Gullikson, E.M.; Perera, R.C.C. [Ernest Orlando Lawrence Berkeley National Lab., CA (United States)

1997-04-01

Perovskite-type titanates, such as Strontium Titanate (STO), Barium Titanate (BTO), and Lead Titanate (PTO) have been widely studied because they show good electric and optical properties. In recent years, thin films of Barium Strontium Titanate (BST) have been paid much attention as dielectrics of dynamic random access memory (DRAM) capacitors. BST is a better insulator with a higher dielectric constant than STO and can be controlled in a paraelectric phase with an appropriate ratio of Ba/Sr composition, however, few studies have been done on the electronic structure of the material. Studies of the electronic structure of such materials can be beneficial, both for fundamental physics research and for improving technological applications. BTO is a famous ferroelectric material with a tetragonal structure, in which Ti and Ba atoms are slightly displaced from the lattice points. On the other hand, BST keeps a paraelectric phase, which means that the atoms are still at the cubic lattice points. It should be of great interest to see how this difference of the local structure around Ti atoms between BTO and BST effects the electronic structure of these two materials. In this report, the authors present the Ti L{sub 2,3} absorption spectra of STO, BTO, and BST measured with very high accuracy in energy of the absorption features.

Electronic structure of barium strontium titanate by soft-x-ray absorption spectroscopy

International Nuclear Information System (INIS)

Uehara, Y.; Underwood, J.H.; Gullikson, E.M.; Perera, R.C.C.

1997-01-01

Perovskite-type titanates, such as Strontium Titanate (STO), Barium Titanate (BTO), and Lead Titanate (PTO) have been widely studied because they show good electric and optical properties. In recent years, thin films of Barium Strontium Titanate (BST) have been paid much attention as dielectrics of dynamic random access memory (DRAM) capacitors. BST is a better insulator with a higher dielectric constant than STO and can be controlled in a paraelectric phase with an appropriate ratio of Ba/Sr composition, however, few studies have been done on the electronic structure of the material. Studies of the electronic structure of such materials can be beneficial, both for fundamental physics research and for improving technological applications. BTO is a famous ferroelectric material with a tetragonal structure, in which Ti and Ba atoms are slightly displaced from the lattice points. On the other hand, BST keeps a paraelectric phase, which means that the atoms are still at the cubic lattice points. It should be of great interest to see how this difference of the local structure around Ti atoms between BTO and BST effects the electronic structure of these two materials. In this report, the authors present the Ti L 2,3 absorption spectra of STO, BTO, and BST measured with very high accuracy in energy of the absorption features

Improvement of β-phase crystal formation in a BaTiO3-modified PVDF membrane

Science.gov (United States)

Lin, SHEN; Lei, GONG; Shuhua, CHEN; Shiping, ZHAN; Cheng, ZHANG; Tao, SHAO

2018-04-01

In this paper, low temperature plasma is used to modify the surface of barium titanate (BaTiO3) nanoparticles in order to enhance the interfacial compatibility between ferroelectric poly(vinylidene fluoride) (PVDF) and BaTiO3 nanoparticles. The results demonstrate that oxygenic groups are successfully attached to the BaTiO3 surface, and the quantity of the functional groups increases with the treatment voltage. Furthermore, the effect of modified BaTiO3 nanoparticles on the morphology and crystal structure of the PVDF/BaTiO3 membrane is investigated. The results reveal that the dispersion of BaTiO3 nanoparticles in the PVDF matrix was greatly improved due to the modification of the BaTiO3 nanoparticles by air plasma. It is worth noting that the formation of a β-phase in a PVDF/modified BaTiO3 membrane is observably promoted, which results from the strong interaction between PVDF chains and oxygenic groups fixed on the BaTiO3 surface and the better dispersion of BaTiO3 nanoparticles in the PVDF matrix. Besides, the PVDF/modified BaTiO3 membrane at the treatment voltage of 24 kV exhibits a lower water contact angle (≈68.4°) compared with the unmodified one (≈86.7°). Meanwhile, the dielectric constant of PVDF/BaTiO3 nanocomposites increases with the increase of working voltage.

Impregnation of sodium titanate onto DMAPAA-grafted fiber under mild reaction conditions and its strontium removal performance from seawater

International Nuclear Information System (INIS)

Katagiri, Mizuki; Kono, Michitaka; Goto, Shun-ichi; Kawai-Noma, Shigeko; Umeno, Daisuke; Saito, Kyoichi; Fujiwara, Kunio; Sugo, Takanobu

2015-01-01

Sodium titanate was impregnated onto a commercially available 6-nylon fiber by means of radiation-induced graft polymerization of dimethyaminopropyl acrylamide (DMAPAA) and subsequent chemical modifications. A peroxo complex of titanium anions was bound onto the DMAPAA-grafted fiber before the bound titanium species was converted to sodium titanate through precipitation with sodium hydroxide. Impregnation percentage of sodium titanate of the fiber was constant at 20% in the range of sodium hydroxide concentration in a mixture of methanol and water at a volume fraction of methanol of 80% of 0.001 to 1 M, whereas the removal percentage of strontium from seawater leveled off at 80% above a sodium hydroxide concentration in water of 0.1 M. Determination of adsorption isotherms in seawater demonstrates that the sodium-titanate-impregnated fiber with an impregnation percentage of 10% exhibited 2.6-fold higher amount of strontium adsorbed in seawater per g of sodium titanate (8.8 mg-Sr/g) than a commercially available granular adsorbent for strontium, SrTreat ® (3.4 mg-Sr/g). (author)

Synthesis and characterization of nickel oxide doped barium strontium titanate ceramics

Energy Technology Data Exchange (ETDEWEB)

Banerjee, M. [Dept. of Electrical Engineering, Bengal Institute of Technology Kolkata (India); Mukherjee, S. [Dept. of Metallurgical Engineering, Jadavpur University, Kolkata (India); Maitra, S. [Govt. College of Engg. and Ceramic Technology, Kolkata (India)

2012-01-15

Barium strontium titanate (BST) ceramics (Ba{sub 0.6}Sr{sub 0.4})TiO{sub 3} were synthesized by solid state sintering using barium carbonate, strontium carbonate and rutile as the precursor materials. The samples were doped with nickel oxide in different proportions. Different phases present in the sintered samples were determined from X-ray diffraction investigation and the distribution of different phases in the microstructure was assessed from scanning electron microscopy study. It was observed that the dielectric properties of BST were modified significantly with nickel oxide doping. These ceramics held promise for applications in tuned circuits. (author)

Textured strontium titanate layers on platinum by atomic layer deposition

International Nuclear Information System (INIS)

Blomberg, T.; Anttila, J.; Haukka, S.; Tuominen, M.; Lukosius, M.; Wenger, Ch.; Saukkonen, T.

2012-01-01

Formation of textured strontium titanate (STO) layers with large lateral grain size (0.2–1 μm) and low X-ray reflectivity roughness (∼ 1.36 nm) on Pt electrodes by industry proven atomic layer deposition (ALD) method is demonstrated. Sr(t-Bu 3 Cp) 2 , Ti(OMe) 4 and O 3 precursors at 250 °C were used to deposit Sr rich STO on Pt/Ti/SiO 2 /Si ∅200 mm substrates. After crystallization post deposition annealing at 600 °C in air, most of the STO grains showed a preferential orientation of the {001} plane parallel to the substrate surface, although other orientations were also present. Cross sectional and plan view transmission electron microscopy and electron diffraction analysis revealed more than an order of magnitude larger lateral grain sizes for the STO compared to the underlying multicrystalline {111} oriented platinum electrode. The combination of platinum bottom electrodes with ALD STO(O 3 ) shows a promising path towards the formation of single oriented STO film. - Highlights: ► Amorphous strontium titanate (STO) on platinum formed a textured film after annealing. ► Single crystal domains in 60 nm STO film were 0.2–1 μm wide. ► Most STO grains were {001} oriented.

Thickness dependent charge transport in ferroelectric BaTiO3 heterojunctions

Science.gov (United States)

Singh, Pooja; Rout, P. K.; Singh, Manju; Rakshit, R. K.; Dogra, Anjana

2015-09-01

We have investigated the effect of ferroelectric barium titanate (BaTiO3) film thickness on the charge transport mechanism in pulsed laser deposited epitaxial metal-ferroelectric semiconductor junctions. The current (I)-voltage (V) measurements across the junctions comprising of 20-500 nm thick BaTiO3 and conducting bottom electrode (Nb: SrTiO3 substrate or La2/3Ca1/3MnO3 buffer layer) demonstrate the space charge limited conduction. Further analysis indicates a reduction in the ratio of free to trapped carriers with increasing thickness in spite of decreasing trap density. Such behaviour arises the deepening of the shallow trap levels (I-V curves implies a bipolar resistive switching behaviour, which can be explained in terms of charge trapping and de-trapping process.

Simulation of iron impurity in BaTiO3 crystals

International Nuclear Information System (INIS)

Stashans, Arvids; Castillo, Darwin

2009-01-01

Iron-doped barium titanate (BaTiO 3 ) has been simulated taking into account cubic and tetragonal crystallographic lattices of the crystal. A quantum-chemical method based on the Hartree-Fock formalism has been used throughout the study. The calculated equilibrium structures of Fe-doped crystals reveal the defect-inward displacements of the Ti and O atoms whereas the shifts for the Ba atoms are encountered to be away with respect to the Fe impurity. According to the analysis of electron density population and electron band structure it is found that some unusual chemical bonding might take place between the Fe atom and its six adjacent O atoms. The role of Fe impurity in the ferroelectric polarization of the tetragonal BaTiO 3 crystal has been discussed too.

Solution based approaches for the morphology control of BaTiO3 particulates

Directory of Open Access Journals (Sweden)

Florentina Maxim

2010-09-01

Full Text Available Within the action COST 539 - ELENA our contribution was aimed at studying solution based approaches for the morphology control of BaTiO3 particulates. Initially, our kinetic analysis and systematic structural and morphological studies, demonstrated that during hydrothermal synthesis from layered titanate nanotubes (TiNTS, BaTiO3 forms via two mechanisms depending on the temperature and time. At low temperatures (90°C, “wild” type BaTiO3 dendritic particles with cubic structure were formed through a phase boundary topotactic reaction. At higher temperatures and/or for longer times time, the reaction is controlled by a dissolution precipitation mechanism and “seaweed” type BaTiO3 dendrites are formed. Our results unambiguously elucidated why TiNTs do not routinely act as templates for the formation of 1D BaTiO3.In our subsequent investigations, the effect of additives on the aqueous and hydrothermal synthesis of BaTiO3 was assessed. We reported that although the tested additives influenced the growth of BaTiO3, their behaviour varied; poly(acrylic acid (PAA adsorbed on specific crystallographic faces changing the growth kinetics and inducing the oriented attachment of the particles; poly(vinyl pyrrolidone (PVP, sodium dodecylsulfate (SDS and hydroxypropylmethylcellulose (HPMC act as growth inhibitors rather than crystal habit modifiers; and DFructose appeared to increase the activation energy for nucleation, resulting in small crystals (26 nm. Our work clearly indicates that the synthesis of 1D nanostructures of complex oxides by chemical methods is non trivial.

THE APPLICATION OF STEREOLOGY METHOD FOR ESTIMATING THE NUMBER OF 3D BaTiO3 – CERAMIC GRAINS CONTACT SURFACES

Directory of Open Access Journals (Sweden)

Vojislav V Mitić

2011-05-01

Full Text Available Methods of stereological study are of great importance for structural research of electronic ceramic materials including BaTiO3-ceramic materials. The broad application of ceramics, based on barium-titanate, in advanced electronics nowadays demands a constant research of its structure, that through the correlation structureproperties, a fundamental in the basic materials properties prognosis triad (technology-structure-properties, leads to further prognosis and properties design of these ceramics. Microstructure properties of BaTiO3- ceramic material, expressed in grains' boundary contact, are of basic importance for electric properties of this material, particularly the capacity. In this paper, a significant step towards establishing control under capacitive properties of BaTiO3-ceramics is being done by estimating the number of grains contact surfaces. Defining an efficient stereology method for estimating the number of BaTiO3-ceramic grains contact surfaces, we have started from a mathematical model of mutual grains distribution in the prescribed volume of BaTiO3-ceramic sample. Since the real microstructure morphology of BaTiO3-ceramics is in some way disordered, spherical shaped grains, using computer-modelling methods, are approximated by polyhedra with a great number of small convex polygons. By dividing the volume of BaTiO3-ceramic sample with the definite number of parallel planes, according to a given pace, into the intersection plane a certain number of grains contact surfaces are identified. According to quantitative estimation of 2D stereological parameters the modelled 3D internal microstructure is obtained. Experiments were made by using the scanning electronic microscopy (SEM method with the ceramic samples prepared under pressing pressures up to 150 MPa and sintering temperature up to 1370°C while the obtained microphotographs were used as a base of confirming the validity of presented stereology method. This paper, by applying

Hydrothermal growth of highly textured BaTiO3 films composed of nanowires

International Nuclear Information System (INIS)

Zhou Zhi; Tang Haixiong; Sodano, Henry A; Lin Yirong

2013-01-01

Textured barium titanate (BaTiO 3 ) films are attracting immense research interest due to their lead-free composition and excellent piezoelectric and dielectric properties. Most synthesis methods for these films require a high temperature, leading to the formation of a secondary phase and an overall decrease in the electrical properties of the ceramic. In order to alleviate these issues, a novel fabrication method is introduced by transferring oriented rutile TiO 2 nanowires to a textured BaTiO 3 film at temperatures below 160 °C. The microstructure and thickness of the fabricated BaTiO 3 films were characterized by scanning electron microscopy, and the crystal structure and degree of orientation were evaluated by x-ray diffraction patterns using the Lotgering method. It is shown that the thickness of the BaTiO 3 film can be controlled by the length of TiO 2 nanowire array template, and the degree of orientation of the textured BaTiO 3 films is highly dependent on the film thickness; the crystallographic orientation has been measured to reach up to 87%. The relative dielectric constant (ε r = 1300) and ferroelectric properties (P r = 2.7 μC cm −2 , E c = 4.0 kV mm −1 ) of the textured BaTiO 3 films were also characterized to demonstrate their potential application in sensors, random access memory, and micro-electromechanical systems. (paper)

Microstructure and dielectric parameters of epitaxial SrRuO3/BaTiO3/SrRuO3 heterostructures

Science.gov (United States)

Boikov, Yu. A.; Claeson, T.

2001-05-01

Epitaxial films of ferroelectric barium titanate are desirable in a number of applications but their properties are inferior to those of bulk material. Relations between microstructure and dielectric properties may give better understanding of limitations. Trilayer heterostructures SrRuO3/BaTiO3/SrRuO3 were grown by laser ablation on (100)LaAlO3 and (100)MgO substrates. The BaTiO3 layer was granular in structure. When grown on (100)SrRuO3/(100)LaAlO3, it was preferentially a-axis oriented due to tensile mechanical stress. Using (100)MgO as a substrate, on the other hand, produced a mixture of about equal value of a-axis and c-axis oriented grains of BaTiO3. The dielectric permittivity, ɛ, of the BaTiO3 layer was almost twice as large, at T>200 K and f=100 kHz, for the LaAlO3 substrate as compared to the MgO one. Its maximum value (ɛ/ɛ0≈6200) depended on temperature of growth, grain size, and electric field and compares well with optimal values commonly used for ceramic material. The maximum in the ɛ(T) shifted from about 370 to 320 K when the grain size in the BaTiO3 film decreased from 100 to 40 nm. At T300 K, hysteresis loops in polarization versus electric field were roughly symmetric. The BaTiO3 films grown on (100)SrRuO3/(100)MgO exhibit the largest remnant polarizations and coercive fields in the temperature range 100-380 K.

Magnetostriction in composites of LiFe5O8-BaTiO3

International Nuclear Information System (INIS)

Sarah, P.; Suryanarayana, S.V.

2003-01-01

Polycrystalline lithium ferrite, LiFe 5 O 8 was prepared by adopting two preparation techniques, the solid-state double sintering method and the sol-gel method. This ferrite powder was thoroughly mixed with barium titanate, BaTiO 3 for preparation of di-phasic composites of lithium ferrite and barium titanate. X-ray diffraction study of these composites revealed the presence of both the phases. Magnetostriction of these composites was measured in varying magnetic fields. The value of magnetostriction for the composites prepared by the sol-gel method was found to be higher than the values obtained in case of composites prepared by the solid-state method. Magnetostriction was found to decrease with increasing content of barium titanate. The saturation field was found to increase with the introduction of barium titanate

Textured strontium titanate layers on platinum by atomic layer deposition

Energy Technology Data Exchange (ETDEWEB)

Blomberg, T., E-mail: tom.blomberg@asm.com [ASM Microchemistry Ltd., Vaeinoe Auerin katu 12 A, 00560 Helsinki (Finland); Anttila, J.; Haukka, S.; Tuominen, M. [ASM Microchemistry Ltd., Vaeinoe Auerin katu 12 A, 00560 Helsinki (Finland); Lukosius, M.; Wenger, Ch. [IHP, Im Technologiepark 25, 15236 Frankfurt (Oder) (Germany); Saukkonen, T. [Aalto University, Puumiehenkuja 3, 02150 Espoo (Finland)

2012-08-31

Formation of textured strontium titanate (STO) layers with large lateral grain size (0.2-1 {mu}m) and low X-ray reflectivity roughness ({approx} 1.36 nm) on Pt electrodes by industry proven atomic layer deposition (ALD) method is demonstrated. Sr(t-Bu{sub 3}Cp){sub 2}, Ti(OMe){sub 4} and O{sub 3} precursors at 250 Degree-Sign C were used to deposit Sr rich STO on Pt/Ti/SiO{sub 2}/Si Empty-Set 200 mm substrates. After crystallization post deposition annealing at 600 Degree-Sign C in air, most of the STO grains showed a preferential orientation of the {l_brace}001{r_brace} plane parallel to the substrate surface, although other orientations were also present. Cross sectional and plan view transmission electron microscopy and electron diffraction analysis revealed more than an order of magnitude larger lateral grain sizes for the STO compared to the underlying multicrystalline {l_brace}111{r_brace} oriented platinum electrode. The combination of platinum bottom electrodes with ALD STO(O{sub 3}) shows a promising path towards the formation of single oriented STO film. - Highlights: Black-Right-Pointing-Pointer Amorphous strontium titanate (STO) on platinum formed a textured film after annealing. Black-Right-Pointing-Pointer Single crystal domains in 60 nm STO film were 0.2-1 {mu}m wide. Black-Right-Pointing-Pointer Most STO grains were {l_brace}001{r_brace} oriented.

Mechanical and Microstructural Evaluation of Barium Strontium Titanate Thin Films for Improved Antenna Performance and Reliability

National Research Council Canada - National Science Library

Hubbard, C

1999-01-01

Ferroelectric barium strontium titanate (Ba(1-x)SrxTiO3 BSTO) films of 1-micron nominal thickness were deposited on single crystals of sapphire and electroded substrates at substrate temperatures varying from 30 deg C to 700 deg C...

Combining x-ray diffraction contrast tomography and mesoscale grain growth simulations in strontium titanate: An integrated approach for the investigation of microstructure evolution

DEFF Research Database (Denmark)

Syha, Melanie; Baürer, Michael; Rheinheimer, Wolfgang

2013-01-01

Motivated by the recently reported a growth anomaly in strontium titatate bulk samples1, the microstructure of bulk strontium titanate has been investigated by an integrated approach comprising conventional metallography, three dimensional X-ray diffraction contrast tomography (DCT)2, and the obs......Motivated by the recently reported a growth anomaly in strontium titatate bulk samples1, the microstructure of bulk strontium titanate has been investigated by an integrated approach comprising conventional metallography, three dimensional X-ray diffraction contrast tomography (DCT)2......, and the observation of pore shapes in combination with mesoscale grain growth simulations. The microstructural evolution in strontium titanate has been characterized alternating ex-situ annealing and high energy X-ray DCT measurements, resulting in three dimensional microstructure reconstructions which...

Effects of Reaction Medium on the Phase Synthesis and Particle Size Evolution of BaTiO3

NARCIS (Netherlands)

Stawski, Thomasz M.; Veldhuis, Sjoerd A.; Göbel, Ole; ten Elshof, Johan E.; Blank, David H.A.

2010-01-01

The low-temperature alkoxide–hydroxide precipitation synthesis of nanosized crystalline barium titanate (BaTiO3) in nonaqueous media is presented. In this report, we show the influence of the reaction medium on the nature of the product by investigating the reaction of titanium (IV) isopropoxide

Factors influencing formation of highly dispersed BaTiO3 nanospheres with uniform sizes in static hydrothermal synthesis

International Nuclear Information System (INIS)

Gao, Jiabing; Shi, Haiyue; Dong, Huina; Zhang, Rui; Chen, Deliang

2015-01-01

Highly dispersed BaTiO 3 nanospheres with uniform sizes have important applications in micro/nanoscale functional devices. To achieve well-dispersed spherical BaTiO 3 nanocrystals, we carried out as reported in this paper the systematic investigation on the factors that influence the formation of BaTiO 3 nanospheres by the static hydrothermal process, including the NaOH concentrations [NaOH], molar Ba/Ti ratios (R Ba/Ti ), hydrothermal temperatures, and durations, with an emphasis on understanding the related mechanisms. Barium nitrate and TiO 2 sols derived from tetrabutyl titanate were used as the starting materials. The as-synthesized BaTiO 3 samples were characterized by X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray analysis, thermogravimetry, differential thermal analysis, and FT-IR spectra. The highly dispersed BaTiO 3 nanospheres (76 ± 13 nm) were achieved under the optimum hydrothermal conditions at 200 °C for 10 h: [NaOH] = 2.0 mol L −1 and R Ba/Ti  = 1.5. Higher NaOH concentrations, higher Ba/Ti ratios, higher hydrothermal temperatures, and longer hydrothermal durations are favorable in forming BaTiO 3 nanospheres with larger fractions of tetragonal phase and higher yields; but too long hydrothermal durations resulted in abnormal growth and reduced the uniformity in particle sizes. The possible formation mechanisms for BaTiO 3 nanocrystals under the static hydrothermal conditions were investigated

Dielectric characterization of low-loss calcium strontium titanate fibers produced by laser floating zone technique for wireless communication

International Nuclear Information System (INIS)

Amaral, F.; Valente, M.A.; Costa, L.C.; Costa, F.M.

2014-01-01

Wireless communication technology assisted to a huge development during the last two decades, responding to the growing demand for small size and low weight devices such as cell phones and global positioning systems. The need for miniaturization and higher autonomy resulted in the development of new dielectric oxide ceramics with very specific properties, to be applied as dielectric resonators in filters, oscillators, and antennas. Some crucial properties as a high quality factor, high dielectric constant, and near zero temperature coefficient of resonant frequency must be considered during the selection of the appropriate materials. The present work deals with the preparation of calcium titanate (CaTiO 3 ), strontium titanate (SrTiO 3 ), and calcium strontium titanate (Ca x Sr 1-x TiO 3 ) fibers produced by laser floating zone (LFZ) technique. Our results show that fibers grown at lower pulling rates exhibit higher ε', for all the studied frequency range, including the microwave region. Moreover, the quality factor is always high envisaging the possibility to include these materials in future wireless device applications. (copyright 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Dielectric characterization of low-loss calcium strontium titanate fibers produced by laser floating zone technique for wireless communication

Energy Technology Data Exchange (ETDEWEB)

Amaral, F. [Department of Physics and I3N, University of Aveiro, 3810-193, Aveiro (Portugal); Polytechnic Institute of Coimbra, 3000-271, Coimbra (Portugal); Valente, M.A.; Costa, L.C.; Costa, F.M. [Department of Physics and I3N, University of Aveiro, 3810-193, Aveiro (Portugal)

2014-09-15

Wireless communication technology assisted to a huge development during the last two decades, responding to the growing demand for small size and low weight devices such as cell phones and global positioning systems. The need for miniaturization and higher autonomy resulted in the development of new dielectric oxide ceramics with very specific properties, to be applied as dielectric resonators in filters, oscillators, and antennas. Some crucial properties as a high quality factor, high dielectric constant, and near zero temperature coefficient of resonant frequency must be considered during the selection of the appropriate materials. The present work deals with the preparation of calcium titanate (CaTiO{sub 3}), strontium titanate (SrTiO{sub 3}), and calcium strontium titanate (Ca{sub x}Sr{sub 1-x}TiO{sub 3}) fibers produced by laser floating zone (LFZ) technique. Our results show that fibers grown at lower pulling rates exhibit higher ε', for all the studied frequency range, including the microwave region. Moreover, the quality factor is always high envisaging the possibility to include these materials in future wireless device applications. (copyright 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Effects of focused ion beam milling on electron backscatter diffraction patterns in strontium titanate and stabilized zirconia

DEFF Research Database (Denmark)

Saowadee, Nath; Agersted, Karsten; Bowen, Jacob R.

2012-01-01

This study investigates the effect of focused ion beam (FIB) current and accelerating voltage on electron backscatter diffraction pattern quality of yttria‐stabilized zirconia (YSZ) and Nb‐doped strontium titanate (STN) to optimize data quality and acquisition time for 3D‐EBSD experiments by FIB...

Barium strontium titanate powders prepared by spray pyrolysis

International Nuclear Information System (INIS)

Brankovic, G.; Brankovic, Z.; Goes, M.S.; Paiva-Santos, C.O.; Cilense, M.; Varela, J.A.; Longo, E.

2005-01-01

Ultasonic spray pyrolysis (SP) has been investigated for the production of the barium strontium titanate (BST) powders from the polymeric precursors. The processing parameters, such as flux of aerosol and temperature profile inside the furnace, were optimized to obtain single phase BST. The powders were characterized by the methods of X-ray diffraction analysis, SEM, EDS and TEM. The obtained powders were submicronic, consisting of spherical, polycrystalline particles, with internal nanocrystalline structure. Crystallite size of 10 nm, calculated using Rietveld refinement, is in a good agreement with results of HRTEM

Effect of the synthesis temperature of sodium nona-titanate on batch kinetics of strontium-ion adsorption from aqueous solution

International Nuclear Information System (INIS)

Merceille, A.; Weinzaepfel, E.; Grandjean, A.; Merceille, A.; Weinzaepfel, E.; Barre, Y.

2011-01-01

Sodium titanate materials are promising inorganic ion exchangers for the adsorption of strontium from aqueous solutions. Sodium nona-titanate exhibits a layered structure consisting of titanate layers and exchangeable sodium ions between the layers. The materials used in this study include samples synthesized by a hydrothermal method at temperatures between 60 degrees C and 200 degrees C. Their structure, composition, and morphology were investigated with X-Ray diffraction measurements; thermogravimetric, compositional and surface area analyses, and scanning electron microscopy. The structure, composition, and morphology depended on the synthesis temperature. Batch kinetics experiments for the removal of strontium from aqueous solutions were performed, and the data were fitted by a pseudo-second-order reaction model and a diffusive model. The strontium extraction capacity also depended on the synthesis temperature and exhibited a maximum for samples synthesized at 100 degrees C. The sorption process occurs in one or two diffusion-controlled steps that also depend on the synthesis temperature. These diffusion-limited steps are the boundary-layer diffusion and intra-particle diffusion in the case of pure nona-titanate synthesized at temperatures lower than 170 degrees C, and only intra-particle diffusion in the case of nona-titanate synthesized at 200 degrees C. (authors)

Assessment of full ceramic solid oxide fuel cells based on modified strontium titanates

DEFF Research Database (Denmark)

Holtappels, Peter; Ramos, Tania; Sudireddy, Bhaskar Reddy

2014-01-01

stimulated the development for full ceramic anodes based on strontium titanates. Furthermore, the Ni-cermet is primarily a hydrogen oxidation electrode and efficiency losses might occur when operating on carbon containing fuels. In the European project SCOTAS-SOFC full ceramic cells comprising CGO...

Anion and cation diffusion in barium titanate and strontium titanate; Anionen- und Kationendiffusion in Barium- und Strontiumtitanat

Energy Technology Data Exchange (ETDEWEB)

Kessel, Markus Franz

2012-12-19

Perovskite oxides show various interesting properties providing several technical applications. In many cases the defect chemistry is the key to understand and influence the material's properties. In this work the defect chemistry of barium titanate and strontium titanate is analysed by anion and cation diffusion experiments and subsequent time-of-flight secondary ion mass spectrometry (ToF-SIMS). The reoxidation equation for barium titanate used in multi-layer ceramic capacitors (MLCCs) is found out by a combination of different isotope exchange experiments and the analysis of the resulting tracer diffusion profiles. It is shown that the incorporation of oxygen from water vapour is faster by orders of magnitude than from molecular oxygen. Chemical analysis shows the samples contain various dopants leading to a complex defect chemistry. Dysprosium is the most important dopant, acting partially as a donor and partially as an acceptor in this effectively acceptor-doped material. TEM and EELS analysis show the inhomogeneous distribution of Dy in a core-shell microstructure. The oxygen partial pressure and temperature dependence of the oxygen tracer diffusion coefficients is analysed and explained by the complex defect chemistry of Dy-doped barium titanate. Additional fast diffusion profiles are attributed to fast diffusion along grain boundaries. In addition to the barium titanate ceramics from an important technical application, oxygen diffusion in cubic, nominally undoped BaTiO{sub 3} single crystals has been studied by means of {sup 18}O{sub 2}/{sup 16}O{sub 2} isotope exchange annealing and subsequent determination of the isotope profiles in the solid by ToF-SIMS. It is shown that a correct description of the diffusion profiles requires the analysis of the diffusion through the surface space-charge into the material's bulk. Surface exchange coefficients, space-charge potentials and bulk diffusion coefficients are analysed as a function of oxygen partial

Barium Titanate Nanoparticles for Biomarker Applications

International Nuclear Information System (INIS)

Matar, O; Hondow, N S; Brydson, R M D; Milne, S J; Brown, A P; Posada, O M; Wälti, C; Saunders, M; Murray, C A

2015-01-01

A tetragonal crystal structure is required for barium titanate nanoparticles to exhibit the nonlinear optical effect of second harmonic light generation (SHG) for use as a biomarker when illuminated by a near-infrared source. Here we use synchrotron XRD to elucidate the tetragonal phase of commercially purchased tetragonal, cubic and hydrothermally prepared barium titanate (BaTiO 3 ) nanoparticles by peak fitting with reference patterns. The local phase of individual nanoparticles is determined by STEM electron energy loss spectroscopy (EELS), measuring the core-loss O K-edge and the Ti L 3 -edge energy separation of the t 2g , e g peaks. The results show a change in energy separation between the t 2g and e g peak from the surface and core of the particles, suggesting an intraparticle phase mixture of the barium titanate nanoparticles. HAADF-STEM and bright field TEM-EDX show cellular uptake of the hydrothermally prepared BaTiO 3 nanoparticles, highlighting the potential for application as biomarkers. (paper)

Review on dielectric properties of rare earth doped barium titanate

International Nuclear Information System (INIS)

Ismail, Fatin Adila; Osman, Rozana Aina Maulat; Idris, Mohd Sobri

2016-01-01

Rare earth doped Barium Titanate (BaTiO_3) were studied due to high permittivity, excellent electrical properties and have wide usage in various applications. This paper reviewed on the electrical properties of RE doped BaTiO_3 (RE: Lanthanum (La), Erbium (Er), Samarium (Sm), Neodymium (Nd), Cerium (Ce)), processing method, phase transition occurred and solid solution range for complete study. Most of the RE doped BaTiO_3 downshifted the Curie temperature (T_C). Transition temperature also known as Curie temperature, T_C where the ceramics had a transition from ferroelectric to a paraelectric phase. In this review, the dielectric constant of La-doped BaTiO_3, Er-doped BaTiO_3, Sm-doped BaTiO_3, Nd-doped BaTiO_3 and Ce-doped BaTiO_3 had been proved to increase and the transition temperature or also known as T_C also lowered down to room temperature as for all the RE doped BaTiO_3 except for Er-doped BaTiO_3.

A novel solvothermal route for obtaining strontium titanate nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Marquez-Herrera, A., E-mail: alfredo.marquez@uaslp.mx [Universidad Autonoma de San Luis Potosi, Departamento de Ingenieria Mecanica Administrativa, Coordinacion Academica Region Altiplano (COARA) (Mexico); Ovando-Medina, Victor M.; Corona-Rivera, Miguel A. [Universidad Autonoma de San Luis Potosi, Departamento de Ingenieria Quimica, Coordinacion Academica Region Altiplano (COARA) (Mexico); Hernandez-Rodriguez, E.; Zapata-Torres, M. [Centro de Investigacion en Ciencia Aplicada y Tecnologia Avanzada, Unidad Legaria IPN (Mexico); Campos-Gonzalez, E.; Guillen-Cervantes, A.; Zelaya-Angel, O.; Melendez-Lira, M. [CINVESTAV-IPN, Departamento de Fisica (Mexico)

2013-04-15

Strontium titanate (SrTiO{sub 3}) has attracted a lot of attention because of its possible applications in new microelectronic devices. It is a material with a high dielectric constant, low leakage current, and some of its properties can be changed by adding or modifying the concentration of a dopant, which can be used for a wide range of functional purposes, from simple capacitors to complicated microwave devices. Therefore, in this work, we report the development of a new route to synthesize SrTiO{sub 3} nanoparticles based on the solvothermal method by employing two precursor solutions: strontium chloride and titanium(IV) butoxide. Our route allows the production of cubic SrTiO{sub 3} nanoparticles with a narrow size distribution. The particle sizes range between 8 and 24 nm, forming agglomerates of SrTiO{sub 3} in the range of 128-229 nm. It was demonstrated that the Ti/Sr molar ratio employed into the precursor solution has an important effect onto the chemical composition of the resulting SrTiO{sub 3} nanoparticles: when using Ti/Sr < 1, the formation and incorporation of the SrCO{sub 3} compound into the nanoparticles was observed while with Ti/Sr {>=} 1 nanoparticles are free of contaminants. The as-prepared nanoparticles were characterized by energy-dispersive X-ray spectroscopy, X-ray diffraction, transmission electron microscopy, high-resolution TEM, selected area electron diffraction, scanning electron microscopy, and dynamic light scattering.

Thermal Transport and Phonon Hydrodynamics in Strontium Titanate

Science.gov (United States)

Martelli, Valentina; Jiménez, Julio Larrea; Continentino, Mucio; Baggio-Saitovitch, Elisa; Behnia, Kamran

2018-03-01

We present a study of thermal conductivity, κ , in undoped and doped strontium titanate in a wide temperature range (2-400 K) and detecting different regimes of heat flow. In undoped SrTiO3 , κ evolves faster than cubic with temperature below its peak and in a narrow temperature window. Such behavior, previously observed in a handful of solids, has been attributed to a Poiseuille flow of phonons, expected to arise when momentum-conserving scattering events outweigh momentum-degrading ones. The effect disappears in the presence of dopants. In SrTi1 -xNbx O3 , a significant reduction in lattice thermal conductivity starts below the temperature at which the average inter-dopant distance and the thermal wavelength of acoustic phonons become comparable. In the high-temperature regime, thermal diffusivity becomes proportional to the inverse of temperature, with a prefactor set by sound velocity and Planckian time (τp=(ℏ/kBT ) ).

Effects of Nb and Sr doping on crystal structure of epitaxial BaTiO3 thin films on MgO substrates

International Nuclear Information System (INIS)

Kim, Yongsam; Chen, Chunhua; Saiki, Atsushi; Wakiya, Naoki; Shinozaki, Kazuo; Mizutani, Nobuyasu

2002-01-01

Niobium (Nb) and strontium (Sr) doped barium titanate (BT) films were deposited by radio frequency (RF) magnetron sputtering with Nb and Sr doped BT ceramic targets, respectively. The effect of Nb and Sr doping on the crystal structure of epitaxial BaTiO 3 thin films on MgO substrates was investigated. The crystal structure of the films was examined using the reciprocal space mapping measurement. All the films exhibit a cube-on-cube relation with respect to the substrates. As the amount of doped Sr increased, both of the in-plane and out-of-plane lattice constants of Sr doped BT films slowly approached the BT bulk values. On the other hand, the lattice constants of Nb doped BT films were rapidly coming close to the bulk values. These indicated that the lattices of doped BT films were relaxed as the amount of doped elements increased. In addition, Nb doping had greater influence on the relaxation of the films than Sr doping for the same content of dopant. (author)

Observation of potential barriers on barium strontium titanate PTCR ceramics by electrostatic force microscopy

International Nuclear Information System (INIS)

Manfredini, J.P.; Paulin Filho, P.I.; Gheno, S.M.

2011-01-01

A composition of PTCR ceramic based in barium titanate with isovalent replacement of part of barium by strontium using lanthanum and manganese as additives was investigated. The transition temperature, typical of these materials, was shifted below the room temperature by the presence of strontium, whose behavior was detected by tests of DC resistivity and impedance spectroscopy. The observation of potential barriers at grain boundaries was possible through the technique of electrostatic force microscopy (EFM). The results also showed the presence of space charges in regions inside grains, possibly at subgrain boundaries. (author)

Three-dimensional grain structure of sintered bulk strontium titanate from X-ray diffraction contrast tomography

DEFF Research Database (Denmark)

Syha, M.; Rheinheimer, W.; Bäurer, M.

2012-01-01

The three-dimensional grain boundary network of sintered bulk strontium titanate is reconstructed using X-ray diffraction contrast tomography, a non-destructive technique for determining the grain shape and crystallographic orientation in polycrystals that is ideally suited for detailed studies...

Electrooptic and piezoelectric measurements in photorefractive barium titanate and strontium barium niobate

International Nuclear Information System (INIS)

Ducharme, S.; Feinberg, J.; Neurgaonkar, R.R.

1987-01-01

The authors measured the low-frequency (''unclamped'') electrooptic and piezoelectric coefficients in undoped BaTiO/sub 3/ and Sr/sub x/Ba/sub 1-x/Nb/sub 2/O/sub 6/ (chi - 0.61) crystals using interferometric techniques. The contribution of the piezoelectric effect to the Pockels measurement is discussed. For an applied ac electric field in the range 0.1-200 V/cm, the electrooptic and piezoelectric effects are linear in the magnitude of of the applied field and independent of its frequency in the range of 10 Hz-100 kHz. The unclamped electrooptic coefficients of poled BaTiO/sub 3/ single crystals are r/sub 13/ = 19.5 +- 1 pm/V and r/sub 33/ = 97 +- 7 pm/V, and for strontium barium niobate are r/sub 13/ = 47 +- 5 pm/V and r/sub 33/ = 235 +- 21 pm/V, all measured at a wavelength of 514.5 nm and at T = 23 0 C. For the barium titanate samples the measured Pockels coefficient r/sub c/ identical to r/sub 33/ - (n/sub 1//n/sub 3/)/sup 3/r/sub 13/ = 79 +- 6 pm/V in good agreement with the value r/sub c/ = 76 +- 7 pm/V computed from the above values of r/sub 13/ and r/sub 33/, where n/sub 1/ and n/sub 3/ are the ordinary and extraordinary indexes of refraction, respectively. The measured piezoelectric coefficient is d/sub 23/ = +28.7 +- 2 pm/V for barium titanate, and is d/sub 23/ = +24.6 +- 2 pm/V for strontium barium niobate. They also measured the photoreflective coupling of two optical beams in the crystals, and they show that the dependence of the coupling strength on beam polarization is in fair agreement with the measured values of the Pockels coefficients

Local manifestations of a static magnetoelectric effect in nanostructured BaTiO3-BaFe12O9 composite multiferroics

Science.gov (United States)

Trivedi, Harsh; Shvartsman, Vladimir V.; Lupascu, Doru C.; Medeiros, Marco S. A.; Pullar, Robert C.; Kholkin, Andrei L.; Zelenovskiy, Pavel; Sosnovskikh, Andrey; Shur, Vladimir Ya.

2015-02-01

A study on magnetoelectric phenomena in the barium titanate-barium hexaferrite (BaTiO3-BaFe12O19) composite system, using high resolution techniques including switching spectroscopy piezoresponse force microscopy (SSPFM) and spatially resolved confocal Raman microscopy (CRM), is presented. It is found that both the local piezoelectric coefficient and polarization switching parameters change on the application of an external magnetic field. The latter effect is rationalized by the influence of magnetostrictive stress on the domain dynamics. Processing of the Raman spectral data using principal component analysis (PCA) and self-modelling curve resolution (SMCR) allowed us to achieve high resolution phase distribution maps along with separation of average and localized spectral components. A significant effect of the magnetic field on the Raman spectra of the BaTiO3 phase has been revealed. The observed changes are comparable with the classical pressure dependent studies on BaTiO3, confirming the strain mediated character of the magnetoelectric coupling in the studied composites.

Elastic wave excitation in centrosymmetric strontium titanate crystals

International Nuclear Information System (INIS)

Yushin, N.K.; Sotnikov, A.V.

1980-01-01

The main experimental dependencies are measured and the excitation mechanism of elastic waves in centrosymmetric crystals is established. The surface generation of three-dimensional elastic waves of the 30 MHz frequency in strontium titanate crystals is observed and studied. Elastic wave excitation is observed in the 4 350 K temperature range. The efficiency of hysteresis excitation depends on the external electric field. The effect of light irradiation on the amplitude of excited elastic waves is observed. It is shown that escitation is connected with linearization of electrostriction by the constant electric field appearing in a near-surface crystal layer due to phenomena in the Schottky barrier and appearance of electretic near-electrode layers

Persistent optically induced magnetism in oxygen-deficient strontium titanate.

Science.gov (United States)

Rice, W D; Ambwani, P; Bombeck, M; Thompson, J D; Haugstad, G; Leighton, C; Crooker, S A

2014-05-01

Strontium titanate (SrTiO3) is a foundational material in the emerging field of complex oxide electronics. Although its bulk electronic and optical properties are rich and have been studied for decades, SrTiO3 has recently become a renewed focus of materials research catalysed in part by the discovery of superconductivity and magnetism at interfaces between SrTiO3 and other non-magnetic oxides. Here we illustrate a new aspect to the phenomenology of magnetism in SrTiO3 by reporting the observation of an optically induced and persistent magnetization in slightly oxygen-deficient bulk SrTiO3-δ crystals using magnetic circular dichroism (MCD) spectroscopy and SQUID magnetometry. This zero-field magnetization appears below ~18 K, persists for hours below 10 K, and is tunable by means of the polarization and wavelength of sub-bandgap (400-500 nm) light. These effects occur only in crystals containing oxygen vacancies, revealing a detailed interplay between magnetism, lattice defects, and light in an archetypal complex oxide material.

Full Ceramic Fuel Cells Based on Strontium Titanate Anodes, An Approach Towards More Robust SOFCs

DEFF Research Database (Denmark)

Holtappels, Peter; Irvine, J.T.S.; Iwanschitz, B.

2013-01-01

The persistent problems with Ni-YSZ cermet based SOFCs, with respect to redox stability and tolerance towards sulfur has stimulated the development of a full ceramic cell based on strontium titanate(ST)- based anodes and anode support materials, within the EU FCH JU project SCOTAS-SOFC. Three...

Characterization of individual barium titanate nanorods and their assessment as building blocks of new circuit architectures

International Nuclear Information System (INIS)

Zagar, Kristina; Recnik, Aleksander; Ceh, Miran; Hernandez-Ramirez, Francisco; Morante, Joan Ramon; Prades, Joan Daniel

2011-01-01

In this work, we report on the integration of individual BaTiO 3 nanorods into simple circuit architectures. Polycrystalline BaTiO 3 nanorods were synthesized by electrophoretic deposition (EPD) of barium titanate sol into aluminium oxide (AAO) templates and subsequent annealing. Transmission electron microscopy (TEM) observations revealed the presence of slabs of hexagonal polymorphs intergrown within cubic grains, resulting from the local reducing atmosphere during the thermal treatment. Electrical measurements performed on individual BaTiO 3 nanorods revealed resistivity values between 10 and 100 Ω cm, which is in good agreement with typical values reported in the past for oxygen-deficient barium titanate films. Consequently the presence of oxygen vacancies in their structure was indirectly validated. Some of these nanorods were tested as proof-of-concept humidity sensors. They showed reproducible responses towards different moisture concentrations, demonstrating that individual BaTiO 3 nanorods may be integrated in complex circuit architectures with functional capacities.

A FAMILY OF PEROXO-TITANATE MATERIALS TAILORED FOR OPTIMAL STRONTIUM ANDACTINIDE SORPTION

International Nuclear Information System (INIS)

Hobbs, D

2006-01-01

Achieving global optimization of inorganic sorbent efficacy, as well as tailoring sorbent specificity for target sorbates would facilitate increased wide-spread use of these materials in applications such as producing potable water or nuclear waste treatment. Sodium titanates have long been known as sorbents for radionuclides; 90 Sr and transuranic elements in particular. We have developed a related class of materials, which we refer to as peroxo-titanates: these are sodium titanates or hydrous titanates synthesized in the presence of or treated post-synthesis with hydrogen peroxide. Peroxo-titanates show remarkable and universal improved sorption behavior with respect to separation of actinides and strontium from Savannah River Site (SRS) nuclear waste simulants. Enhancement in sorption kinetics can potentially result in as much as an order of magnitude increase in batch processing throughput. Peroxo-titanates have been produced by three different synthetic routes: post-synthesis peroxide-treatment of a commercially produced monosodium titanate, an aqueous-peroxide synthetic route, and an isopropanol-peroxide synthetic route. The peroxo-titanate materials are characteristically yellow to orange, indicating the presence of protonated or hydrated Ti-peroxo species; and the chemical formula can be generally written as H v Na w Ti 2 O 5 -(xH 2 O)[yH z O 2 ] where (v+w) = 2, z = 0-2, and total volatile species accounts for 25-50 wt % of the solid. Further enhancement of sorption performance is achieved by processing, storing and utilizing the peroxo-titanate as an aqueous slurry rather than a dry powder, and post-synthesis acidification. All three synthesis modifications; addition of hydrogen peroxide, use of a slurry form and acidification can be applied more broadly to the optimization of other metal oxide sorbents and other ion separations processes

DEVELOPMENT OF PROTOTYPE TITANATE ION EXCHANGE LOADED MEMBRANES FOR STRONTIUM, CESIUM AND ACTINIDE DECONTAMINATION FROM AQUEOUS MEDIA

Energy Technology Data Exchange (ETDEWEB)

Oji, L; Keisha Martin, K; David Hobbs, D

2008-05-30

We have successfully incorporated high surface area particles of titanate ion exchange materials (monosodium titanate and crystalline silicotitanate) with acceptable particle size distribution into porous and inert support membrane fibrils consisting of polytetrafluoroethylene (Teflon{reg_sign}), polyethylene and cellulose materials. The resulting membrane sheets, under laboratory conditions, were used to evaluate the removal of surrogate radioactive materials for cesium-137 and strontium-90 from high caustic nuclear waste simulants. These membrane supports met the nominal requirement for nonchemical interaction with the embedded ion exchange materials and were porous enough to allow sufficient liquid flow. Some of this 47-mm size stamped out prototype titanium impregnated ion exchange membrane discs was found to remove more than 96% of dissolved cesium-133 and strontium-88 from a caustic nuclear waste salt simulants. Since in traditional ion exchange based column technology monosodium titanate (MST) is known to have great affinity for the sorbing of other actinides like plutonium, neptunium and even uranium, we expect that the MST-based membranes developed here, although not directly evaluated for uptake of these three actinides because of costs associated with working with actinides which do not have 'true' experimental surrogates, would also show significant affinity for these actinides in aqueous media. It was also observed that crystalline silicotitanate impregnated polytetrafluoroethylene or polyethylene membranes became less selective and sorbed both cesium and strontium from the caustic aqueous salt simulants.

History and challenges of barium titanate: Part I

Directory of Open Access Journals (Sweden)

Vijatović M.M.

2008-01-01

Full Text Available Barium titanate is the first ferroelectric ceramics and a good candidate for a variety of applications due to its excellent dielectric, ferroelectric and piezoelectric properties. Barium titanate is a member of a large family of compounds with the general formula ABO3 called perovskites. Barium titanate can be prepared using different methods. The synthesis method depends on the desired characteristics for the end application. The used method has a significant influence on the structure and properties of barium titanate materials. In this review paper, Part I contains a study of the BaTiO3 structure and frequently used synthesis methods.

Synthesis and characterization of multilayered BaTiO3/NiFe2O4 thin films

Directory of Open Access Journals (Sweden)

Branimir Bajac

2013-03-01

Full Text Available Presented research was focused on the fabrication of multiferroic thin film structures, composed of ferrielectric barium titanate perovskite phase and magnetostrictive nickel ferrite spinel phase. The applicability of different, solution based, deposition techniques (film growth from solution, dip coating and spin coating for thefabrication of multilayered BaTiO3 /NiFe2O4 thin films was investigated. It was shown that only spin coating produces films of desired nanostructure, thickness and smooth and crackfree surfaces.

Study of the dielectric properties of barium titanate-polymer composites

International Nuclear Information System (INIS)

Pant, H.C.; Patra, M.K.; Verma, Aditya; Vadera, S.R.; Kumar, N.

2006-01-01

A comparative study of complex dielectric properties has been carried out at the X-band of microwave frequencies of composites of barium titanate (BaTiO 3 ) with two different polymer matrices: insulating polyaniline (PANI) powder (emeraldine base) and maleic resin. From these studies, it is observed that the composites of BaTiO 3 with maleic resin show normal composite behavior and the dielectric constant follows the asymmetric Bruggeman model. In contrast, the composites of BaTiO 3 with PANI show an unusual behavior wherein even at a low concentration of PANI (5 wt.%) there is a drastic reduction in the dielectric constant of BaTiO 3 . This behavior of the dielectric constant is explained on the basis of coating of BaTiO 3 particles by PANI which in turn is attributed to the highly surface adsorbing character. The materials have also been characterized using Fourier transform infrared spectroscopy, powder X-ray diffraction, scanning electron microscopy and optical microscopy studies

High temperature dielectric relaxation anomaly of Y3+ and Mn2+ doped barium strontium titanate ceramics

International Nuclear Information System (INIS)

Yan, Shiguang; Mao, Chaoliang; Wang, Genshui; Yao, Chunhua; Cao, Fei; Dong, Xianlin

2014-01-01

Relaxation like dielectric anomaly is observed in Y 3+ and Mn 2+ doped barium strontium titanate ceramics when the temperature is over 450 K. Apart from the conventional dielectric relaxation analysis method with Debye or modified Debye equations, which is hard to give exact temperature dependence of the relaxation process, dielectric response in the form of complex impedance, assisted with Cole-Cole impedance model corrected equivalent circuits, is adopted to solve this problem and chase the polarization mechanism in this paper. Through this method, an excellent description to temperature dependence of the dielectric relaxation anomaly and its dominated factors are achieved. Further analysis reveals that the exponential decay of the Cole distribution parameter n with temperature is confirmed to be induced by the microscopic lattice distortion due to ions doping and the interaction between the defects. At last, a clear sight to polarization mechanism containing both the intrinsic dipolar polarization and extrinsic distributed oxygen vacancies hopping response under different temperature is obtained.

LIGHT INTENSITY INFLUENCE ON STRONTIUM TITANATE BASED PHOTO- ELECTROCHEMICAL CELLS

Directory of Open Access Journals (Sweden)

D. Hertkorn

2017-07-01

Full Text Available The influence of light intensity on photo-electrochemical cells (PECs consisting of an n-type strontium titanate (SrTiO₃ photoanode and nickel cathode in potassium hydroxide electrolyte is studied. The band levels of an electrolyte-metal-semiconductor-electrolyte system are presented and the effect of different light intensities on the energy levels is investigated. Photocurrent density, quantum efficiency, and open circuit potential measurements are performed on the processed PECs under different light intensities (375 nm. It is demonstrated that a threshold value of the light intensity has to be reached in order to obtain positive photo activity and that beyond this value the performance remains nearly constant.

Doping site dependent thermoelectric properties of epitaxial strontium titanate thin films

KAUST Repository

Abutaha, Anas I.; Sarath Kumar, S. R.; Mehdizadeh Dehkordi, Arash; Tritt, Terry M.; Alshareef, Husam N.

2014-01-01

We demonstrate that the thermoelectric properties of epitaxial strontium titanate (STO) thin films can be improved by additional B-site doping of A-site doped ABO3 type perovskite STO. The additional B-site doping of A-site doped STO results in increased electrical conductivity, but at the expense of Seebeck coefficient. However, doping on both sites of the STO lattice significantly reduces the lattice thermal conductivity of STO by adding more densely and strategically distributed phononic scattering centers that attack wider phonon spectra. The additional B-site doping limits the trade-off relationship between the electrical conductivity and total thermal conductivity of A-site doped STO, leading to an improvement in the room-temperature thermoelectric figure of merit, ZT. The 5% Pr3+ and 20% Nb5+ double-doped STO film exhibits the best ZT of 0.016 at room temperature. This journal is

Synthesis and characterization of BaTiO3 ferroelectric material

International Nuclear Information System (INIS)

Osman, K.I.

2011-01-01

BaTiO 3 powder was prepared at low temperatures using the solid-state reaction, starting with two different precursors; the BaCO 3 /TiO 2 and the Ba(NO 3 ) 2 /TiO 2 powder mixtures. It was found that, a single phase BaTiO 3 was formed after calcination at 750 degree C for 10 h and at 600 degree C for 6 h for the first and second mixtures, respectively. Thermal and XRD analyses were used to study the formation kinetics of BaTiO 3 . Contracting volume reaction model was found to control both reactions. The SEM of the as milled powder, TMA, TG and thermodynamics analysis have been used to propose a realistic approach describing the reaction mechanism of BaTiO 3 . Characterization and the dielectric properties of the sintered BaTiO 3 were investigated. The relative permittivity and the dielectric loss measured at room temperature and at 1 khz were 2028.5 and 0.043 for BaTiO 3 prepared from BaCO 3 /TiO 2 , while they were 1805.33 and 0.41 for BaTiO 3 prepared from Ba(NO 3 ) 2 /TiO 2 .

Wet routes of high purity BaTiO3 nanopowders

International Nuclear Information System (INIS)

Wang Liqiu; Liu Liang; Xue Dongfeng; Kang Hongmin; Liu Changhou

2007-01-01

High purity BaTiO 3 nanopowders were prepared in wet routes through stearic acid gel (SAG) and acetic acid gel (AAG) techniques, respectively. BaTiO 3 samples were characterized by X-ray diffraction, transmission electron microscope, Fourier transform infrared spectrometry, X-ray fluorescence spectrometry, and thermal gravimetric analysis. The present results indicate that both methods have a similar reaction process during calcination, while BaTiO 3 crystallites were initially formed at 550 deg. C by SAG and 800 deg. C by AAG. Both methods could produce BaTiO 3 powders with a cubic perovskite structure, while they had different grain size distributions within 25-50 nm for SAG and 50-80 nm for AAG. BaTiO 3 samples prepared by SAG had a lower agglomeration than those by AAG. SAG has shown many distinctive advantages in the preparation of high purity BaTiO 3 nanopowders, without Ba and Ti losses and hazardous wastes

Synthesis of Barium Titanate from Titanyl Acylate Precursor by Sol-precipitate Method

International Nuclear Information System (INIS)

Thandar Win; Kyaw Naing; Khin Mar Tun

2008-03-01

Nanometersize barium titanates (BaTiO3:BT) powders can be obtained by sol-precipitate method in the presence of polyoxyethylene (20) sorbiton monooleate (Tween-80) as a polymeric surface modifier in a strong alkaline solution (pH > 13). FT-IR, TG/DTA, SEM and XRD were used to investigate the effects of the surfactant influence on the morphology of the obtained BaTiO3 powders. With adding surfactant, a slower rate of hydrolyzation is observed and the rate of condensation is slower. The addition of Tween-80 surfactant in general leads to the formation of smaller particle size of BaTi)3 (70-100 nm). Without adding surfactant, larger particle size of BaTiO3 (100-200 nm) was obtained. The nanometersize BaTiO3 powders were readily sintered at 1000-1200C. Raman-active modes of tetragonal phase BT were detected from Raman spectra of BaTiO3 between 800 0 C to 1200 0 C.

Concurrent atomistic and continuum simulation of bi-crystal strontium titanate with tilt grain boundary.

Science.gov (United States)

Yang, Shengfeng; Chen, Youping

2015-03-08

In this paper, we present the development of a concurrent atomistic-continuum (CAC) methodology for simulation of the grain boundary (GB) structures and their interaction with other defects in ionic materials. Simulation results show that the CAC simulation allows a smooth passage of cracks through the atomistic-continuum interface without the need for additional constitutive rules or special numerical treatment; both the atomic-scale structures and the energies of the four different [001] tilt GBs in bi-crystal strontium titanate obtained by CAC compare well with those obtained by existing experiments and density function theory calculations. Although 98.4% of the degrees of freedom of the simulated atomistic system have been eliminated in a coarsely meshed finite-element region, the CAC results, including the stress-strain responses, the GB-crack interaction mechanisms and the effect of the interaction on the fracture strength, are comparable with that of all-atom molecular dynamics simulation results. In addition, CAC simulation results show that the GB-crack interaction has a significant effect on the fracture behaviour of bi-crystal strontium titanate; not only the misorientation angle but also the atomic-level details of the GB structure influence the effect of the GB on impeding crack propagation.

Large electrical manipulation of permittivity in BaTiO3 and Pb(Zr,Ti)O3 bimorph heterostructure

International Nuclear Information System (INIS)

Ci, Penghong; Liu, Guoxi; Dong, Shuxiang; Zhang, Li

2014-01-01

We report a strain-mediated electric field manipulation of permittivity in BaTiO 3 (barium titanate, BT) ceramic by a Pb(Zr,Ti)O 3 (PZT) bimorph. This BT/PZT heterostructure exhibited a relatively large permittivity tunability of BT up to ±10% in a wide frequency range under an electric field of ±4 kV/cm applied to the PZT bimorph. The permittivity tunability is attributed to the strain in BT produced by the PZT bimorph. Calculations of the relationship between permittivity and applied electric field were developed, and corresponded well with measurements. The BT/PZT heterostructure has potential for applications in broadband field tunable smart electronic devices.

Quantitative Voxel-to-Voxel Comparison of TriBeam and DCT Strontium Titanate Three-Dimensional Data Sets (Postprint)

Science.gov (United States)

2015-02-09

materials such as alumina (Gonzalez et al., 2013), titanium (King et al., 2010) and aluminium (Ludwig, King et al., 2009). 2.1.2. TriBeam data collection...nickel alloys (Echlin, Lenthe et al., 2014), and geological samples (Echlin et al., 2015). The strontium titanate sample was serially sectioned in the

Dielectric enhancement of BaTiO3/SrTiO3 superlattices with embedded Ni nanocrystals

International Nuclear Information System (INIS)

Xiong Zhengwei; Sun Weiguo; Wang Xuemin; Jiang Fan; Wu Weidong

2012-01-01

Highlights: ► The BaTiO 3 /SrTiO 3 superlattices with embedded Ni NCs were successfully fabricated by L-MBE. ► The influence with the various concentrations of Ni nanocrystals embedded in BaTiO 3 /SrTiO 3 superlattices was also discussed. ► The BaTiO 3 /SrTiO 3 superlattices with lower concentration of embedded Ni NCs had higher permittivity and dielectric loss compared with the pure BaTiO 3 /SrTiO 3 superlattices. ► The dielectric enhancement of BaTiO 3 /SrTiO 3 superlattices with embedded Ni NCs was proposed to explained by Drude quasi-free-electron theory. - Abstract: The self-organized Ni nanocrystals (NCs) were embedded in BaTiO 3 /SrTiO 3 superlattices using laser molecular beam epitaxy (L-MBE). The stress of the composite films was increased with the increasing concentration of embedded Ni NCs, as investigation in stress calculation. The influence with the various concentrations of Ni NCs embedded in BaTiO 3 /SrTiO 3 superlattices was also discussed. The internal stress of the films was too strong to epitaxial growth of BaTiO 3 /SrTiO 3 superlattices. Compared with the pure BaTiO 3 /SrTiO 3 superlattices, the BaTiO 3 /SrTiO 3 superlattices with lower concentration of embedded Ni NCs had higher permittivity and dielectric loss. Furthermore, the dielectric enhancement of BaTiO 3 /SrTiO 3 superlattices with embedded Ni NCs was proposed to explained by Drude quasi-free-electron theory.

Synthesis of Barium Titanate (BT) Nano Particles via Hydrothermal Route for the Production of BT-Polymer Nanocomposite

Science.gov (United States)

Habib, A.; Haubner, R.; Jakopic, G.; Stelzer, N.

2007-08-01

Barium titanate (high-k dielectric material) nano-powders (approx. 30 nm to 60 nm) were synthesised using hydrothermal route under moderate conditions. Effect of temperature and time was studied using transmission electron microscopy (TEM), scanning electron microscopy (SEM) and X-ray diffraction techniques. Obtained barium titanate nano-powders were dispersed in thermoplastic polymethyl methacrylate (PMMA) to get homogeneous dispersions. Thin layers were obtained using these dispersions to achieve BaTiO3 endorsed polymer layers by dip-coating for improved polymer insulators on various substrates e.g., glass, and Au sputtered silicon wafers. SEM and focused ion beam (FIB) techniques were used to study the dispersion of barium titanate nano-particles in PMMA. The layers obtained showed homogenous distribution of BaTiO3 nano particles with no agglomeration.

Size effect in barium titanate powders synthesized by different hydrothermal methods

International Nuclear Information System (INIS)

Sun Weian

2006-01-01

The size effect in barium titanate (BaTiO 3 ) was investigated both experimentally and theoretically. Tetragonal BaTiO 3 powders with average sizes from 80 to 420 nm were directly prepared by different hydrothermal methods. The tetragonality of the hydrothermal BaTiO 3 decreased with decreasing particle size, which exhibited a dependence on the synthesis method. A phenomenological model for the size effect was proposed to interpret the experimental observations. The influence of the defects, mainly the lattice hydroxyl, on the size effect was investigated to understand the correlation between the size effect and synthesis condition. The permittivities of BaTiO 3 powder at different particle sizes were calculated, which predicted a maximum permittivity of over 16 000 around the room-temperature critical size of ∼70 nm. The prediction was in good accordance with the experimental data reported recently

Small-scale dislocation plasticity in strontium titanate

Energy Technology Data Exchange (ETDEWEB)

Stukowski, Alexander; Javaid, Farhan; Durst, Karsten; Albe, Karsten [Technische Universitaet Darmstadt (Germany)

2016-07-01

Strontium titanate (STO) is an optically transparent perovskite oxide ceramic material. In contrast to other ceramics, single crystal STO plastically deforms under ambient condition, without showing a phase transition or early fracture. This remarkable ductility makes it a prime candidate for different technological applications. However, while the mechanical behavior of bulk STO has been studied extensively using uniaxial compression testing techniques, little is known about the local, small-scale behavior and the details of dislocation-based nanoplasticity in this perovskite material. In this contribution we compare results obtained from new nanoindentation experiments and corresponding large-scale molecular dynamics simulations. The evolution of the plastic zone and dislocation structures that form underneath the indenter is investigated using etch-pit methods in experiments and a novel three-dimensional defect identification technique in atomistic computer models. The latter allows tracing the evolution of the complete dislocation line network as function of indentation depth, quantifying the activity of different slip systems, and correlating this information with the recorded load-displacement curves and hardness data.

Implanted strontium titanate single crystals for energy storage applications

Energy Technology Data Exchange (ETDEWEB)

Stoeber, Max; Cherkouk, Charaf; Walter, Juliane; Strohmeyer, Ralph; Leisegang, Tilmann; Meyer, Dirk Carl [TU Bergakademie, Freiberg (Germany); Schelter, Matthias; Zosel, Jens [Kurt Schwabe Institute, Meinsberg (Germany); Prucnal, Slawomir [Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf (Germany)

2016-07-01

A rapid increase of the demand on efficient energy storage solutions requires new approaches beyond the Li-ion technology. In particular, metal-air batteries as well as solid-state fuel cells offer a great potential for high-energy-density storage devices. Since the efficiency of such devices is significantly limited by the activation of both the oxygen reduction reaction (ORR) and the ionic and electronic conductivities, an adequate porosity as well as a controlled doping are required. The ion implantation is a key technology to achieve this goal. In this work, p- and n-doped strontium titanate (SrTiO{sub 3}) single crystals were used as oxidic materials. The oxygen exchange kinetics as well as the structural changes of the SrTiO{sub 3} crystal surface induced by the ion implantation were investigated. On one hand, the depth profile of dopant concentration and dopant valence state were determined using sputtered X-ray photoelectron spectroscopy (XPS). On the other hand, the overall oxygen exchange kinetic of the implanted SrTiO{sub 3} crystal was quantitatively described by means of coulometric titration using Zirox system (ZIROX GmbH, Germany). Furthermore, the surface morphology of the samples was investigated using atomic force microscopy (AFM).

Study of a Flexible Low Profile Tunable Dipole Antenna Using Barium Strontium Titanate Varactors

Science.gov (United States)

Cure, David; Weller, Thomas; Miranda, Felix A.

2014-01-01

In this paper a flexible low profile dipole antenna using a frequency selective surface (FSS) with interdigital barium strontium titanate (BST) varactor-tuned unit cells is presented. The varactor chips were placed only along one dimension of the FSS to avoid the use of vias and simplify the DC bias network. The antenna uses overlapping metallic plates that resemble fish scales as a ground plane to improve the flexibility of the multi-material stack structure. The measured data of the antenna demonstrate tunability from 2.42 GHz to 2.66 GHz and 1.3 dB gain drop when using overlapping metallic plates instead of continuous ground plane. The total antenna thickness is approximately lambda/24.

Síntese de BaTIO3 e SrTIO3 pelo método hidrotermal assistido por micro-ondas utilizando anatase como precursor de titânio

Directory of Open Access Journals (Sweden)

Renata S. Magalhães

Full Text Available In this work barium titanate (BT and strontium titanate (ST were prepared by Microwave-Assisted Hydrothermal (MAH method, using a Ti precursor different from those shown in the literature and various concentrations (1, 3 e 6 mol L-1 of KOH mineralizer. As a titanium precursor, an anatase complex with hydrogen peroxide were used. For the precursors of barium and strontium, chlorides were used. The materials resulting from the synthesis processes were characterized in room temperature by different techniques as like: X-Ray Diffraction (XRD, micro-Raman Spectroscopy, UV-Vis, Scanning Electron Microscopy (SEM and Photoluminescence (PL. The results show that there were differences in crystallinity, morphology, number of phases and photoluminescence depending on the concentration of the mineralizer.

Scaling up aqueous processing of A-site deficient strontium titanate for SOFC anode supports

DEFF Research Database (Denmark)

Verbraeken, Maarten C.; Sudireddy, Bhaskar Reddy; Vasechko, Viacheslav

2018-01-01

All ceramic anode supported half cells of technically relevant scale were fabricated in this study, using a novel strontium titanate anode material. The use of this material would be highly advantageous in solid oxide fuel cells due to its redox tolerance and resistance to coking and sulphur...... poisoning. Successful fabrication was possible through aqueous tape casting of both anode support and electrolyte layers and subsequent lamination. Screen printing of electrolyte layers onto green anode tapes was also attempted but resulted in cracked electrolyte layers upon firing. Microstructural...

Production of BaTiO3 nanoparticles through the sol-gel route using humic substances from river water

International Nuclear Information System (INIS)

Lima, C.H.S.; Lima, S.S.S.; Gomes, M.A.; Novaes, S.M.V.; Macedo, Z.S.

2016-01-01

A new route of synthesis, low cost and low environmental impact, has been developed for the production of barium titanate (BaTiO3). This material is widely used in the electronics industry due to its dielectric properties, ferroelectric and piezoelectric. Its crystal structure of perovskite type also has the ability to host dopants of different sizes, allowing a wide variety of ions is accommodated in BaTiO3 structure. The synthesis route proposed in this paper explores the complexation capacity of natural organic matter (NOM). Parameters such as concentration, pH and calcination temperature were investigated during production, with the aim of developing a simple, efficient and low energy cost procedure. Samples produced with concentration 0.5 g / ml showed a single phase after calcination at 1200 °C for 5 h. The crystallite size was estimated by Scherrer equation around 28 nm and the particle size, determined by scanning electron microscopy (SEM-FEG) was from 80 to 180nm order. The sample produced also presented heterogeneous morphology with spherical particles, rods and needles. (author)

Quantitative analysis of UV excitation bands for red emissions in Pr3+-doped CaTiO3, SrTiO3 and BaTiO3 phosphors by peak fitting

International Nuclear Information System (INIS)

Fujiwara, Rei; Sano, Hiroyuki; Shimizu, Mikio; Kuwabara, Makoto

2009-01-01

A quantitative spectral analysis of the ultraviolet (UV) broad excitation bands, which are located in the range 300-400 nm, for red emissions at around 610 nm in Pr-doped CaTiO 3 , SrTiO 3 :Al and BaTiO 3 :Mg phosphors has been carried out using a peak fitting technique. The obtained results demonstrate that the UV broad band of CaTiO 3 :Pr consists of four primary excitation bands centered around 330, 335, 365 and 380 nm and those of both SrTiO 3 :Al and BaTiO 3 :Mg consist of three primary bands centered around 310, 345 and 370 nm. Based on the behavior patterns and the values of the respective primary excitation bands' parameters, i.e. center gravity (λ top ), maximum height (I max ) and full-width at half-maximum (FWHM), the UV-to-red relaxation processes in these titanate phosphors can be explained to be essentially the same, except for the existence of an additional relaxation pathway via electron-trap states in CaTiO 3 :Pr, which gives a characteristic shape of its UV excitation spectrum in the wavelength range of >360 nm

The Novel Formation of Barium Titanate Nanodendrites

Directory of Open Access Journals (Sweden)

Chien-Jung Huang

2014-01-01

Full Text Available The barium titanate (BaTiO3 nanoparticles with novel dendrite-like structures have been successfully fabricated via a simple coprecipitation method, the so-called BaTiO3 nanodendrites (BTNDs. This method was remarkable, fast, simple, and scalable. The growth solution is prepared by barium chloride (BaCl2, titanium tetrachloride (TiCl4, and oxalic acid. The shape and size of BaTiO3 depend on the amount of added BaCl2 solvent. To investigate the influence of amount of BaCl2 on BTNDs, the amount of BaCl2 was varied in the range from 3 to 6 mL. The role of BaCl2 is found to have remarkable influence on the morphology, crystallite size, and formation of dendrite-like structures. The thickness and length of the central stem of BTND were ~300 nm and ~20 μm, respectively. The branchings were found to occur at irregular intervals along the main stem. Besides, the formation mechanism of BTND is proposed and discussed.

Direct large-scale synthesis of perovskite barium strontium titanate nano-particles from solutions

International Nuclear Information System (INIS)

Qi Jianquan; Wang Yu; Wan Pingchen; Long Tuli; Chan, Helen Lai Wah

2005-01-01

This paper reports a wet chemical synthesis technique for large-scale fabrication of perovskite barium strontium titanate nano-particles near room temperature and under ambient pressure. The process employs titanium alkoxide and alkali earth hydroxides as starting materials and involves very simple operation steps. Particle size and crystallinity of the particles are controllable by changing the processing parameters. Observations by X-ray diffraction, scanning electron microscopy and transmission electron microscopy TEM indicate that the particles are well-crystallized, chemically stoichiometric and ∼50nm in diameter. The nanoparticles can be sintered into ceramics at 1150 deg. C and show typical ferroelectric hysteresis loops

Caracterización eléctrica y microestructural de cerámicas densificadas de BaTiO3 obtenido por pechini

Directory of Open Access Journals (Sweden)

Rivera, E.

2010-12-01

Full Text Available The barium titanate BaTiO3 is a material of great technological interest due to their dielectric properties. The functionality of this mixed oxide is mainly determined by its structure. Different synthesis methods have been used to improve the electrical response of BaTiO3. In this work BaTiO3 powders were synthesized using the polymeric precursor method, Pechini, obtaining the compound at 650 ° C, with uniform nanometric particle size (~ 20nm. The nature of the synthesized powders was analyzed using X-ray diffraction (XRD and differential scanning calorimetry (DSC. The results indicate that the crystalline phase present in the sample treated at 650 ° C is cubic and at 1100 ° C is tetragonal, with a relation c/a ≈ 1.007. The samples sinterized at 1100 ° C showed a ferroelectric-paraelectric transition at a temperature of T . 123ºC. The ceramic powders of barium titanate tetragonal, pressed and densified, was electrical characterizing with curves current-voltage (I-V at different temperatures. Additionally, we measured the change in electrical resistance versus temperature (R-T and we tested the behavior thermistor (PTCR of the material for different pressures. Also the electric response of the material with the variation of the frequency, for different temperatures, was measured.El titanato de bario BaTiO3 es un compuesto de gran interés tecnológico debido a sus propiedades dieléctricas. La funcionalidad de este oxido mixto está determinada, principalmente, por su estructura. Diferentes métodos de síntesis se han utilizado para mejorar la respuesta eléctrica del BaTiO3. En el presente trabajo se sintetizaron polvos de BaTiO3 utilizando el método de precursor polimérico, Pechini, obteniéndose el compuesto a una temperatura de 650 °C, con un tamaño de partícula nanométrico (~20nm y uniforme. La naturaleza de los polvos sintetizados se analizo utilizando difracción de rayos X (DRX y calorimetría diferencial de barrido (DSC

Origin of thermally stable ferroelectricity in a porous barium titanate thin film synthesized through block copolymer templating

Directory of Open Access Journals (Sweden)

Norihiro Suzuki

2017-07-01

Full Text Available A porous barium titanate (BaTiO3 thin film was chemically synthesized using a surfactant-assisted sol-gel method in which micelles of amphipathic diblock copolymers served as structure-directing agents. In the Raman spectrum of the porous BaTiO3 thin film, a peak corresponding to the ferroelectric tetragonal phase was observed at around 710 cm−1, and it remained stable at much higher temperature than the Curie temperature of bulk single-crystal BaTiO3 (∼130 °C. Measurements revealed that the ferroelectricity of the BaTiO3 thin film has high thermal stability. By analyzing high-resolution transmission electron microscope images of the BaTiO3 thin film by the fast Fourier transform mapping method, the spatial distribution of stress in the BaTiO3 framework was clearly visualized. Careful analysis also indicated that the porosity in the BaTiO3 thin film introduced anisotropic compressive stress, which deformed the crystals. The resulting elongated unit cell caused further displacement of the Ti4+ cation from the center of the lattice. This displacement increased the electric dipole moment of the BaTiO3 thin film, effectively enhancing its ferro(piezoelectricity.

Properties of barium strontium titanate at millimeter wave frequencies

Energy Technology Data Exchange (ETDEWEB)

Osman, Nurul [Department of Physics, Universiti Putra Malaysia (Malaysia); Free, Charles [Department of Engineering and Design, University of Sussex (United Kingdom)

2015-04-24

The trend towards using higher millimetre-wave frequencies for communication systems has created a need for accurate characterization of materials to be used at these frequencies. Barium Strontium Titanate (BST) is a ferroelectric material whose permittivity is known to change as a function of applied electric field and have found varieties of application in electronic and communication field. In this work, new data on the properties of BST characterize using the free space technique at frequencies between 145 GHz and 155 GHz for both thick film and bulk samples are presented. The measurement data provided useful information on effective permittivity and loss tangent for all the BST samples. Data on the material transmission, reflection properties as well as loss will also be presented. The outcome of the work shows through practical measurement, that BST has a high permittivity with moderate losses and the results also shows that BST has suitable properties to be used as RAM for high frequency application.

Strontium titanate/silicon-based terahertz photonic crystal multilayer stack

Energy Technology Data Exchange (ETDEWEB)

Xin, J.Z.; Jim, K.L.; Tsang, Y.H.; Chan, H.L.W.; Leung, C.W. [Hong Kong Polytechnic University, Department of Applied Physics and Materials Research Centre, Kowloon, Hong Kong (China); Yang, J.; Gong, X.J.; Chen, L.Q.; Gao, F. [Chinese Academy of Sciences, Institute of Biomedical and Health Engineering, Shenzhen Institutes of Advanced Technology, Shenzhen (China)

2012-04-15

A one-dimensional photonic crystal working in the terahertz (THz) range was designed and implemented. To facilitate the design, the transmission properties of strontium titanate crystals were characterized by THz-time-domain spectroscopy. Relatively high refractive index ({proportional_to}18.5) and transmission ratio (0.08) were observed between 0.2 to 1 THz. A stacked structure of (Si d{sub Si}/STO d{sub STO}){sub N} /Si d{sub Si} was then designed, with transmission spectra calculated by the transfer matrix method. The effects of the filling ratio (d{sub STO}/(d{sub Si}+d{sub STO})), periodicity (d{sub Si}+d{sub STO}) and the number of repeats N on the transmission of PC were investigated. The effect of introducing a defect layer was also studied. Based on these, Si/STO multilayers with STO defect thickness of 125 {mu}m and 200 {mu}m were measured. The shift of the defect mode was observed and compared with the calculations. (orig.)

Strontium titanate/silicon-based terahertz photonic crystal multilayer stack

International Nuclear Information System (INIS)

Xin, J.Z.; Jim, K.L.; Tsang, Y.H.; Chan, H.L.W.; Leung, C.W.; Yang, J.; Gong, X.J.; Chen, L.Q.; Gao, F.

2012-01-01

A one-dimensional photonic crystal working in the terahertz (THz) range was designed and implemented. To facilitate the design, the transmission properties of strontium titanate crystals were characterized by THz-time-domain spectroscopy. Relatively high refractive index (∝18.5) and transmission ratio (0.08) were observed between 0.2 to 1 THz. A stacked structure of (Si d Si /STO d STO ) N /Si d Si was then designed, with transmission spectra calculated by the transfer matrix method. The effects of the filling ratio (d STO /(d Si +d STO )), periodicity (d Si +d STO ) and the number of repeats N on the transmission of PC were investigated. The effect of introducing a defect layer was also studied. Based on these, Si/STO multilayers with STO defect thickness of 125 μm and 200 μm were measured. The shift of the defect mode was observed and compared with the calculations. (orig.)

Microstructural properties of BaTiO3 ceramics and thin films

International Nuclear Information System (INIS)

Fundora C, A.; Portelles, J.J.; Siqueiros, J.M.

2000-01-01

A microstructural study of BaTiO 3 ceramics obtained by the conventional ceramic method is presented. Targets were produced to grow BaTiO 3 thin films by pulsed laser deposition on Pt/Ti/Si (100) substrates. X-ray diffraction, Auger Electron Spectroscopy, X-ray Photon Spectroscopy and Scanning Electron Microscopy were used to study the properties of the BaTiO 3 ceramic samples and thin films, as deposited and after an annealing process. (Author)

Magnetoelectric coupling in multiferroic BaTiO3-CoFe2O4 composite nanofibers via electrospinning

Science.gov (United States)

Fu, Bi; Lu, Ruie; Gao, Kun; Yang, Yaodong; Wang, Yaping

2015-07-01

Magnetoelectric (ME) coupling in Pb-based multiferroic composites has been widely investigated due to the excellent piezoelectric property of lead zirconate titanate (PZT). In this letter, we report a strategy to create a hybrid Pb-free ferroelectric and ferromagnetic material and detect its ME coupling at the nanoscale. Hybrid Pb-free multiferroic BaTiO3-CoFe2O4 (BTO-CFO) composite nanofibers (NFs) were generated by sol-gel electrospinning. The perovskite structure of BTO and the spinel structure of CFO nanograins were homogenously distributed in the composite NFs and verified by bright-field transmission electron microscopy observations along the perovskite [111] zone axis. Multiferroicity was confirmed by amplitude-voltage butterfly curves and magnetic hysteresis loops. ME coupling was observed in terms of a singularity on a dM/dT curve at the ferroelectric Curie temperature (TC) of BaTiO3. The lateral ME coefficient was investigated by the evolution of the piezoresponse under an external magnetic field of 1000 Oe and was estimated to be α31 =0.78× 104 \\text{mV cm}-1 \\text{Oe}-1 . These findings could enable the creation of nanoscale Pb-free multiferroic composite devices.

Effect of lithium doping in BaTiO3 ceramics for vibration sensor application

Science.gov (United States)

Praveen, E.; Murugan, S.; Jayakumar, K.

2018-04-01

Phase pure undoped and Lithium doped BaTiO3 particles have been synthesized by high temperature solid-state reaction method. Substitution of Lithium at the Ba2+ site in BaTiO3 lattice has been investigated. The structural, vibrational, electrical and mechanical characterization have been carried out. The poled samples were used as a sensing element for the detection of mechanical oscillations and the presence of 80 Hz pulse in the output spectrum manifest the response of the sensor element to the applied mechanical stress. In comparison with pure BaTiO3 the sensitivity of Li doped BaTiO3 is 14 times greater than the pure BaTiO3. This confirms that Li doped BaTiO3 could be an efficient candidate for the functionalization of vibration sensors in space application.

Self-Organized Ni Nanocrystal Embedded in BaTiO3 Epitaxial Film

Directory of Open Access Journals (Sweden)

Ge FF

2010-01-01

Full Text Available Abstract Ni nanocrystals (NCs were embedded in BaTiO3 epitaxial films using the laser molecular beam epitaxy. The processes involving the self-organization of Ni NCs and the epitaxial growth of BaTiO3 were discussed. With the in situ monitoring of reflection high-energy electron diffraction, the nanocomposite films were engineered controllably by the fine alternation of the self-organization of Ni NCs and the epitaxial growth of BaTiO3. The transmission electron microscopy and the X-ray diffraction characterization confirmed that the composite film consists of the Ni NCs layers alternating with the (001/(100-oriented epitaxial BaTiO3 separation layers.

Comparative study of broadband electrodynamic properties of single-crystal and thin-film strontium titanate

International Nuclear Information System (INIS)

Findikoglu, A. T.; Jia, Q. X.; Kwon, C.; Reagor, D. W.; Kaduchak, G.; Rasmussen, K. Oe.; Bishop, A. R.

1999-01-01

We have used a coplanar waveguide structure to study broadband electrodynamic properties of single-crystal and thin-film strontium titanate. We have incorporated both time- and frequency-domain measurements to determine small-signal effective refractive index and loss tangent as functions of frequency (up to 4 GHz), dc bias (up to 10 6 V/m), and cryogenic temperature (17 and 60 K). The large-signal impulse response of the devices and the associated phenomenological nonlinear wave equation illustrate how dissipation and nonlinearity combine to produce the overall response in the large-signal regime. (c) 1999 American Institute of Physics

Synthesis and characterization of Ho{sup 3+}-doped strontium titanate downconversion nanocrystals and its application in dye-sensitized solar cells

Energy Technology Data Exchange (ETDEWEB)

Li, Y.Y. [Department of Inorganic Nonmetallic Materials Engineering, Dalian Polytechnic University, Dalian 116034 (China); Liaoning Provincial College Key Laboratory of New Materials and Material Modification, Dalian Polytechnic University, Dalian 116034 (China); Hao, H.S., E-mail: beike1952@163.com [Department of Inorganic Nonmetallic Materials Engineering, Dalian Polytechnic University, Dalian 116034 (China); Liaoning Provincial College Key Laboratory of New Materials and Material Modification, Dalian Polytechnic University, Dalian 116034 (China); Qin, L. [National Engineering Research Center of Seafood, Dalian Polytechnic University, Dalian 116034 (China); Wang, H.L.; Nie, M.Q.; Hu, Z.Q.; Gao, W.Y.; Liu, G.S. [Department of Inorganic Nonmetallic Materials Engineering, Dalian Polytechnic University, Dalian 116034 (China); Liaoning Provincial College Key Laboratory of New Materials and Material Modification, Dalian Polytechnic University, Dalian 116034 (China)

2015-02-15

Highlights: • A new downconversion (DC) nanocrystal (SrTiO{sub 3}:Ho{sup 3+}) was synthesized. • The effect of SrTiO{sub 3}:Ho{sup 3+} as a photoanode in DSSCs was investigated. • SrTiO{sub 3}:Ho{sup 3+} absorb ultraviolet light and downconvert it to visible light. • DC SrTiO{sub 3}:Ho{sup 3+} as a photoanode achieve the higher photoelectric conversion efficiency. - Abstract: Ho{sup 3+}-doped strontium titanate (SrTiO{sub 3}:Ho{sup 3+}) downconversion (DC) nanocrystals are synthesized by the solid state interaction of titanium dioxide, strontium nitrate, holmium oxide and sodium chloride and then used as a photoanode in dye-sensitized solar cells (DSSCs) to investigate the effect of DC nanocrystals in DSSCs. Differential thermal analysis, X-ray diffraction, scanning electronic microscope, energy dispersive spectroscopy and Brunauer-Emmet-Teller analysis confirmed the formation of cubic structured SrTiO{sub 3}:Ho{sup 3+} nanocrystals with diameters of 40-400 nm, pore size of ∼45 nm, sintering temperature of 950 °C. The photofluorescence and UV-Vis absorption spectra of the SrTiO{sub 3}:Ho{sup 3+} nanocrystals revealed strong emission intensity and visible light absorption when doped content of holmium oxide was between 1 wt% and 3 wt%. Compared with the pure SrTiO{sub 3} photoanode, SrTiO{sub 3}:Ho{sup 3+} DC photoanode showed a greater photovoltaic efficiency. The photoelectric conversion efficiency (η) of the DSSCs with a SrTiO{sub 3}:Ho{sup 3+} photoanode doped with 1 wt% holmium oxide was 59% higher than that with a pure SrTiO{sub 3} photoanode. This phenomenon could be explained by SrTiO{sub 3}:Ho{sup 3+} nanocrystals’ ability to absorb ultraviolet light and downconvert it to visible light, which extends spectral response range of DSSC to the ultraviolet region and increased the short-circuit current density (Jsc) of DSSCs.

Modified titanate perovskites in photocatalytic water splitting

Energy Technology Data Exchange (ETDEWEB)

Wlodarczak, M.; Ludwiczak, M.; Laniecki, M. [A. Mickiewicz Univ. (Poland)

2010-07-01

Received materials have structure of perovskite, what was shown by XRD diffraction patterns. Perovskite structure is present in all samples with strontium, barium and one sample with calcium. Moreover, received barium and strontium titanate are very similar to pattern materials. XRD results show, that temperature 500 C is too low to create perovskite structure in CaTiO{sub 3}. However, it is high enough in case of SrTiO{sub 3} and BaTiO{sub 3}. One regularity is obvious, surface area increases for samples calcined in lower temperature. There is a connection between surface area and dispersion of platinum. Both of them reach the greatest value to the calcium titanate. Catalytic activity was shown by all of received samples. Measurable values were received to samples calcined in 700 C. Calcium titanate had the best catalytic activity, both an amount of hydrogen and a ratio of hydrogen to platinum. There is one regularity to all samples, the ration of hydrogen to platinum increase when amount of platinum decrease. (orig.)

Barium titanate thick films prepared by screen printing technique

Directory of Open Access Journals (Sweden)

Mirjana M. Vijatović

2010-06-01

Full Text Available The barium titanate (BaTiO3 thick films were prepared by screen printing technique using powders obtained by soft chemical route, modified Pechini process. Three different barium titanate powders were prepared: i pure, ii doped with lanthanum and iii doped with antimony. Pastes for screen printing were prepared using previously obtained powders. The thick films were deposited onto Al2O3 substrates and fired at 850°C together with electrode material (silver/palladium in the moving belt furnace in the air atmosphere. Measurements of thickness and roughness of barium titanate thick films were performed. The electrical properties of thick films such as dielectric constant, dielectric losses, Curie temperature, hysteresis loop were reported. The influence of different factors on electrical properties values was analyzed.

Study of grain boundary tunneling in barium-titanate ceramic films

CERN Document Server

Wong, H; Poon, M C

1999-01-01

The temperature and the electric-field dependences of the current-voltage characteristics and the low-frequency noise of barium-titanate ceramic films are studied. An abnormal field dependence is observed in the resistivity of BaTiO sub 3 materials with a small average grain size. In addition, experiments show that the low-frequency noise behaviors are governed by grain-boundary tunneling at room temperature and by trapping-detrapping of grain-boundary states at temperatures above the Curie point. Physical models for the new observations are developed. Results suggest that grain-boundary tunneling of carriers is as important as the double Schottky barrier in the current conduction in BaTiO sub 3 materials with small grain sizes.

Effect of donor and acceptor dopants on crystallization, microstructural and dielectric behaviors of barium strontium titanate glass ceramics

Energy Technology Data Exchange (ETDEWEB)

Yadav, Avadhesh Kumar, E-mail: yadav.av11@gmail.com [Department of Physics, Dr. Bheem Rao Ambedkar Government Degree College, Anaugi, Kannauj (India); Gautam, C.R. [Department of Physics, University of Lucknow, Lucknow 226007 (India); Singh, Prabhakar [Department of Physics, Indian Institute of Technology (Banaras Hindu University), Varanasi 221005 (India)

2016-07-05

Bulk transparent barium strontium titanate borosilicate glasses in glass system (65-x)[(Ba{sub 0.6}Sr{sub 0.4}).TiO{sub 3}]-30[2SiO{sub 2}.B{sub 2}O{sub 3}]-5[K{sub 2}O]-x[A{sub 2}O{sub 3}], A = La, Fe (x = 2, 5 and 10) were prepared by rapid melt-quench technique and subsequently, converted into glass ceramics by regulated heat treatment process. The phase identification was carried out by X-ray powder diffraction and their surface morphology was studied by scanning electron microscopy. The dielectric properties were studied by impedance spectroscopic technique. Investigated glass samples were crystallized into major and secondary phases of Ba{sub 1.91}Sr{sub 0.09}TiO{sub 4} and Ba{sub 2}TiSi{sub 2}O{sub 8}, respectively. A very high dielectric constant having value upto 68000 was found in glass ceramic sample BST5K10F. This high value of dielectric constant was attributed to interfacial polarization, which arose due to conductivity difference among semiconducting crystalline phases, conducting grains and insulating grain boundaries. Donor dopant La{sub 2}O{sub 3} and acceptor dopant Fe{sub 2}O{sub 3} play an important role for enhancing crystallization, dielectric constant and retardation of dielectric loss in the samples. Moreover, higher value of dielectric constant and lower value of dielectric loss was found in Fe{sub 2}O{sub 3} doped samples in comparison to La{sub 2}O{sub 3} doped samples. - Highlights: • Bulk transparent barium strontium titanate glasses are successfully prepared. • A very high dielectric constant upto 68000 was found in glass ceramics. • La{sub 2}O{sub 3} and Fe{sub 2}O{sub 3} play role for enhancing value of dielectric constant. • Higher dielectric constant with low dielectric loss was found in Fe{sub 2}O{sub 3} doped sample. • Such glass ceramics may be used in making capacitors for high energy storage.

A plasmonic modulator based on metal-insulator-metal waveguide with barium titanate core

DEFF Research Database (Denmark)

Babicheva, Viktoriia; Lavrinenko, Andrei

2013-01-01

We design a plasmonic modulator which can be utilized as a compact active device in photonic integrated circuits. The active material, barium titanate (BaTiO3), is sandwiched between metal plates and changes its refractive index under applied voltage. Some degree of switching of ferroelectric...

Enhancement of tetragonality and role of strontium vacancies in heterovalent doped SrTiO.sub.3./sub..

Czech Academy of Sciences Publication Activity Database

Tkach, A.; Almeida, A.; Moreira, J.A.; Correia, T.M.; Chaves, M. R.; Okhay, O.; Vilarinho, P. M.; Gregora, Ivan; Petzelt, Jan

2011-01-01

Roč. 98, č. 5 (2011), "052903-1"-"052903-2" ISSN 0003-6951 R&D Projects: GA AV ČR KAN301370701 Institutional research plan: CEZ:AV0Z10100520 Keywords : strontium titanate * doping * phase transition * Raman spectroscopy Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.844, year: 2011

Multiphase nanodomains in a strained BaTiO3 film on a GdScO3 substrate

Science.gov (United States)

Kobayashi, Shunsuke; Inoue, Kazutoshi; Kato, Takeharu; Ikuhara, Yuichi; Yamamoto, Takahisa

2018-02-01

Controlling the crystal structure of ferroelectric materials via epitaxial strain, which is a well-known technique in strain engineering, can lead to the formation of unique domain structures generating non-intrinsic phenomena such as electronic conductivity, photovoltages, and enhanced piezoelectric characteristics. Strained BaTiO3 films are promising ferroelectric materials as theoretical modeling predicts that different domain morphologies can introduce additional properties not observed in conventional BaTiO3 ceramics. To rationally design materials for practical application, a thorough understanding of the formation mechanisms and stabilities of different domain structures in strained BaTiO3 films is required. However, there have been very few experimental reports on this topic, and details about the domain structures in strained BaTiO3 films are currently lacking. In this paper, we report multiphase nanodomains in a strained BaTiO3 film deposited on an orthorhombic GdScO3 substrate. The phase-transition behavior of the strained BaTiO3 film reveals that it contains multiple phases at room temperature; the film first undergoes a phase-transition upon heating at around 550 K, and then a paraelectric phase forms at temperatures above 690 K. A picometer-scale analysis of the Ti ion displacements, using an advanced scanning transmission electron microscopy technique, is used to characterize the complex multiphase nanodomains, providing useful insights into the control of domain structures in BaTiO3 films by applying epitaxial strain.

Texturing of sodium bismuth titanate-barium titanate ceramics by templated grain growth

Science.gov (United States)

Yilmaz, Huseyin

2002-01-01

Sodium bismuth titanate modified with barium titanate, (Na1/2Bi 1/2)TiO3-BaTiO3 (NBT-BT), is a candidate lead-free piezoelectric material which has been shown to have comparatively high piezoelectric response. In this work, textured (Na1/2Bi1/2)TiO 3-BaTiO3 (5.5mol% BaTiO3) ceramics with pc (where pc denotes the pseudocubic perovskite cell) orientation were fabricated by Templated Grain Growth (TGG) or Reactive Templated Grain Growth (RTGG) using anisotropically shaped template particles. In the case of TGG, molten salt synthesized SrTiO3 platelets were tape cast with a (Na1/2Bi1/2)TiO3-5.5mol%BaTiO3 powder and sintered at 1200°C for up to 12 hours. For the RTGG approach, Bi4Ti3O12 (BiT) platelets were tape cast with a Na2CO3, Bi2O3, TiO 2, and BaCO3 powder mixture and reactively sintered. The TGG approach using SrTiO3 templates gave stronger texture along [001] compared to the RTGG approach using BiT templates. The textured ceramics were characterized by X-ray and electron backscatter diffraction for the quality of texture. The texture function was quantified by the Lotgering factor, rocking curve, pole figures, inverse pole figures, and orientation imaging microscopy. Electrical and electromechanical property characterization of randomly oriented and pc textured (Na1/2Bi1/2)TiO 3-5.5 mol% BaTiO3 rhombohedral ceramics showed 0.26% strain at 70 kV/cm, d33 coefficients over 500 pC/N have been obtained for highly textured samples (f ˜ 90%). The piezoelectric coefficient from Berlincourt was d33 ˜ 200 pC/N. The materials show considerable hysteresis. The presence of hysteresis in the unipolar-electric field curve is probably linked to the ferroelastic phase transition seen in the (Na 1/2Bi1/2)TiO3 system on cooling from high temperature at ˜520°C. The macroscopic physical properties (remanent polarization, dielectric constant, and piezoelectric coefficient) of random and textured ([001] pc) rhombohedral perovskites were estimated by linear averaging of single

A theoretical investigation of the influence of the surface effect on the ferroelectric property of strained barium titanate film

Science.gov (United States)

Fang, Chao; Liu, Wei Hua

2017-07-01

The influence of the surface effect on the ferroelectric property of strained barium titanate film has been investigated. In this study, based on time-dependent Ginsburg-Landau-Devonshire thermodynamic theory, the surface effects have been simulated by introducing a surface constant, which leads to the strained BaTiO3 film consisting of inner tetragonal core and gradient lattice strain layer. Further, surface effects produce a depolarization field which has a dominant effect on the ferroelectric properties of the films. The spontaneous polarization, dielectric properties and ferroelectric hysteresis loop of BaTiO3 film are calculated under different boundary conditions. Theoretical and experimental results for strained BaTiO3 film are compared and discussed.

Effect of crystal structure on strontium titanate thin films and their dielectric properties

Science.gov (United States)

Kampangkeaw, Satreerat

Strontium titanate (SrTiO3 or STO) has application in radio and microwave-frequency tunable capacitor devices particularly at low temperatures due to its high dielectric constant, low loss and the electric field tunability of its dielectric constant. The main goal of improving the performance in these devices is to increase the tunability and decrease the dielectric loss at the same time, especially at microwave frequencies. Thin films of STO however, show dramatic differences compared to the bulk. The dielectric constant of bulk STO increases nonlinearly from 300 at room temperature to 30000 at 4 K and the loss range is 10-3--10 -4. On the other hand. STO thin films, while showing a dielectric constant close to 300 at room temperature, typically reach a maximum between 1000 and 10000 in the 30 K to 100 K range before decreasing, and the high-loss range is 10-2--10-3. We have grown strontium titanate thin films using a pulsed laser deposition technique on substrates selected to have a small lattice mismatch between the film and substrate. Neodymium gallate (NdGaO3 or NGO) and lanthanum aluminate (LaAlO3 or LAO) substrates were good candidates due to only 1--2% mismatching. Film capacitor devices were fabricated with 25 micron gap separation. 1.5 mm total gap length and an overall 1 x 2 mm dimension using standard lithography and gold metal evaporative techniques. Their nonlinear dielectric constant and loss tangent were measured at low frequencies and also at 2 GHz, and from room temperature down to 4 K. The resulting films show significant variations of dielectric properties with position on the substrates with respect to the deposition plume axis. In the presence of DC electric fields up to +/-4 V/mum, STO films show improved dielectric tunability and low loss in regions far from the plume axis. We found that the films grown on NCO have lower dielectric loss than those on LAO due to a closer match of the NCO lattice to that of STO. We investigated the possible

Development of a metrology method for composition and thickness of barium strontium titanate thin films

International Nuclear Information System (INIS)

Remmel, Thomas; Werho, Dennis; Liu, Ran; Chu, Peir

1998-01-01

Thin films of barium strontium titanate (BST) are being investigated as the charge storage dielectric in advanced memory devices, due to their promise for high dielectric constant. Since the capacitance of BST films is a function of both stoichiometry and thickness, implementation into manufacturing requires precise metrology methods to monitor both of these properties. This is no small challenge, considering the BST film thicknesses are 60 nm or less. A metrology method was developed based on X-ray Fluorescence and applied to the measurement of stoichiometry and thickness of BST thin films in a variety of applications

Conduction Mechanisms in Multiferroic Multilayer BaTiO3/NiFe2O4/BaTiO3 Memristors

Science.gov (United States)

Samardzic, N.; Bajac, B.; Srdic, V. V.; Stojanovic, G. M.

2017-10-01

Memristive devices and materials are extensively studied as they offer diverse properties and applications in digital, analog and bio-inspired circuits. In this paper, we present an important class of memristors, multiferroic memristors, which are composed of multiferroic multilayer BaTiO3/NiFe2O4/BaTiO3 thin films, fabricated by a spin-coating deposition technique on platinized Si wafers. This cost-effective device shows symmetric and reproducible current-voltage characteristics for the actuating voltage amplitude of ±10 V. The origin of the conduction mechanism was investigated by measuring the electrical response in different voltage and temperature conditions. The results indicate the existence of two mechanisms: thermionic emission and Fowler-Nordheim tunnelling, which alternate with actuating voltage amplitude and operating temperature.

Structure, Raman, dielectric behavior and electrical conduction mechanism of strontium titanate

Science.gov (United States)

Trabelsi, H.; Bejar, M.; Dhahri, E.; Graça, M. P. F.; Valente, M. A.; Khirouni, K.

2018-05-01

Strontium titanate was prepared by solid-state reaction method. According to the XRD, it was single phase and has a cubic perovskite structure. The Raman spectroscopic investigation was carried out at room-temperature, and the second-order Raman modes were observed. By employing impedance spectroscopy, the dielectric relaxation and electrical properties were investigated over the temperature range of 500-700 K at various frequencies. The activation energies evaluated from dielectric and modulus studies are in good agreement and these values are attributed to the bulk relaxation. The impedance data were well fitted to an (R1//C1)-(R2//CPE1) equivalent electrical circuit. It could be concluded that the grain boundaries are more resistive and capacitive than the grains. The ac conductivity was found to follow the Jonscher's universal dynamic law ωS and the correlated barrier hopping model (CBH) has been proposed to describe the conduction mechanism.

Growth and self-assembly of BaTiO3 nanocubes for resistive switching memory cells

International Nuclear Information System (INIS)

Chu, Dewei; Lin, Xi; Younis, Adnan; Li, Chang Ming; Dang, Feng; Li, Sean

2014-01-01

In this work, the self-assembled BaTiO 3 nanocubes based resistive switching memory capacitors are fabricated with hydrothermal and drop-coating approaches. The device exhibits excellent bipolar resistance switching characteristics with ON/OFF ratio of 58–70, better reliability and stability over various polycrystalline BaTiO 3 nanostructures. It is believed that the inter cube junctions is responsible for such a switching behaviour and it can be described by the filament model. The effect of film thickness on switching ratio (ON/OFF) was also investigated in details. - Graphical abstract: This work describes a novel resistive switching memory cell based on self-assembled BaTiO 3 nanocubes. - Highlights: • BaTiO 3 nanocubes were prepared by one step facile hydrothermal method. • Self-assembled BaTiO 3 nanocubes thin films were obtained by drop-coating approach. • The BaTiO 3 nanocubes show excellent resistive switching properties for memory applications

Characterization of barium strontium titanate thin films on sapphire substrate prepared via RF magnetron sputtering system

Science.gov (United States)

Jamaluddin, F. W.; Khalid, M. F. Abdul; Mamat, M. H.; Zoolfakar, A. S.; Zulkefle, M. A.; Rusop, M.; Awang, Z.

2018-05-01

Barium Strontium Titanate (Ba0.5Sr0.5TiO3) is known to have a high dielectric constant and low loss at microwave frequencies. These unique features are useful for many electronic applications. This paper focuses on material characterization of BST thin films deposited on sapphire substrate by RF magnetron sputtering system. The sample was then annealed at 900 °C for two hours. Several methods were used to characterize the structural properties of the material such as X-ray diffraction (XRD) and atomic force microscopy (AFM). Field emission scanning electron microscopy (FESEM) was used to analyze the surface morphology of the thin film. From the results obtained, it can be shown that the annealed sample had a rougher surface and better crystallinity as compared to as-deposited sample.

Synthesis and luminescence properties of BaTiO3:RE (RE = Gd , Dy ...

Indian Academy of Sciences (India)

thermoluminescence (TL) properties of BaTiO3 samples doped with Gd3+, Dy3+, Tb3+ and Lu3+ were investigated. ... electron microscope using an accelerating voltage of 20 kV. .... doping of 1% mole Gd3+ ion into the BaTiO3 compound.

First-principles calculations on the four phases of BaTiO3.

Science.gov (United States)

Evarestov, Robert A; Bandura, Andrei V

2012-04-30

The calculations based on linear combination of atomic orbitals basis functions as implemented in CRYSTAL09 computer code have been performed for cubic, tetragonal, orthorhombic, and rhombohedral modifications of BaTiO(3) crystal. Structural and electronic properties as well as phonon frequencies were obtained using local density approximation, generalized gradient approximation, and hybrid exchange-correlation density functional theory (DFT) functionals for four stable phases of BaTiO(3). A comparison was made between the results of different DFT techniques. It is concluded that the hybrid PBE0 [J. P. Perdew, K. Burke, M. Ernzerhof, J. Chem. Phys. 1996, 105, 9982.] functional is able to predict correctly the structural stability and phonon properties both for cubic and ferroelectric phases of BaTiO(3). The comparative phonon symmetry analysis in BaTiO(3) four phases has been made basing on the site symmetry and irreducible representation indexes for the first time. Copyright © 2012 Wiley Periodicals, Inc.

Characterization of barium titanate powder doped with sodium and potassium ions by using Rietveld refining

International Nuclear Information System (INIS)

Andrade, M.C.; Assis, J.T.; Pereira, F.R.

2009-01-01

A solid-reaction synthesis of doped barium titanate was done by employing barium carbonates, sodium, potassium and titanium oxides with classic procedures. Rietveld refining of X ray diffraction data of perovskite samples with tetragonal symmetry was applying and show good agreement. Besides, the treatment performed from 600 deg C produces nanocrystals of barium titanate with average size of 33 nm. The presence of endothermic peaks related to BaTiO 3 formation at relatively low temperatures was determined by thermal analysis. A pseudo-Voigt Thompson-Cox-Hastings function was used to fit the standard samples of barium titanate. The Rietveld method has showed be efficient to detect the influences of temperature and doping on barium titanate microstructures. (author)

Hydrothermal–galvanic couple synthesis of directionally oriented BaTiO3 thin films on TiN-coated substrates

International Nuclear Information System (INIS)

Yang, Chia-Jung; Tsai, Di-You; Chan, Pei-Hsuan; Wu, Chu-Tsun; Lu, Fu-Hsing

2013-01-01

BaTiO 3 films were synthesized on TiN-coated Si substrate below 100 °C by a hydrothermal–galvanic couple technique in barium contained alkaline solutions. X-ray diffraction and electron backscatter diffraction results show that the BaTiO 3 thin films were directionally oriented grown on the TiN/Si substrates, i.e., (111) BaTiO 3 over (111) TiN. The surface morphologies revealed that BaTiO 3 nucleated and grew over the TiN surface with a single layer. From kinetic analyses, the growth rates of BaTiO 3 films prepared by the hydrothermal–galvanic couple technique were faster than a hydrothermal method. The galvanic effects were confirmed by investigating the induced currents and energies. The galvanic currents were generated and controlled by both the dissolution of TiN and the formation of BaTiO 3 . The output electric energies increased rapidly with the reaction time and leveled off at the full coverage of BaTiO 3 . - Highlights: • Cubic BaTiO 3 films are synthesized by a hydrothermal–galvanic couple method (HT–GC). • Growth rates of BaTiO 3 films made by HT–GC are faster than a hydrothermal method. • BaTiO 3 films are directionally oriented grown on the TiN/Si substrates. • Galvanic currents are controlled by dissolution of TiN and formation of BaTiO 3

Atomic layer deposition of epitaxial layers of anatase on strontium titanate single crystals: Morphological and photoelectrochemical characterization

Energy Technology Data Exchange (ETDEWEB)

Kraus, Theodore J.; Nepomnyashchii, Alexander B.; Parkinson, B. A., E-mail: bparkin1@uwyo.edu [Department of Chemistry, School of Energy Resources, University of Wyoming, Laramie, Wyoming 82071 (United States)

2015-01-15

Atomic layer deposition was used to grow epitaxial layers of anatase (001) TiO{sub 2} on the surface of SrTiO{sub 3} (100) crystals with a 3% lattice mismatch. The epilayers grow as anatase (001) as confirmed by x-ray diffraction. Atomic force microscope images of deposited films showed epitaxial layer-by-layer growth up to about 10 nm, whereas thicker films, of up to 32 nm, revealed the formation of 2–5 nm anatase nanocrystallites oriented in the (001) direction. The anatase epilayers were used as substrates for dye sensitization. The as received strontium titanate crystal was not sensitized with a ruthenium-based dye (N3) or a thiacyanine dye (G15); however, photocurrent from excited state electron injection from these dyes was observed when adsorbed on the anatase epilayers. These results show that highly ordered anatase surfaces can be grown on an easily obtained substrate crystal.

Synthesis of BaTiO3 powder from barium titanyl oxalate (BTO ...

Indian Academy of Sciences (India)

Unknown

the synthesis of BaTiO3 from the mixture of barium car- bonate and titanium dioxide employing microwave heat- ing. They observed that hypostoichiometric TiO2 (TiO2–x) reacted with BaCO3 in the presence of microwave field at temperature as low as 350°C to give the mixture of hexa- gonal and tetragonal forms of BaTiO3 ...

Excimer laser assisted re-oxidation of BaTiO3 thin films on Ni metal foils

International Nuclear Information System (INIS)

Bharadwaja, S. S. N.; Ko, S. W.; Qu, W.; Clark, T.; Rajashekhar, A.; Motyka, M.; Podraza, N.; Randall, C. A.; Trolier-McKinstry, S.

2016-01-01

Excimer laser assisted re-oxidation for reduced, crystallized BaTiO 3 thin films on Ni-foils was investigated. It was found that the BaTiO 3 can be re-oxidized at an oxygen partial pressure of ∼50 mTorr and substrate temperature of 350 °C without forming a NiO x interface layer between the film and base metal foil. The dielectric permittivity of re-oxidized films was >1000 with loss tangent values <2% at 100 Hz, 30 mV rms excitation signal. Electron Energy Loss Spectroscopy indicated that BaTiO 3 thin films can be re-oxidized to an oxygen stoichiometry close to ∼3 (e.g., stoichiometric). High resolution cross sectional transmission electron microscopy showed no evidence of NiO x formation between the BaTiO 3 and the Ni foil upon excimer laser re-oxidation. Spectroscopic ellipsometry studies on laser re-oxidized [001] C and [111] C BaTiO 3 single crystals indicate that the re-oxidation of BaTiO 3 single crystals is augmented by photo-excitation of the ozone, as well as laser pulse induced temperature and local stress gradients

Preparation of meta-stable phases of barium titanate by Sol-hydrothermal method

Directory of Open Access Journals (Sweden)

Mahalakshmi Selvaraj

2015-11-01

Full Text Available Two low-cost chemical methods of sol–gel and the hydrothermal process have been strategically combined to fabricate barium titanate (BaTiO3 nanopowders. This method was tested for various synthesis temperatures (100 °C to 250 °C employing barium dichloride (BaCl2 and titanium tetrachloride (TiCl4 as precursors and sodium hydroxide (NaOH as mineralizer for synthesis of BaTiO3 nanopowders. The as-prepared BaTiO3 powders were investigated for structural characteristics using x-ray diffraction (XRD, scanning electron microscopy (SEM and transmission electron microscopy (TEM. The overall analysis indicates that the hydrothermal conditions create a gentle environment to promote the formation of crystalline phase directly from amorphous phase at the very low processing temperatures investigated. XRD analysis showed phase transitions from cubic - tetragonal - orthorhombic - rhombohedral with increasing synthesis temperature and calculated grain sizes were 34 – 38 nm (using the Scherrer formula. SEM and TEM analysis verified that the BaTiO3 nanopowders synthesized by this method were spherical in shape and about 114 - 170 nm in size. The particle distribution in both SEM and TEM shows that as the reaction temperature increases from 100 °C to 250 °C, the particles agglomerate. Selective area electron diffraction (SAED shows that the particles are crystalline in nature. The study shows that choosing suitable precursor and optimizing pressure and temperature; different meta-stable (ferroelectric phases of undoped BaTiO3 nanopowders can be stabilized by the sol-hydrothermal method.

Positron annihilation lifetime study of positive temperature coefficient BaTiO3 samples

International Nuclear Information System (INIS)

Ling Chen; Mingkang Teng; Guanghou Wang; Xiaoyun Li; Tianchang Lu

1989-01-01

In order to investigate the doped vacancies in BaTiO 3 samples as well as their influence on the positive temperature coefficient (PTC) the positron annihilation lifetime spectroscopy was applied. Two groups of BaTiO 3 samples with BaO excess were prepared by doping different concentrations of La 2 O 3 and Nb 2 O 5 , respectively in the range from 0.1 to 3 at%. A third group of samples of two Sb-doped PTC BaTiO 3 semiconductors with excess BaO or TiO 2 were studied by the aid of positron technique before and after being reduced. It is shown that the positron lifetime parameters are sensitive to changes in the vacancy concentration in BaTiO 3 ceramics near the 0.1 mol% region. But they are almost unchanged during reduction processing; the resistivity of samples changed by one to two orders of magnitude through the reduction. It can be concluded that the PTC effect is due to oxygen on the grain boundary rather than vacancies, and that the Heywang-Jonker model is more reasonable

Dielectric loss of strontium titanate thin films

Science.gov (United States)

Dalberth, Mark Joseph

1999-12-01

Interest in strontium titanate (STO) thin films for microwave device applications continues to grow, fueled by the telecommunications industry's interest in phase shifters and tunable filters. The optimization of these devices depends upon increasing the phase or frequency tuning and decreasing the losses in the films. Currently, the dielectric response of thin film STO is poorly understood through lack of data and a theory to describe it. We have studied the growth of STO using pulsed laser deposition and single crystal substrates like lanthanum aluminate and neodymium gallate. We have researched ways to use ring resonators to accurately measure the dielectric response as a function of temperature, electric field, and frequency from low radio frequencies to a few gigahertz. Our films grown on lanthanum aluminate show marked frequency dispersion in the real part of the dielectric constant and hints of thermally activated loss behavior. We also found that films grown with conditions that optimized the dielectric constant showed increased losses. In an attempt to simplify the system, we developed a technique called epitaxial lift off, which has allowed us to study films removed from their growth substrates. These free standing films have low losses and show obvious thermally activated behavior. The "amount of tuning," as measured by a figure of merit, KE, is greater in these films than in the films still attached to their growth substrates. We have developed a theory that describes the real and imaginary parts of the dielectric constant. The theory models the real part using a mean field description of the ionic motion in the crystal and includes the loss by incorporating the motion of charged defects in the films.

Structural characterization and dielectric properties of BaTiO3 thin films obtained by spin coating

Directory of Open Access Journals (Sweden)

Branimir Bajac

2014-12-01

Full Text Available Barium titanate thin films were prepared by spin coating deposition technique of an acetic precursor sol and sintered at 750, 900 and 1050 °C. Phase composition of the obtained thin films was characterized by X-ray diffraction and Raman spectroscopy. Their morphology was analysed by scanning electron microscopy and atomic force microscopy. Dielectric properties of thin films sintered at 750 and 900 °C were characterized by LCD device, where the influence of sintering temperature on dielectric permittivity and loss tangent was inspected. It was concluded that higher sintering temperature increases grain size and amount of tetragonal phase, hence higher relative permittivity was recorded. The almost constant relative permittivity in the measured frequency (800 Hz–0.5 MHz and temperature (25–200 °C ranges as well as low dielectric loss are very important for the application of BaTiO3 films in microelectronic devices.

Dynamic Displacement Disorder of Cubic BaTiO3

Science.gov (United States)

Paściak, M.; Welberry, T. R.; Kulda, J.; Leoni, S.; Hlinka, J.

2018-04-01

The three-dimensional distribution of the x-ray diffuse scattering intensity of BaTiO3 has been recorded in a synchrotron experiment and simultaneously computed using molecular dynamics simulations of a shell model. Together, these have allowed the details of the disorder in paraelectric BaTiO3 to be clarified. The narrow sheets of diffuse scattering, related to the famous anisotropic longitudinal correlations of Ti ions, are shown to be caused by the overdamped anharmonic soft phonon branch. This finding demonstrates that the occurrence of narrow sheets of diffuse scattering agrees with a displacive picture of the cubic phase of this textbook ferroelectric material. The presented methodology allows one to go beyond the harmonic approximation in the analysis of phonons and phonon-related scattering.

Electrical characterization of strontium titanate borosilicate glass ceramics system with bismuth oxide addition using impedance spectroscopy

International Nuclear Information System (INIS)

Thakur, O.P.; Kumar, Devendra; Parkash, Om; Pandey, Lakshman

2003-01-01

The ac electrical data, measured in the frequency range 0.1 kHz-1 MHz, were used to study the electrical response of strontium titanate borosilicate glass ceramic system with bismuth oxide addition. Complex plane plots from these electrical data for various glass ceramic samples reveal contributions from simultaneously operating polarization mechanisms to overall dielectric behavior. The complex modulus (M * ) representation of electrical data for various glass ceramic samples were found to be more informative. Equivalent circuit models, which represent the electrical behavior of glass ceramic samples, were determined using complex non-linear least square (CNLS) fitting. An attempt has been made to understand the dielectric behavior of various glass ceramics in terms of contributions arising from different polarization processes occurring at glassy matrix, crystalline phases, glass to crystal interface region and blocking electrodes. Glass ceramics containing SrTiO 3 and TiO 2 (rutile) phases show thermally stable dielectric behavior

Nucleation control and inhibition of BaTiO3 films using hydrothermal-electrochemical method

International Nuclear Information System (INIS)

Escobar, Ivan; Silva, Carmen; Silva, Eric; Vargas, Tomas; Fuenzalida, Victor

1999-01-01

The microstructure of BaTiO 3 films on titanium by the hydrothermal-electrochemical method was investigated using a three electrode high pressure electrochemical cell in a 0.2 M Ba(OH) 2 electrolyte at 150 0 C. The spontaneous initial linked to pure hydrothermal BaTiO 3 formation can be inhibited by cathodically protecting titanium electrode since its immersion in the electrolyte. The application of initial nucleation pulses of varying the cathodic potentials affected the grain size of the deposit. It is suggested that the formation of a titanium oxide layers is a necessary step previous to the nucleation of BaTiO 3

Spin-Coating and Characterization of Multiferroic MFe2O4 (M=Co, Ni) / BaTiO3 Bilayers

Science.gov (United States)

Quandt, Norman; Roth, Robert; Syrowatka, Frank; Steimecke, Matthias; Ebbinghaus, Stefan G.

2016-01-01

Bilayer films of MFe2O4 (M=Co, Ni) and BaTiO3 were prepared by spin coating of N,N-dimethylformamide/acetic acid solutions on platinum coated silicon wafers. Five coating steps were applied to get the desired thickness of 150 nm for both the ferrite and perovskite layer. XRD, IR and Raman spectroscopy revealed the formation of phase-pure ferrite spinels and BaTiO3. Smooth surfaces with roughnesses in the order of 3 to 5 nm were found in AFM investigations. Saturation magnetization of 347 emu cm-3 for the CoFe2O4/BaTiO3 and 188 emu cm-3 for the NiFe2O4/BaTiO3 bilayer, respectively were found. For the CoFe2O4/BaTiO3 bilayer a strong magnetic anisotropy was observed with coercivity fields of 5.1 kOe and 3.3 kOe (applied magnetic field perpendicular and parallel to film surface), while for the NiFe2O4/BaTiO3 bilayer this effect is less pronounced. Saturated polarization hysteresis loops prove the presence of ferroelectricity in both systems.

Effects of vacancies on atom displacement threshold energy calculations through Molecular Dynamics Methods in BaTiO3

Science.gov (United States)

Gonzalez Lazo, Eduardo; Cruz Inclán, Carlos M.; Rodríguez Rodríguez, Arturo; Guzmán Martínez, Fernando; Abreu Alfonso, Yamiel; Piñera Hernández, Ibrahin; Leyva Fabelo, Antonio

2017-09-01

A primary approach for evaluating the influence of point defects like vacancies on atom displacement threshold energies values Td in BaTiO3 is attempted. For this purpose Molecular Dynamics Methods, MD, were applied based on previous Td calculations on an ideal tetragonal crystalline structure. It is an important issue in achieving more realistic simulations of radiation damage effects in BaTiO3 ceramic materials. It also involves irradiated samples under severe radiation damage effects due to high fluency expositions. In addition to the above mentioned atom displacement events supported by a single primary knock-on atom, PKA, a new mechanism was introduced. It corresponds to the simultaneous excitation of two close primary knock-on atoms in BaTiO3, which might take place under a high flux irradiation. Therefore, two different BaTiO3 Td MD calculation trials were accomplished. Firstly, single PKA excitations in a defective BaTiO3 tetragonal crystalline structure, consisting in a 2×2×2 BaTiO3 perovskite like super cell, were considered. It contains vacancies on Ba and O atomic positions under the requirements of electrical charge balance. Alternatively, double PKA excitations in a perfect BaTiO3 tetragonal unit cell were also simulated. On this basis, the corresponding primary knock-on atom (PKA) defect formation probability functions were calculated at principal crystal directions, and compared with the previous one we calculated and reported at an ideal BaTiO3 tetrahedral crystal structure. As a general result, a diminution of Td values arises in present calculations in comparison with those calculated for single PKA excitation in an ideal BaTiO3 crystal structure.

Contribution of the irreversible displacement of domain walls to the piezoelectric effect in barium titanate and lead zirconate titanate ceramics

CERN Document Server

Damjanovic, D

1997-01-01

The contribution from the irreversible displacement of non-180 deg domain walls to the direct longitudinal piezoelectric d sub 3 sub 3 coefficient of BaTiO sub 3 and Pb(Zr, Ti)O sub 3 ceramics was determined quantitatively by using the Rayleigh law. Effects of the crystal structure and microstructure of the ceramics as well as the external d.c. pressure on the domain wall contribution to d sub 3 sub 3 were examined. In barium titanate, this domain wall contribution is large (up to 35% of the total d sub 3 sub 3 , under the experimental conditions used) and dependent on the external d.c. pressure in coarse grained ceramics, and much smaller and independent of the external d.c. pressure in fine-grained samples. The presence of internal stresses in fine-grained ceramics could account for the observed behaviour. The analysis shows that the domain-wall contribution to the d sub 3 sub 3 in lead zirconate titanate ceramics is large in compositions close to the morphotropic phase boundary that contain a mixture of te...

Study of radiation damage in BaTiO3, using Molecular-dynamics simulations

International Nuclear Information System (INIS)

Gonzalez, E.; Abreu, Y.; Cruz, C. M.; Pinnera, I.; Leyva, A.

2015-01-01

Molecular-dynamics (MD) simulations were used to calculate atomic displacement probability curves along main crystallographic directions in BaTiO 3 perovskite. A primary knock-on atom (PKA) with a energy range between 10 to 300 eV in principal crystallographic directions at 300 K was introduced. For each sublattice, the simulation was repeated from different initial conditions to estimate the variation in the defect formation process. The formation of Frenkel pairs vary considerably with crystallographic direction and sublattice. Major quantity oxygen defects were found for all the simulated crystallographic directions. Threshold displacement energies are calculated for each atomic specie in the BaTiO 3 material. Also simulations with SRIM code, modeling + Mn implantation in a BaTiO 3 target, at 250 keV were made. (Author)

Characterization and dielectric properties of BaTiO3 prepared from Ba(NO3)2-TiO2 mixture

International Nuclear Information System (INIS)

Othman, K.I.; Hassan, A.A.; Ali, M.E.; Abdelal, O.A.; Salah El Dien, F.E.; El-Raghy, S.M.; Abdel-Karim, R.

2012-01-01

BaTiO 3 powder was prepared through a solid-state reaction between the Ba(NO 3 ) 2 and TiO 2 . The thermal analysis and XRD techniques were used to study its formation. A single phase BaTiO 3 was formed after calcination at 600 degree C for 6 hrs. The dielectric properties of the sintered BaTiO 3 were determined in the temperature range from room temperature to 20 degree C at a frequency ranging from 500 Hz to 100 khz. The relative permittivity and the dielectric loss of the sintered pellets at 1 khz, measured at room temperature,were 1805 and 0.419 respectively.

Synthesis and characterization of novel lanthanide- and actinide-containing titanates and zircono-titanates; relevance to nuclear waste disposal

International Nuclear Information System (INIS)

Shoup, S.L.S.

1995-08-01

Before experiments using actinide elements are performed, synthetic routes are tested using lanthanides of comparable ionic radii as surrogates. Compound and solid solution formation in several lanthanide-containing titanate and zircono-titanate systems have been established using X-ray diffraction (XRD) analysis, which helped to define interesting and novel experiments, some of which have been performed and are discussed, for selected actinide elements. The aqueous solubilities of several lanthanide- and actinide-containing compounds, representative of the systems studied, were tested in several leachants, including the WIPP open-quotes Aclose quotes brine, following modified Materials Characterization Center procedures (MCC-3). The WIPP open-quotes Aclose quotes brine is a synthetic substitute for that found in nature at the Waste Isolation Pilot Plant (WIPP) in New Mexico. The concentrations of cerium, used as a surrogate for plutonium, leached by the WIPP open-quotes Aclose quotes brine from all the cerium-containing compounds and solid solutions tested were below the Inductively Coupled Plasma (ICP) atomic emission spectrometry limit of detection (10 ppm) established for cerium in this brine. The concentrations of plutonium leached from the two plutonium-containing solid solutions were less than 1 ppm as determined by gross alpha counting and alpha pulse height analysis. Concentrations of strontium leached by the WIPP brine from stable strontium containing titanate compounds, studied as possible immobilizers of both 90 Sr and actinide elements, were also quite low. These compound and solid solution formation investigations and the aqueous solubility studies suggest that the types of titanate and zircono-titanate compounds and solid solutions studied in this work appear to be useful as host matrices for nuclear waste immobilization

The effects of additive on microstructure and electrical properties of batio3 ceramics

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Paunović Vesna V.

2004-01-01

Full Text Available In this paper comparative investigations of microstructure and dielectric properties of BaTiO3 ceramics doped with 1.0 wt% of Nb2O5, MnCO3 and CaZrO3 have been done. BaTiO3 samples were prepared using conventional method of solid state sintering at 13000C for two hours. Two distinguish micro structural regions can be observed in sample doped with Nb2O5. The first one, with a very small grained microstructure and the other one, with a rod like grains. In MnCO3 and CaZrO3 doped ceramics the uniform microstructure is formed with average grain size about 0.5- 2µm and 3-5µm respectively. The highest value of dielectric permittivity at room temperature and the greatest change of permittivity in function of temperature were observed in MnCO3/BaTiO3. In all investigated samples dielectric constant after initially large value at low frequency attains a constant value at f = 6kHz. A dissipation factor is independent of frequency greater than 10 kHz and, depending of systems, lies in the range from 0.035 to 0.25. At temperatures above Curie temperatures, the permittivity of all investigated samples follows a Curie- Weiss law. A slight shift of Curie temperature to the lower temperatures, in respect of Curie temperature for undoped BaTiO3, was observed in all investigated samples.

Highly piezoelectric BaTiO3 nanorod bundle arrays using epitaxially grown TiO2 nanomaterials.

Science.gov (United States)

Jang, Seon-Min; Yang, Su Chul

2018-06-08

Low-dimensional piezoelectric nanostructures such as nanoparticles, nanotubes, nanowires, nanoribbons and nanosheets have been developed for potential applications as energy harvesters, tunable sensors, functional transducers and low-power actuators. In this study, lead-free BaTiO 3 nanorod bundle arrays (NBA) with highly piezoelectric properties were successfully synthesized on fluorine-doped tin oxide (FTO) substrate via a two-step process consisting of TiO 2 epitaxial growth and BaTiO 3 conversion. Through the TiO 2 epitaxial growth on FTO substrate, (001) oriented TiO 2 nanostructures formed vertically-aligned NBA with a bundle diameter of 80 nm and an aspect ratio of six. In particular, chemical etching of the TiO 2 NBA was conducted to enlarge the surface area for effective Ba 2+ ion diffusion during the perovskite conversion process from TiO 2 to BaTiO 3 . The final structure of perovskite BaTiO 3 NBA was found to exhibit a feasible piezoelectric response of 3.56 nm with a clear phase change of 180° from the single BaTiO 3 bundle, by point piezoelectric forced microscopy (PFM) analysis. Consequently, highly piezoelectric NBA could be a promising nanostructure for various nanoscale electronic devices.

Highly piezoelectric BaTiO3 nanorod bundle arrays using epitaxially grown TiO2 nanomaterials

Science.gov (United States)

Jang, Seon-Min; Yang, Su Chul

2018-06-01

Low-dimensional piezoelectric nanostructures such as nanoparticles, nanotubes, nanowires, nanoribbons and nanosheets have been developed for potential applications as energy harvesters, tunable sensors, functional transducers and low-power actuators. In this study, lead-free BaTiO 3 nanorod bundle arrays (NBA) with highly piezoelectric properties were successfully synthesized on fluorine-doped tin oxide (FTO) substrate via a two-step process consisting of TiO2 epitaxial growth and BaTiO3 conversion. Through the TiO2 epitaxial growth on FTO substrate, (001) oriented TiO2 nanostructures formed vertically-aligned NBA with a bundle diameter of 80 nm and an aspect ratio of six. In particular, chemical etching of the TiO2 NBA was conducted to enlarge the surface area for effective Ba2+ ion diffusion during the perovskite conversion process from TiO2 to BaTiO3. The final structure of perovskite BaTiO3 NBA was found to exhibit a feasible piezoelectric response of 3.56 nm with a clear phase change of 180° from the single BaTiO3 bundle, by point piezoelectric forced microscopy (PFM) analysis. Consequently, highly piezoelectric NBA could be a promising nanostructure for various nanoscale electronic devices.

Growth and micro structural studies on Yittria Stabilized Zirconia (YSZ) and Strontium Titanate (STO) buffer layers

Energy Technology Data Exchange (ETDEWEB)

Srinivas, S.; Bhatnagar, A.K. [Univ. of Hyderabad (India); Pinto, R. [Solid State Electronics Group, Bombay (India)] [and others

1994-12-31

Microstructure of Yittria Stabilized Zirconia (YSZ) and Strontium Titanate (STO) of radio frequency magnetron sputtered buffer layers was studied at various sputtering conditions on Si<100>, Sapphire and LaAlO{sub 3} <100> substrates. The effect of substrate temperatures upto 800 C and sputtering gas pressures in the range of 50 mTorr. of growth conditions was studied. The buffer layers of YSZ and STO showed a strong tendency for columnar structure with variation growth conditions. The buffer layers of YSZ and STO showed orientation. The tendency for columnar growth was observed above 15 mTorr sputtering gas pressure and at high substrate temperatures. Post annealing of these films in oxygen atmosphere reduced the oxygen deficiency and strain generated during growth of the films. Strong c-axis oriented superconducting YBa{sub 2}Cu{sub 9}O{sub 7-x} (YBCO) thin films were obtained on these buffer layers using pulsed laser ablation technique. YBCO films deposited on multilayers of YSZ and STO were shown to have better superconducting properties.

Synthesis of BaTiO3 nanoparticles from TiO2-coated BaCO3 particles derived using a wet-chemical method

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Yuuki Mochizuki

2014-03-01

Full Text Available BaCO3 particles coated with amorphous TiO2 precursor are prepared by a wet chemical method to produce BaTiO3 nanoparticles at low temperatures. Subsequently, we investigate the formation behavior of BaTiO3 particles and the particle growth behavior when the precursor is subjected to heat treatment. The state of the amorphous TiO2 coating on the surface of BaCO3 particles depends on the concentration of NH4HCO3, and the optimum concentration is found to be in the range 0.5–1.0 M. Thermogravimetric curves of the BaCO3 particles coated with the TiO2 precursor, prepared from BaCO3 particles of various sizes, show BaTiO3 formation occurring mainly at 550–650 °C in the case of fine BaCO3 particles. However, as evidenced from the curves, the temperature of formation of BaTiO3 shifts to higher values with an increase in the size of the BaCO3 particles. The average particle size of single phase BaTiO3 at heat-treatment temperature of 650–900 °C is observed to be in the range 60–250 nm.

Nanocomposites of ferroelectric polymers with surface-hydroxylated BaTiO 3 nanoparticles for energy storage applications

KAUST Repository

Almadhoun, Mahmoud Nassar Mahmoud

2012-01-01

A facile surface hydroxylation treatment using hydrogen peroxide to modify the surface of BaTiO 3 nanofillers dispersed in a ferroelectric copolymer host has been investigated. We demonstrate that the surface functionalization of the BaTiO 3 nanofillers (<100 nm) with hydroxyl groups results in as much as two orders of magnitude reduction in the leakage current of nanocomposite thin-film capacitors. This reduction is observed concurrently with the enhancement of the effective permittivity and breakdown strength of the thin-film nanocomposites. Surface modified BaTiO 3 particles display better dispersion within the polymer matrix, resulting in enhanced relative permittivity and reduced dielectric loss. The dielectric behavior of the nanocomposite films containing up to 30 vol.% BaTiO 3 agreed well with the Bruggeman model. These results demonstrate the potential of facile surface hydroxylation of nanoparticles towards the fabrication of higher energy-density nanocomposites. © 2012 The Royal Society of Chemistry.

Flow method for rapid production of Batio3 nanoparticles in supercritical water

International Nuclear Information System (INIS)

Atashfaraz, M.; Shariati-Niassar, M.; Ohara, Satoshi; Takami, S.; Umetsu, M.; Naka, T.; Adschiri, T.

2006-01-01

Fine BaTiO 3 nanoparticles were obtained by hydrothermal synthesis under supercritical conditions with batch and flow type experimental methods. Mixture of barium hydroxide and titanium oxide starting solution was treated in the supercritical wafer at 400 d eg C and 30 MPa. The size of nanoparticles synthesized in the flow type experiment was smaller than that in the batch type. Rapid heating in a flow, reactor is effective to synthesize smaller size and narrower particle size distribution for the BaTiO 3 , nanoparticles. The mechanism for this result was discussed based on the solubility of titanium oxide

Lattice distortion under an electric field in BaTiO3 piezoelectric single crystal

International Nuclear Information System (INIS)

Tazaki, Ryoko; Fu Desheng; Daimon, Masahiro; Koshihara, Shin-ya; Itoh, Mitsuru

2009-01-01

Lattice distortions under an electric field in a mono-domain of BaTiO 3 ferroelectric crystal have been detected with synchrotron x-ray radiation. The variation of the lattice constant with an electric field observed with high angle diffraction shows a linear response nature of the piezoelectric effect. When an electric field is applied along the spontaneous polarization direction, the c-axis of the lattice elongates and the a-axis of the lattice shrinks at a rate of d 33 = 149 ± 54 pm V -1 and d 31 = -82 ± 61 pm V -1 ; these represent the longitudinal and transverse piezoelectric coefficients of BaTiO 3 crystal, respectively. These results give an insight into the intrinsic piezoelectric response on the lattice scale in BaTiO 3 that has been widely used to explore high performance lead-free piezoelectric alloys.

Study of thin films of carrier-doped strontium titanate with emphasis on their interfaces with organic thin films

Energy Technology Data Exchange (ETDEWEB)

Sato, Naoki [Laboratory of Molecular Aggregation Analysis, Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011 (Japan)]. E-mail: naokis@e.kuicr.kyoto-u.ac.jp; Harada, Youichiro [Laboratory of Molecular Aggregation Analysis, Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011 (Japan); Terashima, Takahito [International Research Center of Elements Science, Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011 (Japan); Kanda, Ryoko [International Research Center of Elements Science, Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011 (Japan); Takano, Mikio [International Research Center of Elements Science, Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011 (Japan)

2005-05-15

Fifty nanometer-thick metal-doped strontium titanate (M:STO, M = La and V) films deposited epitaxially on single crystalline STO substrates were characterized in comparison with indium tin oxide (ITO) covered glasses, to check their applicability to optically transparent anode materials for organic optoelectronic devices. M:STO, in particular V:STO, films turned out to have distinct surface flatness, needfully low electric resistivities and notably large work functions. While their optical transmittances are lower than those of ITOs at this moment, we suggest that M:STO films have a potential to take the place of ITO films. Further, we have observed energy level alignments for copper phthalocyanine thin films at the interface of V:STO.

Band-offsets at BaTiO3/Cu2O heterojunction and enhanced photoelectrochemical response: theory and experiment(Conference Presentation)

Science.gov (United States)

Sharma, Dipika; Satsangi, Vibha R.; Dass Kaura, Sahab; Shrivastav, Rohit; Waghmare, Umesh V.

2016-10-01

Band-offsets at BaTiO3/Cu2O heterojunction and enhanced photoelectrochemical response: theory and experiment Dipika Sharmaa, Vibha R. Satsangib, Rohit Shrivastava, Umesh V. Waghmarec, Sahab Dassa aDepartment of Chemistry, Dayalbagh Educational Institute, Agra-282 110 (India) bDepartment of Physics and Computer Sciences, Dayalbagh Educational Institute, Agra-282 110 (India) cTheoretical Sciences Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, Bangalore-560 064 (India) * Phone: +91-9219695960. Fax: +91-562-2801226. E-mail: drsahabdas@gmail.com. Study on photoelectrochemical activity of pristine BaTiO3, Cu2O and BaTiO3/Cu2O heterojunction has been carried out using DFT based band offsets and charge carriers effective mass calculations and their experimental verification. The results of DFT calculations show that BaTiO3 and Cu2O have staggered type band alignment after the heterojunction formation and high mobility of electrons in Cu2O as compared to the electrons in BaTiO3. Staggered type band edges alignment and high mobility of electrons and holes improved the separation of photo-generated charge carriers in BaTiO3/Cu2O heterojunction. To validate the theoretical results experiments were carried out on pristine BaTiO3, Cu2O and BaTiO3/Cu2O heterojunction with varying thickness of Cu2O. All samples were characterized by X- Ray Diffractometer, SEM and UV-Vis spectrometry. Nanostructured thin films of pristine BaTiO3, Cu2O and BaTiO3/Cu2O heterojunction were used as photoelectrode in the photoelectrochemical cell for water splitting reaction. Maximum photocurrent density of 1.44 mA/cm2 at 0.90 V/SCE was exhibited by 442 nm thick BaTiO3/Cu2O heterojunction photoelectrode Increased photocurrent density and enhanced photoconversion efficiency, exhibited by the heterojunction may be attributed to improved conductivity and enhanced separation of the photogenerated carriers at the BaTiO3/Cu2O interface. The experimental results and first

Computational study of structures of yttria-stabilised zirconia/strontium titanate multilayers

Energy Technology Data Exchange (ETDEWEB)

Cheah, Wei Li; Finnis, Mike [Imperial College London (United Kingdom)

2012-07-01

Growing interest in the field of functional oxide multilayered nano-heterostructures may be attributed to their unusual interfacial properties that are not yet fully understood. For instance, the nature of the unexpectedly high conductivity reported in a trilayer of 1-nm thick epitaxial yttria-stabilised zirconia (YSZ) film sandwiched between strontium titanate (STO) layers still remains controversial. In an effort to investigate the source of conductivity in this system, we first establish an unexpected YSZ lattice within such hetero-system using a combination of techniques - a genetic algorithm in which the interatomic forces are described by classical pair potentials, and a pseudo-potential-based DFT method as implemented in the plane-wave code CASTEP. We find this structure to be more stable than an anatase zirconia epitaxial lattice on STO which has been previously found as the most stable structure if yttrium dopants were not incorporated within the zirconia layer. Analysis of charge density of this new structure reveals not localised vacancies, but several small pockets of low charge densities for each expected vacancy. We examine the mobility of oxide ions in the hetero-system using classical molecular dynamics simulation and attempt to relate the results to experimental conductivity values.

Characterization, dielectric and electrical behaviour of BaTiO3 ...

Indian Academy of Sciences (India)

Administrator

of λ = 0⋅1542 nm, for crystal structure determination. Scherrer's equation and ... ion, releasing one molecule of propanol and one molecule of triethanolamine in .... The OH, CO2 and CO3 peaks were reduced in the sam- ple of BaTiO3 when ...

Síntesis de polvos de BaTiO3 por mecanoquímica

Directory of Open Access Journals (Sweden)

Villaquirán Raigoza, C. F.

2002-02-01

Full Text Available The barium titanato, BaTiO3, is one of the electronic ceramics with more history of technological application in the industry of the ceramic capacitores. The actual technological demands, and the high quality required for the electronic devices, have driven to new alternatives of prosecution of these materials and to optimize the traditional techniques of raw materials synthesis it prevails. An alternative synthesis is to use the mechanical energy to modify the physiochemical properties of the dispersed system and to favor the obtaining of powders of BaTiO3. In this work the results are indicated obtained when using mechanical activation, physicochemistry, in the obtaining of the BaTiO3. It has been analyzed the effect of the time of mill and the nature of the precursor of the titanium on the transformation of phases in the samples during the thermal treatment to that are subjected. X-ray diffraction, DRX, was used to study the phases evolution and infrared spectroscopy, FTIR, to determine the functional groups present in the samples.El titanato de bario, BaTiO3, es uno de los cerámicos electrónicos con mayor historia de aplicación tecnológica en la industria de los capacitores cerámicos. Las demandas tecnológicas actuales, y la alta calidad requerida para los dispositivos electrónicos, han conducido a nuevas alternativas de procesamiento de estos materiales y a optimizar las técnicas tradicionales de síntesis de materia prima. Una alternativa de síntesis es utilizar la energía mecánica para modificar las propiedades fisicoquímicas del sistema disperso y favorecer la obtención de polvos de BaTiO3. En este trabajo se indican los resultados obtenidos al utilizar activación mecánica, mecanoquímica, en la obtención del BaTiO3. Se ha analizado el efecto del tiempo de molienda y la naturaleza del precursor del titanio sobre la transformación de fases que experimentan las muestras durante el tratamiento térmico a que son sometidas

Microwave-Hydrothermal Synthesis and Characterization of High-Purity Nb Doped BaTiO3 Nanocrystals

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A. Khanfekr

2014-01-01

Full Text Available The synthesis of Nb doped BaTiO3 has been investigated under Microwave-Hydrothermal (MH conditions in the temperature of 150°C for only 2 h using C16H36O4Ti, BaH2O2.8H2O and NbCl5 as Ba, Ti and  Nb sources, respectively.  Typical experiments performed on MH processing have not yet reported for Nb doped BaTiO3.  In the MH process, the formation of high purity nano tetragonal Nb-BaTiO3 was strongly enhanced. New hydrothermal method was used instead of the previous solid state reaction for the BaTiO3±Nb2O3 system. The new method uses high pressure to create nano dimension particles in a lower time and temperature. In case of the phase evolution studies, the XRD pattern measurements and Raman spectroscopy were performed. TEM and FE-SEM images were taken for the detailed analysis of the particle size, surface and morphology.  Synthesis of Nb doped BaTiO3 with the Microwave-hydrothermal provides an advantage of fast crystallization and reduced crystal size when compared to existing methods.

Direct Observation of Surface Potential Distribution in Insulation Resistance Degraded Acceptor-Doped BaTiO3 Multilayered Ceramic Capacitors

Science.gov (United States)

Hong, Kootak; Lee, Tae Hyung; Suh, Jun Min; Park, Jae-Sung; Kwon, Hyung-Soon; Choi, Jaeho; Jang, Ho Won

2018-05-01

Insulation resistance (IR) degradation in BaTiO3 is a key issue for developing miniaturized multilayer ceramic capacitors (MLCCs) with high capacity. Despite rapid progress in BaTiO3-based MLCCs, the mechanism of IR degradation is still controversial. In this study, we demonstrate the Al doping effect on IR degradation behavior of BaTiO3 MLCCs by electrical measurements and scanning Kelvin probe microscopy (SKPM). As the Al doping concentration in BaTiO3 increases, IR degradation of MLCCs seems to be suppressed from electrical characterization results. However, SKPM results reveal that the conductive regions near the cathode become lager with Al doping after IR degradation. The formation of conducting regions is attributed to the migration of oxygen vacancies, which is the origin of IR degradation in BaTiO3, in dielectric layers. These results imply that acceptor doping in BaTiO3 solely cannot suppress the IR degradation in MLCC even though less asymmetric IR characteristics and IR degradation in MLCCs with higher Al doping concentration are observed from electrical characterization. Our results strongly suggest that observing the surface potential distribution in IR degraded dielectric layers using SKPM is an effective method to unravel the mechanism of IR degradation in MLCCs.

Fabrication of BaTiO3/Ni composite particles and their electro-magneto responsive properties

International Nuclear Information System (INIS)

Lu, Yaping; Gao, Lingxiang; Wang, Lijuan; Xie, Zunyuan; Gao, Meixiang; Zhang, Weiqiang

2017-01-01

Graphical abstract: The spherical BaTiO 3 /Ni particles with excellent structure were made by one-step method through fixing the metal Ni(0) reduced by a specific reducing agent (N 2 H 4 ·H 2 O) on the surface of the BaTiO 3 particles with grain diameter of ∼500 nm. BaTiO 3 /Ni particle has double responses of electric and magnetic field simultaneously. Consequentially, coating magnetic metal on BT particle is proposed an effective method to prepare novel electro-magneto responsive particles and one basis of electro-magneto responsive elastomers. - Highlights: • The BaTiO 3 /Ni composite particles were fabricated. • The content of Ni(0) in nickel sheath is 70.2%. • The BaTiO 3 /Ni particles have double responses of electric and magnetic field. - Abstract: BaTiO 3 (BT)/Ni composite particles were made by one-step method through agglomerating the metal Ni(0) nanoparticles reduced by a specific reducing agent (N 2 H 4 ·H 2 O) on the surface of BT sphere with diameter of ∼500 nm. The BT/Ni composite particles were characterized by the means of scanning electron microscope (SEM), transmission electron microscopy (TEM), X-ray diffractometer (XRD) and X-ray photoelectron spectroscopy (XPS). In BT/Ni particles, pure BT spherical particle was coated with Ni nanoparticles agglomerated on its surface. The average thickness of the Ni sheath was ∼30 nm and the content of Ni(0) and Ni (II) in the sheath were 70.2% and 29.8%, respectively. The responsive effects of BT/Ni particles filled in hydrogel elastomer were investigated by the viscoelastic properties. The results indicate that the BT/Ni particles exhibit electro and magneto coordinated responsive properties (E = 1 kV/mm, H = 0.1 T/mm), which is superior to BT particles with individual electro response.

Enhancement of polarization property of silane-modified BaTiO3 nanoparticles and its effect in increasing dielectric property of epoxy/BaTiO3 nanocomposites

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Thi Tuyet Mai Phan

2016-03-01

Full Text Available The surface modification of synthesized nano-BaTiO3 particles was carried out using γ-aminopropyl trimethoxy silane (γ-APS in an ethanol/water solution. The modified particles were characterized by FTIR, TGA, surface charge analysis, and by dielectric constant measurement. The silane molecules were attached to the surface of BaTiO3 particles through SiOBaTiO3 bonds. The γ-APS grafted on BaTiO3 made the dielectric constant of the particles increase at frequencies ≥0.3 kHz in a wide range of temperature (25 °C–140 °C, due to the presence of NH2 groups. The dependence of the polarization vs. electrical field was measured in order to elucidate the dielectric behavior of the silane treated BaTiO3 in comparison to untreated BaTiO3. The nanocomposite based on epoxy resin containing BaTiO3 nanoparticles untreated and treated with γ-APS was also prepared and characterized. The results indicated that the γ-APS-modified BaTiO3 surfaces significantly enhanced the dielectric property of the nanocomposite.

Fabrication and electrical investigations of Pb-doped BaTiO_3 ceramics

International Nuclear Information System (INIS)

Sareecha, N.; Shah, W.A.; Maqsood, A.; Anis-ur-Rehman, M.; Latif Mirza, M.

2017-01-01

Electrical properties of Pb doped BaTiO_3; PBT are investigated in the wide range of temperatures (40–700 °C) at 1 kHz frequency. PBT ceramics were fabricated through solid state sintering method. Pre fired BaTiO_3 prepared with Ba/Ti molar ratio of 0.98 was doped with PbCO_3 (<1 mole %). XRD patterns indicated perovskite phase with tetragonal structures (P4mm). Morphological studies (SEM) revealed grain development with increasing lead contents. With lead doping and its variation, Curie temperature (T_C) was shifted from 120 to 200 °C with broad dielectric constant peaks and dielectric anomalies with relaxor behavior were observed. Resistivity decreased with increasing temperature, all specimens showed semiconductor behavior with negative temperature coefficient of resistivity (NTCR) characteristics. Mobility of electrons increased with thermal activation due to hopping of charge carriers from one site to another. Ohmic conductivities and associated activation energies were evaluated by impedance spectroscopy. Conductivity followed the Arrhenius law with E_a = 1.187–1.169 eV which can be attributed to the ionic conduction owning to doubly ionized oxygen vacancies. Well-defined hysteresis P-E loops measured at room temperature depicted ferroelectric properties of the materials. - Graphical abstract: Temperature dependence of dielectric constant (Ɛ′) and resistivity (ρ) for pure and Pb-doped BaTiO_3 ceramics at 1 k Hz frequency. - Highlights: • Pb-doped BaTiO_3ceramics were fabricated through solid state sintering. • Electrical properties were studied at the temperatures 40–700 °C at 1 kHz. • Specimens showed negative temperature coefficient of resistivity characteristics. • Conductivity followed the Arrhenius law with E_a = 1.187–1.169 eV. • Ionic conduction was supposed to be responsible for conduction process.

Scandium doped Strontium Titanate Ceramics: Structure, Microstructure, and Dielectric Properties

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Tkach, Alexander

2008-08-01

Full Text Available Sc-doped strontium titanate (ST ceramics were synthesised by solid state reaction, according to the composition Sr_1-1.5xSc_xTiO₃ with x = 0-0.01. Structural properties and microstructure development was examined by XRD and SEM. The dielectric properties were evaluated as a function of the temperature and frequency in the radio frequency range. Lattice parameter, density and grain size, were found to decrease slightly with increasing Sc content. The dielectric permittivity and losses decrease also. Sc-doping has only a weak effect on the quantum paraelectric behaviour of ST and no dielectric anomaly was observed, what is probably related to the limited solubility of Sc on the Sr site of the perovskite lattice of ST.

Se sintetizaron materiales cerámicos de titanato de estroncio dopado con escandio mediante reacción en estado sólido De acuerdo a la composición Sr_1-1.5xSc_xTiO₃ con x= 0-0.1. Las propiedades estructurales y el desarrollo microestructural se estudiaron mediante XRD y SEM. La propiedades dieléctricas se estudiaron como función de la temperatura y de la frecuencia en el rango de la frecuencias de radio. Se observó que los parámetros de red, la densidad y el tamaño del grano disminuyen ligeramente con el contenido en Sc. La permitividad dieléctrica y las perdidas también disminuyen. El dopado con Sc tiene un efecto muy ligero sobre el comportamiento paraeléctrico cuántico del titanato de estroncio y no se observó anomalías dioeléctricas , lo que está probablemente relacionado con la baja solubilidad del Sc en posiciones del Sr en la estructura tipo perovskita del titanato de estroncio.

Electrical properties of (1 0 0)-predominant BaTiO3 films derived from alkoxide solutions of two concentrations

International Nuclear Information System (INIS)

Guo Yiping; Suzuki, Kazuyuki; Nishizawa, Kaori; Miki, Takeshi; Kato, Kazumi

2006-01-01

Lead-free piezoelectric films with thickness larger than 1 μm integrated on silicon substrates have been receiving considerable attention because of environmental concerns and their potential applications in microelectromechanical systems. We demonstrate that, by chemical solution deposition, it is possible to process (1 0 0)-predominant 1 μm BaTiO 3 films on LaNiO 3 /Pt/TiO x /SiO 2 /Si substrates using thinner high-crystallinity columnar BaTiO 3 films as buffer layers. We point out that this kind of buffer layer prepared with a lower concentration solution on the surface of an LaNiO 3 /Pt electrode is effective in enhancing the crystallinity and orientation degree of final BaTiO 3 films prepared with a higher concentration solution. The 1 μm BaTiO 3 films show good dielectric and insulating characteristics against an applied field, and the conduction current shows Schottky emission behavior at modest voltage and space-charge-limited behavior at higher voltage. We also demonstrate that the (1 0 0)-predominant 1 μm BaTiO 3 films have excellent piezoelectric properties: piezoelectric coefficients d 33 higher than 50 pm/V have been determined for the bare films using atomic force microscopy, which are comparable to those of Pb(Zr,Ti)O 3 films. These results indicate that the (1 0 0)-predominant BaTiO 3 films should be promising candidates for microelectromechanical systems applications

Digital to analog resistive switching transition induced by graphene buffer layer in strontium titanate based devices.

Science.gov (United States)

Wan, Tao; Qu, Bo; Du, Haiwei; Lin, Xi; Lin, Qianru; Wang, Da-Wei; Cazorla, Claudio; Li, Sean; Liu, Sidong; Chu, Dewei

2018-02-15

Resistive switching behaviour can be classified into digital and analog switching based on its abrupt and gradual resistance change characteristics. Realizing the transition from digital to analog switching in the same device is essential for understanding and controlling the performance of the devices with various switching mechanisms. Here, we investigate the resistive switching in a device made with strontium titanate (SrTiO 3 ) nanoparticles using X-ray diffractometry, scanning electron microscopy, Raman spectroscopy, and direct electrical measurements. It is found that the well-known rupture/formation of Ag filaments is responsible for the digital switching in the device with Ag as the top electrode. To modulate the switching performance, we insert a reduced graphene oxide layer between SrTiO 3 and the bottom FTO electrode owing to its good barrier property for the diffusion of Ag ions and high out-of-plane resistance. In this case, resistive switching is changed from digital to analog as determined by the modulation of interfacial resistance under applied voltage. Based on that controllable resistance, potentiation and depression behaviours are implemented as well. This study opens up new ways for the design of multifunctional devices which are promising for memory and neuromorphic computing applications. Copyright © 2017 Elsevier Inc. All rights reserved.

Ab Initio Calculations for the BaTiO3 (001) Surface Structure

Institute of Scientific and Technical Information of China (English)

XUE Xu-Yan; WANG Chun-Lei; ZHONG Wei-Lie

2004-01-01

@@ The ab initio method within the local density approximation is applied to calculate cubic BaTiO3 (001) surface relaxation and rumpling for two different terminations (BaO and TiO2). Our calculations demonstrate that cubic perovskite BaTiO3 crystals possess surface polarization, accompanied by the presence of the relevant electric field.We analyse their electronic structures (band structure, density of states and the electronic density redistribution with emphasis on the covalency effects). The results are also compared with that of the previous ab initio calculations. Considerable increases of Ti-O chemical bond covalency nearby the surface have been observed.The band gap reduces especially for the TiO2 termination.

TAILORING INORGANIC SORBENTS FOR SRS STRONTIUM AND ACTINIDE SEPARATIONS: OPTIMIZED MONOSODIUM TITANATE PHASE II FINAL REPORT

International Nuclear Information System (INIS)

Hobbs, D; Thomas Peters, T; Michael Poirier, M; Mark Barnes, M; Major Thompson, M; Samuel Fink, S

2007-01-01

This document provides a final report of Phase II testing activities for the development of a modified monosodium titanate (MST) that exhibits improved strontium and actinide removal characteristics compared to the baseline MST material. The activities included determining the key synthesis conditions for preparation of the modified MST, preparation of the modified MST at a larger scale by a commercial vendor, demonstration of the strontium and actinide removal characteristics with actual tank waste supernate and measurement of filtration characteristics. Key findings and conclusions include the following. Testing evaluated three synthetic methods and eleven process parameters for the optimum synthesis conditions for the preparation on an improved form of MST. We selected the post synthesis method (Method 3) for continued development based on overall sorbate removal performance. We successfully prepared three batches of the modified MST using Method 3 procedure at a 25-gram scale. The laboratory prepared modified MST exhibited increased sorption kinetics with simulated and actual waste solutions and similar filtration characteristics to the baseline MST. Characterization of the modified MST indicated that the post synthesis treatment did not significantly alter the particle size distribution, but did significantly increase the surface area and porosity compared to the original MST. Testing indicated that the modified MST exhibits reduced affinity for uranium compared to the baseline MST, reducing risk of fissile loading. Shelf-life testing indicated no change in strontium and actinide performance removal after storing the modified MST for 12-months at ambient laboratory temperature. The material releases oxygen during the synthesis and continues to offgas after the synthesis at a rapidly diminishing rate until below a measurable rate after 4 months. Optima Chemical Group LLC prepared a 15-kilogram batch of the modified MST using the post synthesis procedure (Method

Barium Titanate Photonic Crystal Electro-Optic Modulators for Telecommunication and Data Network Applications

Science.gov (United States)

Girouard, Peter D.

The microwave, optical, and electro-optic properties of epitaxial barium titanate thin films grown on (100) MgO substrates and photonic crystal electro-optic modulators fabricated on these films were investigated to demonstrate the applicability of these devices for telecommunication and data networks. The electrical and electro-optical properties were characterized up to modulation frequencies of 50 GHz, and the optical properties of photonic crystal waveguides were determined for wavelengths spanning the optical C band between 1500 and 1580 nm. Microwave scattering parameters were measured on coplanar stripline devices with electrode gap spacings between 5 and 12 mum on barium titanate films with thicknesses between 230 and 680 nm. The microwave index and device characteristic impedance were obtained from the measurements. Larger (lower) microwave indices (impedances) were obtained for devices with narrower electrode gap spacings and on thicker films. Thinner film devices have both lower index mismatch between the co-propagating microwave and optical signals and lower impedance mismatch to a 50O system, resulting in a larger predicted electro-optical 3 dB bandwidth. This was experimentally verified with electro-optical frequency response measurements. These observations were applied to demonstrate a record high 28 GHz electro-optic bandwidth measured for a BaTiO3 conventional ridge waveguide modulator having 1mm long electrodes and 12 mum gap spacing on a 260nm thick film. The half-wave voltage and electro-optic coefficients of barium titanate modulators were measured for films having thicknesses between 260 and 500 nm. The half-wave voltage was directly measured at low frequencies using a polarizer-sample-compensator-analyzer setup by over-driving waveguide integrated modulators beyond their linear response regime. Effective in-device electro-optic coefficients were obtained from the measured half-wave voltages. The effective electro-optic coefficients were

Ajuste teórico de las curvas PTCR de BaTiO3 dopado con niobio

Directory of Open Access Journals (Sweden)

Castro, M. S.

2002-02-01

Full Text Available In this work, a theoretical fitting to the experimental PTCR effect in slightly Nb-doped BaTiO3 from the Heywang-Jonker model is simulated. Besides, a qualitative approach was used to evaluate the GBBL characteristics of strongly Nb - doped BaTiO3. In both cases, a link between the electrical properties and the defect profile developed in these based - BaTiO3 ceramics was established. From the results, good agreement between experimental and calculated results was obtained for the PTCR ceramics. Asmall increment in Nb2O5 concentration leads to an increasing in the concentration of occupied acceptor states, the energy of the surface state and also the barrier height. In these cases, microstructural observations shown an important grain growth with average grain size between 10 and 100μm. EPR results clearly indicate low concentration of cationic vacancies for these materials. This phenomenon is associated to a charge-compensation mechanism in slightly-doped BaTiO3, that result in a semiconducting behaviour. On the other hand, the electrical behaviour of strongly–doped BaTiO3 moves away from the PTCR effect, and the material becomes insulating with noticeable GBBL characteristics. In this case, microstructural observations along defect structure analysis encourage the hypothesis in which barium vacancies act as acceptor at grain boundaries and play and important role in restricting grain growth of Nb2O5-BaTiO3 ceramics.En este trabajo se determinó la influencia de la concentración de Nb2O5 sobre el comportamiento PTCR de cerámicos basados en BaTiO3. Por otra parte, se estudió el impacto de una gran concentración del dopante sobre el comportamiento GBBL del BaTiO3. En ambos casos, se estableció una relación entre las propiedades eléctricas observadas y la estructura de defectos iónicos desarrollada. La aplicación del modelo de Heywang-Jonker permite el ajuste teórico de las curvas de resistividad – temperatura de los cerámicos PTCR

Frequency and Temperature Dependent Dielectric Properties of Free-standing Strontium Titanate Thin Films.

Science.gov (United States)

Dalberth, Mark J.; Stauber, Renaud E.; Anderson, Britt; Price, John C.; Rogers, Charles T.

1998-03-01

We will report on the frequency and temperature dependence of the complex dielectric function of free-standing strontium titanate (STO) films. STO is an incipient ferroelectric with electric-field tunable dielectric properties of utility in microwave electronics. The films are grown epitaxially via pulsed laser deposition on a variety of substrates, including lanthanum aluminate (LAO), neodymium gallate (NGO), and STO. An initial film of yttrium barium cuprate (YBCO) is grown on the substrate, followed by deposition of the STO layer. Following deposition, the sacrificial YBCO layer is chemically etched away in dilute nitric acid, leaving the substrate and a released, free-standing STO film. Coplanar capacitor structures fabricated on the released films allow us to measure the dielectric response. We observe a peak dielectric function in excess of 5000 at 35K, change in dielectric constant of over a factor of 8 for 10Volt/micron electric fields, and temperature dependence above 50K that is very similar to bulk material. The dielectric loss shows two peaks, each with a thermally activated behavior, apparently arising from two types of polar defects. We will discuss the correlation between dielectric properties, growth conditions, and strain in the free-standing STO films.

Microstructure Control of Barium Titanate Grain-oriented Ceramics and Their Piezoelectric Properties

International Nuclear Information System (INIS)

Mori, Rintaro; Nakashima, Koichi; Fujii, Ichiro; Wada, Satoshi; Hayashi, Hiroshi; Nagamori, Yoshitaka; Yamamoto, Yuichi

2011-01-01

The Barium titanate (BaTiO 3 , BT) [110] grain-oriented ceramics along [110] direction were prepared by a templated grain growth (TGG) method. The [110] oriented BT platelike particles (t-BT) were used as template particles. The relationship between poling treatment program and piezoelectric constant was investigated. The change in the poling conditions did not greatly influence domain size and the piezoelectric constant. The relationship between piezoelectric properties and domain size in BT grain-oriented ceramics was investigated. The smaller domain size was required to increase the piezoelectric constant.

Interface control in BaTiO3 based supercapacitors

Science.gov (United States)

Maglione, Mario; Elissalde, Catherine; Chung, U.-Chan

2010-03-01

Core shell BaTiO3 based particles sintered using advanced processes provide a high control of grain boundaries in bulk composites. As a result, supercapacitor behavior was evidenced which came from the balance between inner grain conductivity and grain boundary dielectric barrier. Thanks to the core-shell structure of the starting particles, improved control of the effective dielectric parameters can be achieved.

Dielectric properties of a BaTiO3 ceramic prepared by using the freeze drying method

International Nuclear Information System (INIS)

Al-Shakarchi, Emad K.

2010-01-01

A modified catecholate process has been developed to synthesize high-purity barium titanate by using a freeze drying method to produce ultra-fine powders from a barium titanium catechol complex, Ba[Ti(C 6 H 4 O 2 ) 3 ]. The complex prepared from TiCl 4 , C 6 H 4 (OH) 2 and BaCO 3 . The freeze drying of the complex Ba[Ti(C 6 H 4 O 2 ) 3 ] under a primary vacuum at a freezing temperature of -50 .deg. C for a long time 24 hrs is necessary to transfer the complex Ba[Ti(C 6 H 4 O 2 ) 3 ] from a liquid phase to a solid phase. A subsequent calcination of the complex for 12 hrs at a temperature of 700 .deg. C was very important to remove the acetates from the mixture. Finally, a sintering process was required for the pellets so that high density samples could be investigated. The dielectric properties, the structural phase, and the particle size of the sintered pellets have investigated as functions of frequency and temperature in order to determine the critical temperature for the phase transition. X-ray diffraction was used to investigate the structural properties and the particle size. The tetragonal phase of BaTiO 3 with the lattice constants a = b = 3.9734 A, and c = 4.012 A was successfully obtained.

Ferroelectric BaTiO3 and LiNbO3 Nanoparticles Dispersed in Ferroelectric Liquid Crystal Mixtures: Electrooptic and Dielectric (Postprint)

Science.gov (United States)

2016-10-14

strength for non- doped LF4 and LiNbO3/LF4 nanocolloids at temperature 30C. 146 R. K . SHUKLA ET AL. 6 Distribution A. Approved for public release (PA...AFRL-RX-WP-JA-2017-0210 FERROELECTRIC BaTiO3 AND LiNbO3 NANOPARTICLES DISPERSED IN FERROELECTRIC LIQUID CRYSTAL MIXTURES: ELECTROOPTIC...COMMAND UNITED STATES AIR FORCE Ferroelectric BaTiO3 and LiNbO3 nanoparticles dispersed in ferroelectric liquid crystal mixtures: Electrooptic and

Ferroelectric BaTiO3 thin films on Ti substrate fabricated using pulsed-laser deposition.

Science.gov (United States)

He, J; Jiang, J C; Liu, J; Collins, G; Chen, C L; Lin, B; Giurgiutiu, V; Guo, R Y; Bhalla, A; Meletis, E I

2010-09-01

We report on the fabrication of ferroelectric BaTiO3 thin films on titanium substrates using pulsed laser deposition and their microstructures and properties. Electron microscopy studies reveal that BaTiO3 films are composed of crystalline assemblage of nanopillars with average cross sections from 100 nm to 200 nm. The BaTiO3 films have good interface structures and strong adhesion with respect to Ti substrates by forming a rutile TiO2 intermediate layer with a gradient microstructure. The room temperature ferroelectric polarization measurements show that the as-deposited BTO films possess nearly the same spontaneous polarization as the bulk BTO ceramics indicating formation of ferroelectric domains in the films. Successful fabrication of such ferroelectric films on Ti has significant importance for the development of new applications such as structural health monitoring spanning from aerospace to civil infrastructure. The work can be extended to integrate other ferroelectric oxide films with various promising properties to monitor the structural health of materials.

Zn2+ in-situ substitution behavior during the formation of BaTiO3 coatings from plasma-sprayed powders collected in liquid nitrogen

Science.gov (United States)

Liu, Zhe; Xing, Zhiguo; Wang, Haidou; Xue, Zifan; Chen, Shuying; Cui, Xiufang; Jin, Guo

2018-04-01

The dielectric performance of BaTiO3 ceramic coatings is enhanced significantly by the addition of ZnO. In this study, the maximum relative permittivity value (εr ≈ 923) was measured in BaTiO3 coatings with ZnO added at 6 wt%. The Curie temperature (Tc) was in the range of 111 °C-121 °C for all of the ZnO-modified BaTiO3 coatings. Tc shifted to low temperatures as the ZnO content increased. Detailed analyses were performed to determine the phase composition and optical band gaps of powders collected in liquid nitrogen, which showed that the Zn2+ ions were incorporated into the BaTiO3 lattice where they substituted into the Ti4+ sites, and the composite powders (BaTiO3 + 6 wt% ZnO) tolerated high temperatures in the plasma beam. In addition, some residual Zn accumulated in the grain boundary in the form of ZnO. X-ray diffraction and Raman spectroscopy showed that the substitution led to changes in the compositional and structural properties. The red shift in the optical band gap of BaTiO3 indicated that the ZnTi'' defects caused by the dopants acted as carriers in the doped BaTiO3 coatings.

Properties of TiO2 prepared by acid treatment of BaTiO3

International Nuclear Information System (INIS)

Okada, Kiyoshi; Yanagisawa, Tomoki; Kameshima, Yoshikazu; Nakajima, Akira

2007-01-01

TiO 3 powders were prepared by acid treatment of BaTiO 3 and their properties were investigated. The BaTiO 3 powder was subjected to HNO 3 in concentrations ranging from 10 -3 to 8 M at 90 deg. C for 0.5-6 h. Dissolution of BaTiO 3 and precipitation of TiO 2 occurred at acid concentrations of 2-5 M. BaTiO 3 dissolves completely to form a clear solution at reaction times of 0.5-1 h, but a rutile precipitate is formed after 2 h of acid treatment. By contrast, anatase is precipitated by adjusting the pH of the clear solution to 2-3 using NaOH or NH 4 OH solution. The rutile crystals were small and rod-shaped, consisting of many small coherent domains connected by grain boundaries with small inclination angles and edge dislocations, giving them a high specific surface area (S BET ). With increasing HNO 3 concentration, the S BET value increased from 100 to 170 m 2 /g while the crystallite size decreased from 25 to 11 nm. The anatase crystals obtained here were very small equi-axial particles with a smaller crystallite size than the rutile and S BET values of about 270 m 2 /g (higher than the rutile samples). The photocatalytic activity of these TiO 2 was determined from the decomposition rate of Methylene Blue under ultraviolet irradiation. Higher decomposition rates were obtained with larger crystallite sizes resulting from heat treatment. The maximum decomposition rates were obtained in samples heated at 500-600 deg. C. The photocatalytic activity of the TiO 2 was found to depend more strongly on the sample crystallite size than on S BET

Linear electro-optical properties of tetragonal BaTiO 3

Indian Academy of Sciences (India)

Linear optical susceptibility and clamped linear electro-optical tensor coefficients of tetragonal BaTiO3 are calculated using a formalism based on bond charge theory. Calculated values are in close agreement with experimental data. The covalent Ti–O bonds constituting distorted TiO6 octahedral groups are found to be ...

HRTEM analysis on nanocrystalline BaTiO3 and PbTiO3: size effects on ferroelectric phase transition temperature

International Nuclear Information System (INIS)

Bursill, L.A.; Jiang, B.; Peng, J.L.; Zhong, W.L.; Zhang, P.L.

1997-01-01

High-Resolution Transmission Electron Microscopic studies of nanocrystaline particles of BaTiO 3 and PbTiO 3 are reported. There are characteristic differences observed for BaTiO 3 prepared using sol gel (SG) and steric acid gel (SAG) methods. The former exhibit a critical size below which there is no paraelectric/ferroelectric phase transition, whereas BaTiO 3 prepared via the SAG route remained cubic for all conditions. The SAG preparations always showed chemical intergrowth defects whereas the SG preparations were single phase. Atomic resolution images of both varieties showed interesting surface steps and surface relaxations/reconstructions of some facets. Nanocrystalline PbTiO 3 prepared by the SG route remains tetragonal, albeit with decreasing c/a ratio, down to 25nm diameter. HRTEM observations of nanocrystalline PbTiO 3 are also presented. X-ray diffraction, dielectric and Raman scattering measurements also demonstrate pronounced size effects. The relationship between the observed nanostructures and size effects on the physical properties is discussed. 6 refs., 1 tab., 6 figs

Thermal analysis of formation of nano-crystalline BaTiO3 using Ba(NO32 and TiO2

Directory of Open Access Journals (Sweden)

Md. Jawed Ansaree

2015-12-01

Full Text Available The reaction of Ba(NO32 with TiO2 was studied by thermogravimetric (TG and differential scanning calorimetric (DSC techniques up to 1000 °C and in nitrogen atmosphere. It was found that the formation of BaTiO3 takes place above 600 °C and that precursor mixing time and heating rate have no effect on the reaction temperature. BaTiO3 powder was prepared by calcination of Ba(NO32 and TiO2 precursor mixture at 800 °C for 8 h. X-ray diffraction analysis of the synthesized BaTiO3 confirmed the formation of tetragonal phase with lattice parameters a = 3.9950±0.0003 Å and c = 4.0318±0.0004 Å. Thermal analysis of the synthesized BaTiO3 powder showed weight loss within temperature range 40–1000 °C of only 0.40%. This small amount of weight loss was connected with some impurity phase, and identified as BaCO3 using Fourier transform infrared (FTIR technique.

Effect of Nb on barium titanate prepared from citrate solutions

Directory of Open Access Journals (Sweden)

Stojanović Biljana D.

2002-01-01

Full Text Available The influence of the addition of dopants on the microstructure development and electrical properties of BaTiO3 doped with 0.2, 0.4, 0.6, 0.8 mol% of Nb and 0.01 mol% of Mn based compounds was studied. Doped barium titanate was prepared using the polymeric precursor method from citrate solutions. The powders calcined at 700°C for 4 hours were analysed by infrared (IR spectroscopy to verify the presence of carbonates, and by X-ray diffraction (XRD for phase formation. The phase composition, microstructure and dielectric properties show a strong dependence on the amount of added niobium.

Highly uniform bipolar resistive switching characteristics in TiO2/BaTiO3/TiO2 multilayer

International Nuclear Information System (INIS)

Ma, W. J.; Zhang, X. Y.; Wang, Ying; Zheng, Yue; Lin, S. P.; Luo, J. M.; Wang, B.; Li, Z. X.

2013-01-01

Nanoscale multilayer structure TiO 2 /BaTiO 3 /TiO 2 has been fabricated on Pt/Ti/SiO 2 /Si substrate by chemical solution deposition method. Highly uniform bipolar resistive switching (BRS) characteristics have been observed in Pt/TiO 2 /BaTiO 3 /TiO 2 /Pt cells. Analysis of the current-voltage relationship demonstrates that the space-charge-limited current conduction controlled by the localized oxygen vacancies should be important to the resistive switching behavior. X-ray photoelectron spectroscopy results indicated that oxygen vacancies in TiO 2 play a crucial role in the resistive switching phenomenon and the introduced TiO 2 /BaTiO 3 interfaces result in the high uniformity of bipolar resistive switching characteristics

Luminescent Properties of Surface Functionalized BaTiO3 Embedded in Poly(methyl methacrylate)

Science.gov (United States)

Requena, Sebastian; Lacoul, Srijan; Strzhemechny, Yuri M.

2014-01-01

As-received BaTiO3 nanopowders of average grain sizes 50 nm and 100 nm were functionalized by (3-aminopropyl)triethoxysilane (APTES) and mixed with poly(methyl methacrylate)/toluene solution. The nanocomposite solution was spin coated on Si substrates to form thin films. The photoluminescence spectrum of the pure powder was composed of a bandgap emission at 3.0 eV and multiple bands centered about 2.5 eV. Surface functionalization of the BaTiO3 powder via APTES increases overall luminescence at room temperature while only enhancing bandgap emission at low-temperature. Polymer coating of the functionalized nanoparticles significantly enhances bandgap emissions while decreasing emissions associated with near-surface lattice distortions at 2.5 eV. PMID:28788468

Luminescent Properties of Surface Functionalized BaTiO3 Embedded in Poly(methyl methacrylate

Directory of Open Access Journals (Sweden)

Sebastian Requena

2014-01-01

Full Text Available As-received BaTiO3 nanopowders of average grain sizes 50 nm and 100 nm were functionalized by (3-aminopropyltriethoxysilane (APTES and mixed with poly(methyl methacrylate/toluene solution. The nanocomposite solution was spin coated on Si substrates to form thin films. The photoluminescence spectrum of the pure powder was composed of a bandgap emission at 3.0 eV and multiple bands centered about 2.5 eV. Surface functionalization of the BaTiO3 powder via APTES increases overall luminescence at room temperature while only enhancing bandgap emission at low-temperature. Polymer coating of the functionalized nanoparticles significantly enhances bandgap emissions while decreasing emissions associated with near-surface lattice distortions at 2.5 eV.

BaTiO3–P(VDF-HFP) nanocomposite dielectrics—Influence of surface modification and dispersion additives

International Nuclear Information System (INIS)

Ehrhardt, Claudia; Fettkenhauer, Christian; Glenneberg, Jens; Münchgesang, Wolfram; Pientschke, Christoph; Großmann, Thomas; Zenkner, Mandy; Wagner, Gerald; Leipner, Hartmut S.; Buchsteiner, Alexandra; Diestelhorst, Martin; Lemm, Sebastian; Beige, Horst; Ebbinghaus, Stefan G.

2013-01-01

Highlights: • Polymer composites were prepared using a sol–gel synthesized BaTiO 3 . • BaTiO 3 surface hydroxyle groups act as linkers for surfactant molecules. • The effect of chemical adjustment between surfactant and polymer host is studied. • A positive effect of an additional dispersant was found. • Dielectric properties of the resulting composite films are presented. -- Abstract: We report on BaTiO 3 –polymer composites as dielectrics for film capacitors. BaTiO 3 was synthesized by a sol–gel soft-chemistry method leading to spherical nanoparticles with a high degree of surface hydroxyl groups which turned out to be important for the bonding of surfactant molecules. As surfactants, n-octylphosphonic acid and 2,3,4,5,6-pentafluorobenzyl phosphonic acid were used to inhibit particle agglomeration and to improve the wetting behaviour with the polymer. The phosphonic acid-coated BaTiO 3 nanoparticles were dispersed in solutions of poly(vinylidefluoride-co-hexafluoropropylene). Composite films were prepared by the spin-coating technique. A systematic study was performed on the influence of varying oxide fractions, different surfactants and the effect of additional dispersion aids such as sodium dodecyl sulphate or BYK-W 9010 on the quality and dielectric properties of the films obtained. The chemical adjustment of the 2,3,4,5,6-pentaflourobenzyl phosphonic acid within the fluorinated organic host form a more uniform particle distribution and increase relative permittivity of the resulting composite material compared to the unflourinated surfactant. Additionally, an enhancement of the relative permittivity can be realized by adding of dispersants. These two components can increase the relative permittivity by factor 5 compared to the pure polymer material

Oxygen 1s excitation and tetragonal distortion from core-hole effect in BaTiO3

Science.gov (United States)

Bugnet, Matthieu; Radtke, Guillaume; Botton, Gianluigi A.

2013-11-01

The accurate description of the O 1s excitation in BaTiO3 has been elusive so far. In this Rapid Communication, the electronic structure and the high-resolution electron energy-loss near-edge structures of the O K edge in tetragonal BaTiO3 are investigated using first-principles calculations. The results demonstrate a clear correlation between the broadening of the lower energy fine structure and the anisotropic effects induced by the core-hole potential, which are directly related to the structural distortion occurring in tetragonal BaTiO3. Moreover, we show that a significant improvement of the description of higher-lying structures can be obtained when correcting the energy position of the Ba 4f states. This demonstrates that the O 1s spectrum can be a very effective probe of the distortion and changes in the local electronic structure, and be used as a sensitive tool for studying new materials and ferroelectric transitions.

Enhanced photoelectrochemical properties of 100 MeV Si8+ ion irradiated barium titanate thin films

International Nuclear Information System (INIS)

Solanki, Anjana; Choudhary, Surbhi; Satsangi, Vibha R.; Shrivastav, Rohit; Dass, Sahab

2013-01-01

Highlights: ► Effect of 100 MeV Si 8+ ion irradiation on photoelectrochemical (PEC) properties of BaTiO 3 thin films was studied. ► Films were deposited on Indium doped Tin Oxide (ITO) coated glass by sol–gel spin coating technique. ► Optimal irradiation fluence for best PEC response was 5 × 10 11 ion cm −2 . ► Maximum photocurrent density was observed to be 0.7 mA cm −2 at 0.4 V/SCE. ► Enhanced photo-conversion efficiency was due to maximum negative flatband potential, donor density and lowest resistivity. -- Abstract: Effects of high electronic energy deposition on the structure, surface topography, optical property and photoelectrochemical behavior of barium titanate (BaTiO 3 ) thin films were investigated by irradiating films with 100 MeV Si 8+ ions at different ion fluences in the range of 1 × 10 11 –2 × 10 13 ions cm −2 . BaTiO 3 thin films were deposited on indium tin oxide coated glass substrate by sol gel spin coating method. Irradiation induced modifications in the films were analyzed using the results from XRD, SEM, cross sectional SEM, AFM and UV–Vis spectrometry. Maximum photocurrent density of 0.7 mA cm −2 at 0.4 V/SCE and applied bias hydrogen conversion efficiency (ABPE) of 0.73% was observed for BaTiO 3 film irradiated at 5 × 10 11 ions cm −2 , which can be attributed to maximum negative value of the flatband potential and donor density and lowest resistivity

Magneto electric effects in BaTiO3-CoFe2O4 bulk composites

Science.gov (United States)

Agarwal, Shivani; Caltun, O. F.; Sreenivas, K.

2012-11-01

Influence of a static magnetic field (HDC) on the hysteresis and remanence in the longitudinal and transverse magneto electric voltage coefficients (MEVC) observed in [BaTiO3]1-x-[CoFe2O4]x bulk composites are analyzed. Remanence in MEVC at zero bias (HDC=0) is stronger in the transverse configuration over the longitudinal case. The observed hysteretic behavior in MEVC vs. HDC is correlated with the changes observed in the magnetostriction characteristics (λ and dλ/dH) reported for [BaTiO3]1-x-[CoFe2O4]x bulk composites.

Electric double layer transistors with ferroelectric BaTiO3 channels

NARCIS (Netherlands)

Ito, M.; Matsubara, Y.; Kozuka, Y.; Takahashi, K. S.; Kagawa, F.; Ye, J. T.; Iwasa, Y.; Ueno, K.; Tokura, Y.; Kawasaki, M.

2014-01-01

We report the surface conduction of a BaTiO3 thin film using electric double layer transistor (EDLT) structure. A transistor operation was observed at 220 K with an on/off ratio exceeding 10(5), demonstrating that ionic liquid gating is effective to induce carriers at the surface of ferroelectric

Study of mineral ion exchangers for strontium removal from nuclear waste waters

International Nuclear Information System (INIS)

Merceille, A.

2012-01-01

The problems of chemical pollution of water have become a major concern and a priority for the nuclear industry. The aim of this work is to study some ion exchangers used for the removal of strontium ions because 90 Sr is one of a major pollutant in nuclear liquid wastes. This study allows linking the physical and chemical properties of these materials and their sorption properties. This work presents therefore the synthesis of two materials - sodium nona-titanate and zeolite A - selected for their specific sorption properties of strontium: A second part of this work is dedicated to the study of specific exchange capacities of these materials for the strontium in presence of other elements such as sodium and calcium. Batch experiments were performed and kinetic and ion exchange models have been applied to understand the selectivity of the materials for strontium removal. Sodium nona-titanate and zeolite A are also studied in actual effluents. Monoliths of zeolite A have been also tested in dynamic ion exchange process. This material is promising for the treatment of radioactive effluents in continuous flow because it joins the sorption properties of the zeolite powder with the advantage of a solid with a macroporous network. (author) [fr

Surface structures and dielectric response of ultrafine BaTiO3 particles

International Nuclear Information System (INIS)

Jiang, B.; Peng, J.L.; Bursill, L.A.

1998-01-01

Characteristic differences are observed for the dielectric response and microstructures of BaTiO 3 nanoscale fine powders prepared using sol gel (SG) and steric acid gel (SAG) methods. The former exhibit a critical size below which there is no paraelectric/ferroelectric phase transition whereas BaTiO 3 prepared via the SAG route remained cubic for all conditions. Atomic resolution images of both varieties showed a high density of interesting surface steps and facets. Computer simulated images of surface structure models showed that the outer (100) surface was typically a BaO layer and that at corners and ledges the steps are typically finished with Ba+2 ions; i.e. the surfaces and steps are Ba-rich. Otherwise the surfaces were typically clean and free of amorphous layers. The relationship between the observed surfaces structures and theoretical models for size effects on the dielectric properties is discussed. (authors)

BaTiO3-based piezoelectrics: Fundamentals, current status, and perspectives

Science.gov (United States)

Acosta, M.; Novak, N.; Rojas, V.; Patel, S.; Vaish, R.; Koruza, J.; Rossetti, G. A.; Rödel, J.

2017-12-01

We present a critical review that encompasses the fundamentals and state-of-the-art knowledge of barium titanate-based piezoelectrics. First, the essential crystallography, thermodynamic relations, and concepts necessary to understand piezoelectricity and ferroelectricity in barium titanate are discussed. Strategies to optimize piezoelectric properties through microstructure control and chemical modification are also introduced. Thereafter, we systematically review the synthesis, microstructure, and phase diagrams of barium titanate-based piezoelectrics and provide a detailed compilation of their functional and mechanical properties. The most salient materials treated include the (Ba,Ca)(Zr,Ti)O3, (Ba,Ca)(Sn,Ti)O3, and (Ba,Ca)(Hf,Ti)O3 solid solution systems. The technological relevance of barium titanate-based piezoelectrics is also discussed and some potential market indicators are outlined. Finally, perspectives on productive lines of future research and promising areas for the applications of these materials are presented.

Electrical transport across nanometric SrTiO3 and BaTiO3 barriers in conducting/insulator/conducting junctions

Science.gov (United States)

Navarro, H.; Sirena, M.; González Sutter, J.; Troiani, H. E.; del Corro, P. G.; Granell, P.; Golmar, F.; Haberkorn, N.

2018-01-01

We report the electrical transport properties of conducting/insulator/conducting heterostructures by studying current-voltage IV curves at room temperature. The measurements were obtained on tunnel junctions with different areas (900, 400 and 100 μm2) using a conducting atomic force microscope. Trilayers with GdBa2Cu3O7 (GBCO) as the bottom electrode, SrTiO3 or BaTiO3 (thicknesses between 1.6 and 4 nm) as the insulator barrier, and GBCO or Nb as the top electrode were grown by DC sputtering on (100) SrTiO3 substrates For SrTiO3 and BaTiO3 barriers, asymmetric IV curves at positive and negative polarization can be obtained using electrodes with different work function. In addition, hysteretic IV curves are obtained for BaTiO3 barriers, which can be ascribed to a combined effect of the FE reversal switching polarization and an oxygen vacancy migration. For GBCO/BaTiO3/GBCO heterostructures, the IV curves correspond to that expected for asymmetric interfaces, which indicates that the disorder affects differently the properties at the bottom and top interfaces. Our results show the role of the interface disorder on the electrical transport of conducting/insulator/conduction heterostructures, which is relevant for different applications, going from resistive switching memories (at room temperature) to Josephson junctions (at low temperatures).

Phase stabilization in plasma sprayed BaTiO3

Czech Academy of Sciences Publication Activity Database

Ctibor, Pavel; Seiner, Hanuš; Sedláček, J.; Pala, Zdeněk; Vaněk, Přemysl

2013-01-01

Roč. 39, č. 5 (2013), s. 5039-5048 ISSN 0272-8842 R&D Projects: GA ČR(CZ) GA101/09/0702 Institutional support: RVO:61389021 ; RVO:61388998 ; RVO:68378271 Keywords : Spectroscopy * BaTiO3 * Plasma spraying * Spark plasma sintering Subject RIV: JH - Ceramics, Fire-Resistant Materials and Glass; BJ - Thermodynamics (UT-L); JH - Ceramics, Fire-Resistant Materials and Glass (FZU-D) Impact factor: 2.086, year: 2013 http://www.sciencedirect.com/science/article/pii/S0272884212013582

Human Internal Contamination with Strontium-90 Titanate; Contamination Interne du Corps Humain par le Titanate de Strontium 90; 0412 041d 0414 ; Contaminacion Interna del Cuerpo Humano con Titanato de Estroncio-90

Energy Technology Data Exchange (ETDEWEB)

Bradley, F. J.; Wald, N.; Wechsler, R. L. [Graduate School of Public Health and School of Medicine, University of Pittsburgh, Pittsburgh, PA (United States)

1964-11-15

Strontium-90 has been used in multikilocurie quantities recently as a heat source for thermoelectric generators. The titanate was carefully selected for this purpose as the chemical form which best met requirements including inertness to corrosive attack in the event of accidental release to the environment. An industrial accidental exposure of one worker on 26 June 1963 to strontium-90 titanate powder, originally in the form of particles of about 120 {mu}m and less, provided an opportunity to attempt the assessment of the human body burden of this supposedly highly insoluble compound. Because of the physical and biological behaviour of the particles, it was assumed that the actual particle size which was dispersed and ingested and/or inhaled by the exposed person was in the range of 1 to 30 {mu}m. Three techniques were used to estimate the body burden. Whole-body radiation counting carried out by Dr. Charles H. Miller at Argonne National Laboratory, which only gave an upper limit because of the non-specific Bremsstrahlung spectrum from strontium-90, yttrium-90 indicated an initial total-body burden of 4.8 {mu}c. The second method, total urinary and faecal output collection, totalled 5.0 for the first 20 d. Combining that amount with an estimate of the amount retained in the body, an initial total-body burden of 5.2 {mu}c was obtained. The third technique, blood radioactivity determination, indicated an initial total-body burden of 6 {mu}c. The ratio of faecal to urinary output in the first 20 d was 15 to 1, and 94% of the total strontium-90 excretion was via the gastro-intestinal tract. It is of interest, however, that a significant fraction was evidently soluble. By the 20th post-incident day, it was estimated that the retained body burden was only 5% of the total intake. Methods used in that period to enhance faecal excretion by MgSO{sub 4} and urinary excretion by a combination of Ca-gluconate and NH{sub 4}CI are described. Subsequent excretion patterns and the

Preparation and characterization of self-assembled percolative BaTiO3–CoFe2O4 nanocomposites via magnetron co-sputtering

Directory of Open Access Journals (Sweden)

Qian Yang

2014-04-01

Full Text Available BaTiO3–CoFe2O4 composite films were prepared on (100 SrTiO3 substrates by using a radio-frequency magnetron co-sputtering method at 750 °C. These films contained highly (001-oriented crystalline phases of perovskite BaTiO3 and spinel CoFe2O4, which can form a self-assembled nanostructure with BaTiO3 well-dispersed into CoFe2O4 under optimized sputtering conditions. A prominent dielectric percolation behavior was observed in the self-assembled nanocomposite. Compared with pure BaTiO3 films sputtered under similar conditions, the nanocomposite film showed higher dielectric constants and lower dielectric losses together with a dramatically suppressed frequency dispersion. This dielectric percolation phenomenon can be explained by the 'micro-capacitor' model, which was supported by measurement results of the electric polarization and leakage current.

Oxygen-vacancy defects on BaTiO3 (001) surface: a quantum chemical study

International Nuclear Information System (INIS)

Duque, Carlos; Stashans, Arvids

2003-01-01

A quantum-chemical study of technologically important BaTiO 3 crystal and oxygen-vacancy defects on its (001) surface is reported in the present work. The computations are made using a quantum-chemical method developed for periodic systems (crystals), which is based on the Hartree-Fock theory. The atomic rearrangement due to the surface creation is obtained for a pure BaTiO 3 by means of the periodic large unit cell (LUC) model and using an automated geometry optimisation procedure. The same technique is employed to study the electronic and structural properties of the material due to the presence of an O vacancy and F centre (two electrons trapped in an oxygen vacancy). The computations are carried out for both cubic and tetragonal lattices

Optical Second Harmonic Generation in the BaTiO3 phase of magnetically aligned multiferroic nanofibers

Science.gov (United States)

Gasperi, Katia

Multiferroic materials enable the exploration of electrical control of magnetic properties and vice versa. Their increasing interest is especially due to their potential applications in the industry of information storage. Thanks to recent progress in nanotechnology, they have also been found to have many other applications such as transducers and sensors, and they already occupy a unique place in the biomedical field. The objective of this project is to study multiferroic nanofibers made of cobalt ferrite CoFe2O 4 (CFO) and barium titanate BaTiO3 (BTO) with a specific focus in the characterization of the ferroelectric phase. We researched the state of knowledge concerning the size effects on phase transition for nanoparticles and polycrystals BTO. The ferroelectric phase transition of BTO occurs when it changes from a tetragonal (anisotropic) crystal structure to a cubic (isotropic) structure. This change suggests that optical second harmonic generation (SHG) is a good measurement technique for monitoring the phase transition of the BTO half of the nanofibers. We designed and prepared a temperature dependent SHG experiment on magnetically aligned fibers in transmission with the possibility to investigate the polarization dependence of the signal. We also prepared interdigital electrodes on glass for the future study of the fibers in an external electric field.

Off Axis Growth of Strontium Titanate Films with High Dielectric Constant Tuning and Low Loss

Science.gov (United States)

Kampangkeaw, Satreerat

2002-03-01

Using off-axis pulsed laser deposition, we have grown strontium titanate (STO) films on neodymium gallate (NGO) and lanthanum aluminate (LAO) substrates. We measured the film dielectric constant and loss tangent as a function of temperature in the 10kHz to 1 MHz frequency range. We found that the loss is less than 0.01 We also obtained a figure of merit from the relative variation of the dielectric constant divided by the loss tangent. The obtained figured of merit at 35K and 1MHz is about 1000 comparable to bulk values. The dielectric constant of these films can be changed by a factor of 4-8 in the presence of a DC electric field up to 5V/μm. The films show significant variations of dielectric properties grown on different substrates at different locations respect to the axis of the plume. The STO films on LAO having high dielectric constant and dielectric tuning were grown in region near the center of the plume. On the other hand, STO on NGO shows this effect only on the films grown far from the plume axis.

Grain-size effects on thermal properties of BaTiO3 ceramics

Indian Academy of Sciences (India)

Administrator

decreasing grain size. Furthermore, the Curie temperature shifts to lower temperature with decreasing grain size. Keywords. Nanocrystalline ceramics; thermal properties; size effect. 1. Introduction. BaTiO3 has been widely used in the electronic industry for its high dielectric constant and low losses above room temperature ...

Impact of Strontium Nitrate and Sodium Permanganate Addition on Solid-Liquid Separation of SRS High Level Waste

International Nuclear Information System (INIS)

Poirier, M.R.

2002-01-01

As a pretreatment step for the caustic side solvent extraction (CSSX) flowsheet, the process contacts the incoming salt solution containing entrained sludge with monosodium titanate (MST) to adsorb strontium and actinides. An operation filters the resulting slurry to remove the sludge and MST. Previous work for the River Protection Program at Hanford suggests that addition of strontium nitrate and sodium permanganate for strontium and actinide removal, rather than MST, improves the filtration rate for comparable waste streams

Orientation dependence of magnetoelectric coefficient in 1-3-type BaTiO3/CoFe2O4

Science.gov (United States)

Jian, Gang; Shao, Hui; Zhang, Cheng; Yan, Chao; Zhao, Ning; Song, Bo; Wong, C. P.

2018-03-01

Orientation dependence of magnetoelectric coefficient αE33 in 1-3-type BaTiO3/CoFe2O4 composites was calculated in arbitrary directions by three-dimensional coordinate transformation method. The space distributions of pc11‧, pc12‧, e31‧ for piezoelectric phase and mc11‧, mc12‧, q31‧ for magnetic phase were obtained independently using relative experimental data and original matrices for 4mm BaTiO3 and m3m CoFe2O4. Elastic stiffness coefficients show little orientation differences, while e31‧ and q31‧ exhibit high dependence on crystal orientation, with the MAX absolute e31‧ = 2.96 C/m2 and the MAX q31‧ = 556 × 10-12 m/A are found at θ = 0° and θ = 0°, ϕ = 45°, respectively. For space distribution of αE33‧, BaTiO3||[0 0 1]/CoFe2O4||[0 0 1] combination has the maximum value which applies to both 1-3 p/m (1.485 V/A) and 1-3 m/p composites (1.529 V/A). Volume fraction is quite independent of orientations of both piezoelectric and magnetic phases and the volume fraction for magnetic phase f around 0.5 obtains the largest αE33. The results suggest an approach to significantly enhancing magnetoelectric coefficient of composite multiferroic materials through crystal orientation controls of single crystals and textured ceramics.

Structural, morphological and Raman studies on hybridized PVDF/BaTiO3 nanocomposites

Science.gov (United States)

Rajamanickam, N.; Jayakumar, K.; Ramachandran, K.

2017-05-01

Hybridized nanocomposites of polyvinylidene fluoride (PVDF) and nano - barium titanate (BaTiO3) were prepared using the solution casting method for different concentrations of nano-BaTiO3 and were characterized by X-ray diffraction and scanning electron microscopy. The flower like structure for morphology was observed in SEM. Raman analysis showed that the modified BaTiO3 particles, due to higher specific surfaces, induce, predominantly, the crystallization of the electrically active β-phase of PVDF, while the initial micron size particles induce the formation of the most common but non-polar α-crystal form.

Critical behavior of the spontaneous polarization and the dielectric susceptibility close to the cubic-tetragonal transition in BaTiO3

Directory of Open Access Journals (Sweden)

H. Yurtseven

2015-09-01

Full Text Available Using Landau mean field model, the spontaneous polarization and the dielectric susceptibility are analyzed as functions of temperature and pressure close to the cubic–tetragonal (ferroelectric–paraelectric transition in BaTiO3. From the analysis of the dielectric susceptibility and the spontaneous polarization, the critical exponents are deduced in the classical and quantum limits for BaTiO3. From the critical behavior of the dielectric susceptibility, the spontaneous polarization can be described for the ferroelectric–paraelectric (cubic to tetragonal transition between 4 and 8 GPa at constant temperatures of 0 to 200 K in BaTiO3 within the Landau mean field model given here.

Defect controlled room temperature ferromagnetism in Co-doped barium titanate nanocrystals

International Nuclear Information System (INIS)

Ray, Sugata; Kolen'ko, Yury V; Watanabe, Tomoaki; Yoshimura, Masahiro; Itoh, Mitsuru; Kovnir, Kirill A; Lebedev, Oleg I; Turner, Stuart; Erni, Rolf; Tendeloo, Gustaaf Van; Chakraborty, Tanushree

2012-01-01

Defect mediated high temperature ferromagnetism in oxide nanocrystallites is the central feature of this work. Here, we report the development of room temperature ferromagnetism in nanosized Co-doped barium titanate particles with a size of around 14 nm, synthesized by a solvothermal drying method. A combination of x-ray diffraction with state-of-the-art electron microscopy techniques confirms the intrinsic doping of Co into BaTiO 3 . The development of the room temperature ferromagnetism was tracked down to the different donor defects, namely hydroxyl groups at the oxygen site and oxygen vacancies and their relative concentrations at the surface and the core of the nanocrystal, which could be controlled by post-synthesis drying and thermal treatments.

Controlled Confinement of Half-metallic 2D Electron Gas in BaTiO3/Ba2FeReO6/BaTiO3 Heterostructures: A First-principles Study

Science.gov (United States)

Saha-Dasgupta, Tanusri; Baidya, Santu; Waghmare, Umesh; Paramekanti, Arun

Using density functional theory calculations, we establish that the half-metallicity of bulk Ba2FeReO6 survives down i to 1 nm thickness in BaTiO3/Ba2FeReO6/BaTiO3 heterostructures grown along the (001) and (111) directions. The confinement of the two-dimensional (2D) electron gas in this quantum well structure arises from the suppressed hybridization between Re/Fe d states and unoccupied Ti d states, and it is further strengthened by polar fields for the (111) direction. This mechanism, distinct from the polar catastrophe, leads to an order of magnitude stronger confinement of the 2D electron gas than that at the LaAlO3/SrTiO3 interface. We further show low-energy bands of (111) heterostructure display nontrivial topological character. Our work opens up the possibility of realizing ultra-thin spintronic devices. Journal Ref: Phys. Rev. B 92, 161106(R) (2015) S.B. and T.S.D thank Department of Science and Technology, India for the support through Thematic Unit of Excellence. AP was supported by NSERC (Canada).

Spin injection and detection in lanthanum- and niobium-doped SrTiO3 using the Hanle technique

KAUST Repository

Han, Wei

2013-07-08

There has been much interest in the injection and detection of spin-polarized carriers in semiconductors for the purposes of developing novel spintronic devices. Here we report the electrical injection and detection of spin-polarized carriers into Nb-doped strontium titanate single crystals and La-doped strontium titanate epitaxial thin films using MgO tunnel barriers and the three-terminal Hanle technique. Spin lifetimes of up to ∼100 ps are measured at room temperature and vary little as the temperature is decreased to low temperatures. However, the mobility of the strontium titanate has a strong temperature dependence. This behaviour and the carrier doping dependence of the spin lifetime suggest that the spin lifetime is limited by spin-dependent scattering at the MgO/strontium titanate interfaces, perhaps related to the formation of doping induced Ti 3+. Our results reveal a severe limitation of the three-terminal Hanle technique for measuring spin lifetimes within the interior of the subject material. © 2013 Macmillan Publishers Limited. All rights reserved.

Nitrogen induced ferromagnetism in Cobalt doped BaTiO3

Directory of Open Access Journals (Sweden)

Chandrima Mitra

2012-09-01

Full Text Available The electronic structure and magnetism of Cobalt doped BaTiO3 (BaTi1−xCoxO3 is investigated. Substitutional Nitrogen on an Oxygen site is found to play an important role in inducing net magnetic moments in the system. The presence of a Nitrogen atom as nearest neighbour to a Cobalt atom is crucial in producing spin splitting of both the Nitrogen and Cobalt states thereby introducing a net local magnetic moment. The introduction of Nitrogen is further found to enhance ferromagnetic interactions between Cobalt atoms.

The influences of mole composition of strontium (x) on properties of barium strontium titanate (Ba{sub 1−x}Sr{sub x}TiO{sub 3}) prepared by solid state reaction method

Energy Technology Data Exchange (ETDEWEB)

Sandi, Dianisa Khoirum; Supriyanto, Agus; Iriani, Yofentina, E-mail: yopen-2005@yahoo.com [Physics Department, Faculty of Mathematics and Natural Science, Sebelas Maret University (Indonesia); Jamaluddin, Anif [Physics Department, Faculty of Teacher Training and Education, Sebelas Maret University (Indonesia)

2016-02-08

Barium Strontium Titanate (Ba{sub 1-x}Sr{sub x}TiO{sub 3}) or BST was prepared by solid state reaction method. Raw materials are BaCO{sub 3}, SrCO{sub 3}, and TiO{sub 2}. Those materials are mixed for 8 h, pressed, and sintered at temperature 1200°C for 2 h. Mole composition of Sr (x) was varied to study its influences on structural, morphological, and electrical properties of BST. Variation of (x) are x = 0; x = 0.1; and x = 0.5. XRD patterns showed a single phase of BST, which mean that mixture of raw materials was homogenous. Crystal structure was influenced by x. BaTiO{sub 3} and Ba{sub 0.9}Ti{sub 0.1}TiO{sub 3} have tetragonal crystal structure, while Ba{sub 0.5}Sr{sub 0.5}TiO{sub 3} is cubic. The diffraction angle shifted to right side (angle larger) as the increases of x. Crystalline size of BaTiO{sub 3}, Ba{sub 0.9}Sr{sub 0.1}TiO{sub 3}, and Ba{sub 0.5}Sr{sub 0.5}TiO{sub 3} are 38.13 nm; 38.62 nm; and 37.13 nm, respectively. SEM images showed that there are still of pores which were influenced by x. Ba{sub 0.9}Sr{sub 0.1}TiO{sub 3} has densest surface (pores are few and small in size). Sawyer Tower circuit showed that BaTiO{sub 3} and Ba{sub 0.9}Sr{sub 0.1} TiO{sub 3} is ferroelectric, while Ba{sub 0.5}Sr{sub 0.5}TiO{sub 3} is paraelectric. The dielectric constants of BaTiO{sub 3}, Ba{sub 0.9}Sr{sub 0.1}TiO{sub 3} and Ba{sub 0.5}Sr{sub 0.5}TiO{sub 3} at frequency of 1 KHz are 156; 196; and 83, respectively. Ba{sub 0.9}Sr{sub 0.1}TiO{sub 3} has relatively highest dielectric constant. It is considered that Ba{sub 0.9}Sr{sub 0.1}TiO{sub 3} has densest surface.

First-principles calculations on thermodynamic properties of BaTiO3 rhombohedral phase.

Science.gov (United States)

Bandura, Andrei V; Evarestov, Robert A

2012-07-05

The calculations based on the linear combination of atomic orbitals have been performed for the low-temperature phase of BaTiO(3) crystal. Structural and electronic properties, as well as phonon frequencies were obtained using hybrid PBE0 exchange-correlation functional. The calculated frequencies and total energies at different volumes have been used to determine the equation of state and thermal contribution to the Helmholtz free energy within the quasiharmonic approximation. For the first time, the bulk modulus, volume thermal expansion coefficient, heat capacity, and Grüneisen parameters in BaTiO(3) rhombohedral phase have been estimated at zero pressure and temperatures form 0 to 200 K, based on the results of first-principles calculations. Empirical equation has been proposed to reproduce the temperature dependence of the calculated quantities. The agreement between the theoretical and experimental thermodynamic properties was found to be satisfactory. Copyright © 2012 Wiley Periodicals, Inc.

DFT study of the polarization behaviors of various distorted barium titanate crystals: The role of atomic displacements

Science.gov (United States)

Mirseraji, Mojtaba; Shahraki, Mehran Gholipour

2018-06-01

A Local Density Approximation (LDA) was employed to investigate the influence of applied strains on valence charge distributions, atomic displacements, Tisbnd O (3) bond distances and the total polarizations in barium titanate (BaTiO3). Four types of various strains were imposed on perfect tetragonal BaTiO3 along the a, c, ab and abc axial directions. Electromechanical properties of BaTiO3 were evaluated in LDA framework and a good agreement with previous results was achieved. The results show that, in the cases of a, ab strains, the values of polarization are almost constant in negative strains and increased by gradual increasing of the positive strains after a sudden enhancement at about +0.1% strain. In the case of c-strain, axial oxygen and Ti atoms underwent the highest displacements and the polarization linearly increased by applied strain. The case of abc-strain, represent the both types of features. In negative abc-strain show a similar polarization behavior like c-strain case and in positive region, polarization behavior is the same as a- and ab-strain cases. In the abc-strains of -0.3% and +0.1%, an abrupt jump in total polarization curve and a small change, are observed due to abnormal atomic displacements. In the most cases a direct relation between polarization and Tisbnd O (3) bond distance was also beheld. Finally, the effects of valence charge distributions on the atomic displacements and total polarizations are studied. It is found that there is a direct relation between polarization and Valence Charge Asymmetry of 3d -orbitals.

Poly (vinylidene fluoride-trifluoroethylene/barium titanate nanocomposite for ferroelectric nonvolatile memory devices

Directory of Open Access Journals (Sweden)

Uvais Valiyaneerilakkal

2013-04-01

Full Text Available The effect of barium titanate (BaTiO3 nanoparticles (particle size <100nm on the ferroelectric properties of poly (vinylidenefluoride-trifluoroethylene P(VDF-TrFE copolymer has been studied. Different concentrations of nanoparticles were added to P(VDF-TrFE using probe sonication, and uniform thin films were made. Polarisation - Electric field (P-E hysteresis analysis shows an increase in remnant polarization (Pr and decrease in coercive voltage (Vc. Piezo-response force microscopy analysis shows the switching capability of the polymer composite. The topography and surface roughness was studied using atomic force microscopy. It has been observed that this nanocomposite can be used for the fabrication of non-volatile ferroelectric memory devices.

Low leakage Ru-strontium titanate-Ru metal-insulator-metal capacitors for sub-20 nm technology node in dynamic random access memory

Energy Technology Data Exchange (ETDEWEB)

Popovici, M., E-mail: Mihaela.Ioana.Popovici@imec.be; Swerts, J.; Redolfi, A.; Kaczer, B.; Aoulaiche, M.; Radu, I.; Clima, S.; Everaert, J.-L.; Van Elshocht, S.; Jurczak, M. [Imec, Leuven 3001 (Belgium)

2014-02-24

Improved metal-insulator-metal capacitor (MIMCAP) stacks with strontium titanate (STO) as dielectric sandwiched between Ru as top and bottom electrode are shown. The Ru/STO/Ru stack demonstrates clearly its potential to reach sub-20 nm technology nodes for dynamic random access memory. Downscaling of the equivalent oxide thickness, leakage current density (J{sub g}) of the MIMCAPs, and physical thickness of the STO have been realized by control of the Sr/Ti ratio and grain size using a heterogeneous TiO{sub 2}/STO based nanolaminate stack deposition and a two-step crystallization anneal. Replacement of TiN with Ru as both top and bottom electrodes reduces the amount of electrically active defects and is essential to achieve a low leakage current in the MIM capacitor.

Ferroelectric properties of barium strontium titanate thin films grown by RF co-sputtering

International Nuclear Information System (INIS)

Zapata-Navarro, A.; Marquez-Herrera, A.; Cruz-Jauregui, M.P.; Calzada, M.L.

2005-01-01

In this work, we present the variation of the ferroelectric properties of Ba 1-x Sr x TiO 3 films deposited on Pt/TiO 2 /SiO 2 /Si substrates by RF co-sputtering with 0≤x≤1. The co-sputtering was done using a single magnetron with BaTiO 3 /SrTiO 3 targets in a pie mosaics configuration. Smooth and uniform films were obtained using the same conditions of growth and annealing temperature. The X-ray diffraction and EDS results show that the processes were managed to obtain crystalline materials with x from 0 to 1. The behaviour of P-E loops suggests that the ferroelectric properties of the films were tuned by changing the concentration of the cation. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Calcul théorique de l’hystérésis thermique de BaTiO3 pur et dopé au fer

NARCIS (Netherlands)

Aattar, M.; Khatib, D.; Noheda, B.

1999-01-01

Theory of thermal hysteresis of pure and iron doped BaTiO3. The value of the thermal hysteresis of pure and iron doped BaTiO3 was calculated using an effective field model taking into account dipolar and quadripolar interactions. The calculation is performed using a self-consistent method. The

Chromite/titanate based perovskites for application as anodes in solid oxide fuel cells

NARCIS (Netherlands)

Pudmich, G.; Boukamp, Bernard A.; Gonzalez Cuenca, M.M.; Jungen, W.; Zipprich, W.M.; Tietz, F.

2000-01-01

Perovskites containing lanthanides, partially substituted by alkaline-earth elements and transition metals like Cr, Ti, Fe or Co show a very broad range of physical properties. Therefore several perovskite materials, based on lanthanum chromite and strontium titanate were synthesised and

Structural and magnetic properties of single-crystalline Co-doped barium titanate nanoparticles

International Nuclear Information System (INIS)

Liu Hongxue; Cao Baobao; O'Connor, Charles J.

2010-01-01

Undoped and Co-doped BaTiO 3 nanoparticles were synthesized by a one-step sol-precipitation method. For all the samples, X-ray diffraction showed characteristic diffraction lines for BaTiO 3 without the indication of secondary phases. High-resolution transition electron microscopy images showed that BaTiO 3 nanoparticles exhibit the nature of single-crystal. Magnetometry revealed that all the Co-doped BaTiO 3 samples show paramagnetic behaviors and Co ions in BaTiO 3 are present as isolated paramagnetic centers. This is contrasted to several reported cases of ferromagnetism in Co-doped BaTiO 3 .

Improvement in crystallization and electrical properties of barium strontium titanate thin films by gold doping using metal-organic deposition method

International Nuclear Information System (INIS)

Wang, H.-W.; Nien, S.-W.; Lee, K.-C.; Wu, M.-C.

2005-01-01

The effect of gold (Au) on the crystallization, dielectric constant and leakage current density of barium strontium titanate (BST) thin films was investigated. BST thin films with various gold concentrations were prepared via a metal-organic deposition process. The X-ray diffraction shows enhanced crystallization as well as expanded lattice constants for the gold-doped BST films. Thermal analysis reveals that the gold dopant induces more complete decomposition of precursor for the doped films than those of undoped ones. The leakage current density of BST films is greatly reduced by the gold dopant over a range of biases (1-5 V). The distribution of gold was confirmed by electron energy loss spectroscopy and found to be inside the BST grains, not in the grain-boundaries. Gold acted as a catalyst, inducing the nucleation of crystallites and improving the crystallinity of the structure. Its addition is shown to be associated to the improvement of the electrical properties of BST films

Effect of multi-layered bottom electrodes on the orientation of strontium-doped lead zirconate titanate thin films

Energy Technology Data Exchange (ETDEWEB)

Bhaskaran, M. [Microelectronics and Materials Technology Centre, School of Electrical and Computer Engineering, RMIT University, GPO Box 2476V, Melbourne, Victoria 3001 (Australia)], E-mail: madhu.bhaskaran@gmail.com; Sriram, S. [Microelectronics and Materials Technology Centre, School of Electrical and Computer Engineering, RMIT University, GPO Box 2476V, Melbourne, Victoria 3001 (Australia); Mitchell, D.R.G.; Short, K.T. [Institute of Materials Engineering, Australian Nuclear Science and Technology Organisation (ANSTO), PMB 1, Menai, New South Wales 2234 (Australia); Holland, A.S. [Microelectronics and Materials Technology Centre, School of Electrical and Computer Engineering, RMIT University, GPO Box 2476V, Melbourne, Victoria 3001 (Australia)

2008-09-30

This article discusses the results from X-ray diffraction (XRD) analysis of piezoelectric strontium-doped lead zirconate titanate (PSZT) thin films deposited on multi-layer coatings on silicon. The films were deposited by RF magnetron sputtering on a metal coated substrate. The aim was to exploit the pronounced piezoelectric effect that is theoretically expected normal to the substrate. This work highlighted the influence that the bottom electrode architecture exerts on the final crystalline orientation of the deposited thin films. A number of bottom electrode architectures were used, with the uppermost metal layer on which PSZT was deposited being gold or platinum. The XRD analysis revealed that the unit cell of the PSZT thin films deposited on gold and on platinum were deformed, relative to expected unit cell dimensions. Experimental results have been used to estimate the unit cell parameters. The XRD results were then indexed based on these unit cell parameters. The choice and the thickness of the intermediate adhesion layers influenced the relative intensity, and in some cases, the presence of perovskite peaks. In some cases, undesirable reactions between the bottom electrode layers were observed, and layer architectures to overcome these reactions are also discussed.

X-ray line profile analysis of BaTiO3 thin film prepared by sol-gel deposition

Science.gov (United States)

Ooi, Zeen Vee; Saif, Ala'eddin A.; Wahab, Yufridin; Jamal, Zul Azhar Zahid

2017-04-01

Barium titanate (BaTiO3) thin film was prepared using sol-gel method and spun-coated on SiO2/Si substrate. The phase and crystallinity of the synthesized film were identified using X-ray diffractometer (XRD), which scanned at the range of 20° to 60°. The phase and lattice parameters of the fabricated film were extracted from the recorded XRD patterns using lattice geometry equations. The crystallite size and lattice strain were determined using X-ray line profile analysis (XLPA) with various approaches. The Scherrer equation was applied to the perovskite peaks of the film to explore the size contribution on the peak broadening. Meanwhile, the Williamson-Hall and size-strain plot (SSP) methods were used to review two main independent contributions, i.e. crystallite sizes and lattice strain, on the X-ray line broadening. From the analysis, it is found that Scherrer method gives smallest crystallite size value by ignoring the strain-induced broadening effect. On the other hand, Williamson-Hall and SSP graphs revealed the existence of the lattice strain within the film, which contributes to the broadening in the Bragg peak. The results that analyzed via both techniques show a linear trend with all data points fitted. However, result obtained from SSP method gives better settlement due to the best fit of the data.

Damage Accumulation and Recovery in Gold-Ion-Irradiated Barium Titanate

Energy Technology Data Exchange (ETDEWEB)

Jiang, Weilin; Weber, William J.; Thevuthasan, Suntharampillai

2001-06-04

Single-crystal barium titanate (BaTiO) wafers were irradiated 60? off the surface normal at 170 and 300 K using 1.0 MeV Au ions over a fluence range from 0.03 to 0.19 ions/nm. Disorder on both the Ba and Ti sublattices has been studied in situ using Rutherford backscattering spectrometry along the <110> axial direction. At these irradiation temperatures, the temperature dependence of disordering is small. The dose for amorphization under these conditions is on the order of 0.5 dpa, which is 50% of that required to amorphize SrTiO under similar conditions. At low damage levels, recovery of disorder is observed at room temperature, suggesting at least one lower temperature recovery stage. For more highly damaged states, two distinct recovery stages have been identified between 420 and 570 K and between 720 and 870 K. The recovery stage between 420 and 570 K is associated with the critical temperature for full amorphization ({approx}550 K) in BaTiO. The higher temperature recovery stage is most likely associated with epitaxial recrystallization.

Effect of BaTiO3 Nanopowder Concentration on Rheological Behaviour of Ceramic Inkjet Inks

Science.gov (United States)

Kyrpal, R.; Dulina, I.; Ragulya, A.

2015-04-01

The relationship between rheological properties of ceramic inkjet inks based on BaTiO3 nanopowder and solid phase concentration has been investigated. In the ink volume takes place the formation periodic colloidal structures (PCS). The determining factor of structure formation is powder-dispersant ratio. Structural constitution of in the system with the low pigment concentration represented as PCS2, that contains solid particles in deflocculated that stabilized by the presence of adsorption-solvate layers. Dilatant structure formation for such inks explained by constrained conditions of the interaction. Samples with high BaTiO3 concentration have been classified as PKS1. Dilatant properties of the PKS1 resulted in particles rearrangement under the influence of the flow. In the region of some values powder-dispersant ratio take place conversation PKS2 to PKS1 and ink structure transformation from monodisperse to aggregate state.

Pulsed Laser Deposition of BaTiO3 Thin Films on Different Substrates

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Yaodong Yang

2010-01-01

Full Text Available We have studied the deposition of BaTiO3 (BTO thin films on various substrates. Three representative substrates were selected from different types of material systems: (i SrTiO3 single crystals as a typical oxide, (ii Si wafers as a semiconductor, and (iii Ni foils as a magnetostrictive metal. We have compared the ferroelectric properties of BTO thin films obtained by pulsed laser deposition on these diverse substrates.

Structure and properties of plasma sprayed BaTiO3 coatings after thermal posttreatment

Czech Academy of Sciences Publication Activity Database

Ctibor, Pavel; Sedláček, J.; Pala, Zdeněk

2015-01-01

Roč. 41, č. 6 (2015), s. 7453-7460 ISSN 0272-8842 Institutional support: RVO:61389021 Keywords : Electrical properties * BaTiO3 * Plasma spraying * Annealing * Microstructure Subject RIV: JH - Ceramics, Fire-Resistant Materials and Glass Impact factor: 2.758, year: 2015 http://dx.doi.org/10.1016/j.ceramint.2015.02.065

Nanoscale strontium titanate photocatalysts for overall water splitting.

Science.gov (United States)

Townsend, Troy K; Browning, Nigel D; Osterloh, Frank E

2012-08-28

SrTiO(3) (STO) is a large band gap (3.2 eV) semiconductor that catalyzes the overall water splitting reaction under UV light irradiation in the presence of a NiO cocatalyst. As we show here, the reactivity persists in nanoscale particles of the material, although the process is less effective at the nanoscale. To reach these conclusions, Bulk STO, 30 ± 5 nm STO, and 6.5 ± 1 nm STO were synthesized by three different methods, their crystal structures verified with XRD and their morphology observed with HRTEM before and after NiO deposition. In connection with NiO, all samples split water into stoichiometric mixtures of H(2) and O(2), but the activity is decreasing from 28 μmol H(2) g(-1) h(-1) (bulk STO), to 19.4 μmol H(2) g(-1) h(-1) (30 nm STO), and 3.0 μmol H(2) g(-1) h(-1) (6.5 nm STO). The reasons for this decrease are an increase of the water oxidation overpotential for the smaller particles and reduced light absorption due to a quantum size effect. Overall, these findings establish the first nanoscale titanate photocatalyst for overall water splitting.

La-doped BaTiO3 heterostructures: Compensating the polarization discontinuity

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D. P. Kumah

2013-12-01

Full Text Available We demonstrate a route to manipulate the polarization and internal electric field of a complex oxide heterostructure using a layering sequence based on the LaAlO3-SrTiO3 interface. By combining sensitive atomic-level mapping of the structure using direct x-ray phase-retrieval methods with theoretical modeling of the electrostatic charge and polarization, we have devised a novel single-domain polar heterostructure. We find that ionic rearrangement results in strain and free energy minimization, and eliminates the polarization discontinuity leading to a two-fold increase of the spontaneous polarization towards the surface of an ultra-thin single-domain BaTiO3 film.

Size Tunable Synthesis of Highly Crystalline BaTiO3 Nanoparticles using Salt-Assisted Spray Pyrolysis

International Nuclear Information System (INIS)

Itoh, Yoshifumi; Lenggoro, I. Wuled; Okuyama, Kikuo; Maedler, Lutz; Pratsinis, Sotiris E.

2003-01-01

Highly crystalline, dense BaTiO 3 nanoparticles in a size range from 30 to 360nm with a narrow size distribution (σ g = 1.2-1.4) were prepared at various synthesis temperatures using a salt-assisted spray pyrolysis (SASP) method without the need for post-annealing. The effect of synthesis temperature on particle size, crystallinity and surface morphology of the nanoparticles were characterized by X-ray diffraction and scanning/transmission electron microscopy. The nature of the crystalline structure was analyzed by Rietveld refinement and Raman spectroscopy. The particle size decreased with decreasing operation temperature. The crystal phase was transformed from tetragonal to cubic at a particles size of about 50nm at room temperature. SASP can be used to produce high weight fraction of tetragonal BaTiO 3 nanoparticles down to 64nm in a single step

Flux Growth of Highly Crystalline Photocatalytic BaTiO3 Particle Layers on Porous Titanium Sponge Substrate and Insights into the Formation Mechanism

Science.gov (United States)

Wang, Q.; Li, B.

2017-09-01

A unique architecture of idiomorphic and highly crystalline BaTiO3 particle layers directly grown on a porous titanium sponge substrate was successfully achieved for the first time using a facile molten salt method at a relatively low temperature of 700 °C. Specifically, the low-melting KCl-NaCl eutectic salts and barium hydroxide octahydrate were employed as the reaction medium and barium source, respectively. Powder X-ray diffraction (XRD), scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM) and UV-vis diffuse reflectance spectrophotometry were used to characterize the structure, morphology and optical property of the obtained samples. The results revealed that the flux-grown tetragonal BaTiO3 products had well-defined and uniform morphology with an average size of 300 nm and a band gap of ∼3.16 eV. Based on XRD, EDS, SEM, and TEM, the possible formation mechanism responsible for the well-developed architecture of BaTiO3 particle layers was proposed and discussed. Furthermore, the photocatalytic activity of the flux-grown BaTiO3 products for organic pollutant degradation under simulated sunlight irradiation was also investigated.

Reduced energy loss in poly(vinylidene fluoride) nanocomposites by filling with a small loading of core-shell structured BaTiO3/SiO2 nanofibers

Science.gov (United States)

Liu, Shaohui; Xue, Shuangxi; Shen, Bo; Zhai, Jiwei

2015-07-01

Homogeneous ceramic-polymer nanocomposites consisting of core-shell structured BaTiO3/SiO2 nanofibers and a p oly(vinylidene fluoride) (PVDF) polymer matrix have been prepared. The correlation between the energy discharged density and interfacial polarization is studied in PVDF nanocomposites by the measurements of the discharge performance and impedance spectroscopy. According to the results of dielectric constant, breakdown strength, and complex impedance analysis, coating SiO2 layers on the surface of BaTiO3 nanofibers can block the movement of charge carriers through the nanocomposites by playing a shielding role on the charge-rich inter layer, which resulted in weak Maxwell-Wagner-Sillars interfacial polarization and thus reduces the energy loss and improved the energy discharged density of the nanocomposites. The energy discharged density in the nanocomposite with 2.5 vol. % BaTiO3/SiO2 core-shell nanofibers is 6.28 J/cm3 at 3.3 MV/cm, which is over 11.94% higher than that of nanocomposite with BaTiO3 nanofibers at the same electric field.

Piezoelectric properties of electrospun nanofibers of BaTiO3; Propiedades piezoeletricas de nanofibras eletrofiadas de BaTiO3

Energy Technology Data Exchange (ETDEWEB)

Carvalho, L.F.R.M.; Melo, G.F.; Goncalves, A.M.; Eiras, J.A.; Bretas, R.E.S., E-mail: bretas@ufscar.br [Universidade Federal de Sao Carlos (UFSCar), SP (Brazil)

2016-07-01

BaTiO3 nanofibers were produced by the electrospinning method from a mixture of a solution of the precursors Ba (CH{sub 3}COO){sub 2} and [(CH{sub 3}){sub 2}CHO]{sub 4}Ti in acetic acid and a solution of poly(vinylpyrrolidone) in ethanol. A voltage of 10 kV and a working distance of 4.6 cm were used for the electrospinning, at controlled room temperature and humidity of 21 °C and 60% respectively. Nanofibers as spun were dried in air on an air-circulating oven at 100 °C for one hour to remove residual solvent and were subsequently calcined at 750 °C during 2 h. The morphology, crystallographic structure and piezoelectric properties of the nanofibers were analyzed by scanning electron microscopy (SEM), X-ray angle (WAXS) and Piezoresponse Force Microscopy (PFM), respectively. The average diameter of the nanofibers was 414 nm with an aspect ratio of 40. By PFM, there was strong evidence that the nanofibers had piezoelectric activity. (author)

Effects of ultrasonication and conventional mechanical homogenization processes on the structures and dielectric properties of BaTiO3 ceramics.

Science.gov (United States)

Akbas, Hatice Zehra; Aydin, Zeki; Yilmaz, Onur; Turgut, Selvin

2017-01-01

The effects of the homogenization process on the structures and dielectric properties of pure and Nb-doped BaTiO 3 ceramics have been investigated using an ultrasonic homogenization and conventional mechanical methods. The reagents were homogenized using an ultrasonic processor with high-intensity ultrasonic waves and using a compact mixer-shaker. The components and crystal types of the powders were determined by Fourier-transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) analyses. The complex permittivity (ε ' , ε″) and AC conductivity (σ') of the samples were analyzed in a wide frequency range of 20Hz to 2MHz at room temperature. The structures and dielectric properties of pure and Nb-doped BaTiO 3 ceramics strongly depend on the homogenization process in a solid-state reaction method. Using an ultrasonic processor with high-intensity ultrasonic waves based on acoustic cavitation phenomena can make a significant improvement in producing high-purity BaTiO 3 ceramics without carbonate impurities with a small dielectric loss. Copyright © 2016 Elsevier B.V. All rights reserved.

Effect of crystal orientation on the phase diagrams, dielectric and piezoelectric properties of epitaxial BaTiO3 thin films

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Huaping Wu

2016-01-01

Full Text Available The influence of crystal orientations on the phase diagrams, dielectric and piezoelectric properties of epitaxial BaTiO3 thin films has been investigated using an expanded nonlinear thermodynamic theory. The calculations reveal that crystal orientation has significant influence on the phase stability and phase transitions in the misfit strain-temperature phase diagrams. In particular, the (110 orientation leads to a lower symmetry and more complicated phase transition than the (111 orientation in BaTiO3 films. The increase of compressive strain will dramatically enhance the Curie temperature TC of (110-oriented BaTiO3 films, which matches well with previous experimental data. The polarization components experience a great change across the boundaries of different phases at room temperature in both (110- and (111-oriented films, which leads to the huge dielectric and piezoelectric responses. A good agreement is found between the present thermodynamics calculation and previous first-principles calculations. Our work provides an insight into how to use crystal orientation, epitaxial strain and temperature to tune the structure and properties of ferroelectrics.

Facile Low Temperature Hydrothermal Synthesis of BaTiO3 Nanoparticles Studied by In Situ X-ray Diffraction

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Ola G. Grendal

2018-06-01

Full Text Available Ferroelectric materials are crucial for today’s technological society and nanostructured ferroelectric materials are important for the downscaling of devices. Controlled and reproducible synthesis of these materials are, therefore, of immense importance. Hydrothermal synthesis is a well-established synthesis route, with a large parameter space for optimization, but a better understanding of nucleation and growth mechanisms is needed for full utilization and control. Here we use in situ X-ray diffraction to follow the nucleation and growth of BaTiO3 formed by hydrothermal synthesis using two different titanium precursors, an amorphous titania precipitate slurry and a Ti-citric acid complex solution. Sequential Rietveld refinement was used to extract the time dependency of lattice parameters, crystallite size, strain, and atomic displacement parameters. Phase pure BaTiO3 nanoparticles, 10–15 nm in size, were successfully synthesized at different temperatures (100, 125, and 150 °C from both precursors after reaction times, ranging from a few seconds to several hours. The two precursors resulted in phase pure BaTiO3 with similar final crystallite size. Finally, two different growth mechanisms were revealed, where the effect of surfactants present during hydrothermal synthesis is discussed as one of the key parameters.

Effects of content and surface hydrophobic modification of BaTiO3 on the cooling properties of ASA (acrylonitrile-styrene-acrylate copolymer)

Science.gov (United States)

Xiang, Bo; Zhang, Jun

2018-01-01

For the field of cool material, barium titanate (BaTiO3, BT) is still a new member that needs to be further studied. Herein, the effects of both content and surface hydrophobic modification of BT on the cooling properties of acrylonitrile-styrene-acrylate copolymer (ASA) were detailedly investigated, aiming to fabricate composited cool material. Butyl acrylate (BA) was employed to convert the surface of BT from hydrophilic to hydrophobic. The addition of unmodified BT could significantly improve the solar reflectance of ASA, especially when the addition amount is 3 vol%, the near infrared (NIR) reflectance increased from 22.02 to 72.60%. However, serious agglomeration occurred when the addition amount increased to 5 vol% and therefore led to a relatively smaller increase in solar reflectance and an obvious decline in impact strength. After surface hydrophobic modification, the modified BT (M-BT) presented better dispersibility in ASA matrix, which contributed to the improvement of both solar reflectance and impact strength. In addition, the temperature test provided a more sufficient and intuitive way to evaluate the cooling effect of the composited cool materials, and a significant decrease (over 10 °C) could be achieved in the temperature test when M-BT particles were introduced.

The composition dependence of the photochemical reactivity of strontium barium titanate

Science.gov (United States)

Bhardwaj, Abhilasha

The efficiency of particulate water photolysis catalysts is impractically low due to the recombination of intermediate species and charge carriers. The back reaction can occur easily if the oxidation and reduction sites on the surface of the catalyst are not far enough apart. It is hypothesized that it will be possible to increase the separation of the sites of the two half reactions and reduce the recombination of photogenerated charge carriers by using a ferroelectric material with permanent internal dipolar fields. This separation of the reaction sites may significantly increase the efficiency of the process. The present work compares the photochemical reactivities of ferroelectric and nonferroelectric materials (SrxBa1-xTiO 3, 0.0≤ x ≤1.0) with similar composition and structure. The reactivities are compared by measuring the color change of methylene blue dye after the aqueous dye solution reacts on the surface of ceramic sample pellets as a result of exposure to UV light. The reactivities are also compared by measuring the amount of silver that is formed when an aqueous AgNO3 solution photochemically reacts on the surface. The change in the color of the dye is measured by diffuse reflectance spectroscopy and absorbance measurements. The amount of silver is measured by atomic force microscopy. The photochemical reactivity of SrxBa1-xTiO3 shows a local maximum at the composition of the ferroelectric to non-ferroelectric transition. Also, the reactivities decrease as BaTiO3 and SrTiO3 become less pure. The dominant factors causing this trend in reactivities of SrxBa1-xTiO3 are the dielectric constant and alloy scattering. It is found that higher values of the dielectric constant increase the photochemical reactivity by enlarging the space charge region. The increase in alloy scattering in SrxBa1-xTiO 3 solid solutions as x increases from zero or decreases from 1, has adverse effect on reactivity. There are other factors such as ferroelectric polarization

Complementary resistive switching in BaTiO3/NiO bilayer with opposite switching polarities

Science.gov (United States)

Li, Shuo; Wei, Xianhua; Lei, Yao; Yuan, Xincai; Zeng, Huizhong

2016-12-01

Resistive switching behaviors have been investigated in the Au/BaTiO3/NiO/Pt structure by stacking the two elements with different switching types. The conducting atomic force microscope measurements on BaTiO3 thin films and NiO thin films suggest that with the same active resistive switching region, the switching polarities in the two semiconductors are opposite to each other. It is in agreement with the bipolar hysteresis I-V curves with opposite switching polarities for single-layer devices. The bilayer devices show complementary resistive switching (CRS) without electroforming and unipolar resistive switching (URS) after electroforming. The coexistence of CRS and URS is mainly ascribed to the co-effect of electric field and Joule heating mechanisms, indicating that changeable of resistance in this device is dominated by the redistribution of oxygen vacancies in BaTiO3 and the formation, disruption, restoration of conducting filaments in NiO. CRS in bilayer with opposite switching polarities is effective to solve the sneak current without the introduction of any selector elements or an additional metal electrode.

Lanthanum-doped mesostructured strontium titanates synthesized via sol–gel combustion route using citric acid as complexing agent

Energy Technology Data Exchange (ETDEWEB)

Sukpanish, Polthep [Department of Chemical Technology, Faculty of Science, Chulalongkorn University, Patumwan, Bangkok 10330 (Thailand); Center of Excellence on Petrochemical and Materials Technology (PETROMAT), Chulalongkorn University, Patumwan, Bangkok 10330 (Thailand); Lertpanyapornchai, Boontawee [Program in Petrochemistry, Faculty of Science, Chulalongkorn University, Patumwan, Bangkok 10330 (Thailand); Yokoi, Toshiyuki [Division of Catalytic Chemistry, Chemical Resources Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503 (Japan); Ngamcharussrivichai, Chawalit, E-mail: Chawalit.Ng@chula.ac.th [Department of Chemical Technology, Faculty of Science, Chulalongkorn University, Patumwan, Bangkok 10330 (Thailand); Center of Excellence on Petrochemical and Materials Technology (PETROMAT), Chulalongkorn University, Patumwan, Bangkok 10330 (Thailand)

2016-09-15

In the present work, a series of lanthanum-doped mesostructured strontium titanate (LMST) materials with different La/Sr ratios were synthesized via a sol–gel combustion method in the presence of citric acid as a complexing agent and Pluronic P123 as a templating agent. The effects of the amount of doped La and calcination temperature on the physicochemical properties of the LMSTs were examined using various techniques. Powder X-ray diffraction confirmed the substitution of La{sup 3+} into the SrTiO{sub 3} lattice, generating cubic perovskite La{sub x}Sr{sub 1−x}TiO{sub 3}, for the LMST materials calcined at 600 °C. The purity and crystallinity of the desired perovskite phase were enhanced by citric acid addition. The solubility limit of La{sup 3+} substitution at an La/Sr ratio of 0.43 was determined by structural and morphological studies. Increasing the La doping amount decreased the crystallinity and compositional homogeneity, because an La-rich amorphous phase segregated on the surface, but improved the mesoporosity. N{sub 2} physisorption measurements indicated that the LMSTs had a bimodal pore size distribution, of which the larger one was characterized by the crystallite size of mixed oxides, and the specific surface area of 24.9–37.3 m{sup 2} g{sup −1}. The formation of mesopores in the LMST materials synthesized via sol–gel combustion was explained based on a combination of soft- and hard-templating chemistries. - Highlights: • La-doped mesoporous SrTiO{sub 3} (LMST) was prepared first time via sol-gel combustion. • Pluronic P123 triblock copolymer was used as a cheap templating agent. • Citric acid as a complexing agent enhanced the purity and crystallinity of SrTiO{sub 3}. • The textural properties of LMST were improved by increasing the La doping amount. • Mesopore formation was explained by a combined soft- and hard-templating route.

Estudio del perfil de defectos y de las propiedades eléctricas de BaTiO3 dopado con Nb y La

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Castro, M. S.

2002-02-01

Full Text Available The aim of this work is to study the impact of two different and typical donor –dopants; Nb2O5 and La2O3, on the electrical properties of BaTiO3. Besides, the influence of Nb5+ and La3+ on the charge compensation mechanism was evaluated. On this way, it was determined that, the defect structure is not only affected by the dopant ion but also by its concentration. Amount of dopant also affects the electrical properties of BaTiO3 ceramics. In fact, for low Nb2O5 or La2O3 concentration, electronic compensation prevails, leading to a low – resistive material with an important PTCR effect. By EPR an increases in the oxygen vacancies with a low lanthanum addition was determined. This phenomenon could be associated to the lanthanum acceptor behavior. On the other hand, high dopant concentration leads to a high – resistive material showing GBBL characteristics. In this case, a high content of double – ionized barium vacancies able to trap electrons, and a thin glassy – phase film covering the BaTiO3 grains lead to a high – resistive material. This phenomenon encourages the hypothesis in which barium vacancies act as acceptor centers at the grain boundaries in BaTiO3 ceramics.En este trabajo, se estudia el impacto de la adición de Nb2O5 o La2O3 sobre las propiedades eléctricas de cerámicos basados en BaTiO3. Asimismo, se estudia la influencia de estos dos típicos dopantes en los mecanismos de compensación de cargas. En este sentido, se ha determinado que la estructura de defectos en el BaTiO3 no sólo se encuentra afectada por el tipo de dopante sino tambien por su concentración. En efecto, para bajas concentraciones de Nb2O5 o La2O3, predomina un mecanismo de compensación de cargas por generación de electrones. Sin embargo, los resultados de EPR muestran que la adición de una pequeña cantidad de La2O3 produce un notable incremento en la concentración de vacantes de oxígeno respecto del BaTiO3 sin dopar. Este fenómeno podr

Effect of double layer thickness on magnetoelectric coupling in multiferroic BaTiO3-Bi0.95Gd0.05FeO3 multilayers

Science.gov (United States)

Hohenberger, S.; Lazenka, V.; Temst, K.; Selle, S.; Patzig, C.; Höche, T.; Grundmann, M.; Lorenz, M.

2018-05-01

The effect of double-layer thickness and partial substitution of Bi3+ by Gd3+ is demonstrated for multiferroic BaTiO3–BiFeO3 2–2 heterostructures. Multilayers of 15 double layers of BaTiO3 and Bi0.95Gd0.05FeO3 were deposited onto (0 0 1) oriented SrTiO3 substrates by pulsed laser deposition with various double layer thicknesses. X-ray diffraction and high resolution transmission electron microscopy investigations revealed a systematic strain tuning with layer thickness via coherently strained interfaces. The multilayers show increasingly enhanced magnetoelectric coupling with reduced double layer thickness. The maximum magnetoelectric coupling coefficient was measured to be as high as 50.8 V cm‑1 Oe‑1 in 0 T DC bias magnetic field at room temperature, and 54.9 V cm‑1 Oe‑1 above 3 T for the sample with the thinnest double layer thickness of 22.5 nm. This enhancement is accompanied by progressively increasing perpendicular magnetic anisotropy and compressive out-of-plane strain. To understand the origin of the enhanced magnetoelectric coupling in such multilayers, the temperature and magnetic field dependency of is discussed. The magnetoelectric performance of the Gd3+ substituted samples is found to be slightly enhanced when compared to unsubstituted BaTiO3–BiFeO3 multilayers of comparable double-layer thickness.

(Nd0⋅065Ti0⋅87Nb0⋅065)O3 ceramic

Indian Academy of Sciences (India)

Unknown

Polycrystalline ceramic samples of sodium bismuth titanate with simultaneous doping at A and B sites have been studied for the influence of ... of Nd and Nb at B site in BaTiO3 (BaNdxTi1–2xNbxO3). (Mahboob et al 2005a). Dielectric ..... hence the conduction arises due to short range translation hopping via large polarons.

A first-principles study of phase transitions in ultrathin films of BaTiO 3

Indian Academy of Sciences (India)

We determine the effects of film thickness, epitaxial strain and the nature of electrodes on ferroelectric phase transitions in ultrathin films of BaTiO3 using a first-principles effective Hamiltonian in classical molecular dynamics simulations. We present results for polarization and dielectric properties as a function of temperature ...

Use of titanates in decontamination of defense waste

International Nuclear Information System (INIS)

Dosch, R.G.

1978-06-01

Sodium titanate, an inorganic ion exchange material, has been evaluated for use in a process to remove strontium from Defense Waste or other high-sodium, caustic solutions. Distribution coefficients on the order of 10 5 were observed at sub part per million concentrations of Sr, and the effects of other cation impurities and complexants in the waste were investigated. The preparation and general chemical properties of the exchange material are discussed. This information was used in developing a commercial source which has since supplied a 200 kg batch of the material for evaluation. In column ion exchange experiments with 85 Sr-doped simulated waste, decontamination factors of 500 or greater were observed in the first 2000 to 3500 bed volumes of effluent, depending on the impurities in the simulant. A -40 to +130 mesh range of sodium titanate powder was used as the baseline material, but a study to produce alternate forms of the titanate was carried in parallel. This has resulted in two materials which appear promising with respect to both simplification of handling and chemical properties. One of the materials is an agglomerated form of the titanate formed by extrusion pelletizing using water as a binder, and the second is a macroreticular organic anion resin which was loaded with 30 to 40% (by weight) of sodium titanate. The results of initial testing of these materials are discussed

Study on the Key Technology of High Purity Strontium Titanate Powder Synthesized from Oxalic Acid Co-sediment Precipitation

Science.gov (United States)

Bi, Xiaoguo; Dong, Yingnan; Li, Yingjie; Niu, Wei; Tang, Jian; Ding, Shuang; Li, Meiyang

2017-09-01

Oxalate coprecipitation is applied in this paper, high purity titanium tetrachloride, and after the purification of strontium chloride, match with a certain concentration of solution, oxalate and strontium chloride and titanium tetrachloride in 1.005:1.000 make strontium titanium mixture ratio, slowly under 60°C to join in oxalic acid solution, aging around 4 h, get oxygen titanium strontium oxalate (SrTiO(C2O4)2 • 4H2 ) precipitation, after washing, drying and other process made oxygen titanium strontium oxalate powder.

Hybrid chitosan–Pluronic F-127 films with BaTiO3:Co nanoparticles: Synthesis and properties

International Nuclear Information System (INIS)

Fuentes, S.; Dubo, J.; Barraza, N.; González, R.; Veloso, E.

2015-01-01

In this study, magnetic BaTiO 3 :Co (BT:Co) nanoparticles prepared using a combined sol–gel–hydrothermal technique were dispersed in a chitosan/Pluronic F-127 solution (QO/Pl) to obtain a nanocomposite hybrid films. Nanoparticles and hybrid films were characterized by X-ray powder diffraction, Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and alternating gradient magnetometry (AGM). Experimental results indicated that the BT:Co nanoparticles were encapsulated in the QO/Pl hybrid films and that the magnetic properties of the QO/Pl/BT:Co nanocomposites are similar to the naked BT:Co nanoparticles. Results indicate that Co doping produces an enhancement in the ferromagnetic behavior of the BT nanoparticle. The coating restricts this enhancement only to low-fields, leaving the diamagnetic behavior of BT at high-fields. Magnetically stable sizes (PSD) were obtained at 3% Co doping for both naked nanoparticles and hybrid films. These show an increased magnetic memory capacity and a softer magnetic hardness with respect to non-doped BT nanoparticles. - Highlights: • We described the synthesis of magnetic BaTiO 3 :Co dispersed in chitosan (QO)/Pluronic F-127 (Pl) solution by sonication to obtain nanocomposite hybrid films. • We describe the physical and magnetic properties of BaTiO 3 :Co nanoparticles and QO/Pl/BT:Co hybrid films. • The magnetic properties are defines by the presence of magnetic domains. These magnetic domains are close related with the amount of Co in the host lattice. • The prepared phases could be considered as multifunctional materials, with magnetic and ferri-electrical properties, with potential uses in the design of devices

Synthesis and colloidal properties of anisotropic hydrothermal barium titanate

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Yosenick, Timothy James

2005-11-01

Nanoparticles of high dielectric constant materials, especially BaTiO3, are required to achieve decreased layer thickness in multilayer ceramic capacitors (MLCCs). Tabular metal nanoparticles can produce thin metal layers with low surface roughness via electrophoretic deposition (EPD). To achieve similar results with dielectric layers requires the synthesis and dispersion of tabular BaTiO3 nanoparticles. The goal of this study was to investigate the deposition of thin BaTiO3 layers using a colloidal process. The synthesis, interfacial chemistry and colloidal properties of hydrothermal BaTiO3 a model particle system, was investigated. After characterization of the material system particulates were deposited to form thin layers using EPD. In the current study, the synthesis of BaTiO3 has been investigated using a hydrothermal route. TEM and AFM analyses show that the synthesized particles are single crystal with a majority of the particle having a zone axis and {111} large face. The particles have a median thickness of 5.8 +/- 3.1 nm and face diameter of 27.1 +/- 12.3 nm. Particle growth was likely controlled by the formation of {111} twins and the synthesis pH which stabilizes the {111} face during growth. With limited growth in the direction, the particles developed a plate-like morphology. Physical property characterization shows the powder was suitable for further processing with high purity, low hydrothermal defect concentration, and controlled stoichiometry. TEM observations of thermally treated powders indicate that the particles begin to loose the plate-like morphology by 900 °C. The aqueous passivation, dispersion, and doping of nanoscale BaTiO 3 powders was investigated. Passivation BaTiO3 was achieved through the addition of oxalic acid. The oxalic acid selectively adsorbs onto the particle surface and forms a chemically stable 2-3 nm layer of barium oxalate. The negative surface charge of the oxalate effectively passivated the BaTiO3 providing a surface

Microstructural and dielectrical characterization of Ho doped BaTiO3 ceramics

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Marjanović Miloš

2014-01-01

Full Text Available The Ho doped BaTiO3 ceramics, with different Ho2O3 content, ranging from 0.01 to 1.0 wt % Ho, were investigated regarding their microstructural and dielectric characteristics. Doped BaTiO3 were prepared using conventional solid state reaction and sintered at 1380°C for four hours. SEM analysis of Ho/BaTiO3 doped ceramics showed that the low doped samples exhibit mainly fairly uniform and homogeneous microstructure with the grain size ranged from 20-40 μm. In the samples with the higher dopant concentration the abnormal grain growth is inhibited and the grain size ranged between 2-10 μm. Measurements of dielectric properties were carried out as a function of temperature up to 180 °C at different frequencies. The samples doped with 0.01wt % of Ho, exhibit the high value of dielectric permittivity (εr = 2160 at room temperature. A nearly flat permittivity-response was obtained in specimens with higher additive content. Using a Curie-Weiss law and modified Curie-Weiss law the Curie constant (C, Curie temperature (Tc and a critical exponent of nonlinearity (g were calculated. The Curie temperature of doped samples were ranged from 128 to 130°C. The Curie constant for all series of samples decrease with increase of dopant concentration and the lowest values were observed on samples doped with 0.01 wt % of holmium. [Projekat Ministarstva nauke Republike Srbije, br. OI 172057: Directed synthesis, structure and properties of multifunctional materials i br. TR 32026

Multiferroic properties of BiFeO3/BaTiO3 multilayered thin films

International Nuclear Information System (INIS)

Sharma, Savita; Tomar, Monika; Kumar, Ashok; Puri, Nitin K.; Gupta, Vinay

2014-01-01

Multilayered structures of multiferroic BiFeO 3 (BFO) and ferroelectric BaTiO 3 (BTO) have been fabricated using pulsed laser deposition (PLD). Ferromagnetic and ferroelectric properties of the multilayered system (BFO/BTO) have been investigated. It could be inferred that the magnetization increases with the incorporation of BTO buffer layer, which indicates a coupling between the ferroelectric and ferromagnetic orders. Vibrating sample magnetometer (VSM) measurements performed on the prepared multiferroic samples show that the magnetization is significantly increased (M s =56.88 emu/cm 3 ) for the multilayer system with more number of layers (four) keeping the total thickness of the multilayered system constant (350 nm) meanwhile maintaining the sufficiently enhanced ferroelectric properties (P r =29.68 µC/cm 2 )

Reflectance of Co- and Nb-doped BaTiO3 for photon energies from 1.8 to 70 eV

International Nuclear Information System (INIS)

Goudonnet, J.P.; Godefroy, G.; Inagaki, T.; Moretti, P.; Williams, M.W.; Arakawa, E.T.

1985-01-01

The reflectance spectra of Co- and Nb-doped BaTiO 3 crystals have been measured for photon energies from 1.8 to 70 eV. For both types of crystal, structures observed in the 1.8 to 2.3 eV range can be attributed to the presence of residual impurities. Between 2.3 and 3.2 eV the peaks in the reflectance of the Co-doped crystal are found to be of an acceptor charge transfer type. For Nb-doped crystals structures appear at the bottom of the conduction band. For energies larger than 3.2 eV the spectra are characteristic of pure BaTiO 3 crystals, in reasonable agreement with those determined by Baeuerle et al. and calculated by Michel-Calendini and Moretti. 15 refs., 4 figs., 1 tab

Understanding the peculiarities of the piezoelectric effect in macro-porous BaTiO3.

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Roscow, James I; Topolov, Vitaly Yu; Bowen, Christopher R; Taylor, John; Panich, Anatoly E

2016-01-01

This work demonstrates the potential of porous BaTiO 3 for piezoelectric sensor and energy-harvesting applications by manufacture of materials, detailed characterisation and application of new models. Ferroelectric macro-porous BaTiO 3 ceramics for piezoelectric applications are manufactured for a range of relative densities, α  = 0.30-0.95, using the burned out polymer spheres method. The piezoelectric activity and relevant parameters for specific applications are interpreted by developing two models: a model of a 3-0 composite and a 'composite in composite' model. The appropriate ranges of relative density for the application of these models to accurately predict piezoelectric properties are examined. The two models are extended to take into account the effect of 90° domain-wall mobility within ceramic grains on the piezoelectric coefficients [Formula: see text]. It is shown that porous ferroelectrics provide a novel route to form materials with large piezoelectric anisotropy [Formula: see text] at 0.20 ≤ α ≤ 0.45 and achieve a high squared figure of merit [Formula: see text] [Formula: see text]. The modelling approach allows a detailed analysis of the relationships between the properties of the monolithic and porous materials for the design of porous structures with optimum properties.

Synthesis of BaTiO{sub 3} and SrTiO{sub 3} by microwave assisted hydrothermal method (MAH) using anatase as titanium precursor

Energy Technology Data Exchange (ETDEWEB)

Magalhães, Renata da Silva; Macedo Junior, Wagner Dias; Souza, Agda Eunice de; Teixeira, Silvio Rainho, E-mail: R.S.Magalhaes@hotmail.com [Universidade Estadual Paulista Julio de Mesquita Filho (FCT/UNESP), Presidente Prudente, SP (Brazil); Li, Maximo Siu [Universidade de Sao Paulo (USP), São Carlos, SP (Brazil). Instituto de Física; Longo, Elson [Universidade Estadual Paulista Julio de Mesquita Filho (UNESP), Araraquara, SP (Brazil). Instituto de Química

2016-07-01

Full text: Strontium and barium titanates (SrTiO{sub 3} (ST) and BaTiO{sub 3} (BT)) in their crystalline form belong to the perovskite (ABO{sub 3}) class. Both display a semiconductor behavior with many interesting properties. The method of synthesis employed and different precursors may influence the morphology and properties of ceramic materials [1,2]. Barium (BT) and strontium (St) titanates were produced using the Microwave Assisted Hydrothermal Method (MAH), different concentrations (1,3 and 6 molL{sup -1}) of mineralizer (KOH) and a different titanium precursor: a complex anatase-hydrogen peroxide. Barium and strontium chloride were used as the other metal precursors. The resulting material were characterized by different techniques such as: X-ray diffraction (XRD), Micro-Raman Spectroscopy (MR), UV-Vis, Scanning Electron microscopy (SEM) and finally their photoluminescent emissions (FL) were recorded at room temperature. The results show that there were differences in crystallinity, morphology, number of formed phases and photoluminescent emission, among the titanate produced with different concentrations of mineralizer. References: [1] A.E. Souza et al., Order–disorder degree of self-assembled clusters: Influence on photoluminescence emission and morphology of Ba{sub x}Sr{sub 1-x}TiO{sub 3} nanocrystals, Chemical Physics Letters 514 (2011) 301–306. [2] T. M. Mazzo et al., Influence of titanium precursor on photoluminescent emission of micro-cube-shaped CaTiO{sub 3}, Journal of Luminescence 165 (2015). (author)

Optical properties of BaTiO3 nanoparticles and silver nanoprisms in polymer host matrices

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Requena, Sebastian

Nanocomposites are materials comprised of a host matrix, such as glass or polymer, with embedded nanoparticles. Embedding nanoparticles into the host makes it possible to create materials with properties that are distinctly unique from those of their host and nanoparticle constituents. Nanocomposites can have superior mechanical, thermal, and optical properties compared to their host materials. We characterized the photoluminescent properties of BaTiO3 polymer nanocomposites and the effects of chemically modifying the nanoparticles surface on said properties. BaTiO3 nanopowders of average grain sizes 50 nm and 100 nm were functionalized by (3-aminopropyl)triethoxysilane (3APTS) and mixed with poly(methyl methacrylate)/toluene solution. The nanocomposites films morphology and chemical structure were studied via AFM and FTIR. The photoluminescence spectrum of the pure nanoparticles was composed of an emission at ˜3.0 eV and multiple bands centered at ˜2.5 eV. Surface functionalization of the BaTiO3 nanoparticles via 3APTS increased overall luminescence at room temperature while only enhancing the ˜3.0 eV emission at low-temperature. On the other hand, polymer coating of the functionalized nanoparticles significantly enhances ˜3.0 eV emissions while decreasing emissions associated with near-surface lattice distortions at ˜2.5 eV. Chemical modification of the surface with 3APTS and PMMA presents a pathway to tune and control the photoluminescent properties of BTO nanoparticles. We also present optical studies of two different size distributions of silver triangular nanoprisms, one with a dipole resonance at ˜520 nm and the other with a dipole resonance at ˜650 nm, placed in different media. The silver nanoprisms were embedded in a polyvinyl alcohol (PVA) polymer matrix and oriented by stretching the polymer/nanoprism nanocomposite films. We observe significantly increased linear dichroism in the region associated with the plasmonic in-plane dipole mode upon

Substantial enhancement of energy storage capability in polymer nanocomposites by encapsulation of BaTiO3 NWs with variable shell thickness.

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Wang, Guanyao; Huang, Yanhui; Wang, Yuxin; Jiang, Pingkai; Huang, Xingyi

2017-08-09

Dielectric polymer nanocomposites have received keen interest due to their potential application in energy storage. Nevertheless, the large contrast in dielectric constant between the polymer and nanofillers usually results in a significant decrease of breakdown strength of the nanocomposites, which is unfavorable for enhancing energy storage capability. Herein, BaTiO 3 nanowires (NWs) encapsulated by TiO 2 shells of variable thickness were utilized to fabricate dielectric polymer nanocomposites. Compared with nanocomposites with bare BaTiO 3 NWs, significantly enhanced energy storage capability was achieved for nanocomposites with TiO 2 encapsulated BaTiO 3 NWs. For instance, an ultrahigh energy density of 9.53 J cm -3 at 440 MV m -1 could be obtained for nanocomposites comprising core-shell structured nanowires, much higher than that of nanocomposites with 5 wt% raw ones (5.60 J cm -3 at 360 MV m -1 ). The discharged energy density of the proposed nanocomposites with 5 wt% mTiO 2 @BaTiO 3 -1 NWs at 440 MV m -1 seems to rival or exceed those of some previously reported nanocomposites (mostly comprising core-shell structured nanofillers). More notably, this study revealed that the energy storage capability of the nanocomposites can be tailored by the TiO 2 shell thickness. Finite element simulations were employed to analyze the electric field distribution in the nanocomposites. The enhanced energy storage capability should be mainly attributed to the smoother gradient of dielectric constant between the nanofillers and polymer matrix, which alleviated the electric field concentration and leakage current in the polymer matrix. The methods and results herein offer a feasible approach to construct high-energy-density polymer nanocomposites with core-shell structured nanowires.

Multicomponent doped barium strontium titanate thin films for tunable microwave applications

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Alema, Fikadu Legesse

In recent years there has been enormous progress in the development of barium strontium titanate (BST) films for tunable microwave applications. However, the properties of BST films still remain inferior compared to bulk materials, limiting their use for microwave technology. Understanding the film/substrate mismatch, microstructure, and stoichiometry of BST films and finding the necessary remedies are vital. In this work, BST films were deposited via radio frequency magnetron sputtering method and characterized both analytically and electrically with the aim of optimizing their properties. The stoichiometry, crystal structure, and phase purity of the films were studied by varying the oxygen partial pressure (OPP) and total gas pressure (TGP) in the chamber. A better stoichiometric match between film and target was achieved when the TGP is high (> 30 mTorr). However, the O2/Ar ratio should be adjusted as exceeding a threshold of 2 mTorr in OPP facilitates the formation of secondary phases. The growth of crystalline film on platinized substrates was achieved only with a lower temperature grown buffer layer, which acts as a seed layer by crystallizing when the temperature increases. Concurrent Mg/Nb doping has significantly improved the properties of BST thin films. The doped film has shown an average tunability of 53%, which is only ˜8 % lower than the value for the undoped film. This drop is associated with the Mg ions whose detrimental effects are partially compensated by Nb ions. Conversely, the doping has reduced the dielectric loss by ˜40 % leading to a higher figure of merit. Moreover, the two dopants ensure a charge neutrality condition which resulted in significant leakage current reduction. The presence of large amounts of empty shallow traps related to Nb Ti localize the free carriers injected from the contacts; thus increase the device control voltage substantially (>10 V). A combinatorial thin film synthesis method based on co-sputtering of two BST

Investigation of Voltage-Activated BAW Devices and Filters

Science.gov (United States)

2016-09-04

strontium titanate (STO) and barium-strontium titanate (BST), with the ultimate objective of creating high- performance, reconfigurable filters and...induced piezoelectricity in thin-film strontium titanate (STO) and barium-strontium titanate (BST), with the ultimate objective of creating high...this work 1. The effect of patterned vs. unpatterned acoustic Bragg reflector on barium strontium titanate solidly mounted resonator. Authors: George

Simulating the 3-D Structure of Titan's Upper Atmosphere

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Bell, J. M.; Waite, H.; Westlake, J.; Magee, B.

2009-05-01

We present results from the 3-D Titan Global Ionosphere-Thermosphere Model (Bell et al [2009], PSS, in review). We show comparisons between simulated N2, CH4, and H2 density fields and the in-situ data from the Cassini Ion Neutral Mass Spectrometer (INMS). We describe the temperature and wind fields consistent with these density calculations. Variations with local time, longitude, and latitude will be addressed. Potential plasma heating sources can be estimated using the 1-D model of De La Haye et al [2007, 2008] and the impacts on the thermosphere of Titan can be assessed in a global sense in Titan-GITM. Lastly, we will place these findings within the context of recent work in modeling the 2-D structure of Titan's upper atmosphere (Mueller-Wodarg et al [2008]).

Pulse-based electron spin transient nutation measurement of BaTiO3 fine particle: Identification of controversial signal around g = 2.00

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Sawai, Takatoshi; Yamaguchi, Yoji; Kitamura, Noriko; Date, Tomotsugu; Konishi, Shinya; Taga, Kazuya; Tanaka, Katsuhisa

2018-05-01

Two dimensional pulse-based electron spin transient nutation (2D-ESTN) spectroscopy is a powerful tool for determining the spin quantum number and has been applied to BaTiO3 fine powder in order to identify the origin of the continuous wave electron spin resonance (CW-ESR) signal around g = 2.00. The signal is frequently observed in BaTiO3 ceramics, and the correlation between the signal intensity and positive temperature coefficient of resistivity (PTCR) properties has been reported to date. The CW-ESR spectrum of BaTiO3 fine particles synthesized by the sol-gel method shows a typical asymmetric signal at g = 2.004. The 2D-ESTN measurements of the sample clearly reveal that the signal belongs to the S = 5/2 high spin state, indicating that the signal is not due to a point defect as suggested by a number of researchers but rather to a transition metal ion. Our elemental analysis, as well as previous studies, indicates that the origin of the g = 2.004 signal is due to the presence of an Fe3+ impurity. The D value (second-order fine structure parameter) reveals that the origin of the signal is an Fe3+ center with distant charge compensation. In addition, we show a peculiar temperature dependence of the CW-ESR spectrum, suggesting that the phase transition behavior of a BaTiO3 fine particle is quite different from that of a bulk single crystal. Our identification does not contradict a vacancy-mediated mechanism for PTCR. However, it is incorrect to use the signal at g = 2.00 as evidence to support the vacancy-mediated mechanism.

Ho2O3 additive effects on BaTiO3 ceramics microstructure and dielectric properties

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Paunović Vesna

2012-01-01

Full Text Available Doped BaTiO3-ceramics is very interesting for their application as PTCR resistors, multilayer ceramic capacitors, thermal sensors etc. Ho doped BaTiO3 ceramics, with different Ho2O3 content, ranging from 0.01 to 1.0 wt% Ho, were investigated regarding their microstructural and dielectric characteristics. The samples were prepared by the conventional solid state reaction and sintered at 1320° and 1380°C in an air atmosphere for 4 hours. The grain size and microstructure characteristics for various samples and their phase composition was carried out using a scanning electron microscope (SEM equipped with EDS system. SEM analysis of Ho/BaTiO3 doped ceramics showed that in samples doped with a rare-earth ions low level, the grain size ranged from 20-30μm, while with the higher dopant concentration the abnormal grain growth is inhibited and the grain size ranged between 2- 10μm. Dielectric measurements were carried out as a function of temperature up to 180°C. The low doped samples sintered at 1380°C, display the high value of dielectric permittivity at room temperature, 2400 for 0.01Ho/BaTiO3. A nearly flat permittivity-response was obtained in specimens with higher additive content. Using a Curie-Weiss low and modified Curie-Weiss low the Curie constant (C, Curie temperature (Tc and a critical exponent of nonlinearity (γ were calculated. The obtained value of γ pointed out that the specimens have almost sharp phase transition. [Projekat Ministarstva nauke Republike Srbije, br. 172057: Directed synthesis, structure and properties of multifunctional materials

Compensation mechanisms at high temperature in Y-doped BaTiO3

International Nuclear Information System (INIS)

Paredes-Olguín, M.; Lira-Hernández, I.A.; Gómez-Yáñez, C.; Espino-Cortés, F.P.

2013-01-01

Samples of BaTiO 3 with different concentrations of Y were synthesized from powders. The mixtures of powders were pressed and sintered at 1500 °C for 1 h. Two groups of samples were processed, one satisfying Ba/(Ti+Y) 3+ occupies the Ti 4+ lattice sites. The conductivity behavior as a function of Y concentration suggests that the compensation mechanisms are hole and oxygen vacancies. Due to the presence of charge carriers in the material, high values for the dielectric constant and dielectric loss were observed. Analysis of the microstructure showed that the average grain size decreases as the Y concentration is increased.

Synthesis of flower-like BaTiO3/Fe3O4 hierarchically structured particles and their electrorheological and magnetic properties.

Science.gov (United States)

Wang, Baoxiang; Yin, Yichao; Liu, Chenjie; Yu, Shoushan; Chen, Kezheng

2013-07-21

Flower-like BaTiO3/Fe3O4 hierarchically structured particles composed of nano-scale structures on micro-scale materials were synthesized by a simple solvothermal approach and characterized by the means of X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), magnetic testing and rotary viscometer. The influences on the morphology and structure of solvothermal times, type and amount of surfactant, EG : H2O ratio, etc. were studied. Magnetic testing results show that the samples have strong magnetism and they exhibit superparamagnetic behavior, as evidenced by no coercivity and the remanence at room temperature, due to their very small sizes, observed on the M-H loop. The saturation magnetization (M(s)) value can achieve 18.3 emu g(-1). The electrorheological (ER) effect was investigated using a suspension of the flower-like BaTiO3/Fe3O4 hierarchically structured particles dispersed in silicone oil. We can observe a slight shear-thinning behavior of shear viscosity at a low shear rate region even at zero applied electric field and a Newtonian fluid behavior at high shear rate regions.

Conformación de termistores utilizando polvos de BaTiO3 sintetizados por el método pechini

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Claudia P. Fernández Perdomo

2010-05-01

Full Text Available El titanato de bario, BaTiO3, es un compuesto de gran interés en el ámbito de la electrocerámica, ya que se utiliza en la fabricación de condensadores, transductores piezoeléctricos y dispositivos resistivos con coeficiente positivo de temperatura (PTCR, así como en la manufactura de piroeléctricos y dispositivos optoelectrónicos, entre otros dispositivos. La mayoría de estos componentes son conformados con polvos cerámicos de elevada pureza y tamaño de partícula adecuado. Esto exige estructurar métodos de síntesis que garanticen es- tos requerimientos. En este trabajo se sintetizaron polvos cerámicos de BaTiO3 por el método de precursor polimérico (Pechini, obteniéndose una materia prima muy pura y con pequeño tamaño de partícula. Los polvos obtenidos se caracterizaron utilizando análisis térmico (ATD/TG, difracción de rayos X (DRX y calorimetría diferencial de barrido (DSC. Los resultados indican que en las muestras tratadas a 650 °C la única fase cristalina presente es el BaTiO3 cúbico y a 1.100 °C la tetragonal, con una relación c/a < 1.007. Las muestras tratadas a 1.100 °C presentaron una transición ferroeléctrica a paraeléctrica a una temperatura de T ≈ 123 °C. Los polvos cerámicos de BaTiO3 tetragonal fueron prensados uniaxialmente y posteriormente sinterizados a 1.200 °C durante 2 horas. Estas muestras se caracterizaron eléctricamente, obteniéndose curvas de resistencia eléctrica en función de la temperatura (R-T, evidenciándose en ellas su comportamiento termistor tipo PTCR. Además, se midió la variación de la corriente-voltaje (I-V a diferentes temperaturas.

Gold nanoparticles decorated on BaTiO3 as photocatalyst: effect of SPR and ferroelectricity

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Miao, Zhilei; Chen, Lei; Wang, Rui; Yuan, Rongchun; Zhou, Fang; Lv, Pengfei; Zhang, Xiuyun; Wang, Qiang

2018-02-01

BaTiO3(BTO) powders with cubic(C) and tetragonal(T) crystalline structures were prepared by sol-gel method followed by calcination at different temperatures, and they were decorated with gold nanoparticles(AuNPs) to form Au-T-BTO and Au-C-BTO respectively. All the samples (C-BTO, T-BTO, Au-C-BTO and Au-T-BTO) were used as photo-catalysts for the degradation of Rhodamine B (RhB). Au-T-BTO exhibits the highest photocatalytic activity due to thecombined effect of surface plasmon resonance (SPR) and the ferroelectricity of the tetragonalphase BTO. The light absorption peaks at 500 to 600 nm verify the presence of SPR effect from Au NPs. Based on density functional theory (DFC) within the generalized gradient approximation (GGA) approach, it was demonstrated that the tetragonal phase BaTiO3 shows a spontaneous polarization with the calculated value of 0.34 C m-2, which is absent in thecubic phase. The internal space charge layer in tetragonal phase BTO enhances the separation of photoexcited carriers due to the spontaneous ferroelectric polarization, which also benefits photocatalytic activities.

Induced Ti magnetization at La0.7Sr0.3MnO3 and BaTiO3 interfaces

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Yaohua Liu

2016-04-01

Full Text Available In artificial multiferroics hybrids consisting of ferromagnetic La0.7Sr0.3MnO3 (LSMO and ferroelectric BaTiO3 epitaxial layers, net Ti moments are found from polarized resonant soft x-ray reflectivity and absorption. The Ti dichroic reflectivity follows the Mn signal during the magnetization reversal, indicating exchange coupling between the Ti and Mn ions. However, the Ti dichroic reflectivity shows stronger temperature dependence than the Mn dichroic signal. Besides a reduced ferromagnetic exchange coupling in the interfacial LSMO layer, this may also be attributed to a weak Ti-Mn exchange coupling that is insufficient to overcome the thermal energy at elevated temperatures.

Thermal stabilities of electromechanical properties in cobalt-modified strontium bismuth titanate (SrBi{sub 4}Ti{sub 4}O{sub 15})

Energy Technology Data Exchange (ETDEWEB)

Wang, Qian; Cao, Zhao-Peng; Wang, Chun-Ming, E-mail: wangcm@sdu.edu.cn; Fu, Qing-Wei; Yin, De-Fu; Tian, Hu-He

2016-07-25

Bismuth layer-structured ferroelectric (BLSF) strontium bismuth titanate (SrBi{sub 4}Ti{sub 4}O{sub 15}, SBT) ceramic oxides with B-site cobalt substitutions have been synthesized using conventional solid–state reaction. The dielectric, piezoelectric, and ferroelectric properties of cobalt-modified SBT are investigated in detail. The results indicate that cobalt is very effective in promoting the piezoelectric performance of SBT. The SBT modified with 3 mol% Co{sup 3+} (SBT-3Co) exhibits the optimized piezoelectric properties, with a piezoelectric constant d{sub 33} of 28 pC/N, which is the highest value among the modified SBT-based piezoelectric ceramics ever reported. The temperature-dependent electrical impedance, resonance frequencies, and electromechanical coupling factors (k{sub p} and k{sub t}) reveal that the cobalt-modified SBT ceramics have good thermal stabilities of electromechanical properties up to 300 °C. These results demonstrate that the cobalt-modified SBT ceramics are promising materials for high temperature piezoelectric sensors applications. - Graphical abstract: The manuscript deals with the thermal stabilities of piezoelectric properties of cobalt-modified SrBi{sub 4}Ti{sub 4}O{sub 15} (SBT) ceramics. The 3 mol% Co{sup 3+} modified SBT (SBT-3Co) ceramics exhibit a piezoelectric constant d{sub 33} of 28 pC/N and a Curie temperature T{sub c} of 528 °C. The SBT-3Co ceramics have good thermal stabilities of electromechanical properties up to 300 °C. - Highlights: • A high level of piezoelectric performance (d{sub 33}∼28 pC/N)is obtained. • High Curie temperature (T{sub c}∼528 °C) is acquired for the optimal composition. • The SBT-3Co exhibits good thermal stabilities of electromechanical properties. • The Co-modified SrBi{sub 4}Ti{sub 4}O{sub 15} is promising as high temperature piezoelectric material.

Growth of single crystalline seeds into polycrystalline strontium titanate: Anisotropy of the mobility, intrinsic drag effects and kinetic shape of grain boundaries

International Nuclear Information System (INIS)

Rheinheimer, Wolfgang; Bäurer, Michael; Handwerker, Carol A.; Blendell, John E.; Hoffmann, Michael J.

2015-01-01

We present a suite of measurements and combined analyses of grain growth in SrTiO 3 for oriented single crystals into polycrystals. The growth distance and standard deviation and the microstructure evolution along the single crystal–matrix interface are used to locally characterize the change in migration behavior as a function of temperature, time and interface orientation. The relative grain boundary mobility was determined between 1250 °C and 1600 °C for four crystallographic orientations {1 0 0}, {1 1 0}, {1 1 1} and {3 1 0}. An absolute mobility of these orientations is estimated. Under fast growth conditions the morphology of single crystals shows macroscopic stepping with parts of the interface rotating to low mobility orientations. This effect represents a kinetic influence on the grain boundary morphology. The results also indicate dragging effects on microstructure coarsening, which indicate the existence of a critical driving force for grain growth. This critical driving force seems to be related to an ‘intrinsic’ interface drag similar to the solute drag, but based on intrinsic defects. At 1460 °C the growth of single crystals was significantly faster than expected from the mobility of the polycrystal and was identified as exaggerated grain growth. The findings give new insights into the recently published grain growth anomaly of strontium titanate, leading to a hypothesis based on the temperature dependent relative mobility of {1 0 0} oriented grain boundaries

Sol-hydrothermal synthesis and optical properties of Eu3+, Tb(3+)-codoped one-dimensional strontium germanate full color nano-phosphors.

Science.gov (United States)

Lin, Liangwu; Sun, Xinyuan; Jiang, Yao; He, Yuehui

2013-12-21

Novel near-UV and blue excited Eu(3+), Tb(3+)-codoped one dimensional strontium germanate full-color nano-phosphors have been successfully synthesized by a simple sol-hydrothermal method. The morphologies, internal structures, chemical constitution and optical properties of the resulting samples were characterized using FE-SEM, TEM, HRTEM, EDS, XRD, FTIR, XPS, PL and PLE spectroscopy and luminescence decay curves. The results suggested that the obtained Eu(3+), Tb(3+)-codoped strontium germanate nanowires are single crystal nanowires with a diameter ranging from 10 to 80 nm, average diameter of around 30 nm and the length ranging from tens to hundreds micrometers. The results of PL and PLE spectra indicated that the Eu(3+), Tb(3+)-codoped single crystal strontium germanate nanowires showed an intensive blue, blue-green, green, orange and red or green, orange and red light emission under excitation at 350-380 nm and 485 nm, respectively, which may attributed to the coexistent Eu(3+), Eu(2+) and Tb(3+) ions, and the defects located in the strontium germanate nanowires. A possible mechanism of energy transfer among the host, Eu(3+) and Tb(3+) ions was proposed. White-emission can be realized in a single-phase strontium germanate nanowire host by codoping with Tb(3+) and Eu(3+) ions. The Eu(3+), Tb(3+)-codoped one-dimensional strontium germanate full-color nano-phosphors have superior stability under electron bombardment. Because of their strong PL intensity, good CIE chromaticity and stability, the novel 1D strontium germanate full-color nano-phosphors have potential applications in W-LEDs.

Experimental studies on 3D printing of barium titanate ceramics for medical applications

Directory of Open Access Journals (Sweden)

Schult Mark

2016-09-01

Full Text Available The present work deals with the 3D printing of porous barium titanate ceramics. Barium titanate is a biocompatible material with piezoelectric properties. Due to insufficient flowability of the starting material for 3D printing, the barium titanate raw material has been modified in three different ways. Firstly, barium titanate powder has been calcined. Secondly, flow additives have been added to the powder. And thirdly, flow additives have been added to the calcined powder. Finally, a polymer has been added to the three materials and specimens have been printed from these three material mixtures. The 3D printed parts were then sintered at 1320°C. The sintering leads to shrinkage which differs between 29.51–71.53% for the tested material mixtures. The porosity of the parts is beneficial for cell growth which is relevant for future medical applications. The results reported in this study demonstrate the possibility to fabricate porous piezoelectric barium titanate parts with a 3D printer that can be used for medical applications. 3D printed porous barium titanate ceramics can especially be used as scaffold for bone tissue engineering, where the bone formation can be promoted by electrical stimulation.

Piezoelectric properties of electrospun nanofibers of BaTiO3

International Nuclear Information System (INIS)

Carvalho, L.F.R.M.; Melo, G.F.; Goncalves, A.M.; Eiras, J.A.; Bretas, R.E.S.

2016-01-01

BaTiO3 nanofibers were produced by the electrospinning method from a mixture of a solution of the precursors Ba (CH_3COO)_2 and [(CH_3)_2CHO]_4Ti in acetic acid and a solution of poly(vinylpyrrolidone) in ethanol. A voltage of 10 kV and a working distance of 4.6 cm were used for the electrospinning, at controlled room temperature and humidity of 21 °C and 60% respectively. Nanofibers as spun were dried in air on an air-circulating oven at 100 °C for one hour to remove residual solvent and were subsequently calcined at 750 °C during 2 h. The morphology, crystallographic structure and piezoelectric properties of the nanofibers were analyzed by scanning electron microscopy (SEM), X-ray angle (WAXS) and Piezoresponse Force Microscopy (PFM), respectively. The average diameter of the nanofibers was 414 nm with an aspect ratio of 40. By PFM, there was strong evidence that the nanofibers had piezoelectric activity. (author)

Titan

Science.gov (United States)

Müller-Wodarg, Ingo; Griffith, Caitlin A.; Lellouch, Emmanuel; Cravens, Thomas E.

2014-03-01

Introduction I. C. F. Müller-Wodarg, C. A. Griffith, E. Lellouch and T. E. Cravens; Prologue 1: the genesis of Cassini-Huygens W.-H. Ip, T. Owen and D. Gautier; Prologue 2: building a space flight instrument: a P.I.'s perspective M. Tomasko; 1. The origin and evolution of Titan G. Tobie, J. I. Lunine, J. Monteux, O. Mousis and F. Nimmo; 2. Titan's surface geology O. Aharonson, A. G. Hayes, P. O. Hayne, R. M. Lopes, A. Lucas and J. T. Perron; 3. Thermal structure of Titan's troposphere and middle atmosphere F. M. Flasar, R. K. Achterberg and P. J. Schinder; 4. The general circulation of Titan's lower and middle atmosphere S. Lebonnois, F. M. Flasar, T. Tokano and C. E. Newman; 5. The composition of Titan's atmosphere B. Bézard, R. V. Yelle and C. A. Nixon; 6. Storms, clouds, and weather C. A. Griffith, S. Rafkin, P. Rannou and C. P. McKay; 7. Chemistry of Titan's atmosphere V. Vuitton, O. Dutuit, M. A. Smith and N. Balucani; 8. Titan's haze R. West, P. Lavvas, C. Anderson and H. Imanaka; 9. Titan's upper atmosphere: thermal structure, dynamics, and energetics R. V. Yelle and I. C. F. Müller-Wodarg; 10. Titan's upper atmosphere/exosphere, escape processes, and rates D. F. Strobel and J. Cui; 11. Titan's ionosphere M. Galand, A. J. Coates, T. E. Cravens and J.-E. Wahlund; 12. Titan's magnetospheric and plasma environment J.-E. Wahlund, R. Modolo, C. Bertucci and A. J. Coates.

Enhanced actuation performance of piezoelectric fiber composites induced by incorporated BaTiO3 nanoparticles in epoxy resin

International Nuclear Information System (INIS)

Wu, Mingliang; Yuan, Xi; Luo, Hang; Chen, Haiyan; Chen, Chao; Zhou, Kechao; Zhang, Dou

2017-01-01

Piezoelectric fiber composites (PFCs) have attracted much interest owing to their flexibility and toughness compared with conventional monolithic piezoceramic wafers. The free strain values and actuation property of PFCs strongly depend on the active electric field applied in Pb(Zr 1−x Ti x )O 3 (PZT) fibers. Reducing the dielectric constant mismatch between PZT fiber and the assembling epoxy resin would greatly increase the active electric field in PZT fiber. Therefore, BaTiO 3 (BT) nanoparticles were introduced into the epoxy resin to enhance the dielectric constant. Homogeneous dispersion of BT nanoparticles and tight adhesion with the epoxy resin were achieved through a surface modification by dopamine. The maximum dielectric constant of dopamine modified BT/epoxy (BT@Dop/epoxy) nanocomposites was 10.38 with 12 wt% BT@Dop content at 1 kHz. The maximum free strain of PFCs reached 1820 ppm with 6 wt% BT@Dop content, while PFCs assembled by pure epoxy showed 790 ppm at the same processing condition. The tip displacement of cantilever beam actuated by PFCs reached the peak of 19 mm at the resonance frequency with 6 wt% BT@Dop, which was improved by 90% comparing to PFCs with pure epoxy. - Highlights: • The effect of dielectric mismatch on effective electric field in piezoceramic fibers was explained by a model. • The dispersibility and adhesion of BaTiO 3 nanoparticles in epoxy was improved by the dopamine modification. • The actuation performance increased firstly and then decreased with adding BaTiO 3 nanoparticles. • The maximum free strain and displacement of cantilever beam were up to 1820 ppm and 19 mm, respectively.

Influence of domain on grain size effects of the dielectric properties of BaTiO3 nanoceramics and nanoparticles

International Nuclear Information System (INIS)

Fang Chao; Chen Liangyan; Zhou Dongxiang

2013-01-01

The dielectric property of BaTiO 3 nanoparticles and nanoceramics has been studied on the basis of Ginsburg-Landau-Devonshire thermodynamic theory. In this paper, considering nanodomains, Landau coefficients have been written as a function of grain size, and the dielectric constant of the material has been calculated at a variety of temperatures and grain size. The results indicate that with decreasing grain size, the dielectric peak decreases. The two lower dielectric peaks of the orthorhombic-rhombohedral phase and tetragonal-orthorhombic phase move to higher temperature, while cubic-tetragonal phase dielectric peak moves to lower temperature. The dielectric constant of BaTiO 3 ceramics decreases with decreasing grain size. The dielectric constant peak at room temperature is at the grain size which is larger than the critical grain size 17-30 nm. The calculated result is consistent with the experimental data.

Anelastic anomalies and negative Poisson's ratio in tetragonal BaTiO3 ceramics

International Nuclear Information System (INIS)

Dong Liang; Stone, Donald S.; Lakes, Roderic S.

2010-01-01

Anelastic anomalies (sharp variations in modulus and damping with temperature) were observed in tetragonal BaTiO 3 via broadband viscoelastic spectroscopy after aging at 50 deg. C for 15 h. The effect was most pronounced under electrical short circuit condition, at low frequency and under small excitation strain (10 -6 ). Softening in bulk modulus and negative Poisson's ratio were observed near 60 deg. C. Effects are attributed to an oxygen vacancy mechanism. A relaxational model cannot account for sharp response at smaller strains. Heterogeneity of negative stiffness is considered as a cause.

Effects of fillers on the properties of liquid silicone rubbers (LSRs)

DEFF Research Database (Denmark)

Yu, Liyun; Vudayagiri, Sindhu; Zakaria, Shamsul Bin

low viscosities, which is favorable for loading of inorganic fillers [5]. In this study, commercially available fillers, such as fumed silica (SiO2), titanium dioxide (TiO2), barium titanate (BaTiO3), copper calcium titanate (CaCu3Ti4O12, CCTO), multi-walled carbon nanotubes (MWCNTs) were added...

Dynamics of ferroelectric nanodomains in BaTiO3 epitaxial thin films via piezoresponse force microscopy

International Nuclear Information System (INIS)

Pertsev, N A; Petraru, A; Kohlstedt, H; Waser, R; Bdikin, I K; Kiselev, D; Kholkin, A L

2008-01-01

Ferroelectric nanodomains were created in BaTiO 3 thin films by applying a voltage to a sharp conducting tip of a scanning force microscope (SFM). The films were epitaxially grown on SrRuO 3 -covered (001)-oriented SrTiO 3 substrates by a high-pressure sputtering. They appeared to be single-crystalline with the (001) crystallographic orientation relative to the substrate. Using the piezoresponse mode of the SFM to detect the out-of-plane film polarization, the domain sizes were measured as a function of the applied writing voltage and the pulse time. It was found that the time dependence of the domain diameter in a 60 nm thick BaTiO 3 film deviates significantly from the logarithmic law observed earlier in Pb(Zr 0.2 Ti 0.8 )O 3 (PZT) films. At a given writing time, the domain size increases nonlinearly with increasing applied voltage, in contrast to the linear behavior reported earlier for PZT films and LiNbO 3 single crystals. The dynamics of domain growth is analyzed theoretically taking into account the strong inhomogeneity of the external electric field in the film and the influence of the bottom electrode. It is shown that the observed writing time and voltage dependences of the domain size can be explained by the domain-wall creep in the presence of random-bond disorder

Interactive effects of vitamin D3 and strontium on performance, nutrient retention and bone mineral composition in laying hens.

Science.gov (United States)

Browning, Linda C; Cowieson, Aaron J

2015-03-30

Strontium is currently prescribed for patients with osteoporosis to increase bone density and reduce bone fractures but its relevance in animal nutrition is obscure. In order to investigate the effect of supplemental strontium and vitamin D3 on performance, egg quality and skeletal integrity in poultry a total of 108 laying hens, 99 weeks of age, were fed three levels of strontium (0, 500, 1000 mg kg(-1) ) and two levels of vitamin D3 (2500, 5,000 iu kg(-1)) over a 12-week period. There was an improvement (P < 0.05) in egg production and feed conversion efficiency with strontium at 500 mg kg(-1) and a significant increase in egg weight in those hens fed additional vitamin D3 . Supplemental strontium increased phosphorus, sodium and strontium retention in birds fed 2500 iu D3 kg(-1) but reduced phosphorus, sodium and strontium retention in birds fed 5000 iu D3 kg(-1), resulting in an interaction (P < 0.01) between strontium and vitamin D3 . Addition of 5000 iu D3 kg(-1) increased egg weight (P < 0.05); predominantly by increased albumen content (P < 0.05), whereas strontium supplementation reduced egg weight (P < 0.001). Similarly, 5000 iu kg(-1) D3 increased apparent metabolizable energy (P < 0.05); in contrast, strontium supplementation reduced (P < 0.05) apparent metabolizable energy. The addition of 500 mg kg(-1) strontium significantly improved egg production and feed efficiency; however, further investigation needs to be undertaken to refine the optimum level of strontium required to maximize hen performance. The interrelationship between strontium and vitamin D3 requires further exploratory study. © 2014 Society of Chemical Industry.

Interface Orientation Distribution during Grain Growth in Bulk SrTiO₃ Measured by Means of 3D X-Ray Diffraction Contrast Tomography

DEFF Research Database (Denmark)

Syha, Melanie; Rheinheimer, Wolfgang; Bäurer, Michael

2012-01-01

3D x-ray diffraction contrast tomography (DCT) is a non-destructive technique for the determination of grain shape and crystallography in polycrystalline bulk materials. Using this technique, a strontium titanate specimen was repeatedly measured between annealing steps.. A systematic analysis...

On stoichiometry and intermixing at the spinel/perovskite interface in CoFe2O4/BaTiO3 thin films.

Science.gov (United States)

Tileli, Vasiliki; Duchamp, Martial; Axelsson, Anna-Karin; Valant, Matjaz; Dunin-Borkowski, Rafal E; Alford, Neil McN

2015-01-07

The performance of complex oxide heterostructures depends primarily on the interfacial coupling of the two component structures. This interface character inherently varies with the synthesis method and conditions used since even small composition variations can alter the electronic, ferroelectric, or magnetic functional properties of the system. The focus of this article is placed on the interface character of a pulsed laser deposited CoFe2O4/BaTiO3 thin film. Using a range of state-of-the-art transmission electron microscopy methodologies, the roles of substrate morphology, interface stoichiometry, and cation intermixing are determined on the atomic level. The results reveal a surprisingly uneven BaTiO3 substrate surface formed after the film deposition and Fe atom incorporation in the top few monolayers inside the unit cell of the BaTiO3 crystal. Towards the CoFe2O4 side, a disordered region extending several nanometers from the interface was revealed and both Ba and Ti from the substrate were found to diffuse into the spinel layer. The analysis also shows that within this somehow incompatible composite interface, a different phase is formed corresponding to the compound Ba2Fe3Ti5O15, which belongs to the ilmenite crystal structure of FeTiO3 type. The results suggest a chemical activity between these two oxides, which could lead to the synthesis of complex engineered interfaces.

Plasma environment of Titan: a 3-D hybrid simulation study

Directory of Open Access Journals (Sweden)

S. Simon

2006-05-01

Full Text Available Titan possesses a dense atmosphere, consisting mainly of molecular nitrogen. Titan's orbit is located within the Saturnian magnetosphere most of the time, where the corotating plasma flow is super-Alfvénic, yet subsonic and submagnetosonic. Since Titan does not possess a significant intrinsic magnetic field, the incident plasma interacts directly with the atmosphere and ionosphere. Due to the characteristic length scales of the interaction region being comparable to the ion gyroradii in the vicinity of Titan, magnetohydrodynamic models can only offer a rough description of Titan's interaction with the corotating magnetospheric plasma flow. For this reason, Titan's plasma environment has been studied by using a 3-D hybrid simulation code, treating the electrons as a massless, charge-neutralizing fluid, whereas a completely kinetic approach is used to cover ion dynamics. The calculations are performed on a curvilinear simulation grid which is adapted to the spherical geometry of the obstacle. In the model, Titan's dayside ionosphere is mainly generated by solar UV radiation; hence, the local ion production rate depends on the solar zenith angle. Because the Titan interaction features the possibility of having the densest ionosphere located on a face not aligned with the ram flow of the magnetospheric plasma, a variety of different scenarios can be studied. The simulations show the formation of a strong magnetic draping pattern and an extended pick-up region, being highly asymmetric with respect to the direction of the convective electric field. In general, the mechanism giving rise to these structures exhibits similarities to the interaction of the ionospheres of Mars and Venus with the supersonic solar wind. The simulation results are in agreement with data from recent Cassini flybys.

Plasma environment of Titan: a 3-D hybrid simulation study

Directory of Open Access Journals (Sweden)

S. Simon

2006-05-01

Full Text Available Titan possesses a dense atmosphere, consisting mainly of molecular nitrogen. Titan's orbit is located within the Saturnian magnetosphere most of the time, where the corotating plasma flow is super-Alfvénic, yet subsonic and submagnetosonic. Since Titan does not possess a significant intrinsic magnetic field, the incident plasma interacts directly with the atmosphere and ionosphere. Due to the characteristic length scales of the interaction region being comparable to the ion gyroradii in the vicinity of Titan, magnetohydrodynamic models can only offer a rough description of Titan's interaction with the corotating magnetospheric plasma flow. For this reason, Titan's plasma environment has been studied by using a 3-D hybrid simulation code, treating the electrons as a massless, charge-neutralizing fluid, whereas a completely kinetic approach is used to cover ion dynamics. The calculations are performed on a curvilinear simulation grid which is adapted to the spherical geometry of the obstacle. In the model, Titan's dayside ionosphere is mainly generated by solar UV radiation; hence, the local ion production rate depends on the solar zenith angle. Because the Titan interaction features the possibility of having the densest ionosphere located on a face not aligned with the ram flow of the magnetospheric plasma, a variety of different scenarios can be studied. The simulations show the formation of a strong magnetic draping pattern and an extended pick-up region, being highly asymmetric with respect to the direction of the convective electric field. In general, the mechanism giving rise to these structures exhibits similarities to the interaction of the ionospheres of Mars and Venus with the supersonic solar wind. The simulation results are in agreement with data from recent Cassini flybys.

Evolución Microestructural de Materiales Cerámicos de BaTiO3 Dopados con Antimonio

Directory of Open Access Journals (Sweden)

Villegas, M.

1999-10-01

Full Text Available Ceramic materials based on BaTiO3 modified with small amounts of antimony show interesting electric properties which make them valuable for electronic industry. These properties depend on the microestructure of the material, which is controlled by both the dopant concentration and the doping process. The aim of the present work is to study the microstructure development of Sb-doped BaTiO3 materials for concentrations ranging from 0.05 to 0.6 mol%. Doping was carried out following two different methods, the traditional mixing of oxides and surface doping starting from Sb(O(CH3CH33. Materials sintered between 1300-1400ºC show quite different microstructure. For surface doped materials, a Sb2O3 concentration of 0.05 mol % leads to well densified matrials with homogeneous fine-grained microstructure. On the other hand, the traditional oxide doped materials show exaggerated grain growth.Los materiales cerámicos basados en titanato de bario con pequeñas cantidades de antimonio, exhiben interesantes propiedades que hacen posible su aplicación en la fabricación de dispositivos electrónicos. Estas propiedades dependen de la microestructura final del material, que está a su vez condicionada por la concentración de dopante y la vía utilizada para su incorporación. En este trabajo se estudia la evolución microestructural de materiales de BaTiO3 dopados con Sb en concentraciones entre 0.05 y 0.60 % mol. El dopado se ha realizado por la vía clásica a partir de Sb2O3 y mediante el proceso de dopado en superficie a partir de Sb(O(CH3CH33. Los materiales sinterizados en el intervalo de temperaturas comprendido entre 1300 y 1400ºC, muestran una microestructura bien diferenciada. Para los materiales dopados en superficie, una concentración equivalente de 0.05 % mol de Sb2O3 permite obtener materiales con elevada densidad y microestructura homogénea con tamaño de grano controlado. En el caso del material dopado por la vía clásica se observa

Dielectric response, functionality and energy storage in epoxy nanocomposites: Barium titanate vs exfoliated graphite nanoplatelets

International Nuclear Information System (INIS)

Patsidis, A.C.; Kalaitzidou, K.; Psarras, G.C.

2012-01-01

Barium titanate/epoxy and exfoliated graphite nanoplatelets/epoxy nanocomposites were prepared and studied varying the filler content. Morphological characteristics were examined via scanning electron microscopy, while structural changes occurring in barium titanate as a function of temperature were investigated by means of X-ray diffraction. Broadband dielectric spectroscopy was employed for determining the dielectric response of the prepared systems. Based on the conducted analysis it was found that three relaxation processes are present in the spectra of the examined materials. From the slower to the faster one, these are interfacial polarization, glass to rubber transition of the polymer matrix, and rearrangement of polar side groups of the polymer chain. Systems' functionality and energy storing efficiency were assessed in terms of dielectric reinforcing function. Finally, the energy density of all systems was evaluated. Composite systems with embedded graphite nanoplatelets exhibit higher energy storing efficiency, while thermally induced structural changes in ferroelectric particles provide functional behavior to barium titanate composites. -- Graphical abstract: Systems' functionality, electrical relaxations and energy storing efficiency were assessed in terms of dielectric permittivity, electric modulus and dielectric reinforcing function (G). Further, the energy density (U) of all systems was evaluated. Composite systems with embedded graphite nanoplatelets exhibit higher energy storing efficiency, while thermally induced structural changes in ferroelectric particles provide functional behavior to barium titanate composites. Highlights: ► Relaxation phenomena were found to be present in all studied systems. ► Two processes emanate from the polymer matrix (α-mode and β-mode). ► Systems' electrical heterogeneity gives rise to interfacial polarization. ► BaTiO 3 /epoxy composites exhibit functional behavior due to structural changes. ► x

Piezoelectric paper fabricated via nanostructured barium titanate functionalization of wood cellulose fibers.

Science.gov (United States)

Mahadeva, Suresha K; Walus, Konrad; Stoeber, Boris

2014-05-28

We have successfully developed hybrid piezoelectric paper through fiber functionalization that involves anchoring nanostructured BaTiO3 into a stable matrix with wood cellulose fibers prior to the process of making paper sheets. This is realized by alternating immersion of wood fibers in a solution of poly(diallyldimethylammonium chloride) PDDA (+), followed by poly(sodium 4-styrenesulfonate) PSS (-), and once again in PDDA (+), resulting in the creation of a positively charged surface on the wood fibers. The treated wood fibers are then immersed in a BaTiO3 suspension, resulting in the attachment of BaTiO3 nanoparticles to the wood fibers due to a strong electrostatic interaction. Zeta potential measurements, X-ray diffraction, and microscopic and spectroscopic analysis imply successful functionalization of wood fibers with BaTiO3 nanoparticles without altering the hydrogen bonding and crystal structure of the wood fibers. The paper has the largest piezoelectric coefficient, d33 = 4.8 ± 0.4 pC N(-1), at the highest nanoparticle loading of 48 wt % BaTiO3. This newly developed piezoelectric hybrid paper is promising as a low-cost substrate to build sensing devices.

Structural evolution of Ba8Ti3Nb4O24 from BaTiO3 using a series of Ba(Ti1−5xNb4x)O3 solid solutions

International Nuclear Information System (INIS)

Barrientos Hernández, F.R.; Lira Hernández, I.A.; Gómez Yáñez, C.; Arenas Flores, A.; Cabrera Sierra, R.; Pérez Labra, M.

2014-01-01

Highlights: • The evolution phase Ba 8 Ti 3 Nb 4 O 24 was obtained through the mechanism Ba(Ti 1-5x Nb 4x )O 3 . • Addition of niobium can accelerate grain growth of BaTiO 3 ceramics. • Ba 8 Ti 3 Nb 4 O 24 presents a dielectric loss of 0.0035 and permittivity value of 54.6. • Electrical measurements showed that Nb 5+ content drops Curie temperature. • Samples with x ⩾ 0.0625 shows an insulating behavior. -- Abstract: In this work, the structural evolution of hexagonal phase Ba 8 Ti 3 Nb 4 O 24 by adding Nb 2 O 5 to perovskite structure of BaTiO 3 was investigated. The compositions Ba(Ti 1-5x Nb 4x )O 3 ceramics, with 0.00025 ⩽ x ⩽ 0.125 were prepared by the conventional solid state route in air atmosphere, the powders precursors, BaTiO 3 , BaCO 3 and Nb 2 O 5 , were mixed in stoichiometric proportions and ground in a ball mill using alumina balls and acetone. The mixed powders were calcined at temperatures up to 1500 °C. The phase transformation of Ba 8 Ti 3 Nb 4 O 24 from BaTiO 3 was studied by DRX, Raman spectroscopy, SEM, electrical measurements (relative permittivity and P–E hysteresis loops); Rietveld’s refinement was used to structurally characterize the samples. For the devices obtained capacitance was measured at 1 kHz; with these values we calculated the relative permittivity. The samples show typical P–E hysteresis loops at room temperature accompanied by saturation polarization (Ps) and remnant polarization (Pr). The DRX and Rietveld’s refinement results show x ⩽ 0.01 has a ferroelectric behavior. When the doped level is increased x ⩾ 0.02, a peak displacement is observed, this is due to the phase transformation of tetragonal to cubic into the unit cell. Finally, with x = 0.125 the crystal structure transforms to the characteristic hexagonal phase Ba 8 Ti 3 Nb 4 O 24 which resonates at microwave frequencies

Local geometric and electronic structures and origin of magnetism in Co-doped BaTiO3 multiferroics

Science.gov (United States)

Phan, The-Long; Thang, P. D.; Ho, T. A.; Manh, T. V.; Thanh, Tran Dang; Lam, V. D.; Dang, N. T.; Yu, S. C.

2015-05-01

We have prepared polycrystalline samples BaTi1-xCoxO3 (x = 0-0.1) by solid-state reaction. X-ray diffraction and Raman-scattering studies reveal the phase separation in crystal structure as changing Co-doping content (x). The samples with x = 0-0.01 are single phase in a tetragonal structure. At higher doping contents (x > 0.01), there is the formation and development of a secondary hexagonal phase. Magnetization measurements at room temperature indicate a coexistence of paramagnetic and weak-ferromagnetic behaviors in BaTi1-xCoxO3 samples with x > 0, while pure BaTiO3 is diamagnetic. Both these properties increase with increasing x. Analyses of X-ray absorption spectra recorded from BaTi1-xCoxO3 for the Co and Ti K-edges indicate the presence of Co2+ and Co3+ ions. They locate in the Ti4+ site of the tetragonal and hexagonal BaTiO3 structures. Particularly, there is a shift of oxidation state from Co2+ to Co3+ when Co-doping content increases. We believe that the paramagnetic nature in BaTi1-xCoxO3 samples is due to isolated Co2+ and Co3+ centers. The addition of Co3+ ions enhances the paramagnetic behavior. Meanwhile, the origin of ferromagnetism is due to lattice defects, which is less influenced by the changes caused by the variation in concentration of Co2+ and Co3+ ions.

Elaboration of strontium ruthenium oxide thin films on metal substrates by chemical solution deposition

International Nuclear Information System (INIS)

Seveno, R.; Braud, A.; Gundel, H.W.

2005-01-01

In order to improve the structural interface between a metal substrate and a lead zirconate titanate (Pb(ZrTi)O 3 , PZT) ferroelectric thin film, the elaboration of strontium ruthenium oxide (SrRuO 3 ) by chemical solution deposition is studied. The SrRuO 3 thin films were realized by multiple spin-coating technique and the temperature of the rapid thermal annealing process was optimized. The crystallization behavior was examined by X-ray diffraction; surface analyses using scanning electron microscope and atomic force microscope techniques showed the influence of the SrRuO 3 layer at the interface PZT/metal on the morphology of the ferroelectric thin film. From the electrical measurements, a coercive electric field around 25 kV/cm and a remanent polarization of approximately 30 μC/cm were found

Direct detection of cysteine using functionalized BaTiO3 nanoparticles film based self-powered biosensor.

Science.gov (United States)

Selvarajan, Sophia; Alluri, Nagamalleswara Rao; Chandrasekhar, Arunkumar; Kim, Sang-Jae

2017-05-15

Simple, novel, and direct detection of clinically important biomolecules have continuous demand among scientific community as well as in market. Here, we report the first direct detection and facile fabrication of a cysteine-responsive, film-based, self-powered device. NH 2 functionalized BaTiO 3 nanoparticles (BT-NH 2 NPs) suspended in a three-dimensional matrix of an agarose (Ag) film, were used for cysteine detection. BaTiO 3 nanoparticles (BT NPs) semiconducting as well as piezoelectric properties were harnessed in this study. The changes in surface charge properties of the film with respect to cysteine concentrations were determined using a current-voltage (I-V) technique. The current response increased with cysteine concentration (linear concentration range=10µM-1mM). Based on the properties of the composite (BT/Ag), we created a self-powered cysteine sensor in which the output voltage from a piezoelectric nanogenerator was used to drive the sensor. The potential drop across the sensor was measured as a function of cysteine concentrations. Real-time analysis of sensor performance was carried out on urine samples by non-invasive method. This novel sensor demonstrated good selectivity, linear concentration range and detection limit of 10µM; acceptable for routine analysis. Copyright © 2016 Elsevier B.V. All rights reserved.

Sonochemically assisted hollow/solid BaTiO3:Dy3+ microspheres and their applications in effective detection of latent fingerprints and lip prints

Directory of Open Access Journals (Sweden)

M. Dhanalakshmi

2017-03-01

Full Text Available Nanostructured materials find potential benefits for surface-based science such as latent fingerprints (LFPs and lip print detection on porous and non-porous surfaces. To encounter the drawbacks viz. low sensitivity, high background hindrance, complicated procedure and high toxicity associated with traditional fluorescent powders were resolved by using hollow/solid BaTiO3:Dy3+ (1–5 mol % microspheres. The visualization of LFPs stained by the optimized BaTiO3:Dy3+ (2 mol % hollow/solid microspheres exhibits well-defined ridge patterns with high sensitivity, low background hindrance, high efficiency and low toxicity on various surfaces. The powder X-ray diffraction results revealed the body centered cubic phase of the prepared samples. The emission spectra exhibit intensive peaks at ∼480, 575, and 637 nm, which were attributed to transitions 4F9/2→6HJ (J = 15/2, 13/2, 11/2 of Dy3+ ions, respectively. Surface morphologies were extensively studied with different sonication times and concentrations of the used barbituric acid. The Commission International De I-Eclairage (CIE and Correlated Color Temperature (CCT analyses revealed that the present phosphor is highly useful for the fabrication of white light emitting diodes.

STRUCTURAL CHARACTERISTICS & DIELECTRIC PROPERTIES OF TANTALUM OXIDE DOPED BARIUM TITANATE BASED MATERIALS

Directory of Open Access Journals (Sweden)

Md. Fakhrul Islam

2013-01-01

Full Text Available In this research, the causal relationship between the dielectric properties and the structural characteristics of 0.5 & 1.0 mole % Ta2O5 doped BaTiO3 based ceramic materials were investigated under different sintering conditions. Dielectric properties and microstructure of BaTio3 ceramics were significantly influenced by the addition of a small amount of Ta2O5. Dielectric properties were investigated by measuring the dielectric constant (k as a function of temperature and frequency. Percent theoretical density (%TD above 90 % was achieved for 0.5 and 1.0 mole %Ta2O5 doped BaTiO3. It was observed that the grain size decreased markedly above a doping concentration of 0.5 mole % Ta2O5. Although fine grain size down to 200 - 300 nm was attained, grain sizes in the range of 1-1.8µm showed the most alluring properties. The fine-grain quality and high density of the Ta2O5 doped BaTiO3 ceramic resulted in tenfold increase of dielectric constant. Stable value of dielectric constant as high as 13000 - 14000 was found in the temperature range of 55 to 80 °C, for 1.0 mole % Ta2O5 doped samples with corresponding shift of Curie point to ~82 °C. Experiments divulged that incorporation of a proper content of Ta2O5 in BaTiO3 could control the grain growth, shift the Curie temperature and hence significantly improve the dielectric property of the BaTiO3 ceramics.

Resistance switching of the interfacial conductance in amorphous SrTiO3 heterostructures

DEFF Research Database (Denmark)

Christensen, Dennis; Trier, Felix; Chen, Yunzhong

Complex oxides have attracted a lot of interest recently as this class of material exhibits a plethora of remarkable properties. In particular, a great variety of properties is observed in the heterostructure composed of lanthanum aluminate (LaAlO3) and strontium titanate (SrTiO3). For instance...

Multiferroic behavior on nanometric La2/3Ca1/3MnO3 / BaTiO3 bilayers

Science.gov (United States)

Prieto, Pedro; Ordoñez, John Edward; Gomez, Maria Elena; Lopera, Wilson

2014-03-01

We have deposited bilayers of the FM La2/3Ca1/3MnO3 and FE BaTiO3 as a route to design systems with artificial magnetoelectric coupling on LCMO/BTO/Nb:STO system. We maintain a fixed magnetic layer thickness (tLCMO = 48 nm) and varying the thickness of the ferroelectric layer (tBTO = 20, 50, 100 nm). We analyze the influence of the thickness ratio (tBTO/ tLCMO) in electrical and magnetic properties of manganite. From X-ray diffraction analysis we observed that the samples grew textured. Magnetization and transport measurements indicate a possible multiferroic behavior in the bilayer. We found an increase in the Curie and metal-insulator transition temperature in the bilayer in comparison with those for LCMO (48nm)/STO. Hysteresis loops on bilayers show ferromagnetic behavior. This work has been supported by the ``El Patrimonio Autónomo Fondo Nacional de Financiamiento para CT&I FJC'' Colciencias-CENM Research Projects: No. 1106-48-925531 and CI7917-CC 10510 contract 0002-2013 COLCIENCIAS-UNIVALLE.

DIELECTRIC AND PYROELECTRIC PROPERTIES OF THE COMPOSITES OF FERROELECTRIC CERAMIC AND POLY(VINYL CHLORIDE

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M.Olszowy

2003-01-01

Full Text Available The dielectric and pyroelectric properties of lead zirconate titanate/poly(vinyl chloride [PZT/PVC] and barium titanate/poly(vinyl chloride [BaTiO3/ PVC] composites were studied. Flexible composites were fabricated in the thin films form (200-400 μm by hot-pressed method. Powders of PZT or BaTiO3 in the shape of ≤ 75 μm ceramics particles were dispersed in a PVC matrix, providing composites with 0-3} connectivity. Distribution of the ceramic particles in the polymer phase was examined by scanning electron microscopy. The analysis of the thermally stimulated currents (TSC have also been done. The changes of dielectric and pyroelectric data on composites with different contents of ceramics up to 40% volume were investigated. The dielectric constants were measured in the frequency range from 600 Hz to 6 MHz at room temperature. The pyroelectric coefficient for BaTiO3/PVC composite at 343 K is about 35 μC/m2K which is higher than that of β-PVDF (10 μC/m2 K.

Decorating TiO2 Nanowires with BaTiO3 Nanoparticles: A New Approach Leading to Substantially Enhanced Energy Storage Capability of High-k Polymer Nanocomposites.

Science.gov (United States)

Kang, Da; Wang, Guanyao; Huang, Yanhui; Jiang, Pingkai; Huang, Xingyi

2018-01-31

The urgent demand of high energy density and high power density devices has triggered significant interest in high dielectric constant (high-k) flexible nanocomposites comprising dielectric polymer and high-k inorganic nanofiller. However, the large electrical mismatch between polymer and nanofiller usually leads to earlier electric failure of the nanocomposites, resulting in an undesirable decrease of electrical energy storage capability. A few studies show that the introduction of moderate-k shell onto a high-k nanofiller surface can decrease the dielectric constant mismatch, and thus, the corresponding nanocomposites can withstand high electric field. Unfortunately, the low apparent dielectric enhancement of the nanocomposites and high electrical conductivity mismatch between matrix and nanofiller still result in low energy density and low efficiency. In this study, it is demonstrated that encapsulating moderate-k nanofiller with high-k but low electrical conductivity shell is effective to significantly enhance the energy storage capability of dielectric polymer nanocomposites. Specifically, using BaTiO 3 nanoparticles encapsulated TiO 2 (BaTiO 3 @TiO 2 ) core-shell nanowires as filler, the corresponding poly(vinylidene fluoride-co-hexafluoropylene) nanocomposites exhibit superior energy storage capability in comparison with the nanocomposites filled by either BaTiO 3 or TiO 2 nanowires. The nanocomposite film with 5 wt % BaTiO 3 @TiO 2 nanowires possesses an ultrahigh discharged energy density of 9.95 J cm -3 at 500 MV m -1 , much higher than that of commercial biaxial-oriented polypropylene (BOPP) (3.56 J cm -3 at 600 MV m -1 ). This new strategy and corresponding results presented here provide new insights into the design of dielectric polymer nanocomposites with high electrical energy storage capability.

Application of titanates, niobates, and tantalates to neutralized defense waste decontamination: materials properties, physical forms, and regeneration techniques. Final report

International Nuclear Information System (INIS)

Dosch, R.G.

1981-01-01

A study of the application of sodium titanate (ST) to the decontamination of neutralized defense waste has been completed. The work was directed at Sr removal from dissolved salt cake, simulated in this work with a 6.0 N NaNO 3 - 0.6 N NaOH solution. Three physical forms of the titanates were developed including powder, pellets, and titanate-loaded resin beads and all were found to be superior to conventional organic ion exchange in this application. When spent, the titanate materials can be calcined to an oxide from which is a stable waste form in itself or can be added directly to a glass melter to become part of a vitrified waste form. Radiation stability of titanate powder and resin forms was assessed in tests in which these materials were exposed to 60 Co radiation. The strontium exchange capacity of the powder remained constant through a dose of 3 x 10 7 rads and retained 50% capacity after a dose of 2 x 10 9 rads. The primary mechanism involved in loss of capacity was believed to be heating associated with the irradiation. The resin forms were unchanged through a dose of 5 x 10 8 rads and retained 30% capacity after a dose of 2 x 10 9 rads. The latter dose resulted in visible degradation of the resin matrix. Anion exchange resins loaded with sodium niobate and sodium tantalate were also prepared by similar methods and evaluated for this application. These materials had Sr sorption properties comparable to the titanate material; however, they would have to provide a significant improvement to justify their higher cost

Determination of radioactive strontium in seawater

International Nuclear Information System (INIS)

Grahek, Zeljko; Rozmaric Macefat, Martina

2005-01-01

This paper describes the procedures of isolating strontium and yttrium from seawater that enable the determination of 89,90 Sr. In one procedure, strontium is directly isolated from seawater on the column filled with Sr resin by binding of strontium to the resin from 3 M HNO 3 in a seawater, and successive elution with HNO 3 . In others, strontium is precipitated from seawater with (NH 4 ) 2 CO 3 , followed by isolation on a Sr column or an anion exchange column. It is shown that strontium precipitation is optimal with concentration of 0.3 M (NH 4 ) 2 CO 3 at pH = 11. In these conditions, 100% Y, 78% Sr, 80% Ca and 50% Mg are precipitated. Strontium is bound on to Sr column from 5 to 8 M HNO 3 , separated from other elements by elution with 3 M HNO 3 and 0.05 M HNO 3 . Strontium and yttrium are bound on to anion exchange column from alcoholic solutions of nitric acid. The optimum mixture of alcohols for sample binding is a mixture of ethanol and methanol with the volume ratio 1:3. Strontium and yttrium are separated from Mg, Ca, K, and other elements by elution with 0.25 M HNO 3 in the mixture of ethanol and methanol. After the separation, yttrium and strontium are eluted from the column with water or methanol. In the procedure of direct isolation from 1 l of the sample, the average recovery of 50% was obtained. In the remaining two procedures, the strontium recovery was about 60% for the Sr column and 65% for anion exchange column. Recovery of yttrium is about 70% for the anion exchange column. It turned out that the procedure with the Sr resin (direct isolation and isolation after precipitation) is simpler and faster in the phase of the isolation on the column in comparison with the procedure with the anion exchanger. The procedure with the anion exchanger, however, enables the simultaneous isolation of yttrium and strontium and rapid determination of 89,90 Sr. These procedures were tested by determination of 89,90 Sr on liquid scintillation counter and Cherenkov

Electrical characterization and impedance response of lanthanum doped barium titanate ceramics

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Mančić D.

2008-01-01

Full Text Available The dielectric permittivity and dissipation factor of La-doped and undoped BaTiO3 were investigated as a function of frequency and temperature. The impedance response was used to study the electrical properties of La-doped BaTiO3 over the temperature range from room temperature (RT to 350°C. La-doped and undoped BaTiO3, obtained by a modified Pechini method, were sintered in air at 1300°C for 2 and 16 hours. The impedance spectra were analyzed in terms of equivalent circuits involving resistors, capacitors and constant phase elements (CPE. The most suitable electrical circuit for the interpretation of experimental results is found to be the equivalent circuit consisting of resistors and CPE elements which replace the capacitor elements. The contribution of grain boundary resistance to the total resistance of a system is remarkable at low temperature. Dielectric permittivity of doped BaTiO3 was in the range of 8000 to 12000 at 1 kHz and the dissipation factor was less than 1%.

High performance fuel electrode for a solid oxide electrochemical cell

DEFF Research Database (Denmark)

2013-01-01

perovskite oxides selected from the group consisting of niobium-doped strontium titanate, vanadium-doped strontium titanate, tantalum-doped strontium titanate and mixtures thereof, thereby obtaining a porous anode backbone, (b) sintering the coated electrolyte at a high temperature, such as 1200 DEG C...

Magnetic behavior of La2/3Ca1/3MnO3 / BaTiO3 bilayers

Science.gov (United States)

Ordonez, John E.; Gomez, Maria E.; Lopera, Wilson; Marin, Lorena; Pardo, Jose A.; Morellon, Luis; Algarabel, Pedro; Prieto, Pedro

2013-03-01

We have grown ferroelectric BaTiO3(BTO) and ferromagnetic La2/3Ca1/3MnO3 (LCMO) onto (001) SrTiO3 and Nb:SrTiO3 by pulsed laser deposition (PLD) at pure oxygen atmosphere, and a substrate temperature of 820° C, seeking for a multiferroic behavior in this structure. From x-ray diffraction (XRD) we found lattice parameter aBTO=4.068 Å, and aLCMO=3.804 Å, for each individual layer. In the BTO/LCMO bilayer, (002)-Bragg peak for BTO maintain its position whereas (002) LCMO peak shift to lower Bragg angle indicating a strained LCMO film. Magnetization measurements reveal an increase in the Curie temperature from 170 K to 220 K for the bilayer when LCMO (t = 47 nm) is deposited on BTO (t=52 nm) film, while depositing the BTO (50 nm) above LCMO (48 nm) the Curie temperature remains at values close to that obtained for a LCMO single layer (~175 K), deposited under identical growth parameters This work has been supported by Instituto de Nanociencias de Aragón, Zaragoza, Spain, ``El Patrimonio Autónomo Fondo Nacional de Financiamiento para CT&I FJC'' COLCIENCIAS-CENM Contract RC 275-2011 and Research Project COLCIENCIAS-UNIVALLE.

Patterned solid state growth of barium titanate crystals

Science.gov (United States)

Ugorek, Michael Stephen

An understanding of microstructure evolution in ceramic materials, including single crystal development and abnormal/enhanced grain growth should enable more controlled final ceramic element structures. In this study, two different approaches were used to control single crystal development in a patterned array. These two methods are: (1) patterned solid state growth in BaTiO 3 ceramics, and (2) metal-mediated single crystal growth in BaTiO 3. With the patterned solid state growth technique, optical photolithography was used to pattern dopants as well as [001] and [110] BaTiO3 single crystal template arrays with a 1000 microm line pattern array with 1000 microm spacings. These patterns were subsequently used to control the matrix grain growth evolution and single crystal development in BaTiO3. It was shown that the growth kinetics can be controlled by a small initial grain size, atmosphere conditions, and the introduction of a dopant at selective areas/interfaces. By using a PO2 of 1x10-5 atm during high temperature heat treatment, the matrix coarsening has been limited (to roughly 2 times the initial grain size), while retaining single crystal boundary motion up to 0.5 mm during growth for dwell times up to 9 h at 1300°C. The longitudinal and lateral growth rates were optimized at 10--15 microm/h at 1300°C in a PO2 of 1x10 -5 atm for single crystal growth with limited matrix coarsening. Using these conditions, a patterned microstructure in BaTiO3 was obtained. With the metal-mediated single crystal growth technique, a novel approach for fabricating 2-2 single crystal/polymer composites with a kerf texture development were studied using both [001] and [110] BaTiO3 single crystals templates. By using a PO 2 of 1x10-11 atm during high temperature heat treatment, matrix coarsening was limited while enabling single crystal boundary motion up to 0.35 mm during growth between 1250°C and 1300°C with growth rates ˜ 3--4 microm/h for both single crystal orientations. By

Structural Characteristics & Dielectric Properties of Tantalum Oxide Doped Barium Titanate Based Materials

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Rubayyat Mahbub

2012-11-01

Full Text Available In this research, the causal relationship between the dielectric properties and the structural characteristics of 0.5 & 1.0 mol% Ta2O5 doped BaTiO3 based ceramic materials were investigated under different sintering conditions. Dielectric properties and microstructure of BaTio3 ceramics were significantly influenced by the addition of a small amount of Ta2O5. Dielectric properties were investigated by measuring the dielectric constant (k as a function of temperature and frequency. Percent theoretical density (%TD above 90% was achieved for 0.5 and 1.0 mol% Ta2O5 doped BaTiO3. It was observed that the grain size decreased markedly above a doping concentration of 0·5 mol% Ta2O5. Although fine grain size down to 200-300nm was attained, grain sizes in the range of 1-1.8µm showed the most alluring properties. The fine-grain quality and high density of the Ta2O5 doped BaTiO3 ceramic resulted in tenfold increase of dielectric constant. Stable value of dielectric constant as high as 13000-14000 was found in the temperature range of  55 to 80°C, for 1.0 mol% Ta2O5 doped samples with corresponding shift of Curie point to ~82°C. Experiments divulged that incorporation of a proper content of Ta2O5 in BaTiO3 could control the grain growth, shift the Curie temperature and hence significantly improve the dielectric property of the BaTiO3 ceramics.

Elaboration of strontium ruthenium oxide thin films on metal substrates by chemical solution deposition

Energy Technology Data Exchange (ETDEWEB)

Seveno, R. [Universite de Nantes, Institut de Recherche en Electrotechnique et Electronique de Nantes Atlantique (IREENA), 2, rue de la Houssiniere, BP 92208, 44322 Nantes Cedex 3 (France)]. E-mail: raynald.seveno@univ-nantes.fr; Braud, A. [Universite de Nantes, Institut de Recherche en Electrotechnique et Electronique de Nantes Atlantique (IREENA), 2, rue de la Houssiniere, BP 92208, 44322 Nantes Cedex 3 (France); Gundel, H.W. [Universite de Nantes, Institut de Recherche en Electrotechnique et Electronique de Nantes Atlantique (IREENA), 2, rue de la Houssiniere, BP 92208, 44322 Nantes Cedex 3 (France)

2005-12-22

In order to improve the structural interface between a metal substrate and a lead zirconate titanate (Pb(ZrTi)O{sub 3}, PZT) ferroelectric thin film, the elaboration of strontium ruthenium oxide (SrRuO{sub 3}) by chemical solution deposition is studied. The SrRuO{sub 3} thin films were realized by multiple spin-coating technique and the temperature of the rapid thermal annealing process was optimized. The crystallization behavior was examined by X-ray diffraction; surface analyses using scanning electron microscope and atomic force microscope techniques showed the influence of the SrRuO{sub 3} layer at the interface PZT/metal on the morphology of the ferroelectric thin film. From the electrical measurements, a coercive electric field around 25 kV/cm and a remanent polarization of approximately 30 {mu}C/cm were found.

Dielectric behaviour of (Ba0.77Ca0.23(Ti0.98Dy0.02O3 ceramics

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Abdul Moquim

2015-06-01

Full Text Available In this study, BaTiO3 is modified with Ca2+ and in addition doped with Dy3+ at the B site lattice. The main idea is to search for new lead-free ferroelectric material and improve their properties. For this purpose, the barium calcium titanate (BCT as a host and the rare earth element Dy3+ as an activator were used to fabricate a multifunctional material. The obtained ceramics was found to be homogeneous, dense and a single phase material with no evidence of secondary phases. The dielectric study showed that TC increases with the addition of dopants and the obtained ceramics behaves like a relaxor ferroelectric. Some important structural parameters and dielectric properties of dysprosium modified barium (calcium titanate ceramics are presented.

Strain and electric field mediated manipulation of magnetism in La_(_1_-_x_)Sr_xMnO_3/BaTiO_3 heterostructures

International Nuclear Information System (INIS)

Schmitz, Markus

2016-01-01

Heterostructures of ferromagnetic La_1_-_xSr_xMnO_3 (LSMO) and ferroelectric BaTiO_3 (BTO) were produced and investigated for their structural and magnetic properties. The combination of these ferroic properties can lead to an artificial multiferroic. Special emphasis was given to the manipulation of magnetic properties by applying electric fields. A magneto-electric coupling could be observed in the heterostructures under investigation. Epitaxial LSMO thin films were grown on BTO substrates using a state-of-the-art oxide molecular beam epitaxy (OMBE) and a high oxygen sputtering system (HOPSS). Stoichiometric La_1_-_xSr_xMnO_3 films with doping levels of x=0.5 and x=0.3 were produced. The film quality in terms of roughness and crystalline structure was confirmed by X-ray scattering methods. The presence of structural domains in the BaTiO_3 single crystal substrate, whose proportion could be altered due to the application of electric fields, was shown by X-ray diffraction. Tensile strain is induced into the epitaxial La_1_-_xSr_xMnO_3 films in the whole temperature range under investigation. The magnetization of LSMO alteres by the variation of strain induced into the film, generated by the different structural phases of single crystal BaTiO_3 substrates. The magnetization shows sharp steps at the structural phase transition temperatures of BTO. The evaluation of magnetic hysteresis loops reveals a change of the magnetic anisotropy of LSMO for each structural phase of BTO, but also within the orthorhombic phase. Special focus was given to the manipulation of magnetic properties by the application of electric fields. A newly established measurement option was used to determine the magnetic response to an applied electric field as a function of temperature and magnetic field. The electrically induced modification of the magnetization is profound near the structural phase transition temperatures. Electrical hysteresis loops give a detailed view on the influence of the

Study of irradiation effects in perovskite: use of this matrix for actinides conditioning; Effets de l'irradiation dans une perovskite: utilisation de cette matrice pour un conditionnement des actinides

Energy Technology Data Exchange (ETDEWEB)

Sabathier, C

2003-07-01

The aim of this work is to study a specific conditioning matrix (ceramics) for actinides: the strontium titanate. At first, the choice of strontium titanate is discussed as well as its structure and its ability to incorporate actinides. The different studies carried out on the irradiation effects on the strontium titanate are reviewed. The main ion-matter interactions considered in the energy range used during our experiments are given. The different devices and techniques used with ion beams to carry out our experiments according to the type of sample: monocrystal or polycrystal are described. The experimental results on the behaviour of strontium titanate in terms of irradiation, temperature and ion flux used to damage the matrix are presented. The experimental results on the different steps of strontium titanate annealing are given as well as the identifying of the defects by different analyses techniques (Rutherford backscattering spectroscopy, transmission electron spectroscopy and x-rays spectroscopy). At last, a model of the behaviour of the strontium titanate in the case of an actinide conditioning is proposed and the evolving of the strontium titanate disorder during the storage is discussed. (O.M.)

The influence of high hydrostatic pressure on lattice parameters of a single crystal of BaTiO3

International Nuclear Information System (INIS)

Malinowski, M.; Lukaszewicz, K.; Asbrink, S.

1986-01-01

The lattice parameters of a single crystal of BaTiO 3 have been measured under high hydrostatic pressure up to 5 GPa using a diamond-anvil high-pressure cell of a new design. The lattice becomes cubic at 2.08(8) GPa and stays cubic at higher pressures. The pressure dependence of the tetragonal-cubic transition temperature is estimated to be -46 K GPa -1 . (orig.)

Effect of Flowing Water on Sr Sorption Changes of Hydrous Sodium Titanate

OpenAIRE

Youko Takahatake; Atsuhiro Shibata; Kazunori Nomura; Tsutomu Sato

2017-01-01

Radioactive contaminated water has been generated at the Fukushima Daiichi Nuclear Power station (F1NPS). Hydrous sodium titanate (SrTreat®) is able to remove radioactive Strontium (Sr) from this water. Knowing the amount of radioactive nuclides in the used as-received SrTreat® is important for effective disposal and deposition of the F1NPS waste. This study investigated changes in the ability of SrTreat® to sorb Sr, and to understand the causes of changes in the sorbing. An investigation of ...

Synthesis and Characterization of Silicon Titanate as Cation Exchanger and Their Use in the Treatment of Radioactive Liquid Waste

International Nuclear Information System (INIS)

El-Naggar, I.M.; Belacy, N.; Mohamed, D.A.; Abou-Mesalam, M.M.

1999-01-01

Anew class of inorganic ion exchanger called crystalline silicon titanates has excellent chemical and radiation stability. The materials exhibited high selectivity for the ion exchange of cesium, strontium and several other radionuclides from highly acidic solutions. The ion exchange capacity was determined for Na +, Cs +, Co 2+ and Sr 2+ ions and found to be 1.17 , 1.9, 1.38 and 1.52 meq./g, respectively. Besides, the drying temperature of silicon titanates have a profound effect on the ion exchange capacities and distribution coefficient values of the above mentioned cations. Moreover, the studied results of distribution coefficient indicating the ability of separation of these radionuclides from radwaste solutions

Quantitative evaluation of the piezoelectric response of unpoled ferroelectric ceramics from elastic and dielectric measurements: Tetragonal BaTiO3

Science.gov (United States)

Cordero, F.

2018-03-01

A method is proposed for evaluating the potential piezoelectric response, that a ferroelectric material would exhibit after full poling, from elastic and dielectric measurements of the unpoled ceramic material. The method is based on the observation that the softening in a ferroelectric phase with respect to the paraelectric phase is of piezoelectric origin, and is tested on BaTiO3. The angular averages of the piezoelectric softening in unpoled ceramics are calculated for ferroelectric phases of different symmetries. The expression of the orientational average with the piezoelectric and dielectric constants of single crystal tetragonal BaTiO3 from the literature reproduces well the softening of the Young's modulus of unpoled ceramic BaTiO3, after a correction for the porosity. The agreement is good in the temperature region sufficiently far from the Curie temperature and from the transition to the orthorhombic phase, where the effect of fluctuations should be negligible, but deviations are found outside this region, and possible reasons for this are discussed. This validates the determination of the piezoelectric response by means of purely elastic measurements on unpoled samples. The method is indirect and, for quantitative assessments, requires the knowledge of the dielectric tensor. On the other hand, it does not require poling of the sample, and therefore is insensitive to inaccuracies from incomplete poling, and can even be used with materials that cannot be poled, for example, due to excessive electrical conductivity. While the proposed example of the Young's modulus of a ceramic provides an orientational average of all the single crystal piezoelectric constants, a Resonant Ultrasound Spectroscopy measurement of a single unpoled ceramic sample through the ferroelectric transition can in principle measure all the piezoelectric constants, together with the elastic ones.

Calculation of strained BaTiO3 with different exchange correlation functionals examined with criterion by Ginzburg-Landau theory, uncovering expressions by crystallographic parameters

Science.gov (United States)

Watanabe, Yukio

2018-05-01

In the calculations of tetragonal BaTiO3, some exchange-correlation (XC) energy functionals such as local density approximation (LDA) have shown good agreement with experiments at room temperature (RT), e.g., spontaneous polarization (PS), and superiority compared with other XC functionals. This is due to the error compensation of the RT effect and, hence, will be ineffective in the heavily strained case such as domain boundaries. Here, ferroelectrics under large strain at RT are approximated as those at 0 K because the strain effect surpasses the RT effects. To find effective XC energy functionals for strained BaTiO3, we propose a new comparison, i.e., a criterion. This criterion is the properties at 0 K given by the Ginzburg-Landau (GL) theory because GL theory is a thermodynamic description of experiments working under the same symmetry-constraints as ab initio calculations. With this criterion, we examine LDA, generalized gradient approximations (GGA), meta-GGA, meta-GGA + local correlation potential (U), and hybrid functionals, which reveals the high accuracy of some XC functionals superior to XC functionals that have been regarded as accurate. This result is examined directly by the calculations of homogenously strained tetragonal BaTiO3, confirming the validity of the new criterion. In addition, the data points of theoretical PS vs. certain crystallographic parameters calculated with different XC functionals are found to lie on a single curve, despite their wide variations. Regarding these theoretical data points as corresponding to the experimental results, analytical expressions of the local PS using crystallographic parameters are uncovered. These expressions show the primary origin of BaTiO3 ferroelectricity as oxygen displacements. Elastic compliance and electrostrictive coefficients are estimated. For the comparison of strained results, we show that the effective critical temperature TC under strain 1000 K from an approximate method combining ab initio

Structure and properties of plasma sprayed BaTiO(3) coatings: Spray parameters versus structure and photocatalytic activity

Czech Academy of Sciences Publication Activity Database

Ctibor, Pavel; Ageorges, H.; Štengl, Václav; Murafa, Nataliya; Píš, I.; Zahoranová, T.; Nehasil, V.; Pala, Zdeněk

2011-01-01

Roč. 37, č. 7 (2011), s. 2561-2567 ISSN 0272-8842 R&D Projects: GA AV ČR IAAX00430803 Institutional research plan: CEZ:AV0Z20430508; CEZ:AV0Z40320502 Keywords : Spectroscopy * Optical properties * BaTiO3 * Plasma spraying * Photocatalysis Subject RIV: JH - Ceramics, Fire-Resistant Materials and Glass Impact factor: 1.751, year: 2011 http://www.sciencedirect.com/science/article/pii/S0272884211002173

Studies on sintered titanates and zeolites as hosts for medium-level radioactive waste

International Nuclear Information System (INIS)

Forberg, S.; Westermark, T.; Faelth, L.

1981-01-01

In Sweden, a system for transferring long-lived activities from organic to inorganic ion exchangers such as titanates and zeolites was demonstrated on a bench scale. The stability of this system depends on the conditioning of the inorganic ion exchangers. The purpose of this paper was to study and compare the quality of the products obtained by hot pressing and hot isostatic pressing in order to guide the choice of full scale equipment. Due to the leakage of argon, the hot isostatic pressing did not appear to have an advantage. The extremely large surfaces of authentic titanates must be ascribed to this phenomenon. The merits of the two sintering methods could not be objectively compared from the results obtained. Therefore, more experiments are needed and planned. These are studies on the conditioning of the titanates previous to the sintering, on the welding technique and performance, and at a higher sintering temperature, 1300 0 C, known to yield very good results. Formally, a leach rate of 3 μg d -1 cm -2 for the zeolites corresponds to the leaching out of cesium from a surface layer of 0.15 cm during 300 years. The same leach rate of strontium from titanates corresponds to a depth of 0.08 cm for 300 years. Bearing in mind that the temperature of the deposit will be at least 80 0 C lower, and the water flow much lower, the examples mentioned here might be quite satisfying. After a more successful sintering, the leach rates may be still better and a leaching test at more realistic conditions might be worthwhile

Shell model for BaTiO3-Bi(Zn1/2Ti1/2)O3 perovskite solid solutions

Science.gov (United States)

Vielma, J.; Jackson, D.; Roundy, D.; Schneider, G.

2010-03-01

Even though the composition of BaTiO3-Bi(Zn1/2Ti1/2)O3 perovskite solid solutions is similar to other ferroelectric compounds, the dielectric response is unusual. Results of permittivity measurements as a function of temperature show a diffuse phase transition indicative of a weakly coupled relaxor behavior.footnotetextC. C. Huang and D. P. Cann, J. Appl. Phys. 104, 024117 (2008) To investigate the weakly coupled relaxor behavior in these materials at intermediate length scales we are developing a newly calibrated shell model based on first-principles supercell calculations of both the solid solution and its compositional endpoints. Initial results for its phase diagram will presented.

Electric controlling of surface metal-insulator transition in the doped BaTiO3 film

Directory of Open Access Journals (Sweden)

Wei Xun

2017-07-01

Full Text Available Based on first-principles calculations, the BaTiO3(BTO film with local La-doping is studied. For a selected concentration and position of doping, the surface metal-insulator transition occurs under the applied electric field, and the domain appears near the surface for both bipolar states. Furthermore, for the insulated surface state, i.e., the downward polarization state in the doped film, the gradient bandgap structure is achieved, which favors the absorption of solar energy. Our investigation can provide an alternative avenue in modification of surface property and surface screening effect in polar materials.

Relaxorlike dielectric behavior in Ba0.7Sr0.3TiO3 thin films

Science.gov (United States)

Zednik, Ricardo J.; McIntyre, Paul C.; Baniecki, John D.; Ishii, Masatoshi; Shioga, Takeshi; Kurihara, Kazuaki

2007-03-01

We present the results of a systematic dielectric study for sputter deposited barium strontium titanate thin film planar capacitors measured over a wide temperature range of 20-575K for frequencies between 1kHz and 1MHz. Our observations of dielectric loss peaks in the temperature and frequency domains cannot be understood in the typical framework of intrinsic phonon losses. We find that the accepted phenomenological Curie-von Schweidler dielectric behavior (universal relaxation law) in our barium strontium titanate films is only applicable over a narrow temperature range. An excellent fit to the Vogel-Fulcher expression suggests relaxorlike behavior in these films. The activation energy of the observed phenomenon suggests that oxygen ion motion play a role in the apparent relaxor behavior, although further experimental work is required to test this hypothesis.

The effect of secondary abnormal grain growth on the dielectric properties of La/Mn co-doped BaTiO3 ceramics

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Živković Lj.M.

2006-01-01

Full Text Available La/Mn-codoped BaTiO3 systems, obtained by solid state reactions, were investigated regarding their microstructure characteristics and ferroelectric properties. Different concentrations of La2O3 were used for doping, ranging from 0.1 to 5.0 at% La, while a content of Mn was constant at 0.05 at%. For all samples sintered below the eutectic temperature (1332°C, a uniform microstructure was formed with average grain size from 1-3 μm. The appearance of secondary abnormal grains with (111 double twins grains with curved or faceted grain boundaries were observed in La/Mn BaTiO3 ceramics after sintering at temperatures above the eutectic temperature. All sintered samples exhibited a high electrical resistivity. Better dielectric performances were obtained for low doped samples (0.1 at% La sintered at 1350°C. For samples with La content above 1.0 at% a lower value in dielectric permittivity at higher sintering temperature is due to secondary abnormal grain growth, and to the presence of a non-ferroelectric phase rich in La. The Curie constant together with other dielectric parameters were also calculated.

Synthesis, microstructure and dielectric properties of (Sr,Bi)TiO{sub 3} borosilicate glass-ceramics

Energy Technology Data Exchange (ETDEWEB)

Gautam, C.R. [Lucknow Univ. (India). Advanced Glass and Glass-Ceramic Research Lab.; Rice Univ., Houston, TX (United States). Dept. of Materials Science and Nano Engineering; Manpoong, C.W.; Gautam, S.S.; Tamuk, M. [North Eastern Regional Institute of Science and Technology, Itanagar (India). Dept. of Mechanical Engineering; Singh, A.K.; Madheshiya, A. [Lucknow Univ. (India). Advanced Glass and Glass-Ceramic Research Lab.

2016-07-01

Strontium bismuth titanate glass compositions were prepared with the conventional melt quench method in the glass system 60[(Sr{sub 1-x}Bi{sub x}).TiO{sub 3}]-39[2SiO{sub 2}B{sub 2}O{sub 3}]-1[CeO{sub 2}]. X-ray diffraction and transmission electron microscopy analyses of the glass samples confirmed their amorphous nature. Scanning electron microscopy and contact angle measurements were performed to study the surface morphology of the major phase crystallites. The addition of CeO{sub 2} resulted in development of well-interconnected crystallites formed as major phase of perovskite strontium titanate. The dielectric constant (ε{sub r}) and dissipation factor (tan δ) were studied as a function of temperature. The effective value of the dielectric constant, ε{sub r}, was observed for glass-ceramic sample SBTC0.0850S with composition, x = 0.0, which is the order of 90 000 at low frequency, 1 Hz.

Room Temperature Monoclinic Phase in BaTiO3 Single Crystals

Science.gov (United States)

Denev, Sava; Kumar, Amit; Barnes, Andrew; Vlahos, Eftihia; Shepard, Gabriella; Gopalan, Venkatraman

2010-03-01

BaTiO3 is a well studied ferroelectric material for the last half century. It is well known to show phase transitions to tetragonal, orthorhombic and rhombohedral phases upon cooling. Yet, some old and some recent studies have argued that all these phases co-exist with a second phase with monoclinic distortion. Using optical second harmonic generation (SHG) at room temperature we directly present evidence for such monoclininc phase co-existing with tetragonal phase at room temperature. We observe domains with the expected tetragonal symmetry exhibiting 90^o and 180^o domain walls. However, at points of higher stress at the tips of the interpenetrating tetragonal domains we observe a well pronounced metastable ``staircase pattern'' with a micron-scale fine structure. Polarization studies show that this phase can be explained only by monoclinic symmetry. This phase is very sensitive to external perturbations such as temperature and fields, hence stabilizing this phase at room temperature could lead to large properties' tunability.

Highly tunable SrTiO.sub.3./sub./DyScO.sub.3./sub. heterostructures for applications in the terahertz range

Czech Academy of Sciences Publication Activity Database

Kužel, Petr; Kadlec, Filip; Petzelt, Jan; Schubert, J.; Panaitov, G.

2007-01-01

Roč. 91, č. 23 (2007), 232911/1-232911/3 ISSN 0003-6951 R&D Projects: GA MŠk LC512; GA ČR(CZ) GA202/06/0286 Grant - others:DAAD-ASCR(XE) D20-CZ4/06-07 Institutional research plan: CEZ:AV0Z10100520 Keywords : ferroelectric * terahertz * strontium titanate * thin film * soft mode Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.596, year: 2007

Fractal corrections of BaTiO3-ceramic sintering parameters

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Mitić V.V.

2014-01-01

Full Text Available Morphology of ceramics grains and pores as well as Brownian character of particle dynamics inside ceramics specimen contributes to better understanding of the sintering process. BaTiO3-ceramics, studied in this paper, has light fractal form and it is emanated in three aspects. First, the surface of grains, even in starting green body as well as distribution of grains shows fractal behavior. Second, existence of pores and their distribution follow the rules of fractal geometry. Third, movement of particles inside viscous flow underlies the rule of Brownian motion, which is essentially a fractal category. These three elements, each in its domain influence sintering dynamics, and can be described by dimensionless quantitative factors, αs αp and αm, being normalized to the interval [0,1]. Following sintering process, the associate formulae of Frenkel, Scherer and Mackenzie-Shuttleworth are shown from the angle of view of ceramics fractal dimension changing that approaches to 3. Also, it is shown that the energy balance is not violated after applying fractal correction to quasi equilibrium of the energy emanating from surface area reduction ES and energy adopted by viscous flow Ef .[Projekat Ministarstva nauke Republike Srbije, br. 172057: Directed synthesis, structure and properties of multifunctional materials

Strontium eluting graphene hybrid nanoparticles augment osteogenesis in a 3D tissue scaffold

Science.gov (United States)

Kumar, Sachin; Chatterjee, Kaushik

2015-01-01

The objective of this work was to prepare hybrid nanoparticles of graphene sheets decorated with strontium metallic nanoparticles and demonstrate their advantages in bone tissue engineering. Strontium-decorated reduced graphene oxide (RGO_Sr) hybrid nanoparticles were synthesized by the facile reduction of graphene oxide and strontium nitrate. X-ray diffraction, transmission electron microscopy, and atomic force microscopy revealed that the hybrid particles were composed of RGO sheets decorated with 200-300 nm metallic strontium particles. Thermal gravimetric analysis further confirmed the composition of the hybrid particles as 22 wt% of strontium. Macroporous tissue scaffolds were prepared by incorporating RGO_Sr particles in poly(ε-caprolactone) (PCL). The PCL/RGO_Sr scaffolds were found to elute strontium ions in aqueous medium. Osteoblast proliferation and differentiation was significantly higher in the PCL scaffolds containing the RGO_Sr particles in contrast to neat PCL and PCL/RGO scaffolds. The increased biological activity can be attributed to the release of strontium ions from the hybrid nanoparticles. This study demonstrates that composites prepared using hybrid nanoparticles that elute strontium ions can be used to prepare multifunctional scaffolds with good mechanical and osteoinductive properties. These findings have important implications for designing the next generation of biomaterials for use in tissue regeneration.The objective of this work was to prepare hybrid nanoparticles of graphene sheets decorated with strontium metallic nanoparticles and demonstrate their advantages in bone tissue engineering. Strontium-decorated reduced graphene oxide (RGO_Sr) hybrid nanoparticles were synthesized by the facile reduction of graphene oxide and strontium nitrate. X-ray diffraction, transmission electron microscopy, and atomic force microscopy revealed that the hybrid particles were composed of RGO sheets decorated with 200-300 nm metallic strontium

Processing/structure/property Relationships of Barium Strontium Titanate Thin Films for Dynamic Random Access Memory Application.

Science.gov (United States)

Peng, Cheng-Jien

The purpose of this study is to see the application feasibility of barium strontium titanate (BST) thin films on ultra large scale integration (ULSI) dynamic random access memory (DRAM) capacitors through the understanding of the relationships among processing, structure and electrical properties. Thin films of BST were deposited by multi-ion -beam reactive sputtering (MIBERS) technique and metallo -organic decomposition (MOD) method. The processing parameters such as Ba/Sr ratio, substrate temperature, annealing temperature and time, film thickness and doping concentration were correlated with the structure and electric properties of the films. Some effects of secondary low-energy oxygen ion bombardment were also examined. Microstructures of BST thin films could be classified into two types: (a) Type I structures, with multi-grains through the film thickness, for amorphous as-grown films after high temperature annealing, and (b) columnar structure (Type II) which remained even after high temperature annealing, for well-crystallized films deposited at high substrate temperatures. Type I films showed Curie-von Schweidler response, while Type II films showed Debted type behavior. Type I behavior may be attributed to the presence of a high density of disordered grain boundaries. Two types of current -voltage characteristics could be seen in non-bombarded films depending on the chemistry of the films (doped or undoped) and substrate temperature during deposition. Only the MIBERS films doped with high donor concentration and deposited at high substrate temperature showed space-charge -limited conduction (SCLC) with discrete shallow traps embedded in trap-distributed background at high electric field. All other non-bombarded films, including MOD films, showed trap-distributed SCLC behavior with a slope of {~}7.5-10 due to the presence of grain boundaries through film thickness or traps induced by unavoidable acceptor impurities in the films. Donor-doping could

Emergence of the sub-THz central peak at phase transitions in artificial BaTiO3/(Ba,Sr)TiO3 superlattices

International Nuclear Information System (INIS)

Tikhonov, Yu.A.; Razumnaya, A.G.; Torgashev, V.I.; Zakharchenko, I.N.; Yuzyuk, Yu.I.; El Marssi, M.; Ortega, N.; Kumar, A.; Katiyar, R.S.

2015-01-01

A prominent central peak in the sub-THz frequency range was observed in the Raman spectra of BaTiO 3 /(Ba,Sr)TiO 3 (BT/BST) superlattice grown on (001)MgO substrate. Both soft and central mode show an anomaly around 200 K and 280 K, which can be correlated with orthorhombic to monoclinic phase transition of BST and BT, respectively. The observed temperature dependence of the central mode enabled us to explain rather broad temperature dependence of the dielectric permittivity previously observed in BT/BST superlattices. (copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Dielectric Performance of High Permitivity Nanocomposites: Impact of Polystyrene Grafting on BaTiO3 and TiO2

Science.gov (United States)

2016-09-22

prepared using high-shear mixing (Ultra-Turrax T18, IKA). All BaTiO3 nanocomposites were solution cast from DMF onto aluminum-coated glass substrates...coated from chlorobenzene onto aluminum-coated glass substrates. Figure 3 a Real dielectric permittivity ε′ measured at 1 kHz for PS@BaTiO3 HNPs... SiO2 nanocomposites, where 15% v/v PS  +  SiO2 blends exhibited degraded energy storage efficiencies when driven above 100 V/μm, while 18% v/v PS@ SiO2

Influence of sintering temperature on microstructures and energy-storage properties of barium strontium titanate glass-ceramics prepared by sol-gel process

Energy Technology Data Exchange (ETDEWEB)

Zhu, Jia; Zhang, Yong; Song, Xiaozhen; Zhang, Qian; Yang, Dongliang; Chen, Yongzhou [Beijing Key Laboratory of Fine Ceramics, State Key Laboratory of New Ceramics and Fine Processing, Institute of Nuclear and New Energy Technology, Tsinghua University, Beijing, 100084 (China)

2015-12-15

The sol-gel processing, microstructures, dielectric properties and energy-storage properties of barium strontium titanate glass-ceramics over the sintering temperature range of 1000-1150 C were studied. Through the X-ray diffraction result, it is revealed that the crystallinity increases as the sintering temperature increased from 1000 to 1080 C and has reached a steady-state regime above 1100 C. Scanning electron microscopy images showed that with the increase of sintering temperature, the crystal size increased. Dielectric measurements revealed that the increase in the sintering temperature resulted in a significant increase in the dielectric constant, a strong sharpness of the temperature-dependent dielectric response and a pronounced decrease of the temperature of the dielectric maximum. The correlation between charge spreading behavior and activation energies of crystal and glass was discussed by the employment of the impedance spectroscopy studies. As a result of polarization-electric field hysteresis loops, both the charged and discharged densities increased with increasing sintering temperature. And the maximum value of energy storage efficiency was found to occur at 1130 C. Finally, the dependence of released energy and power densities calculated from the discharged current-time (I-t) curves on the sintering temperature was studied. The relationship between the energy storage properties and microstructure was correlated. Polarization-electric field hysteresis loops for the BST glass-ceramics sintered at different temperatures. (copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Influence of rare-earth additives (La, Sm and Dy on the microstructure and dielectric properties of doped BaTiO3 ceramics

Directory of Open Access Journals (Sweden)

Paunović Vesna

2010-01-01

Full Text Available A series of La/Mn, Sm/Mn and Dy/Mn codoped BaTiO3 samples were prepared by the conventional solid state procedure with dopant concentrations ranging from 0.1 up to 2.0 at%. The specimens were sintered at 1320°C and 1350°C in an air atmosphere for two hours. The low doped samples demonstrated a mainly uniform and homogeneous microstructure with average grain sizes ranging from 0.3 μm to 5.0 μm. The appearance of secondary abnormal grains in the fine grain matrix and core-shell structure were observed in highly doped La/BaTiO3 and Dy/BaTiO3 sintered at 1350°C. The low doped samples, sintered at 1350°C, display a high value of dielectric permittivity at room temperature, 6800 for Sm/BaTiO3, 5900 for Dy/BaTiO3 and 3100 for La/BaTiO3. A nearly flat permittivity-response was obtained in specimens with 2.0 at% additive content. Using a modified Curie-Weiss law the Curie-like constant C⁄ and a critical exponent γ were calculated. The obtained values of γ pointed out the diffuse phase transformation in heavily doped BaTiO3 samples.

BaTiO3-based nanolayers and nanotubes: first-principles calculations.

Science.gov (United States)

Evarestov, Robert A; Bandura, Andrei V; Kuruch, Dmitrii D

2013-01-30

The first-principles calculations using hybrid exchange-correlation functional and localized atomic basis set are performed for BaTiO(3) (BTO) nanolayers and nanotubes (NTs) with the structure optimization. Both the cubic and the ferroelectric BTO phases are used for the nanolayers and NTs modeling. It follows from the calculations that nanolayers of the different ferroelectric BTO phases have the practically identical surface energies and are more stable than nanolayers of the cubic phase. Thin nanosheets composed of three or more dense layers of (0 1 0) and (0 1 1[overline]) faces preserve the ferroelectric displacements inherent to the initial bulk phase. The structure and stability of BTO single-wall NTs depends on the original bulk crystal phase and a wall thickness. The majority of the considered NTs with the low formation and strain energies has the mirror plane perpendicular to the tube axis and therefore cannot exhibit ferroelectricity. The NTs folded from (0 1 1[overline]) layers may show antiferroelectric arrangement of Ti-O bonds. Comparison of stability of the BTO-based and SrTiO(3)-based NTs shows that the former are more stable than the latter. Copyright © 2012 Wiley Periodicals, Inc.

Enhanced output performance of a lead-free nanocomposite generator using BaTiO3 nanoparticles and nanowires filler

Science.gov (United States)

Baek, Changyeon; Yun, Jong Hyuk; Wang, Hee Seung; Wang, Ji Eun; Park, Hyeonbin; Park, Kwi-Il; Kim, Do Kyung

2018-01-01

Flexible nanocomposite generators based on piezoelectric nanoparticles (NPs)-polymeric matrix have been attracted attention as the energy harvesting device converted the electricity from the mechanical deformations. To enhance the piezo-potential difference introduced inside the piezoelectric nanocomposite, one-dimensional nanostructures such as CNTs, copper nanorods, and Ag nanowires (NWs) should be used inevitably as a dispersing agent for achieving well-distributed piezoelectric nanoparticles in an elastomer. These non-piezoelectric additives showed versatile roles; however, their toxicity to living organism has been an obstacle to realize the bio-eco-friendly flexible energy harvesters. Replacing them with piezoelectric NWs with non-toxic can be a challengeable approach to achieve not only the original purposes of additives but also the improvement of output performance. Here, we synthesized well-crystallized BaTiO3 spherical and acicular NPs via a simple hydrothermal reaction and the two-step hydrothermal reactions, respectively and produced piezoelectric nanocomposite made of piezoelectric BaTiO3 NPs and NWs without toxic dispersion enhancers. Output performance of the fabricated flexible energy harvesters with varying the composition of NPs and NWs were investigated by the well-optimized measurement system during the periodical bending and unbending. A nanocomposite-based energy harvester with 4:1 wt ratio generated the maximum open-circuit voltage and short-circuit current of 60 V and 1.1 μA, respectively.

BaTiO3 thick fi lms obtained by tape casting from powders prepared by the oxalate route

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Adelina Ianculescu

2009-06-01

Full Text Available BaTiO3 powders were prepared by co-precipitation via oxalate route. The size, morphology and particle size distribution of the oxalate powders have been optimized by the control of different synthesis parameters during the precipitation reaction (nature of salts, concentration of different solutions, aging time. The single phase BaTiO3 oxide particles were obtained after a thermal decomposition of the as-synthesized powders at 850°C for 4 hours under air atmosphere. Oxide powders with a suitable specifi c surface area were selected in order to obtain thick fi lms by the tape casting technique. The microstructure and dielectric properties of the thick films varied obviously depending on the deposition-calcination-sintering cycle used. A double depositioncalcination cycle followed by sintering, as well as a two step deposition-calcination-sintering procedure was used in order to improve the compactness and therefore, the dielectric behaviour. A higher dielectric constant value (~ 750 and lower dielectric losses (~ 2 % were achieved at room temperature and at 1 kHz frequency for the dense, double-deposited fi lm obtained after two deposition-calcination-sintering cycles. For this film, a superior value of the dielectric constant (~ 1100, almost frequency independent in the frequency range of 100 Hz – 10 kHz was gained also at the ferroelectric-paraelectric phase transition temperature of 130°C.

Ferroelectric properties of BaTiO3/PbZr0.2Ti.08O3 bilayer thin film

Science.gov (United States)

Salev, Pavel; Yang, Chun; Grigoriev, Alexei

2014-03-01

The thin film ferroelectric BaTiO3/PbZr0.2Ti0.8O3 bilayer was epitaxially grown on SrRuO3/SrTiO3 substrate by RF sputtering. Electrical measurements of polarization switching revealed two different switching regimes - a small ferroelectric hysteresis loop at low applied voltage and a larger loop at a high voltage. The measured dielectric permittivity corresponds to weak electrostatic coupling between two layers according to Landau-Ginsburg-Devonshire theory. This weak coupling may allow for independent polarization states to exist in individual layers. This can lead to stable head-to-head and tail-to-tail polarization domain configurations, which would explain the two switching regimes observed in electrical measurements. The compensation of polarization gradient across the interface can be explained by the enhancement of interface charge carrier density due to strong bending of electron energy bands. This work was supported by NSF award DMR-1057159.

Room temperature surface piezoelectricity in SrTiO.sub.3./sub. ceramics via piezoresponse force microscopy

Czech Academy of Sciences Publication Activity Database

Kholkin, A.; Bdikin, I.; Ostapchuk, Tetyana; Petzelt, Jan

2008-01-01

Roč. 93, č. 22 (2008), 222905/1-222905/3 ISSN 0003-6951 R&D Projects: GA ČR GP202/06/P219 Institutional research plan: CEZ:AV0Z10100520 Keywords : strontium titanate ceramics * piezoresponse force microscopy * flexoelectric effect * polar grain boundaries Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.726, year: 2008

Properties of La0.5Sr0.5CoO3 thin films grown by laser ablation

International Nuclear Information System (INIS)

Drozdov, Yu.N.; Klyuenkov, E.B.; Salashenko, N.N.; Suslov, L.A.

1997-01-01

The epitaxial films of lanthanum-strontium cobaltate La 0.5 Sr 0.5 CoO 3 (LSCO) are obtained on the neodium gallate and strontium titanate substrates. It is established that the LSCO layer lattice has tetragonal distortion, the degree where of depends on the oxygen deficit. The LSCO specific resistance at room temperature is approximately equal to 200 μOhm cm. The resistance dependence on temperature is of metal character. The possibility is shown of utilizing the LSCO as electrode material by fabrication of condenser structures on the basis of DbZr 1-x Ti x O 3 ferroelectric films

Ceramic synthesis of 0.08BiGaO3-0.90BaTiO3-0.02LiNbO3 under high pressure and high temperature

Science.gov (United States)

Hui, Jin; Yong, Li; Mou-Sheng, Song; Lin, Chen; Xiao-Peng, Jia; Hong-An, Ma

2016-07-01

In this paper, the preparation of 0.08BiGaO3-0.90BaTiO3-0.02LiNbO3 is investigated at pressure 3.8 GPa and temperature 1100-1200 °C. Experimental results indicate that not only is the sintered rate more effective, but also the sintered temperature is lower under high pressure and high temperature than those of under normal pressure. It is thought that the adscititious pressure plays the key role in this process, which is discussed in detail. The composition and the structure of the as-prepared samples are recorded by XRD patterns. The result shows that the phases of BaTiO3, BaBiO2.77, and Ba2Bi4Ti5O18 with piezoelectric ceramic performance generate in the sintered samples. Furthermore, the surface morphology characteristics of the typical samples are also investigated using a scanning electron microscope. It indicates that the grain size and surface structure of the samples are closely related to the sintering temperature and sintering time. It is hoped that this study can provide a new train of thought for the preparation of lead-free piezoelectric ceramics with excellent performance. Project supported by the National Natural Science Foundation of China (Grant No. 51172089), the Natural Science Foundation of Education Department of Guizhou Province, China (Grant Nos. KY [2013]183 and LH [2015]7232), and the Research Fund for the Doctoral Program of Tongren University, China (Grant No. DS1302).

Influence of Mg O and B2O3 addition on reaction sintering, properties and microstructure of Aluminum titanate

International Nuclear Information System (INIS)

Ajami, R.; Sarpoolaki, H.; Akbari, G. H.

2007-01-01

The effect of Mg O and B 2 O 3 on the formation, physical properties, phase analysis and microstructure of aluminum titanate was investigated. Density results showed the sample containing of 1 wt percent B 2 O 3 and 2 wt percent Mg O leads to the highest density while the lowest density was seen in samples containing 1 wt percent B 2 O 3 compared to pure aluminum titanate. Regarding the phase analysis of samples, Mg O was found most effective additive on reaction sintering of aluminum titanate through the intermediate phases. Furthermore at the temperatures above 1350 d eg C , B 2 O 3 promote the formation reaction of aluminum titanate. Microstructural analysis showed the samples containing Mg O are fine grain and homogeneous. Thermal expansion coefficient of samples with additives is greater than pure aluminum titanate. Pure aluminum titanate samples and one containing B 2 O 3 additive decompose to Al 2 O 3 and TiO 2 after 5 hours heat treatment at 1150 d eg C while the samples containing 2 wt percent Mg O was stable even after 25 hours

Characterization of BaTiO3 piezoelectric perovskite material for ...

Indian Academy of Sciences (India)

2017-07-28

Jul 28, 2017 ... Barium titanate powders are manufactured at high tem- peratures by solid-state ... quence, this method does not allow the production of materials with a high ...... processing, and use in design (New York: Marcel Dekker Inc.).

Disappearance of dielectric anomaly in spite of presence of structural phase transition in reduced BaTiO3: Effect of defect states within the bandgap

Science.gov (United States)

Sagdeo, Archna; Nagwanshi, Anjali; Pokhriyal, Preeti; Sinha, A. K.; Rajput, Parasmani; Mishra, Vikash; Sagdeo, P. R.

2018-04-01

We report the structural, optical, ferroelectric, and dielectric properties of reduced BaTiO3 samples. For this purpose, oxygen vacancies in BaTiO3 are created by heating these samples with a Ti metal in a vacuum environment at different temperatures. It is observed that with an increase in oxygen deficiencies, the c/a ratio decreases as compared to that of the oxygen treated sample. The ferroelectric properties of the oxygen deficient samples are visibly different as compared to those of the oxygen treated sample. The disappearance of the P-E loop and the anomaly in the temperature variation of the dielectric constant have been observed; however, the structural phase transition corresponding to ferroelectric phase transitions still persists. Thus, it appears that the anomaly in dielectric data and the presence of the P-E loop are getting masked possibly by the Maxwell-Wagner effect. The presence of Ti+3 states in the prepared samples has been confirmed by X-ray absorption near edge structure measurements. The Kubelka-Munk optical absorption shows the presence of extra states below fundamental transition, indicating the emergence of new electronic states within the bandgap, which might be due to Ti+3 states. These new states appear at different energy positions, and with different intensities for different samples, which are reduced in the presence of Ti. These new states within the bandgap appear to modify the electronic structure, thereby reducing the overall bandgap, and hence, they seem to modify the ferroelectric and dielectric properties of the samples. Our results may be treated as experimental evidence for theoretically proposed defect states in oxygen deficient or reduced BaTiO3.

Identifying open-volume defects in doped and undoped perovskite-type LaCoO3, PbTiO3, and BaTiO3

International Nuclear Information System (INIS)

Ghosh, Vinita J.; Nielsen, Bent; Friessnegg, Thomas

2000-01-01

Dopants, vacancies, and impurity-vacancy clusters have a substantial impact on the properties of perovskite-type metal oxides (general formula ABO 3 ). In order to determine synthesis and processing conditions that optimize the desirable properties of these materials a careful study of these defects is required. It is essential to identify the defects and to map the defect densities. Positron annihilation spectroscopy has often been used to identify vacancy-type defects. Calculations of the positron lifetime and Doppler-broadened profiles of the positron-electron annihilation radiation in undoped and doped LaCoO 3 , PbTiO 3 , and BaTiO 3 are reported, and compared with available experimental data. The results show that these positron techniques are excellent for studying open-volume defects, vacancy-impurity complexes, and for identifying the sublattice occupied by the dopants. (c) 2000 The American Physical Society

Ferroelectric properties of NaNbO3-BaTiO3 thin films deposited on SrRuO3/(001)SrTiO3 substrate by pulsed laser deposition

International Nuclear Information System (INIS)

Yamazoe, Seiji; Oda, Shinya; Sakurai, Hiroyuki; Wada, Takahiro; Adachi, Hideaki

2009-01-01

(NaNbO 3 ) 1-x (BaTiO 3 ) x (NN-xBT) thin films with low BaTiO 3 (BT) concentrations x (x=0.05 and 0.10) were fabricated on SrRuO 3 /(001)SrTiO 3 (SRO)/(001)STO) substrate by pulsed laser deposition (PLD). X-ray diffraction pattern (XRD) and transmission electron diffraction pattern (TED) showed that NN-0.10BT thin film was epitaxially grown on SRO/(001)STO substrate with a crystallographic relationship of [001] NN-xBT parallel [001] STO . From reciprocal space maps, the lattice parameters of the out-of-plane direction of NN-xBT thin films became larger with an increase in BT concentration, although the lattice parameter of the in-plane was hardly changed by the BT concentration. The value of relative dielectric constant ε r of the NN-xBT thin films were increased with BT concentration. The ε r and the dielectric loss tanδ of NN-0.10BT were 1220 and 0.02 at 1 kHz, respectively. The P-E hysteresis loops of the NN-xBT thin films showed clear ferroelectricity. Although the value of remanent polarization P r decreased with the BT concentration, the behaviors of ε r , P r , and coercive electric field E c of the NN-xBT thin films against the BT concentration accorded with those of NN-xBT ceramics, in which NN-0.10BT ceramics exhibited the largest piezoelectric property. Therefore, the NN-0.10BT thin film is expected to show high piezoelectricity. (author)

Cytotoxicity of Titanate-Calcium Complexes to MC3T3 Osteoblast-Like Cells

Science.gov (United States)

Drury, Jeanie L.; Moussi, Joelle; Taylor-Pashow, Kathryn M. L.

2016-01-01

Monosodium titanates (MST) are a relatively novel form of particulate titanium dioxide that have been proposed for biological use as metal sorbents or delivery agents, most recently calcium (II). In these roles, the toxicity of the titanate or its metal complex is crucial to its biological utility. The aim of this study was to determine the cytotoxicity of MST and MST-calcium complexes with MC3T3 osteoblast-like cells; MST-Ca(II) complexes could be useful to promote bone formation in various hard tissue applications. MC3T3 cells were exposed to native MST or MST-Ca(II) complexes for 24–72 h. A CellTiter-Blue® assay was employed to assess the metabolic activity of the cells. The results showed that MST and MST-Ca(II) suppressed MC3T3 metabolic activity significantly in a dose-, time-, and cell-density-dependent fashion. MST-Ca(II) suppressed MC3T3 metabolism in a statistically identical manner as native MST at all concentrations. We concluded that MST and MST-Ca(II) are significantly cytotoxic to MC3T3 cells through a mechanism yet unknown; this is a potential problem to the biological utility of these complexes. PMID:28044136

Cytotoxicity of Titanate-Calcium Complexes to MC3T3 Osteoblast-Like Cells

Directory of Open Access Journals (Sweden)

Yen-Wei Chen

2016-01-01

Full Text Available Monosodium titanates (MST are a relatively novel form of particulate titanium dioxide that have been proposed for biological use as metal sorbents or delivery agents, most recently calcium (II. In these roles, the toxicity of the titanate or its metal complex is crucial to its biological utility. The aim of this study was to determine the cytotoxicity of MST and MST-calcium complexes with MC3T3 osteoblast-like cells; MST-Ca(II complexes could be useful to promote bone formation in various hard tissue applications. MC3T3 cells were exposed to native MST or MST-Ca(II complexes for 24–72 h. A CellTiter-Blue® assay was employed to assess the metabolic activity of the cells. The results showed that MST and MST-Ca(II suppressed MC3T3 metabolic activity significantly in a dose-, time-, and cell-density-dependent fashion. MST-Ca(II suppressed MC3T3 metabolism in a statistically identical manner as native MST at all concentrations. We concluded that MST and MST-Ca(II are significantly cytotoxic to MC3T3 cells through a mechanism yet unknown; this is a potential problem to the biological utility of these complexes.

Titan's Ammonia Feature

Science.gov (United States)

Smythe, W.; Nelson, R.; Boryta, M.; Choukroun, M.

2011-01-01

NH3 has long been considered an important component in the formation and evolution of the outer planet satellites. NH3 is particularly important for Titan, since it may serve as the reservoir for atmospheric nitrogen. A brightening seen on Titan starting in 2004 may arise from a transient low-lying fog or surface coating of ammonia. The spectral shape suggests the ammonia is anhydrous, a molecule that hydrates quickly in the presence of water.

Nanofibers obtained by electrospinning of BaTiO3 particles dispersed in polyvinyl alcohol and ethylcellulose

Energy Technology Data Exchange (ETDEWEB)

Avila, Humar A.; Reboredo, Maria M.; Castro, Miriam; Parra, Rodrigo, E-mail: havila@fi.mdp.edu.ar [Instituto de Investigaciones en Ciencia y Tecnologia de Materiales - INTEMA, Consejo Nacional de Investigaciones Cientificas y Tecnicas - CONICET, Universidad Nacional de Mar del Plata - UNMdP, Mar del Plata (Argentina)

2013-11-01

Barium titanate particles (100-300 nm) synthesized by hydrothermal method were dispersed in both polyvinyl alcohol (PVA) and ethylcellulose (EC) solutions. These suspensions were processed by electrospinning. When no particles were added, homogeneous polymeric nanofibers were obtained. Under certain conditions, polymeric suspensions of barium titanate particles were electrospun generating polymeric fibers with BT particles. The effect of a surfactant was also assessed over the formation of nanofibers. The BaTiO{sub 3} particles synthesized by hydrothermal method were characterized by X-Ray diffraction (XRD), field emission-scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and Raman spectroscopy. Fibers were characterized by scanning electron microscopy (SEM). (author)

Kinetics of strontium sorption in calcium phosphate

International Nuclear Information System (INIS)

Bacic, S.; Komarov, V.F.; Vukovic, Z.

1989-01-01

Kinetics of strontium sorption by highly dispersed solids: tricalcium phosphate (Ca 3 (PO 4 ) 2 , TCP) and hydroxyapatite (Ca 5 (PO 4 ) 3 )H, HAP) were investigated. Analysis of sorption data was made taking into consideration composition and morphology of ultra micro particles. Conclusion is that the isomorphous strontium impurity is structurally sensitive element for calcium phosphate. It was determined that the beginning of strontium desorption corresponds to the beginning of transformation of the TCP - HAP (author)

The permittivity and refractive index measurements of doped barium titanate (BT-BCN)

Science.gov (United States)

Meeker, Michael A.; Kundu, Souvik; Maurya, Deepam; Kang, Min-Gyu; Sosa, Alejandro; Mudiyanselage, Rathsara R. H. H.; Clavel, Michael; Gollapudi, Sreenivasulu; Hudait, Mantu K.; Priya, Shashank; Khodaparast, Giti A.

2017-11-01

While piezoelectric- ferroelectric materials offer great potential for nonvolatile random access memory, most commonly implemented ferroelectrics contain lead which imposes a challenge in meeting environmental regulations. One promising candidate for lead-free, ferroelectric material based memory is (1 - x) BaTiO3 - xBa(Cu1 / 3 Nb2 / 3) O3 (BT-BCN), x = 0.025 . The samples studied here were grown on a Si substrate with an HfO2 buffer layer, thereby preventing the interdiffusion of BT-BTCN into Si. This study provides further insight into the physical behavior of BT-BCN that will strengthen the foundation for developing switching devices. The sample thicknesses ranged from 1.5 to 120 nm, and piezoelectric force microscopy was employed in order to understand the local ferroelectric behaviors. Dielectric constant as a function of frequency demonstrated enhanced frequency dispersion indicating the polar nature of the composition. The relative permittivity was found to change significantly with varying bias voltage and exhibited a tunability of 82%. The difference in the peak position during up and down sweeps is due to the presence of the spontaneous polarization. Furthermore, reflectometry was performed to determine the refractive index of samples with differing thicknesses. Our results demonstrate that refractive indices are similar to that of barium titanate. This is a promising result indicating that improved ferroelectric properties are obtained without compromising the optical properties.

Vantage TitanTM 3T 3-tesla MRI system with enhanced serviceability and comfort

International Nuclear Information System (INIS)

Kanazawa, Hitoshi; Okamoto, Kazuya; Yamamoto, Takao

2011-01-01

Since 3-tesla magnetic resonance imaging (MRI) systems appeared on the market, in addition to their clinical usefulness a variety of issues have been pointed out in the clinical setting. The 3-tesla MRI system has therefore gained a reputation as a difficult system suitable only for hospital facilities including university hospitals that specialize in medical research. To rectify this situation, Toshiba Medical Systems Corporation has developed the Vantage Titan TM 3T, which is expected to not only improve the MRI examination environment, but also to be applicable to patients with claustrophobia and those with large physiques for whom MRI examination has not been appropriate until now, while maintaining the clinical usefulness of the 3-tesla MRI system. The Vantage Titan 3T system also incorporates the Pianissimo TM noise reduction mechanism, which has already been introduced in our 1.5-tesla MRI system and has been highly evaluated by the market. This reduces the stress of patients by providing a quieter and more open examination environment compared with conventional MRI systems. (author)

BaxSr1-xTi1.02O3 metal-insulator-metal capacitors on planarized alumina substrates

NARCIS (Netherlands)

Tiggelman, M.P.J.; Reimann, K.; Klee, M.; Mauczok, R.; Keur, W.; Hueting, Raymond Josephus Engelbart

2010-01-01

Nanocrystalline barium strontium titanate (BaxSr1−xTi1.02O3) thin films with a barium content of x=0.8, 0.9 and 1 have been fabricated in a metal–insulator–metal configuration on glass-planarized alumina substrates. Cost-effective processing measures have been utilized by using poly-crystalline

TAILORING INORGANIC SORBENTS FOR SRS STRONTIUM AND ACTINIDE SEPARATIONS: MODIFIED MONOSODIUM TITANATE PHASE III FINAL REPORT

Energy Technology Data Exchange (ETDEWEB)

Taylor-Pashow, K.; Hobbs, D.

2010-09-01

This document provides a final report of Phase III testing activities for the development of modified monosodium titanate (mMST), which exhibits improved strontium and actinide removal characteristics compared to the baseline MST material. The activities included characterization of the crystalline phases present at varying temperatures, solids settling characteristics, quantification of the peroxide content; evaluation of the post-synthesis gas release under different conditions; the extent of desorption of {sup 85}Sr, Np, and Pu under washing conditions; and the effects of age and radiation on the performance of the mMST. Key findings and conclusions include the following. The peroxide content of several mMST samples was determined using iodometric titration. The peroxide content was found to decrease with age or upon extended exposure to elevated temperature. A loss of peroxide was also measured after exposure of the material to an alkaline salt solution similar in composition to the simulated waste solution. To determine if the loss of peroxide with age affects the performance of the material, Sr and actinide removal tests were conducted with samples of varying age. The oldest sample (4 years and 8 months) did show lower Sr and Pu removal performance. When compared to the youngest sample tested (1 month), the oldest sample retained only 15% of the DF for Pu. Previous testing with this sample indicated no decrease in Pu removal performance up to an age of 30 months. No loss in Np removal performance was observed for any of the aged samples, and no uptake of uranium occurred at the typical sorbent loading of 0.2 g/L. Additional testing with a uranium only simulant and higher mMST loading (3.0 g/L) indicated a 10% increase of uranium uptake for a sample aged 3 years and 8 months when compared to the results of the same sample measured at an age of 1 year and 5 months. Performance testing with both baseline-MST and mMST that had been irradiated in a gamma source to

The preparation of a novel layered lead titanate and its conversion to the perovskite lead titanate PbTiO3

NARCIS (Netherlands)

Blake, G.R.; Armstrong, A.R.; Sastre, E.; Wright, P.A.

2001-01-01

A novel layered lead titanate with the approximate composition PbTiO2(CO3)0.3(NO3)0.35(OH) has been synthesized hydrothermally under acidic conditions. The structure has been solved and refined from X-ray and neutron powder diffraction data in the space group P -3 1 m, with cell dimensions a =

Production of Strontium-90 Thermal Power Sources; Fabrication de sources d'energie thermique au strontium-90; Proizvodstvo istochnikov ''teplovoj ehnergii iz Sr''9''0; Preparacion de fuentes de energia termica con estroncio-90

Energy Technology Data Exchange (ETDEWEB)

Cochran, J. S.; Bloom, J. L.; Schneider, A. [Martin Company, Nuclear Division, Baltimore 3, MD (United States)

1963-11-15

One of the most attractive fields for utilization of large quantities of waste fission products is the field of direct-conversion power supplies for remote locations. Strontium-90 is being given the greatest exploitation because of its availability, nuclear properties, and the relative ease with which it can be fabricated into compact heat sources. Strontium-90 fuelled generators are being used to power automatic weather stations and navigational aids, and consideration is being given to the use of strontium-90 as a power source for space vehicles. Evaluation of several potentially useful strontium compounds led to the selection of the titanate as exhibiting overall properties most desirable for this purpose. Strontium-90, separated from crude fission product streams and purified to the requisite degree by the USAEC's Hanford Works, is shipped in the form of the carbonate to a hot cell facility operated by the Martin Company, where it is converted to titanate pellets. This process is an adaption to remote operation of conventional chemical and ceramic techniques. The pellets are encapsulated in Hastelloy C containers for use in thermoelectric power supplies. Unusual operational problems are encountered because the large quantities of strontium-90 handled (potentially millions of curies per year) represent formidable radiation and contamination hazards. Details of the facility, equipment, process, and safety criteria are given. The operational experience gained during the recent processing of the first 250 000 curies of strontium-90 into fuel for a SNAP-7 generator is described. Encapsulation, calorimetry, decontamination, and waste disposal procedures are also outlined. (author) [French] L'une des utilisations les plus interessantes des produits de fission en grande quantite consiste a les employer comme sources d'energie par combustion directe pour des installations geographiquement isolees. C'est le strontium-90 qui est l e plus utilise parce qu'on en dispose en

Microwave heating behavior and microwave absorption properties of barium titanate at high temperatures

Directory of Open Access Journals (Sweden)

K. Kashimura

2016-06-01

Full Text Available The temperature dependence of the microwave absorption behavior of BaTiO3 particles was investigated over various frequencies and temperatures of 25-1000 ∘C. First, using both the coaxial transmission line method and the cavity perturbation method by a network analyzer, the real and imaginary parts of the relative permittivity of BaTiO3 ( ε r ′ and ε r ″ , respectively were measured, in order to improve the reliability of the data obtained at 2.45 GHz. The imaginary parts of the relative permittivity as measured by the two methods were explored by their heating behaviors. Furthermore, the temperature dependence of the microwave absorption behavior of BaTiO3 particles was investigated for frequencies of 2.0-13.5 GHz and temperatures of 25-1000 ∘C using the coaxial transmission line method.

Doped barium titanate nanoparticles

Indian Academy of Sciences (India)

Wintec

nese doped BaTiO3 ceramics, sintered at 1400°C in air, changes from tetragonal to hexagonal between 0⋅5 and. 1⋅7 mole% of manganese (Langhammer et al 2000). As a driving force of the transformation from the cubic to the hexagonal crystal structure, the influence of the Jahn–. Teller distortion is proposed. The grain ...

Quantifying Local and Cooperative Components in the Ferroelectric Distortion of BaTiO3: Learning from the Off-Center Motion in the MnCl65– Complex Formed in KCl:Mn+

DEFF Research Database (Denmark)

García Lastra, Juan Maria; García-Fernández, P.; Calle-Vallejo, F.

2014-01-01

→ C4v → Oh local transformations occurring in the 10–50 K temperature range for the MnCl65– complex formed in KCl:Mn+ that mimic the behavior of BaTiO3. From Boltzmann analysis of the vibronic levels derived from ab initio calculations and considering decoherence introduced by random strains......, the present calculations reproduce the experimental phase sequence and transition temperatures. Furthermore, our calculations show that the off-center instability in KCl:Mn+ would be suppressed by reducing by only 1% the lattice parameter, a situation that then becomes comparable to that found for BaTiO3...

STRONTIUM PRECIPITATION

Science.gov (United States)

McKenzie, T.R.

1960-09-13

A process is given for improving the precipitation of strontium from an aqueous phosphoric-acid-containing solution with nickel or cobalt ferrocyanide by simultaneously precipitating strontium or calcium phosphate. This is accomplished by adding to the ferrocyanide-containing solution calcium or strontium nitrate in a quantity to yield a concentration of from 0.004 to 0.03 and adjusting the pH of the solution to a value of above 8.

Optical and EPR characterization of Er.sup.3+./sup. centers in SrTiO.sub.3./sub. single crystals

Czech Academy of Sciences Publication Activity Database

Skvortsov, A.; Savchenko, Dariia; Potůček, Zdeněk; Jastrabík, Lubomír; Trepakov, Vladimír; Dejneka, Alexandr

2014-01-01

Roč. 251, č. 11 (2014), s. 2270-2273 ISSN 0370-1972 R&D Projects: GA MŠk(CZ) LM2011029; GA TA ČR TA01010517; GA ČR GAP108/12/1941 Grant - others:SAFMAT(XE) CZ.2.16/3.1.00/22132 Institutional support: RVO:68378271 Keywords : electron paramagnetic resonance spectroscopy * optical transmission * rare- earth ions * strontium titanate Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.489, year: 2014

Diurnal variations of Titan

Science.gov (United States)

Cui, J.; Galand, M.; Yelle, R. V.; Vuitton, V.; Wahlund, J.-E.; Lavvas, P. P.; Mueller-Wodarg, I. C. F.; Kasprzak, W. T.; Waite, J. H.

2009-04-01

We present our analysis of the diurnal variations of Titan's ionosphere (between 1,000 and 1,400 km) based on a sample of Ion Neutral Mass Spectrometer (INMS) measurements in the Open Source Ion (OSI) mode obtained from 8 close encounters of the Cassini spacecraft with Titan. Though there is an overall ion depletion well beyond the terminator, the ion content on Titan's nightside is still appreciable, with a density plateau of ~700 cm-3 below ~1,300 km. Such a plateau is associated with the combination of distinct diurnal variations of light and heavy ions. Light ions (e.g. CH5+, HCNH+, C2H5+) show strong diurnal variation, with clear bite-outs in their nightside distributions. In contrast, heavy ions (e.g. c-C3H3+, C2H3CNH+, C6H7+) present modest diurnal variation, with significant densities observed on the nightside. We propose that the distinctions between light and heavy ions are associated with their different chemical loss pathways, with the former primarily through "fast" ion-neutral chemistry and the latter through "slow" electron dissociative recombination. The INMS data suggest day-to-night transport as an important source of ions on Titan's nightside, to be distinguished from the conventional scenario of auroral ionization by magnetospheric particles as the only ionizing source on the nightside. This is supported by the strong correlation between the observed night-to-day ion density ratios and the associated ion lifetimes. We construct a time-dependent ion chemistry model to investigate the effects of day-to-night transport on the ionospheric structures of Titan. The predicted diurnal variation has similar general characteristics to those observed, with some apparent discrepancies which could be reconciled by imposing fast horizontal thermal winds in Titan's upper atmosphere.

Interferometric imaging of Titan's HC$_3$N, H$^{13}$CCCN and HCCC$^{15}$N

OpenAIRE

Cordiner, M. A.; Nixon, C. A.; Charnley, S. B.; Teanby, N. A.; Molter, E. M.; Kisiel, Z.; Vuitton, V.

2018-01-01

We present the first maps of cyanoacetylene isotopologues in Titan's atmosphere, including H$^{13}$CCCN and HCCC$^{15}$N, detected in the 0.9 mm band using the Atacama Large Millimeter/submillimeter array (ALMA) around the time of Titan's (southern winter) solstice in May 2017. The first high-resolution map of HC$_3$N in its $v_7=1$ vibrationally excited state is also presented, revealing a unique snapshot of the global HC$_3$N distribution, free from the strong optical depth effects that adv...

Titan!

Science.gov (United States)

Matson, Dennis L.

2010-05-01

Cassini-Huygens achieved Saturnian orbit on July 1, 2004. The first order of business was the safe delivery of the Huygens atmospheric probe to Titan that took place on January 14, 2005. Huygens descended under parachute obtaining observations all the way down to a safe landing. It revealed Titan for the first time. Stunning are the similarities between Titan and the Earth. Viewing the lakes and seas, the fluvial terrain, the sand dunes and other features through the hazy, nitrogen atmosphere, brings to mind the geological processes that created analogous features on the Earth. On Titan frozen water plays the geological role of rock; liquid methane takes the role of terrestrial water. The atmospheres of both Earth and Titan are predominately nitrogen gas. Titan's atmosphere contains 1.5% methane and no oxygen. The surface pressure on Titan is 1.5 times the Earth's. There are aerosol layers and clouds that come and go. Now, as Saturn proceeds along its solar orbit, the seasons are changing. The effects upon the transport of methane are starting to be seen. A large lake in the South Polar Region seems to be filling more as winter onsets. Will the size and number of the lakes in the South grow during winter? Will the northern lakes and seas diminish or dry up as northern summer progresses? How will the atmospheric circulation change? Much work remains not only for Cassini but also for future missions. Titan has many different environments to explore. These require more capable instruments and in situ probes. This work was conducted at the Jet Propulsion Laboratory, California Institute of Technology under contract with the National Aeronautics and Space Administration.

Giant energy density and high efficiency achieved in bismuth ferrite-based film capacitors via domain engineering.

Science.gov (United States)

Pan, Hao; Ma, Jing; Ma, Ji; Zhang, Qinghua; Liu, Xiaozhi; Guan, Bo; Gu, Lin; Zhang, Xin; Zhang, Yu-Jun; Li, Liangliang; Shen, Yang; Lin, Yuan-Hua; Nan, Ce-Wen

2018-05-08

Developing high-performance film dielectrics for capacitive energy storage has been a great challenge for modern electrical devices. Despite good results obtained in lead titanate-based dielectrics, lead-free alternatives are strongly desirable due to environmental concerns. Here we demonstrate that giant energy densities of ~70 J cm -3 , together with high efficiency as well as excellent cycling and thermal stability, can be achieved in lead-free bismuth ferrite-strontium titanate solid-solution films through domain engineering. It is revealed that the incorporation of strontium titanate transforms the ferroelectric micro-domains of bismuth ferrite into highly-dynamic polar nano-regions, resulting in a ferroelectric to relaxor-ferroelectric transition with concurrently improved energy density and efficiency. Additionally, the introduction of strontium titanate greatly improves the electrical insulation and breakdown strength of the films by suppressing the formation of oxygen vacancies. This work opens up a feasible and propagable route, i.e., domain engineering, to systematically develop new lead-free dielectrics for energy storage.

Enhanced dielectric and ferroelectric characteristics in Ca-modified BaTiO3 ceramics

Directory of Open Access Journals (Sweden)

Xiao Na Zhu

2013-08-01

Full Text Available Synergic modification of BaTiO3 ceramics was investigated by Ca-substitution, and the superior dielectric and ferroelectric properties were determined together with the structure evolution. X-ray diffraction (XRD analysis demonstrated a large solubility limit above x = 0.25 in Ba1−xCaxTiO3 solid solution where the fine grain structure was observed with increasing x. Room temperature dielectric constant as high as 1655 was achieved in the present ceramics together with the significantly reduced dielectric loss of 0.013 (x = 0.20 at 100 kHz, where the Curie temperature kept almost a constant while other two transition temperatures decreased continuously with increasing x. More importantly, the remanent polarization Pr and dielectric strength Eb were significantly enhanced by Ca-substitution, and the best Pr (11.34 μC/cm2 and the highest dielectric strength Eb (75 kV/cm were acquired at x = 0.25. The present ceramics should be very desirable for the applications such as high density energy storage devices.

Highly constrained ferroelectric [BaTiO3](1−x)Λ/[BaZrO3]xΛ superlattices: X-ray diffraction and Raman spectroscopy

International Nuclear Information System (INIS)

Belhadi, J.; El Marssi, M.; Gagou, Y.; El Mendili, Y.; Bouyanfif, H.; Yuzyuk, Yu. I.; Raevski, I. P.; Wolfman, J.

2014-01-01

We report an x-ray diffraction (XRD) and a Raman-scattering investigation of ferroelectric/paraelectric superlattices [BaTiO 3 ] (1−x)Λ /[BaZrO 3 ] xΛ for which the composition varied, 0.15 ≤ x ≤ 0.85, while the superlattice (SL) modulation period Λ was kept constant at about 100 Å. The samples were epitaxially grown by pulsed laser deposition on MgO substrates buffered with La 0.5 Sr 0.5 CoO 3 . Based on the XRD analysis and on polarized Raman spectra, we have showed that the large strain in SLs induced ferroelectricity in BaZrO 3 (BZ) for all SLs, a material that is paraelectric in the bulk form at any temperature and in the single film. The induced polar axis in BZ layers is perpendicular to the plane of substrate while BaTiO 3 (BT) layers exhibit in-plane polar orientation. Raman spectroscopy revealed a lattice ordering in SLs due to the misfit strain generated by the large lattice mismatch between the alternating BZ and BT layers. This strain induced a huge upward frequency of the lowest E(1TO) soft mode from 60 cm −1 in the BT single film to 215 cm −1 in the SL with x = 0.85. These results show that in spite of relatively large periodicity of SLs, they are highly constrained and the variation of BZ ratio allowed modifying strains between layers. The temperature dependence of the Raman spectra for BT 0.3Λ /BZ 0.7Λ and BT 0.7Λ /BZ 0.3Λ samples revealed giant shift of the ferroelectric phase transition. The phase transition temperature was found to be upshifted by about 300 °C with respect to BT single crystal.

Defect and electrical transport properties of Nb-doped SrTiO₃

DEFF Research Database (Denmark)

Blennow Tullmar, Peter; Hagen, Anke; Kammer Hansen, Kent

2008-01-01

analyzed with SEM, XRD, TGA, and XANES. The electrical conductivity of Nb-doped strontium titanate (Sr0.94Ti0.9Nb0.1O3 - sintered in 9% H-2/N-2 at 1400 degrees C for 12 h) decreased with increasing temperature and showed a phonon scattering conduction mechanism with (sigma>120 S/cm at 1000 degrees C (in 9...

Chemical Synthesis of Porous Barium Titanate Thin Film and Thermal Stabilization of Ferroelectric Phase by Porosity-Induced Strain.

Science.gov (United States)

Suzuki, Norihiro; Osada, Minoru; Billah, Motasim; Bando, Yoshio; Yamauchi, Yusuke; Hossain, Shahriar A

2018-03-27

Barium titanate (BaTiO3, hereafter BT) is an established ferroelectric material first discovered in the 1940s and still widely used because of its well-balanced ferroelectricity, piezoelectricity, and dielectric constant. In addition, BT does not contain any toxic elements. Therefore, it is considered to be an eco-friendly material, which has attracted considerable interest as a replacement for lead zirconate titanate (PZT). However, bulk BT loses its ferroelectricity at approximately 130 °C, thus, it cannot be used at high temperatures. Because of the growing demand for high-temperature ferroelectric materials, it is important to enhance the thermal stability of ferroelectricity in BT. In previous studies, strain originating from the lattice mismatch at hetero-interfaces has been used. However, the sample preparation in this approach requires complicated and expensive physical processes, which are undesirable for practical applications. In this study, we propose a chemical synthesis of a porous material as an alternative means of introducing strain. We synthesized a porous BT thin film using a surfactant-assisted sol-gel method, in which self-assembled amphipathic surfactant micelles were used as an organic template. Through a series of studies, we clarified that the introduction of pores had a similar effect on distorting the BT crystal lattice, to that of a hetero-interface, leading to the enhancement and stabilization of ferroelectricity. Owing to its simplicity and cost effectiveness, this fabrication process has considerable advantages over conventional methods.

Production of BaTiO{sub 3} nanoparticles through the sol-gel route using humic substances from river water; Producao de nanoparticulas de BaTiO{sub 3} atraves da rota sol-gel utilizando substancias humicas provenientes da agua de rio

Energy Technology Data Exchange (ETDEWEB)

Lima, C.H.S.; Lima, S.S.S.; Gomes, M.A.; Novaes, S.M.V.; Macedo, Z.S., E-mail: camilahigina@hotmail.com [Universidade Federal de Sergipe (UFS), Sao Cristovao, SE (Brazil)

2016-07-01

A new route of synthesis, low cost and low environmental impact, has been developed for the production of barium titanate (BaTiO3). This material is widely used in the electronics industry due to its dielectric properties, ferroelectric and piezoelectric. Its crystal structure of perovskite type also has the ability to host dopants of different sizes, allowing a wide variety of ions is accommodated in BaTiO3 structure. The synthesis route proposed in this paper explores the complexation capacity of natural organic matter (NOM). Parameters such as concentration, pH and calcination temperature were investigated during production, with the aim of developing a simple, efficient and low energy cost procedure. Samples produced with concentration 0.5 g / ml showed a single phase after calcination at 1200 °C for 5 h. The crystallite size was estimated by Scherrer equation around 28 nm and the particle size, determined by scanning electron microscopy (SEM-FEG) was from 80 to 180nm order. The sample produced also presented heterogeneous morphology with spherical particles, rods and needles. (author)

Chemistry and evolution of Titan's atmosphere

International Nuclear Information System (INIS)

Strobel, D.F.

1982-01-01

The chemistry and evolution of Titan's atmosphere is reviewed in the light of the scientific findings from the Voyager mission. It is argued that the present N 2 atmosphere may be Titan's initial atmosphere rather than photochemically derived from an original NH 3 atmosphere. The escape rate of hydrogen from Titan is controlled by photochemical production from hydrocarbons. CH 4 is irreversibly converted to less hydrogen rich hydrocarbons, which over geologic time accumulate on the surface to a layer thickness of approximately 0.5 km. Magnetospheric electrons interacting with Titan's exosphere may dissociate enough N 2 into hot, escaping N atoms to remove approximately 0.2 of Titan's present atmosphere over geologic time. The energy dissipation of magnetospheric electrons exceeds solar e.u.v. energy deposition in Titan's atmosphere by an order of magnitude and is the principal driver of nitrogen photochemistry. The environmental conditions in Titan's upper atmosphere are favorable to building up complex molecules, particularly in the north polar cap region. (author)

Removal of Strontium from Drinking Water by Conventional ...

Science.gov (United States)

The United States Environmental Protection Agency Contaminant Candidate List 3 lists strontium as a contaminant for potential regulatory consideration in drinking water. There is very little data available on strontium removal from drinking water. As a result, there is an immediate need to perform treatment studies. The objective of this work is to evaluate the effectiveness of conventional and lime-soda ash softening treatments to remove strontium from surface and ground waters. Conventional drinking water treatment with aluminum and iron coagulants were able to achieve 12% and 5.9% strontium removal at best, while lime softening removed as much as 78% from natural strontium-containing ground water. Systematic fundamental experiments showed that strontium removal during the lime-soda ash softening was related to pH, calcium concentration and dissolved inorganic carbon concentration. Final strontium concentration was also directly associated with initial strontium concentration. Precipitated solids showed well-formed crystals or agglomerates of mixed solids, two polymorphs of calcium carbonate (vaterite and calcite), and strontianite, depending on initial water quality conditions. X-ray diffraction analysis suggested that strontium likely replaced calcium inside the crystal lattice and was likely mainly responsible for removal during lime softening. To inform the public.

Single crystal growth of 67%BiFeO3-33%BaTiO3 solution by the floating zone method

Science.gov (United States)

Rong, Y.; Zheng, H.; Krogstad, M. J.; Mitchell, J. F.; Phelan, D.

2018-01-01

The growth conditions and the resultant grain morphologies and phase purities from floating-zone growth of 67%BiFeO3-33%BaTiO3 (BF-33BT) single crystals are reported. We find two formidable challenges for the growth. First, a low-melting point constituent leads to a pre-melt zone in the feed-rod that adversely affects growth stability. Second, constitutional super-cooling (CSC), which was found to lead to dendritic and columnar features in the grain morphology, necessitates slow traveling rates during growth. Both challenges were addressed by modifications to the floating-zone furnace that steepened the temperature gradient at the melt-solid interfaces. Slow growth was also required to counter the effects of CSC. Single crystals with typical dimensions of hundreds of microns have been obtained which possess high quality and are suitable for detailed structural studies.

Single crystal growth of 67%BiFeO 3 -33%BaTiO 3 solution by the floating zone method

Energy Technology Data Exchange (ETDEWEB)

Rong, Y.; Zheng, H.; Krogstad, M. J.; Mitchell, J. F.; Phelan, D.

2018-01-01

The growth conditions and the resultant grain morphologies and phase purities from floating-zone growth of 67%BiFeO3-33%BaTiO3 (BF-33BT) single crystals are reported. We find two formidable challenges for the growth. First, a low-melting point constituent leads to a pre-melt zone in the feed-rod that adversely affects growth stability. Second, constitutional super-cooling (CSC), which was found to lead to dendritic and columnar features in the grain morphology, necessitates slow traveling rates during growth. Both challenges were addressed by modifications to the floating-zone furnace that steepened the temperature gradient at the melt-solid interfaces. Slow growth was also required to counter the effects of CSC. Single crystals with typical dimensions of hundreds of microns have been obtained which possess high quality and are suitable for detailed structural studies.

Preparation and optical properties of gold-dispersed BaTiO3 thin films

Energy Technology Data Exchange (ETDEWEB)

Kineri, T; Mori, M [TDK Corp., Tokyo (Japan). R and D Center; Kadono, K; Sakaguchi, T; Miya, M; Wakabayashi, H [Osaka National Research Inst., Osaka (Japan); Tsuchiya, T [Science Univ. of Tokyo, Tokyo (Japan). Faculty of Industrial Science and Technology

1993-12-01

Recently, metal or semiconductor-doped glasses were widely studied because of their large resonant third-order nonlinearity. These glasses are utilized in an optical information field as all optical logic devices in the future. The gold-doped glass films or thin layers have a large third-order nonlinear susceptibility [chi] and are prepared by r.f. sputtering method, etc. The optical properties, particularly the refractive index or dielectric constant of the matrix, are very important for the optical nonlinearity of these materials. In this study, gold-dispersed BaTiO3 thin films and gold-dispersed SiO2 thin films are prepared using r.f. magnetron sputtering method, and the optical properties of the films are compared. The [chi] of the films are measured and the effect of the matrix of the films on [chi] is investigated. The headings in the paper are: Introduction, Experimental procedure, Results, Discussion, and Conclusion. 13 refs., 9 figs.

Pyroelectrically Induced Pyro-Electro-Chemical Catalytic Activity of BaTiO3 Nanofibers under Room-Temperature Cold–Hot Cycle Excitations

OpenAIRE

Yuntao Xia; Yanmin Jia; Weiqi Qian; Xiaoli Xu; Zheng Wu; Zichen Han; Yuanting Hong; Huilin You; Muhammad Ismail; Ge Bai; Liwei Wang

2017-01-01

A pyro-electro-chemical catalytic dye decomposition using lead-free BaTiO3 nanofibers was realized under room-temperature cold–hot cycle excitation (30–47 °C) with a high Rhodamine B (RhB) decomposition efficiency ~99%, which should be ascribed to the product of pyro-electric effect and electrochemical redox reaction. Furthermore, the existence of intermediate product of hydroxyl radical in pyro-electro-chemical catalytic process was also observed. There is no significant decrease in pyro-ele...

Relationship between tolerance factor and temperature coefficient of permittivity of temperature-stable high permittivity BaTiO3–Bi(MeO3 compounds

Directory of Open Access Journals (Sweden)

Natthaphon Raengthon

2016-03-01

Full Text Available The temperature coefficient of permittivity (TCε of BaTiO3–Bi(MeO3 solid solutions were investigated. It was determined that as the tolerance factor was decreased with the addition of Bi(MeO3, the TCε shifted from large negative values to TCε values approaching zero. It is proposed that the different bonding nature of the dopant cation affects the magnitude and temperature stability of the permittivity. This study suggests that the relationship between tolerance factor and TCε can be used as a guide to design new dielectric compounds exhibiting temperature-stable high permittivity characteristics, which is similar to past research on perovskite and pyrochlore-based microwave dielectrics.

Fixation of Radioactive Strontium in Soil

DEFF Research Database (Denmark)

Gregers-Hansen, Birte

1964-01-01

of the other long-lived fission products. Much work2–5 has, therefore, been concerned with the possibility of bringing down the strontium-90 uptake by plants through ploughing or through the addition of lime or fertilizer to the soil. Another factor, the effect of ageing on the availability of strontium, has...... been considered6,7. In general, these methods appear to be of little practical value, except for deep ploughing and the liming of acid soils, both of which will reduce the strontium uptake by a factor of 3–4....

Titan through Time: Evolution of Titan's Atmosphere and its Hydrocarbon Cycle on the Surface

Science.gov (United States)

Gilliam, Ashley E.

The Introduction and Appendix i-A outline briefly the history of Titan exploration since its discovery by Christiaan Huygens in 1675 through the recent International Mission of Cassini-Huygens.. Chapter 1: This chapter discusses two possible pathways of loss of the two main gases from Titan's post-accretional atmosphere, methane (CH 4) and ammonia (NH3), by the mechanisms of thermal escape and emission from the interior coupled with thermal escape. Chapter 2: In this chapter, a simple photolysis model is created, where the second most abundant component of the present-day Titan atmosphere, methane (CH4), can either escape the atmosphere or undergo photolytic conversion to ethane (C2H6). Chapter 3: This chapter examines different fluvial features on Titan, identified by the Cassini spacecraft, and evaluates the possibilities of channel formation by two mechanisms: dissolution of ice by a concentrated solution of ammonium sulfate, and by mechanical erosion by flow of liquid ammonia and liquid ethane. Chapter 4: This chapter presents: (1) new explicit mathematical solutions of mixed 1st and 2nd order chemical reactions, represented by ordinary differential first-degree and Riccati equations; (2) the computed present-day concentrations of the three gases in Titan's scale atmosphere, treated as at near-steady state; and (3) an analysis of the reported and computed atmospheric concentrations of CH4, CH 3, and C2H6 on Titan, based on the reaction rate parameters of the species, the rate parameters taken as constants representative of their mean values. Chapter 5: This chapter examines the possible reactions of methane formation in terms of the thermodynamic relationships of the reactions that include pure carbon as graphite, the gases H2, CO2, H2 O, and serpentinization and magnetite formation from olivine fayalite. (Abstract shortened by ProQuest.).

Strontium sorption on Savannah River Plant soils

International Nuclear Information System (INIS)

Hoeffner, S.L.

1984-12-01

A laboratory study of strontium-85 sorption was conducted using Savannah River Plant soil and groundwater from the low-level waste burial ground. Systematic variation of soil and water composition indicates that strontium sorption is most strongly a function of pH. Changes in clay content and in K + , Ca 2+ , or Mg 2+ concentrations influence strontium sorption indirectly through the slight pH changes which result. The ions Na + , Cl - , and NO 3 - have no effect. Ferrous ion, added to groundwater to simulate the conditions of water at the bottom of waste trenches, did not account for low strontium sorption observed with some trench waters

Effect of elevated concentrations of strontium and iron on the structural and dielectric characteristics of Ba{sub (1-x-y)}Sr{sub (x)}Ti Fe{sub (y)}O{sub 3} prepared through sol-gel technique

Energy Technology Data Exchange (ETDEWEB)

Nur, Omer; Willander, Magnus; Israr, Muhammad Q. [Department of Science and Technology, Campus Norrkoeping, Linkoeping University, SE-60174, Norrkoeping (Sweden); Desouky, Fawzy G. El; Salem, Mohamed A.; Abou Hamad, Ali B. [National Research Center (NRC), Solid State Physics Department, Giza (Egypt); Battisha, Inas K., E-mail: szbasha@yahoo.com [National Research Center (NRC), Solid State Physics Department, Giza (Egypt)

2012-07-15

Nano-composite Ba{sub 1-x}Sr{sub (x)}TiO{sub 3} (BST), where x=0.01-0.50 and doped with different concentrations of iron Ba{sub (1-x-y)}Sr{sub (x)}TiFe {sub (y)}O{sub 3} (BSTF), where x=0.01 and y=0.01-0.05 powders were prepared by sol-gel method. The effect of increasing the iron and strontium concentrations substituted in Barium strontium titanate system will be studied. The prepared samples have a tetragonal crystalline phase after sintering for 1 h at 750 Degree-Sign C in air. The structural and the morphological features of the systems have been studied using X-ray diffraction (XRD), transmission electron microscope (TEM) and scanning electron microscope (SEM). The dielectric properties of the BST and BSTF systems have been investigated as a function of temperature and frequency. The dielectric measurements are carried out in the frequency range 42 Hz-1 MHz, at a temperature ranging between 25 and 250 Degree-Sign C. The results showed a decrease in T{sub c} temperature giving the following values 90 and 85 Degree-Sign C for B{sub 10}ST and B{sub 10}ST{sub 5}F prepared powder samples, respectively, implying tetragonal, feroelectric phase at lower temperature into cubic, para-electric phase at temperature higher than T{sub c}.

Poly[tetraaqua-μ3-pyridine-3,5-dicarboxylato-strontium(II

Directory of Open Access Journals (Sweden)

Shirin Daneshvar

2008-02-01

Full Text Available The reaction of strontium(II nitrate with the proton-transfer compound (pdaH2(py-3,5-dc·H2O (where pda = propane-1,3-diamine and py-3,5-dcH2 = pyridine-3,5-dicarboxylic acid leads to the formation of the title polymeric compound, [Sr(C7H3NO4(H2O4]n. The propane-1,3-diaminium cation is not incorporated in this crystal structure. The SrII atom lies on an inversion centre and is eight-coordinated by four O atoms from three py-3,5-dc ligands and four O atoms from four coordinated water molecules. The coordination polyhedron of the SrII atom is a distorted dodecahedron. These binuclear units are connected via the carboxylate O atoms to build a one-dimensional polymeric chain. In the crystal structure, non-covalant interactions consisting of hydrogen bonds (X—H...O, with X = O and C and π–π stacking interactions [3.4604 (19 Å] connect the various components to form a supramolecular structure.

Electrical and magnetic behavior of iron doped nickel titanate (Fe{sup 3+}/NiTiO{sub 3}) magnetic nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Lenin, Nayagam; Karthik, Arumugam; Sridharpanday, Mathu; Selvam, Mohanraj; Srither, Saturappan Ravisekaran; Arunmetha, Sundarmoorthy; Paramasivam, Palanisamy; Rajendran, Venkatachalam, E-mail: veerajendran@gmail.com

2016-01-01

Iron doped nickel titanate (Fe{sup 3+}/NiTiO{sub 3}) ferromagnetic nanoparticles with different concentrations of Fe (0.2, 0.4, and 0.6 mol) were synthesized using precipitation route with precursor source such as nickel nitrate and iron nitrate solutions. The prepared magnetic nanopowders were investigated through X-ray diffraction (XRD), Fourier transform infrared, scanning electron microscope, X-ray fluorescence, Brunauer–Emmett–Teller, vibrating sample magnetometer, and electrochemical impedance spectroscopy to explore the structural, ferromagnetic, and dielectric properties. The obtained XRD pattern shows formation of iron doped nickel titanate in orthorhombic structure. The crystallite size ranges from 57 to 21 nm and specific surface area ranges from 11 to 137 m{sup 2} g{sup −1}. The hysteresis loops of nanomagnetic materials show ferromagnetic behavior with higher magnitude of coercivity (H{sub c}) 867–462 Oe. The impedance analysis of ferromagnetic materials explores the ferro-dielectric behavior with enhanced properties of Fe{sup 3+}/NiTiO{sub 3} nanoparticles at higher Fe content. - Highlights: • Iron doped nickel titanate magnetic nanoparticles. • Ferromagnetic magnetism behavior with higher magnitude of coercivity. • Dielectric behavior of ferromagnetic nanoparticles with increase of Fe content.

Raman scattering intensities in BaTiO3 and PbTiO3 prototypical ferroelectrics from density functional theory

International Nuclear Information System (INIS)

Hermet, P; Veithen, M; Ghosez, Ph

2009-01-01

Nonlinear optical susceptibilities and Raman scattering spectra of the ferroelectric phases of BaTiO 3 and PbTiO 3 are computed using a first-principles approach based on density functional theory and taking advantage of a recent implementation based on the nonlinear response formalism and the 2n+1 theorem. These two prototypical ferroelectric compounds were chosen to demonstrate the accuracy of the Raman calculation based both on their complexity and their technological importance. The computation of the Raman scattering intensities has been performed not only for the transverse optical modes, but also for the longitudinal optical ones. The agreement between the measured and computed Raman spectra of these prototypical ferroelectrics is remarkable for both the frequency position and the intensity of Raman lines. This agreement presently demonstrates the state-of-the-art in the computation of Raman responses on one of the most complex systems, ferroelectrics, and constitutes a step forward in the reliable prediction of their electro-optical responses.

Some Aspects of the Failure Mechanisms in BaTiO3-Based Multilayer Ceramic Capacitors

Science.gov (United States)

Liu, David Donhang; Sampson, Michael J.

2012-01-01

The objective of this presentation is to gain insight into possible failure mechanisms in BaTiO3-based ceramic capacitors that may be associated with the reliability degradation that accompanies a reduction in dielectric thickness, as reported by Intel Corporation in 2010. The volumetric efficiency (microF/cm3) of a multilayer ceramic capacitor (MLCC) has been shown to not increase limitlessly due to the grain size effect on the dielectric constant of ferroelectric ceramic BaTiO3 material. The reliability of an MLCC has been discussed with respect to its structure. The MLCCs with higher numbers of dielectric layers will pose more challenges for the reliability of dielectric material, which is the case for most base-metal-electrode (BME) capacitors. A number of MLCCs manufactured using both precious-metal-electrode (PME) and BME technology, with 25 V rating and various chip sizes and capacitances, were tested at accelerated stress levels. Most of these MLCCs had a failure behavior with two mixed failure modes: the well-known rapid dielectric wearout, and so-called 'early failures." The two failure modes can be distinguished when the testing data were presented and normalized at use-level using a 2-parameter Weibull plot. The early failures had a slope parameter of Beta >1, indicating that the early failures are not infant mortalities. Early failures are triggered due to external electrical overstress and become dominant as dielectric layer thickness decreases, accompanied by a dramatic reduction in reliability. This indicates that early failures are the main cause of the reliability degradation in MLCCs as dielectric layer thickness decreases. All of the early failures are characterized by an avalanche-like breakdown leakage current. The failures have been attributed to the extrinsic minor construction defects introduced during fabrication of the capacitors. A reliability model including dielectric thickness and extrinsic defect feature size is proposed in this

Fabrication of Composite Filaments with High Dielectric Permittivity for Fused Deposition 3D Printing.

Science.gov (United States)

Wu, Yingwei; Isakov, Dmitry; Grant, Patrick S

2017-10-23

Additive manufacturing of complex structures with spatially varying electromagnetic properties can enable new applications in high-technology sectors such as communications and sensors. This work presents the fabrication method as well as microstructural and dielectric characterization of bespoke composite filaments for fused deposition modeling (FDM) 3D printing of microwave devices with a high relative dielectric permittivity ϵ = 11 in the GHz frequency range. The filament is composed of 32 vol % of ferroelectric barium titanate (BaTiO 3 ) micro-particles in a polymeric acrylonitrile butadiene styrene (ABS) matrix. An ionic organic ester surfactant was added during formulation to enhance the compatibility between the polymer and the BaTiO 3 . To promote reproducible and robust printability of the fabricated filament, and to promote plasticity, dibutyl phthalate was additionally used. The combined effect of 1 wt % surfactant and 5 wt % plasticizer resulted in a uniform, many hundreds of meters, continuous filament of commercial quality capable of many hours of uninterrupted 3D printing. We demonstrate the feasibility of using the high dielectric constant filament for 3D printing through the fabrication of a range of optical devices. The approach herein may be used as a guide for the successful fabrication of many types of composite filament with varying functions for a broad range of applications.

Vacancy-induced magnetism in BaTiO3(001) thin films based on density functional theory.

Science.gov (United States)

Cao, Dan; Cai, Meng-Qiu; Hu, Wang-Yu; Yu, Ping; Huang, Hai-Tao

2011-03-14

The origin of magnetism induced by vacancies on BaTiO(3)(001) surfaces is investigated systematically by first-principles calculations within density-functional theory. The calculated results show that O vacancy is responsible for the magnetism of the BaO-terminated surface and the magnetism of the TiO(2)-terminated surface is induced by Ti vacancy. For the BaO-terminated surface, the magnetism mainly arises from the unpaired electrons that are localized in the O vacancy basin. In contrast, for the TiO(2)-terminated surface, the magnetism mainly originates from the partially occupied O-2p states of the first nearest neighbor O atoms surrounding the Ti vacancy. These results suggest the possibility of implementing magneto-electric coupling in conventional ferroelectric materials.

3D hybrid simulation of the Titan's plasma environment

Science.gov (United States)

Lipatov, Alexander; Sittler, Edward, Jr.; Hartle, Richard

2007-11-01

Titan plays an important role as a simulation laboratory for multiscale kinetic plasma processes which are key processes in space and laboratory plasmas. A development of multiscale combined numerical methods allows us to use more realistic plasma models at Titan. In this report, we describe a Particle-Ion--Fluid-Ion--Fluid--Electron method of kinetic ion-neutral simulation code. This method takes into account charge-exchange and photoionization processes. The model of atmosphere of Titan was based on a paper by Sittler, Hartle, Vinas et al., [2005]. The background ions H^+, O^+ and pickup ions H2^+, CH4^+ and N2^+ are described in a kinetic approximation, where the electrons are approximated as a fluid. In this report we study the coupling between background ions and pickup ions on the multiple space scales determined by the ion gyroradiis. The first results of such a simulation of the dynamics of ions near Titan are discussed in this report and compared with recent measurements made by the Cassini Plasma Spectrometer (CAPS, [Hartle, Sittler et al., 2006]). E C Sittler Jr., R E Hartle, A F Vinas, R E Johnson, H T Smith and I Mueller-Wodarg, J. Geophys. Res., 110, A09302, 2005.R E Hartle, E C Sittler, F M Neubauer, R E Johnson, et al., Planet. Space Sci., 54, 1211, 2006.

Fabrication and Film Qualification of Sr Modified Pb(Ca) TiO3 Thin Films

International Nuclear Information System (INIS)

Naw Hla Myat San; Khin Aye Thwe; Than Than Win; Yin Maung Maung; Ko Ko Kyaw Soe

2011-12-01

Strontium and calcium - modified lead titanate (Pb0.7 Ca0.15 Sr0.15 ) TiO3 (PCST)thin films were prepared by using spin coating technique. Phase transition of PCST was interpreted by means of Er-T characteristics. Process temperature dependence on micro-structure of PCST film was studied. Charge conduction mechanism of PCST thin film was also investigated for film qualification.

A study on characteristic of selective membrane for strontium analysis

Energy Technology Data Exchange (ETDEWEB)

Moon, Seung Hyun; Choi, Young Woo [Kwang-ju Institute of Science and Technology, Kwangju (Korea)

1999-04-01

In this study, supported liquid membranes (SLMs) using crown ether were prepared in order to separate strontium ion selectively from a calcium contained solution However, at the higher than 3 N nitric acid concentration of a strip solution, stability of a SLM was declined remarkably owing to the hasty loss of carrier impregnated in supporter and, on account of this phenomena, facilitated transports were not accomplished. And DC18C6 as a neutral carrier affected remarkably the selectivity of strontium and the factor determining permeabilities of metal ions was as a role of DNNS. Consequently, in order to be a optimal SLM for the high permeability and the stable selectivity of strontium, concentration of DC18C6 and DNNS should be 0.1 M and 25 mM, respectively and, at this condition, the relative removal ratio of strontium to calcium was 93.3%. And the change of calcium concentration in the feed solution affected the permeability of strontium. In particular, when the ratio of strontium to calcium concentration in the feed solution was in the range of 1/5 - 1/50, strontium could be separated selectively at stable permeabilities. (author). 17 refs., 19 figs., 3 tabs.

Distribution of strontium in milk component

International Nuclear Information System (INIS)

Rosskopfova, O.; Galambos, M.; Rajec, P.

2011-01-01

The distribution of strontium between the milk components, i.e., serum, casein micelles, whey and hydroxyapatite was determined. The sorption on hydroxyapatite was investigated using batch method and radiotracer technique. The aqueous phase comprised of either milk or whey. The sorption of strontium on hydroxyapatite depended on the method of its preparation and on the composition of the aqueous phase. The sorption of strontium was increased with an increase of pH. The presence of citrate species resulted in decrease of the sorption of strontium on hydroxyapatite. The sorption of 85 Sr on hydroxyapatite decreased with the increasing concentration of Ca 2+ ions. Addition of Ca 2+ ions to milk resulted in milk pH decrease. The decrease in pH value after calcium addition to milk is related to exchanges between added calcium and micellar H + . The average value of strontium sorption on casein micelles in milk with presence of hydroxyapatite was (47.3 ± 5.6) %. The average value of sorption of 85 Sr on casein micelles in milk without the addition of hydroxyapatite was (68.9 ± 2.2) %. (author)

High-frequency dielectric spectroscopy of BaTiO3 core - silica shell nanocomposites: problem of interdiffusion

Czech Academy of Sciences Publication Activity Database

Nuzhnyy, Dmitry; Petzelt, Jan; Bovtun, Viktor; Kempa, Martin; Savinov, Maxim; Elissalde, C.; Chung, U.-C.; Michau, D.; Estournes, C.; Maglione, M.

2011-01-01

Roč. 1, č. 3 (2011), 309-317 ISSN 2010-135X R&D Projects: GA ČR GA202/09/0430 Institutional research plan: CEZ:AV0Z10100520 Keywords : core-shell nanocomposites * infrared and THz spectroscopy * barium titanate * effective medium approximation Subject RIV: BM - Solid Matter Physics ; Magnetism

Synthesis, structural characterization and dielectric properties of Nb doped BaTiO3/SiO2 core–shell heterostructure

International Nuclear Information System (INIS)

Cernea, M.; Vasile, B.S.; Boni, A.; Iuga, A.

2014-01-01

Highlights: • Optimal parameters for preparation by sol–gel of core–shell (BT-Nb 0.005 )/SiO 2 are presented in this paper. • Single crystalline BT-Nb 0.005 /SiO 2 core–shell composite with ∼34 nm shell thick was prepared. • The core–shell ceramic exhibits good dielectric properties and ferroelectric characteristics. -- Abstract: Perovskite complex ceramic oxides, BaTiO 3 doped with 0.5 mol%Nb 2 O 5 and then nanocoated with SiO 2 (abbreviated as BT-Nb 0.005 /SiO 2 ) was successful prepared using conventional sol–gel processing. Phase composition, particle morphology, structure, and electric properties of BT-Nb 0.005 core and BT-Nb 0.005 /SiO 2 core–shell were examined and compared, using X-ray diffraction, transmission electron microscopy and, dielectric and ferroelectric measurements. Core–shell composite with well-defined perovskite tetragonal phase of BaTiO 3 was achieved. Furthermore, single crystalline BT-Nb 0.005 /SiO 2 core–nanoshell heterostructure with ∼34 nm shell thick was prepared, which is a novelty in ferroelectrics field. The ferroelectric quality of BT-Nb 0.005 has suffered an alteration when the (BT-Nb 0.005 )/SiO 2 core–shell heterostructure was realized. One-dimensional BT-Nb 0.005 /SiO 2 core–shell heterostructure exhibits an improvement of dielectric losses and a decrease of dielectric constant, compared to uncoated BT-Nb 0.005 . The (BT-Nb 0.005 )/SiO 2 core–shell material could be interesting for application in the composite capacitors

Effects of calcium and magnesium on strontium distribution coefficients

Science.gov (United States)

Bunde, R.L.; Rosentreter, J.J.; Liszewski, M.J.; Hemming, C.H.; Welhan, J.

1997-01-01

The effects of calcium and magnesium on the distribution of strontium between a surficial sediment and simulated wastewater solutions were measured as part of an investigation to determine strontium transport properties of surficial sediment at the Idaho National Engineering Laboratory (INEL), Idaho. The investigation was conducted by the U.S. Geological Survey and Idaho State University, in cooperation with the U.S. Department of Energy. Batch experimental techniques were used to determine strontium linear sorption isotherms and distribution coefficients (K(d)'s) using simulated wastewater solutions prepared at pH 8.0??0.1 with variable concentrations of calcium and magnesium. Strontium linear sorption isotherm K(d)'s ranged from 12??1 to 85??3 ml/g, increasing as the concentration of calcium and magnesium decreased. The concentration of sorbed strontium and the percentage of strontium retained by the sediment were correlated to aqueous concentrations of strontium, calcium, and magnesium. The effect of these cation concentrations on strontium sorption was quantified using multivariate least-squares regression techniques. Analysis of data from these experiments indicates that increased concentrations of calcium and magnesium in wastewater discharged to waste disposal ponds at the INEL increases the availability of strontium for transport beneath the ponds by decreasing strontium sorption to the surficial sediment.

Maintenance procedures for the TITAN-I and TITAN-II reversed field pinch reactors

International Nuclear Information System (INIS)

Grotz, S.P.; Duggan, W.; Krakowski, R.; Najmabadi, F.; Wong, C.P.C.

1989-01-01

The TITAN reactor is a compact, high-power-density (neutron wall loading 18 MW/m 2 ) machine, based on the reversed-field-pinch (RFP) confinement concept. Two designs for the fusion power core have been examined: TITAN-I is based on a self-cooled lithium loop with a vanadium-alloy structure for the first wall, blanket and shield; and TITAN-II is based on an aqueous loop-in-pool design with a LiNO 3 solution as the coolant and breeder. The compact design of the TITAN fusion power core, (FPC) reduces the system to a few small and relatively low mass components, making toroidal segmentation of the FPC unnecessary. A single-piece maintenance procedure is possible. The potential advantages of single-piece maintenance procedures are: (1) Short period of down time; (2) improved reliability; (3) no adverse effects resulting from unequal levels of irradiation; and (4) ability to continually modify the FPC design. Increased availability can be expected from a fully pre-tested, single-piece FPC. Pre-testing of the FPC throughout the assembly process and prior to installation into the reactor vault is discussed. (orig.)

Modelização e estudo experimental de óxidos multiferróicos

CERN Document Server

Fenta, Abel

The main goal of this work was the theoretical and experimental study of multiferroics oxides. This particular approach focused mainly on the ferroelectric material barium titanate. The essence of this theoretical study is the ab initio calculation of hiperfine parameters using the Wien2k software. This software, which uses the selfconsistent $LAPW$ method to solve the Kohn-Sham equations, allowed to determine the electric field gradient and the BaTiO$_3$ system’s total energy in its different structural phases, and study its behaviour in function of the different lattice parameters. The modeling of stratified systems of the (XTiO$_3$).(BaTiO$_3$)$_{n-1}$ and (BaZO$_3$).(BaTiO$_3$ )$_{n-1}$, with X=Cd and Hg and Z=Fe, from n=2 to n=6 type, built from the experimental latice parameters (formula) in the tetragonal sage was also made. This simulation can be related to the physical situation of the epitaxial growth of XTiO$_3$ a layer on n BaTiO$_3$ layers. It was also studied the effect of the Cd ion volume di...

Uptake behavior of titanium molybdophosphate for cesium and strontium

International Nuclear Information System (INIS)

Yavari, R.; Ahmadi, S.J.; Huang, Y.D.

2010-01-01

This study investigates uptake of cesium and strontium from aqueous solution similar to nuclear waste on three samples of titanium molybdophosphate (TMP) synthesized under various conditions. Effects of concentration of sodium nitrate, pH and contact time on the uptake of cesium and strontium have been studied by bath method. The results showed that TMP has high affinity toward cesium and strontium at pH > 2 and relatively low concentration of sodium nitrate. Kinetic data indicated that cesium uptake process to achieve equilibrium was faster than strontium. Cesium and strontium breakthrough curves were examined at 25 deg C using column packed with H 3 O + form of TMP and breakthrough curves showed symmetrical S-shaped profiles. At the same time, the calculated breakthrough capacity for cesium was higher than strontium. The results of desorption studies showed that over 99% of cesium and strontium was washed out of column by using 4 M NH 4 Cl solution. This study suggests that TMP can have great potential applications for the removal of strontium and specially cesium from nuclear waste solution. (author)

Simulating the Transfer of Strontium-90 from Soil to Leafy Vegetables by Using Strontium-88.

Science.gov (United States)

Kuke, Ding; Shujuan, Liu; Yingxue, He; Dong, Yan; Fengshou, Zhang; Shuifeng, Wang; Jinghua, Guo; Wei, Zhang; Xin, Wang; Xiaoyan, Jiang

The transfer, from soil to Chinese cabbage and spinach, of radioactive strontium-90 released as a result of accidents in nuclear power stations was studied using a stable isotope of strontium, namely nuclide strontium-88 ( 88 Sr). The study led to an experimental model for assessing the hazard of radionuclide strontium-90 ( 90 Sr) entering the food chain and for predicting the risk to food safety. Chinese cabbage and spinach were grown in pots in a greenhouse and irrigated with deionized water containing known quantities of strontium. Based on the strontium content of that water, the plants were divided into five groups (treatments) and strontium content of the soil, and 30-day-old plants were determined by inductively coupled plasma atomic emission spectroscopy instrument (ICP-AES). Data on the strontium content of soil and plants enabled the development of a model using MATLAB, a mathematical software package, which included curve fitting and problem solving using regression equations and differential equations. Although strontium curves for leaves, stems, and roots of Chinese cabbage were not exactly the same, all showed a non-linear increase when compared with the increase in the content of strontium in soil. Strontium curves for leaves, stems, and roots of spinach were very similar and showed an initial increase followed by a decrease. Strontium concentrations in both Chinese cabbage and spinach were initially related to the concentrations of sodium and sulfur, the next two relevant nuclides being calcium and magnesium. The relationship between calcium and strontium in Chinese cabbage was different from that in spinach. By using 88 Sr to simulate the transfer of radionuclide 90 Sr from soil to a crop, the relevant data required to deal with accidental release of strontium can be obtained using a fitting curve and regression equations, thereby providing some experimental basis for evaluating the potential hazards posed by such accidents to the food chain.

MP3 - A Meteorology and Physical Properties Package for Titan Air-Sea Studies

Science.gov (United States)

Lorenz, R. D.; Stofan, E.; Lunine, J. I.; Zarnecki, J. C.; Harri, A.-M.; Karkoschka, E.; Newman, C. E.; Bierhaus, E. B.; Clark, B. C.; Yelland, M.; Leese, M. R.; Boldt, J.; Darlington, E.; Neish, C. D.; Sotzen, K.; Arvelo, J.; Rasbach, C.; Kretsch, W.; Strohbehn, K.; Grey, M.; Mann, J.; Zimmerman, H.; Reed, C.

2012-10-01

MP3 is a sensor suite for the proposed Titan Mare Explorer (TiME) Discovery mission to Ligeia Mare. MP3 will measure temperatures, and wind velocity, methane humidity, and pressure, as well as sea turbidity, dielectric properties, and depth via sonar.

Improving dielectric properties of BaTiO_3/poly(vinylidene fluoride) composites by employing core-shell structured BaTiO_3@Poly(methylmethacrylate) and BaTiO_3@Poly(trifluoroethyl methacrylate) nanoparticles

International Nuclear Information System (INIS)

Zhang, Xianhong; Zhao, Sidi; Wang, Fang; Ma, Yuhong; Wang, Li; Chen, Dong; Zhao, Changwen; Yang, Wantai

2017-01-01

Highlights: • Core-shell structured BT@PMMA and BT@PTFEMA nanoparticles were synthesized. • The dispersity of BT nanoparticles in PVDF matrix was improved significantly. • Dielectric properties both of BT@PMMA/PVDF and BT@PTFEMA/PVDF composites were improved. • The frequency dependence of dielectric constant attenuation of BT@PTFEMA/PVDF composites was smaller than that of BT@PMMA/PVDF composites. - Abstract: Polymer based dielectric composites were fabricated through incorporation of core-shell structured BaTiO_3 (BT) nanoparticles into PVDF matrix by means of solution blending. Core-shell structured BT nanoparticles with different shell composition and shell thickness were prepared by grafting methacrylate monomer (MMA or TFEMA) onto the surface of BT nanoparticles via surface initiated atom transfer radical polymerization (SI-ATRP). The content of the grafted polymer and the micro-morphology of the core-shell structured BT nanoparticles were investigated by thermo gravimetric analyses (TGA) and transmission electron microscopy (TEM), respectively. The dielectric properties were measured by broadband dielectric spectroscopy. The results showed that high dielectric constant and low dielectric loss are successfully realized in the polymer based composites. Moreover, the type of the grafted polymer and its content had different effect on the dielectric constant. In detail, the attenuation of dielectric constant was 16.6% for BT@PMMA1/PVDF and 10.7% for BT@PMMA2/PVDF composite in the range of 10 Hz to 100 kHz, in which the grafted content of PMMA was 5.5% and 8.0%, respectively. However, the attenuation of dielectric constant was 5.5% for BT@PTFEMA1/PVDF and 4.0% for BT@PTFEMA2/PVDF composite, in which the grafted content of PTFEMA was 1.5% and 2.0%, respectively. These attractive features of BT@PTFEMA/PVDF composites suggested that dielectric ceramic fillers modified with fluorinated polymer can be used to prepare high performance composites, especially

Isotope exchange of strontium and molybdate ions in strontium polymolybdates

International Nuclear Information System (INIS)

Atun, G.

2002-01-01

The heterogeneous isotopic exchange reactions in strontium polymolybdates of Sr 2+ and MoO 4 2- ions in the strontium nitrate and sodium molybdate solutions have been studied using 90 Sr and 99 Mo as tracers. Electrometric methods have been used to study the compositions of strontium molybdates obtained by adding strontium chloride to a progressively acidified solution of sodium molybdate. It has been found that the exchange fraction increases with increasing chain length of strontium polymolybdate. The exchange equilibrium constant (K ex ) has been calculated between 298 and 348 K as well as ΔG deg, ΔH deg and ΔS deg. The results indicate that Sr 2+ cations have a much higher affinity for exchangers than MoO 4 2- anions. By fitting the data to the Dubinin-Radushkevich (D-R) isotherm it has been shown that the exchange capacity (X m ) for both ions is affected by the ion adsorption process at low temperatures and by the ion exchange process at high temperatures. At high concentrations, the recrystallization process contributes to on the cation exchange but is ineffective on the anion exchange mechanism. (author)

Rheology Of MonoSodium Titanate (MST) And Modified Mst (mMST) Mixtures Relevant To The Salt Waste Processing Facility

Energy Technology Data Exchange (ETDEWEB)

Koopman, D. C.; Martino, C. J.; Shehee, T. C.; Poirier, M. R.

2013-07-31

The Savannah River National Laboratory performed measurements of the rheology of suspensions and settled layers of treated material applicable to the Savannah River Site Salt Waste Processing Facility. Suspended solids mixtures included monosodium titanate (MST) or modified MST (mMST) at various solid concentrations and soluble ion concentrations with and without the inclusion of kaolin clay or simulated sludge. Layers of settled solids were MST/sludge or mMST/sludge mixtures, either with or without sorbed strontium, over a range of initial solids concentrations, soluble ion concentrations, and settling times.

Rheology Of MonoSodium Titanate (MST) And Modified Mst (mMST) Mixtures Relevant To The Salt Waste Processing Facility

International Nuclear Information System (INIS)

Koopman, D. C.; Martino, C. J.; Shehee, T. C.; Poirier, M. R.

2013-01-01

The Savannah River National Laboratory performed measurements of the rheology of suspensions and settled layers of treated material applicable to the Savannah River Site Salt Waste Processing Facility. Suspended solids mixtures included monosodium titanate (MST) or modified MST (mMST) at various solid concentrations and soluble ion concentrations with and without the inclusion of kaolin clay or simulated sludge. Layers of settled solids were MST/sludge or mMST/sludge mixtures, either with or without sorbed strontium, over a range of initial solids concentrations, soluble ion concentrations, and settling times

Lead titanate nanotubes synthesized via ion-exchange method: Characteristics and formation mechanism

International Nuclear Information System (INIS)

Song Liang; Cao Lixin; Li Jingyu; Liu Wei; Zhang Fen; Zhu Lin; Su Ge

2011-01-01

Highlights: → Lead titanate nanotubes PbTi 3 O 7 were firstly synthesized by ion-exchange method. → Sodium titanate nanotubes have ion exchangeability. → Lead titanate nanotubes show a distinct red shift on absorption edge. - Abstract: A two-step method is presented for the synthesis of one dimensional lead titanate (PbTi 3 O 7 ) nanotubes. Firstly, titanate nanotubes were prepared by an alkaline hydrothermal process with TiO 2 nanopowder as precursor, and then lead titanate nanotubes were formed through an ion-exchange reaction. We found that sodium titanate nanotubes have ion exchangeability with lead ions, while protonated titanate nanotubes have not. For the first time, we distinguished the difference between sodium titanate nanotubes and protonated titanate nanotubes in the ion-exchange process, which reveals a layer space effect of nanotubes in the ion-exchange reaction. In comparison with sodium titanate, the synthesized lead titanate nanotubes show a narrowed bandgap.

High-resolution stratigraphy with strontium isotopes.

Science.gov (United States)

Depaolo, D J; Ingram, B L

1985-02-22

The isotopic ratio of strontium-87 to strontium-86 shows no detectable variation in present-day ocean water but changes slowly over millions of years. The strontium contained in carbonate shells of marine organisms records the ratio of strontium-87 to strontium-86 of the oceans at the time that the shells form. Sedimentary rocks composed of accumulated fossil carbonate shells can be dated and correlated with the use of high precision measurements of the ratio of strontium-87 to strontium-86 with a resolution that is similar to that of other techniques used in age correlation. This method may prove valuable for many geological, paleontological, paleooceanographic, and geochemical problems.

Effect of working pressure and annealing temperature on ...

Indian Academy of Sciences (India)

roughness was found at higher temperatures as a result of a more heterogeneous growth and less tensions. Keywords. Barium strontium titanate; thin film; pulsed laser deposition; ferroelectric. 1. Introduction. Perovskite barium strontium titanate (BST) thin films are promising candidates for dynamic random access memory.

Isotherms of ion exchange on titanates of alkaline metals

International Nuclear Information System (INIS)

Fillina, L.P.; Belinskaya, F.A.

1986-01-01

Present article is devoted to isotherms of ion exchange on titanates of alkaline metals. Therefore, finely dispersed hydrated titanates of alkaline metals (lithium, sodium, potassium) with ion exchange properties are obtained by means of alkaline hydrolysis of titanium chloride at high ph rates. Sorption of cations from salts solution of Li 2 SO 4 , NaNO 3 , Ca(NO 3 ) 2 , AgNO 3 by titanates is studied.

Rubidium-strontium method

International Nuclear Information System (INIS)

Dubansky, A.

1980-01-01

The rubidium-strontium geological dating method is based on the determination of the Rb and Sr isotope ratio in rocks, mainly using mass spectrometry. The method is only practical for silicate minerals and rocks, potassium feldspars and slates. Also described is the rubidium-strontium isochrone method. This, however, requires a significant amount of experimental data and an analysis of large quantities of samples, often of the order of tons. The results are tabulated of rubidium-strontium dating of geological formations in the Czech Socialist Republic. (M.S.)

Modified cermet fuel electrodes for solid oxide electrochemical cells

Science.gov (United States)

Ruka, Roswell J.; Spengler, Charles J.

1991-01-01

An exterior porous electrode (10), bonded to a solid oxygen ion conducting electrolyte (13) which is in contact with an interior electrode (14), contains coarse metal particles (12) of nickel and/or cobalt, having diameters from 3 micrometers to 35 micrometers, where the coarse particles are coated with a separate, porous, multiphase layer (17) containing fine metal particles of nickel and/or cobalt (18), having diameters from 0.05 micrometers to 1.75 micrometers and conductive oxide (19) selected from cerium oxide, doped cerium oxide, strontium titanate, doped strontium titanate and mixtures thereof.

Kinetics of isotopic exchange between strontium polymolybdate and strontium ions in aqueous solution

International Nuclear Information System (INIS)

Atun, Gulten; Bilgin, Binay; Kilislioglu, Ayben

2002-01-01

A heterogeneous isotopic exchange reaction of strontium polymolybdate in strontium chloride solution was studied using 90 Sr as a tracer. The effects of low and high strontium chloride concentration on the rate and mechanism of the isotopic exchange reaction were investigated. It was found that, at high concentrations, the rate is independent of strontium concentration, but, at low concentrations, the rate is proportional to the strontium concentration. These results support a hypothesis that, at low concentrations, the rate is controlled by film diffusion, whereas at high concentrations it is controlled by particle diffusion. Experiments were performed at 293, 303 and 313 K. Activation energy of isotopic exchange reaction and thermodynamic parameters ΔH*, ΔS*, and ΔG* were calculated using the Arrhenius and Eyring equations. The results also indicated that recrystallization is a predominant factor in the present exchange reaction

Kinetics of isotopic exchange between strontium polymolybdate and strontium ions in aqueous solution

Energy Technology Data Exchange (ETDEWEB)

Atun, Gulten E-mail: gultena@istanbul.edu.tr; Bilgin, Binay; Kilislioglu, Ayben

2002-06-01

A heterogeneous isotopic exchange reaction of strontium polymolybdate in strontium chloride solution was studied using {sup 90}Sr as a tracer. The effects of low and high strontium chloride concentration on the rate and mechanism of the isotopic exchange reaction were investigated. It was found that, at high concentrations, the rate is independent of strontium concentration, but, at low concentrations, the rate is proportional to the strontium concentration. These results support a hypothesis that, at low concentrations, the rate is controlled by film diffusion, whereas at high concentrations it is controlled by particle diffusion. Experiments were performed at 293, 303 and 313 K. Activation energy of isotopic exchange reaction and thermodynamic parameters {delta}H*, {delta}S*, and {delta}G* were calculated using the Arrhenius and Eyring equations. The results also indicated that recrystallization is a predominant factor in the present exchange reaction.

Dielectric Properties of Sol-Gel Derived Barium Strontium Titanate and Microwave Sintering of Ceramics

Science.gov (United States)

Selmi, Fathi A.

This thesis consists of two areas of research: (1) sol-gel processing of Ba_{rm 1-x}Sr_{rm x} TiO_3 ceramics and their dielectric properties measurement; and (2) microwave versus conventional sintering of ceramics such as Al_2 O_3, Ba_{ rm 1-x}Sr_{rm x}TiO_3, Sb-doped SnO _2 and YBa_2Cu _3O_7. Sol-gel powders of BaTiO_3, SrTiO_3, and their solid solutions were synthesized by the hydrolysis of titanium isopropoxide and Ba and Sr methoxyethoxides. The loss tangent and dielectric constant of both sol-gel and conventionally prepared and sintered Ba_{rm 1-x}Sr _{rm x}TiO _3 ceramics were investigated at high frequencies. The sol-gel prepared ceramics showed higher dielectric constant and lower loss compared to those prepared conventionally. Ba _{rm 1-x}Sr _{rm x}TiO_3 ceramics were tunable with applied bias, indicating the potential use of this material for phase shifter applications. Porous Ba_{0.65}Sr _{0.35}TiO_3 was also investigated to lower the dielectric constant. Microwave sintering of alpha -Al_2O_3 and SrTiO_3 was investigated using an ordinary kitchen microwave oven (2.45 GHz; 600 Watts). The use of microwaves with good insulation of alpha -Al_2O_3 and SrTiO_3 samples resulted in their rapid sintering with good final densities of 96 and 98% of the theoretical density, respectively. A comparison of grain size for conventionally and microwave sintered SrTiO_3 samples did not show a noticeable difference. However, the grain size of microwave sintered alpha-Al_2O _3 was found to be larger than that of conventionally sintered sample. These results show that rapid sintering of ceramics can be achieved by using microwave radiation. The sintering behavior of coprecipitated Sb-doped SnO_2 was investigated using microwave power absorption. With microwave power, samples were sintered at 1450^circC for 20 minutes and showed a density as high as 99.9% of theoretical. However, samples fired in a conventional electric furnace at the same temperature for 4 hours showed only

A combined cesium-strontium extraction/recovery process

International Nuclear Information System (INIS)

Horwitz, E.P.; Dietz, M.L.; Jensen, M.P.

1996-01-01

A new solvent extraction process for the simultaneous extraction of cesium and strontium from acidic nitrate media is described. This process uses a solvent formulation comprised of 0.05 M di-t-butylcyclohexano-18-crown-6 (DtBuCH18C6), 0.1 M Crown 100' (a proprietary, cesium-selective derivative of dibenzo-18-crown-6), 1.2 M tributyl phosphate (TBP), and 5% (v/v) lauryl nitrile in an isoparaffinic hydrocarbon diluent. Distribution ratios for cesium and strontium from 4 M nitric acid are 4.13 and 3.46, respectively. A benchtop batch countercurrent extraction experiment indicates that >98% of the cesium and strontium initially present in the feed solution can be removed in only four extraction stages. Through proper choice of extraction and strip conditions, extracted cesium and strontium can be recovered either together or individually

Measurement of strontium-89 and strontium-90 in environmental waters. A tentative reference method

International Nuclear Information System (INIS)

1976-03-01

A tentative reference method for the measurement of 89 Sr and 90 Sr in environmental waters is described. Samples of environmental water sources are collected, preserved with acid-strontium carrier, and analyzed for 89 Sr and/or 90 Sr. The isotopes are separated from the sample water by precipitating with stable strontium carrier as carbonate. The strontium carbonate is dissolved, 90 Sr separated, the strontium reprecipitated as carbonate, filtered, and counted for the combined 89 Sr and 90 Sr activity. The 90 y is allowed to grow in from the 90 y activity; the strontium carbonate is redissolved; the 90 y is separated, precipitated, and counted for the 90 Sr determination. The 89 Sr activity is then determined by difference of the total 89 Sr and 90 y and the separate 90 Sr activities. Recoveries are determined from the added and found (recovered) strontium carrier. Counting efficiencies are determined with prepared standard reference samples. Results are reported in pCi/liter

Nanocomposite multilayer capacitors comprising BaTiO3@TiO2 and poly(vinylidene fluoride-hexafluoropropylene for dielectric-based energy storage

Directory of Open Access Journals (Sweden)

Mojtaba Rahimabady

2014-04-01

Full Text Available Multilayer dielectric capacitors were fabricated from nanocomposite precursor comprised of BaTiO3@TiO2 core–shell nanosized particles and poly(vinylidene fluoride–hexafluoropropylene (P(VDF–HFP polymer matrix (20 vol%. The multilayer capacitors showed very high discharge speed and high discharged energy density of around 2.5 J/cm3 at its breakdown field (~ 166 MV/m. The energy density of the nanocomposite multilayer capacitors was substantially higher than the energy density of commercially used power capacitors. Low cost, flexible structure, high discharge rate and energy density suggest that the nanocomposite multilayer capacitors are promising for energy storage applications in many power devices and systems.

Barium titanate coated with magnesium titanate via fused salt method and its dielectric property

International Nuclear Information System (INIS)

Chen Renzheng; Cui Aili; Wang Xiaohui; Li Longtu

2003-01-01

Barium titanate fine particles were coated homogeneously with magnesium titanate via the fused salt method. The thickness of the magnesium titanate film is 20 nm, as verified by TEM and XRD. The mechanism of the coating is that: when magnesium chloride is liquated in 800 deg. C, magnesium will replace barium in barium titanate, and form magnesium titanate film on the surface of barium titanate particles. Ceramics sintered from the coated particles show improved high frequency ability. The dielectric constant is about 130 at the frequency from 1 to 800 MHz

Flame Spectrophotometric Determination of Strontium in Water and Biological Material

Energy Technology Data Exchange (ETDEWEB)

Joensson, G

1964-10-15

A flame spectrophotometric method has been developed for the determination of strontium in biological material and water samples. Strontium is determined in the presence of calcium at a wavelength of 4607 A. The intensity of the strontium emission from the sample is increased if n-butanol is added to a solution of the sample in water. With a 6 vol% solution of n-butanol in water, an optimum intensity of 3.5 times that obtained with pure water solution is obtained. Anions and alkali metals which might interfere with the flame spectrophotometric determination are separated from the sample by a simple ion exchange operation. The method allows determination of strontium in solutions down to 0.1{mu}g/ml. In this case the standard deviation is 3.1 % and with a strontium concentration of 1 {mu}g/ml the deviation is 0.9 %. This method has been used for the determination of strontium in samples of varying composition such as bone, meat and skin from fishes, samples of human bones, shell-fish, milk, and water, in which case Sr quantities of 5{mu}g were determined with an analytical error of less than 5 % and Sr{sub q}uantities greater than 10 {mu}g with an error of less than 3 %.