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Papers by Keyword: Barium Strontium Titanate

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Preparation of the Barium Strontium Titanate/Magnesium Oxide Plates by Non-Aqueous Gel-Casting

Authors: Chun Rong Jiao, Da Ming Chen, Jian Feng Tong

Abstract: Barium strontium titanate/magnesium oxide composite ceramic plates were prepared by non-aqueous gel-casting using barium strontium titanate and MgO as the raw materials. The rheological properties of the non-aqueous slurries, the dosages of the catalyst and initiator, micro structures and phase structures of the sintering ceramic plates were investigated and analyzed. The results showed that the slurry with solid content of 50wt% in non-aqueous gel-casting had excellent rheological properties and operating characteristics. Ba0.6Sr0.4TiO3/MgO plates with a smooth surface and dense structure were fabricated through desiccation and sintering at 1300°C, and the relative density is up to 4.14g/cm3. The polished surface of the ceramic substrate was composed of 35% MgO and 65% Ba0.6Sr0.4TiO3, and the content of Ba0.6Sr0.4TiO3 was obviously higher compared to the content in the raw materials which was explained by the phenomena of surface phase enrichment.

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Behavior of Hydrogen Atoms in Perovskite-Type Oxide Thin Films under Electric Fields

Authors: Kentaro Morito, Toshimasa Suzuki, Youichi Mizuno, Isao Sakaguchi, Naoki Ohashi, Kenji Matsumoto, Hajime Haneda

Abstract: The behavior of hydrogen in (Ba,Sr)TiO3 (BST) thin film capacitors under electric fields was investigated by performing secondary ion mass spectroscopy (SIMS) analyses. It was clearly observed that the ingress of atmospheric hydrogen into BST thin film capacitors occurred through the anode and that it diffused toward the cathode under electric fields. In addition, it was found that the deterioration of the I-V properties of the BST thin film capacitors can be interpreted in terms of the distribution of hydrogen concentration in the BST thin films.

281

Wide Range Dielectric Spectroscopy of Barium Strontium Titanate Ceramics

Authors: Takashi Teranishi, Takuya Hoshina, Hiroaki Takeda, Takaaki Tsurumi

Abstract: Wide band dielectric spectroscopy was applied from kHz to THz region for the analysis of both the ionic and the dipole polarization in Ba0.6Sr0.4TiO3 ceramics. The dielectric permittivity above the dielectric maximum temperature (Tm) is mostly dominated by the ionic polarization, while that below Tm is governed by the dipole polarization. Dielectric permittivity given by the dipole polarization increased and the relaxation frequency decreased with decreasing temperature. These phenomena are related to a increase of the size of polar nanoregions (PNRs).

273

Study on Barium Strontium Titanate Thin Films Integrated on Si Substrates by Laser Molecular Beam Epitaxy

Authors: X.Y. Zhou, Yun Zhou, G.Y. Wang, Y. Wang, Helen Lai Wah Chan, C.L. Choy, Guo Zhong Cao

Abstract: (Ba,Sr)TiO3 thin film has been deposited on Si (001) wafer with the SiO2 layer as the block layer through laser molecular-beam epitaxy using an ultra thin Sr layer as template. X-ray diffraction measurements and the cross-sectional observations under transmission electron microscope indicated that BST was well crystallized. This deposition of Sr layer is considered to remove the thin SiO2 layer to produce a layer, which is crystallized and has a lattice structure matching with that of perovskite BST. The maximum in-plane dielectric tunability is calculated to be 50% at 1 GHz under a moderate DC bias field of 13.3 V/µm. This BST/Si structure is believed to be a promising candidate in the development of ferroelectric BST-based microwave devices.

823

Influence of Hydrogen Atoms on Electrical Properties of BST Thin Film Capacitors

Authors: Kentaro Morito, Toshimasa Suzuki, Youichi Mizuno, Isao Sakaguchi, Naoki Ohashi, Hajime Haneda

Abstract: The relationship between the distribution of hydrogen and the electrical properties of (Ba, Sr)TiO3 (BST) thin film capacitors was investigated using secondary ion mass spectroscopy (SIMS) analyses. It has been clearly shown that there is a close relationship between the hydrogen distribution in BST thin film and the frequency dependence of the complex impedance of the BST thin film capacitors. It was confirmed that protons, the interstitial hydrogen impurity dissolved in BST thin films annealed at 400oC, were produced by a thermal equilibrium reaction between the hydrogen in the annealing atmosphere and the BST thin films.

167

Preparation of Barium Strontium Titanate Ceramics via Combustion Method

Authors: Theerachai Bongkarn, C. Wicheanrat

Abstract: This study concentrated on the crystal structure and microstructure of [(Ba0.75Sr0.25)TiO3; (BST)] ceramics at different firing temperatures. The BST powders were prepared by a combustion method. (CO(NH2)2) was used as a fuel. Crystallinity of the calcined powders was improved by increasing the calcining temperature, as indicated by the increase in intensity of the X-ray diffraction peak. The pure perovskite phase of BST powders was obtained with a calcinations condition of 1200 oC. The a axis lattice constant of BST calcined powders and sintered ceramics were calculated and it was found that the crystal structure is a cubic phase. The microstructure of BST calcined powders and sintered ceramics were analyzed by a scanning electron microscope (SEM). The SEM result indicated that the average particle size and average grain size increased with the increase of calcinations and sintering temperatures, respectively. The apparent density of the samples was measured by the Archimedes method.

185

X-Ray Absorption Spectroscopy Study of Ba_1-xSr_xTiO₃(x = 0.0-0.2) at the Ti-K and Ba-L_III Edges

Authors: W. Somphon, Suthum Srilomsak

Abstract: Barium titanate, BaTiO3 is a significant material for electronic components. It was known that Sr2+ substitution on Ba ion can strongly modify ferroelectric properties of BaTiO3 but the structural change has not been fully understood. An X-ray absorption spectroscopy at the Ti K-edge (4966 eV) and the Ba LIII-edge (5247 eV) was employed to investigate the structure of Ba1-xSrxTiO3 (BSTO) with 0

157

Porous Barium Strontium Titanate-Titania Nanocomposites for Photocatalytic Applications

Authors: Guo Ge Zhang, Hai Tao Huang, Helen Lai Wah Chan, Li Min Zhou

Abstract: Porous barium strontium titanate−titania (BST−TiO2) nanocomposite was developed by the combination of electrochemical anodization and hydrothermal synthesis. Self organized titania nanotube arrays were first fabricated by electrochemical anodization of titanium foil in 0.2 wt.% HF. The as-anodized titania was then used as a template and was subject to a hydrothermal treatment in the solution mixture of barium hydroxide and strontium hydroxide with different molar ratios. Well crystallized barium strontium titanate was developed directly from the titania nanotubes. Annealing was carried out to transform residual amorphous titania to crystallized anatase, resulting in the porous BST−TiO2 nanocomposite. The surface morphology and structure of the nanocomposite were characterized. The photoelectrochemical response of the BST−TiO2 composite was investigated and the photocatalytic property was evaluated through the photo-decomposition of an organic dye solution. The effect of hydrothermal parameters on the surface morphology and the photocatalytic activity of the nanocomposite was studied.

936

Synthesis and Properties of Barium Strontium Titanate Thin Films on Copper Foils

Authors: Yan Hua Fan, Shu Hui Yu, Rong Sun, Lei Li, Ruxu Du, Yan Sheng Yin, Ying Bang Yao

Abstract: Ba0.7Sr0.3TiO3 thin films with a thickness of 300~900 nm were prepared with sol-gel method directly on the copper foils. The films have been processed in almost inert atmosphere such that the oxidation of Cu foil was avoided while allowing the film to crystallize. The crystal structure, morphology and dielectric properties of the films were measured and analyzed. The effects of annealing temperatures and film thickness on the electrical properties were discussed.

562

Microstructure and Dielectric Properties of Ba_0.5Sr_0.5TiO₃ Ceramics by Spark Plasma Sintering

Authors: Chun Lai Xu, He Ping Zhou

Abstract: Ba0.5Sr0.5TiO3 (BSTO) ceramics were synthesized by spark plasma sintering (SPS) technique. The phase compositions, microstructure and dielectric properties of BSTO ceramics were investigated. The results indicated that SPS was an alternative sintering technology to synthesize dense BSTO ferroelectric ceramics at low temperature and in a short period.