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Strontium Titanate (strontium + titanate)
Kinds of Strontium Titanate Selected Abstracts{111} Twin Formation and Abnormal Grain Growth in Barium Strontium TitanateJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 1 2003Byoung-Ki Lee Two series of experiments were performed to study the experimental conditions for the formation of {111} twins and related microstructures in barium strontium titanate ((Ba, Sr)TiO3). In the first series, the phase equilibria in the BaTiO3,SrTiO3,TiO2 system were determined. XRD and WDS analysis, done in the BaTiO3 -rich region, of 45(Ba,Sr)TiO3,10TiO2 samples annealed at 1250°C for 200 h in air showed that (Ba,Sr)TiO3 was in equilibrium with Ba6Ti17O40 (B6T17) and Ba4Ti13O30 phases with strontium solubility (Sr/(Ba + Sr)) of ,0.02 and 0.20, respectively. In the second series the microstructures of samples consisting of a mixture of (Ba,Sr)TiO3 and 2.0 mol% TiO2, were observed after sintering at 1250°C for 100 h in air. {111} twins formed only in the samples with faceted B6T17 second phase particles, similar to the case of BaTiO3. In these samples, abnormal grain growth occurred in the presence of the {111} twins. In contrast, no {111} twins formed and no abnormal grain growth occurred in the samples containing second phase particles other than B6T17. With an increased substitution of strontium for barium, the aspect ratio of abnormal grains containing {111} twin lamellae was reduced. This result was attributed to a reduction in the relative stability of the {111} planes with the strontium substitution. [source] Electric-Field-Tunable Low Loss Multiferroic Ferrimagnetic,Ferroelectric HeterostructuresADVANCED MATERIALS, Issue 20 2009Jaydip Das A novel monolithic multilayered ferrimagnetic, ferroelectric multiferroic heterostructure shows a remarkably large tuning of the magnetic response with an electric field. The heteroepitaxial stack is comprised of a near single crystal yttrium iron garnet (YIG) layer, a ferroelectric barium strontium titanate (BSTO) layer with good electric field tunability, and embedded platinum (Pt) electrodes. [source] Synthesis and Photocatalytic Activity of Highly Ordered TiO2 and SrTiO3/TiO2 Nanotube Arrays on Ti SubstratesJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 9 2010Xuming Zhang Highly ordered TiO2 nanotube arrays (TiO2 -NTAs) are produced by electrochemical anodization of a Ti foil in ammonium fluoride (NH4F),ethylene glycol solution. Photocatalytic (PC) investigations indicate that the length of the NTAs plays an important role in their photoactivity. The PC activity increases initially with the NT length and then decreases and the optimum length that yields the highest PC is 6.2 ,m for TiO2 -NTAs. The TiO2 -NTAs are further converted to heterojunction strontium titanate (SrTiO3)/TiO2 -NTAs by a hydrothermal reaction in Sr(OH)2 solution. As the hydrothermal reaction proceeds, more TiO2 is converted into SrTiO3 and the thickness of the SrTiO3 layer increases. The SrTiO3/TiO2 -NTAs exhibit variable PC activities that depend on the hydrothermal reaction time, and the SrTiO3/TiO2 -NTAs hydrothermally treated for 1 h or less have enhanced PC properties. The advantage of combining TiO2 and SrTiO3 stems from the difference in the flatband potential, thereby improving the separation of the photogenerated electron,hole pairs and consequently the PC activity. [source] {111} Twin Formation and Abnormal Grain Growth in Barium Strontium TitanateJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 1 2003Byoung-Ki Lee Two series of experiments were performed to study the experimental conditions for the formation of {111} twins and related microstructures in barium strontium titanate ((Ba, Sr)TiO3). In the first series, the phase equilibria in the BaTiO3,SrTiO3,TiO2 system were determined. XRD and WDS analysis, done in the BaTiO3 -rich region, of 45(Ba,Sr)TiO3,10TiO2 samples annealed at 1250°C for 200 h in air showed that (Ba,Sr)TiO3 was in equilibrium with Ba6Ti17O40 (B6T17) and Ba4Ti13O30 phases with strontium solubility (Sr/(Ba + Sr)) of ,0.02 and 0.20, respectively. In the second series the microstructures of samples consisting of a mixture of (Ba,Sr)TiO3 and 2.0 mol% TiO2, were observed after sintering at 1250°C for 100 h in air. {111} twins formed only in the samples with faceted B6T17 second phase particles, similar to the case of BaTiO3. In these samples, abnormal grain growth occurred in the presence of the {111} twins. In contrast, no {111} twins formed and no abnormal grain growth occurred in the samples containing second phase particles other than B6T17. With an increased substitution of strontium for barium, the aspect ratio of abnormal grains containing {111} twin lamellae was reduced. This result was attributed to a reduction in the relative stability of the {111} planes with the strontium substitution. [source] Determination of the Oxygen Deficiency in Vacuum-Hot-Pressed Ferroelectric Ceramics Using a Thermogravimetric TechniqueJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 2 2000Qi Tan An attempt to measure the oxygen deficiency in vacuum-hot-pressed ferroelectric target materials was made, using a thermogravimetric method. The approach was intended to measure the relative mass increase of oxygen-deficient sheet samples, with respect to an oxidized reference that was annealed in air. A saturation of mass change was achieved, which indicated a saturated oxidation state and provided a basis for further calculation of the oxygen deficiency in the samples. Results were obtained for barium strontium titanate and lead lanthanum zirconate titanate compositions, which shows the feasibility of applying the thermogravimetric method to ferroelectric materials. [source] Low-Temperature Facile Template Synthesis of Crystalline Inorganic Composite Hollow SpheresCHEMISTRY - AN ASIAN JOURNAL, Issue 7 2007Huifang Xu Abstract This report presents a facile approach for the low-temperature synthesis of crystalline inorganic-oxide composite hollow spheres by employing the bulk controlled synthesis of inorganic-oxide nanocrystals with polymer spheres as templates. The sulfonated polystyrene gel layer can adsorb the target precursor and induce inorganic nanocrystals to grow on the template in,situ. The crystalline phase and morphology of the composite shell is tunable. By simply adjusting the acidity of the titania sol, crystalline titania composite hollow spheres with tunable crystalline phases of anatase, rutile, or a mixture of both were achieved. The approach is general and has been extended to synthesize the representative perovskite oxide (barium and strontium titanate) composite hollow spheres. The traditional thermal treatment for crystallite transformation is not required, thus intact shells can be guaranteed. The combination of oxide properties such as high refractive index, high dielectric constant, and catalytic ability with the cavity of the hollow spheres is promising for applications such as opacifiers, photonic crystals, high- , -gate dielectrics, and photocatalysis. [source] | ||||||||||