Preparation And Mechanism Of BaTiO₃ And Tabular SrTiO₃ By Molten Salt Synthesis

Recent studies have shown that rhombohedral xPb(Mg1/3Nb2/3)O3-(l-x) PbTiO3 (PMN-PT) single crystals near the morphotropic phase boundary (MPB) exhibit extraordinarily large elecromechanical coupling coefficients(>90%) and piezoelectric coefficients (d33>2000pC/N) coupled with ultrahigh strains(~1.7%). Single crystals of superior properties have tremendous potential for medical ultrasonic maging, sonar, high-performance actuators. Textured polycrystalline piezoelectric materials are expected to provide improved properties compared to untextured ceramics, and low processing cost compared to single crystals.The Templated Grain Growth(TGG) process was used to texture PMN-PT. The TGG process requires the template to have a strong epitaxial relationship to the crystal structure of the matrix composition. The template must also show the proper size and aspect ratio, otherwise, the template particles must be stable with the matrix at the desired growth temperature and environment.This work emphasized the syntheses of perovskite templates(including SrTiO3 and BaHO3). BaTiO3 were prepared by Molten Salt Synthesis(MSS). Scanning Electron Microscopy (SEM) and X-ray Diffraction patterns (XRD) revealed that there was no aggregation with BaTiO3 powders and spherical particles of BaTiO3 was obtained by MSS. Reacting temperature had much effect on product purity; while reacting time above 1150C had little effect on microstructure; The salt content had some effect on microstructure, it was appropriate that the proportion of the salt and the raw materials was 1:1.The growth process of BaTiO3 powders was controlled by Diffusion mechanism.In the present paper, The synthesis of SrTi03 proceeded through two steps. In the first, precursor Sr3Ti2O7 particles were synthesized. Tabular SrTiO3 crystals were synthesized via the superposition of the SrTiO3 basic cell on the interface of Sr3Ti2O7 particles. SEM and XRD showed that tabular SrTiO3 particles had rectangular faces with an edge length of 10~30 m and a thickness of 2~5 m. And the Measured lattice parameter of the tabular particles was 3.90A, which is in agreement with the previously reported for SrTiO3. The mechanism of the oriented growth of tabular SrTiO3 could be considered as the superposition of coordination polyhedron Ti-O6 octahedron basic cell on the interface of Sr3Ti2O7 particles.