Processing and Application of Ceramics (Dec 2009)
Effect of synthesis route on the microstructure of SiO2 doped bismuth titanate ceramics
Abstract
Synthesis and characterization of SiO2 doped bismuth titanate ceramics were investigated. Four investigated compositions belonging to the system Bi2O3-TiO2-SiO2 are located in the section Bi4Ti3O12-SiO2, near by it and in the binary Bi2O3-TiO2 system. Melt quenching was applied for synthesis of SiO2 doped bismuth titanate ceramics and for the sample 40Bi2O3·60TiO2. The binary sample 70Bi2O3·30TiO2 is prepared by gradient heating of bulk materials near the liquidus temperature (modified solid state reaction). The influence of the thermal treatment on the phase formation and microstructure was evaluated using XRD, EDS and SEM. The binary samples prepared by solid state reaction at low temperature (1000°C) possess poly-phased dense microstructure, while secondary crystallization combined with porosity formation is typical for the sample obtained at high temperature (1150°C). The ternary Bi2O3-TiO2-SiO2 samples, obtained by supercooling of the melts down to room temperature, are thermally treated at 700, 800°C. They consist of elongated crystals in amorphous matrix. The crystals have lower Bi2O3-content and higher TiO2-content than the nominal batch composition. The XRD data show that the main crystalline phases in the ceramics produced by melt quenching method and solid state reaction are β-Bi2O3, Bi4Ti3O12 and one unknown new phase. It is proved that the applied methods of synthesis are suitable for generation of different microstructures in the bulk SiO2 doped bismuth titanate ceramics, which is promising basis for modification of their electrical properties.
