PEROVSKITE-TYPE BATIO3 CERAMICS CONTAINING PARTICULATE SIC

BaTiO3-based composites with nanosized SiC particulates were successfu lly fabricated by a hot-pressing technique in an argon atmosphere. Cry stal structure and phase transformation behaviour were investigated by X-ray diffraction analysis, linear thermal expansion analysis and int ernal friction measurement. It was confirmed that the added SiC partic ulates were uniformly distributed with in the matrix BaTiO3 grains, wi th some larger particulates located at the BaTiO3 grain boundaries. In addition, there were no reaction phases between BaTiO3 matrix and SiC particulates. The crystal structure gradually changed from tetragonal to cubic phase with respect to the SiC content. The Curie temperature , T-c, was lowered as the SiC content increased. Moreover, the transfo rmations in the low-temperature range almost disappeared above 1 vol % SiC. The diffused phase transformation phenomenon was observed as the SiC content increased up to 3 vol %. The results were associated with the grain-size reduction, the existence of oxygen vacancies and the r esidual stresses associated with the thermal expansion mismatch betwee n matrix and SiC particulate. The influence on the domain structure de velopment of SiC particulates dispersed within the matrix grains was a lso discussed.