Perovskite-type BaTiO₃ ceramics containing particulate SiC: Part I. Structure variation and phase transformation

BaTiO₃-based composites with nanosized SiC particulates were successfully fabricated by a hot-pressing technique in an argon atmosphere. Crystal structure and phase transformation behaviour were investigated by X-ray diffraction analysis, linear thermal expansion analysis and internal friction measurement. It was confirmed that the added SiC particulates were uniformly distributed within the matrix BaTiO₃ grains, with 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 transformations 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 residual stresses associated with the thermal expansion mismatch between matrix and SiC particulate. The influence on the domain structure development of SiC particulates dispersed within the matrix grains was also discussed.