Plastic deformation of BaTiO₃ ceramics by high-pressure torsion and changes in phase transformations,optical and dielectric properties

Ceramics are generally brittle at ambient condition and they can hardly be deformed plastically. In this study,severe plastic deformation was successfully imposed on barium titanate ceramic powders by high-pressure torsion. A tetragonal-to-cubic phase transformation occurred,and the fraction and stability of the cubic phase increased by straining because of the formation of nanograins. BaTiO₃ exhibited photoluminescence and the yellow intensity increased after straining because of the formation of large fraction of grain boundaries. The dielectric constant of BaTiO₃ was unusually increased by nanograin formation while the Curie temperature remained constant.