Effect of post-synthesis heat-treatment on the structural and dielectric features of nano-sized BaTiO_3 powders

摘要

The effect of post-synthesis heat-treatment on the structural evolution of nano-sized BaTiO_3 powders prepared by the hydrothermal synthesis method was investigated. The tetragonal fraction of the as-prepared powders was found to be approximately 19% and those of the powders heat-treated at 600, 800 and 1000 °C for 1 h were 21, 56 and 90%, respectively. The relative dielectric constants also increased with increasing heat-treatment temperature. In the case of the as-prepared nano-sized BaTiO_3 powders and those heat-treated at 600 °C, a considerable fraction of cubic-like lattice was present near the surface; the lattice spacing along the a_1-axis was nearly constant, while that along the a_3-axis increased with increasing distance from the surface to the core region of the powder. On the other hand, for the powders heat-treated at 800 and 1000 °C, even the shell region of the powders mostly consisted of the tetragonal-like phase, which indicates that there is little size effect near the surface of the powders.