EFFECT OF GRAIN-SIZE AND MECHANICAL PROCESSING ON THE DIELECTRIC-PROPERTIES OF BATIO3

Dielectric properties of polycrystalline BaTiO3 ceramics having grain sizes of 1 to 40 mu m have been studied. Fine-grained ceramic BaTiO3 of 1 mu m average grain size has 90 degrees domains and has shown higher dielectric constant, lower ferroelectric transition temperature (T-c), and lower transition energy than coarser-grained material. 90 degrees domain switching was preferentially produced in the fine-grained BaTiO3 as a result of abrasion. For the fine-grained BaTiO3, the dielectric constant decreased with one-dimensional pressure, whereas, for the coarse-grained material, the dielectric constant increased before decreasing with the pressure. The one-dimensional pressure resulted in increased T-c of both the fine- and coarse-grained BaTiO3, with the effect being the greatest for the coarse-grained material. The relationship between these results and internal stress, and the effect of external pressure imposed on internally stressed lattice, were discussed.