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 μm have been studied. Fine-grained ceramic BaTiO₃ of 1 μm average grain size has 90°domains and has shown higher dielectric constant, lower ferroelectric transition temperature (T_c), and lower transition energy than coarser-grained material. 90°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.