Grain Size Effect on Dielectric Properties of Ba0.92Ca0.08TiO3 Ceramics

We demonstrated the grain size effect on the dielectric properties of Ba0.92Ca0.08TiO3 ceramics. Fine-grained Ba0.92Ca0.08TiO3 ceramics with micrometer- and nanometer-sized grains were fabricated by the two-step sintering method and aerosol deposition method, respectively. The permittivity of Ba0.92Ca0.08TiO3 ceramics increased with decreasing grain size when the grain size was more than 400 nm, whereas it decreased when the grain size was below 400 nm. The permittivity of Ba0.92Ca0.08TiO3 ceramics with micrometer-sized grains was lower than that of BaTiO3 ceramics. This was caused by the hardening of the soft mode and the decrease in the 90° domain-wall contribution by Ca substitution. Moreover, the grain size that gave the maximum permittivity for Ba0.92Ca0.08TiO3 ceramics was lower than that for BaTiO3 ceramics. This result suggested that the Ba0.92Ca0.08TiO3 was less sensitive to the grain size effect than BaTiO3 ceramics. These features in the grain size dependence of permittivity were explained by the tetragonal structure stability of Ba0.92Ca0.08TiO3.