Grain-size effects on dielectric and piezoelectric properties of poled BaTiO3 ceramics

Barium titanate (BaTiO3) is known historically as the first ceramic piezoelectric material and shows a high possibility of being revitalized as a popular lead-free piezoelectric material. However, few systematic studies of the grain-size effects on the dielectric and piezoelectric properties of poled BaTiO3 ceramics have been carried out to date. In this work, a series of dense BaTiO3 ceramics with uniform grain-size distribution were successfully prepared by the conventional solid-state reaction, and the grain-size effects on the dielectric and piezoelectric properties were explored in their poled states. An interesting physical phenomenon has been found: dielectric permittivity ε′ and the piezoelectric constant d33 increase significantly at room temperature with the reduction of the average grain size g and reach the maxima at g = 0.94 μm. It was revealed that domain structure and relative density play substantial roles in determining the ε′ and d33 behaviors. The average 90° domain width decreases monotonically with g. Both the 90° domain wall density and the area dimension of area dimension domain wall are considered as important factors that greatly influence the d33 value. Extrinsic contribution comprises the major part of the observed d33 values in the fine-grained BaTiO3 ceramics.