Direct and converse piezoelectric grain-size effects in BaTiO3 ceramics with different Ba/Ti ratios

The grain-size effects of the direct piezoelectric coefficient (d33) and the converse piezoelectric coefficient (d33*) of BaTiO3 ceramics with different Ba/Ti ratios were systematically explored. It was found that both d33 and d33* exhibited strong grain size (g) dependences for BaTiO3 ceramics with various Ba/Ti ratios. Although d33 showed similar grain-size dependence for all the Ba/Ti ratios except a subtle shift of the critical grain size from 1 μm to 3 μm, two entirely different grain-size dependence of d33* were observed. By carefully examining the microstructure and ferroelectric properties of the ceramics, the variations of domain configurations and maximum polarization of BaTiO3 ceramics with different Ba/Ti ratios were considered to be responsible for the different grain-size dependence of d33 and d33*, respectively.