LAUSR

Abstract The grain-size effects of the direct piezoelectric coefficient (d 33 ) and the converse piezoelectric coefficient (d 33 *) of BaTiO 3 ceramics with different Ba/Ti ratios were systematically explored. It was found that both d 33 and d 33 * exhibited strong grain size (g) dependences for BaTiO 3 ceramics with various Ba/Ti ratios. Although d 33 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 d 33 * were observed. By carefully examining the microstructure and ferroelectric properties of the ceramics, the variations of domain configurations and maximum polarization of BaTiO 3 ceramics with different Ba/Ti ratios were considered to be responsible for the different grain-size dependence of d 33 and d 33 *, respectively.