Notable grain-size dependence of converse piezoelectric effect in BaTiO3 ceramics

Converse piezoelectric effect is of critical importance to device applications like actuators, but no systematical investigation concerning the influence of microstructure on it has been reported for BaTiO3 ceramics so far. Piezoelectric and ferroelectric properties were inclusively investigated for a group of BaTiO3 ceramics that are fabricated through solid-state reaction route and show various average grain sizes in this study. It was found that the piezoelectric properties of these BaTiO3 ceramics display significant grain-size dependences. The direct piezoelectric coefficient d33 increases with decreasing the average grain size (GS) from 170 pC/N at 40 μm, reaches a maximum value of 413 pC/N at 1.2 μm, and then decreases with a further reduction of GS. Converse piezoelectric effect was characterized by measurement of unipolar strain versus electric field (S–E) curve, and the converse piezoelectric coefficient d33*(E) was quantitatively calculated from the slope of S–E curve at relatively large E. Interestingly, d33*(E) is nearly twice as large as d33 and shows a quite similar trend of change with GS to d33. It increases largely from 350 pm/V to 870 pm/V when reducing the GS value from 40 μm to 1.2 μm, and then decreases to 480 pm/V with the further GS reduction to 0.7 μm. Meanwhile, the remanent polarization Pr shows an increase with the decreasing of GS, reaches a maximum at 3.3 μm, and then decreases with the further GS reduction. Domain structure is considered to play an essential role in determining the notable grain-size dependence of converse piezoelectric effect.