A modified lead-free piezoelectric BZT-xBCT system with higher TC

Very recently, a high-performance Pb-free piezoelectric system Ba(Zr0.2Ti0.8)O-3-x(Ba0.7Ca0.3)TiO3 (abbreviated as BZT-xBCT) has been reported, showing a very high d(33) of 620 pCN(-1) at x = 50. However, the Curie temperature T-C (for x = 50) is relatively low (93 degrees C), thus restricting its applications. We report a method to increase the T-C of the lead-free system BZT-xBCT, that is, increasing the T-C of both tetragonal and rhombohedral terminals. The modified system Ba(Zr0.15Ti0.85) O-3-x(Ba0.8Ca0.2) TiO3 showed a higher T-C of 114 degrees C at x = 53. We also found that both d(33) and epsilon along the morphotropic phase boundary (MPB) decreased with a deviation from the cubic-tetragonal-rhombohedral triple point. This result is explained by considering an increase in polarization rotation barrier with a deviation in composition from the triple point. Our results implied that to achieve a high d(33) with a high T-C, a nearly vertical MPB is required. Our work may give a new insight into how to design 'ideal' Pb-free piezoelectrics with both high piezoelectricity and high T-C.