A modified lead-free piezoelectric BZT–xBCT system with higher T C

Very recently, a high-performance Pb-free piezoelectric system Ba(Zr 0.2 Ti 0.8 )O 3 – x (Ba 0.7 Ca 0.3 )TiO 3 (abbreviated as BZT– x BCT) has been reported, showing a very high d 33 of 620 pC N −1 at x = 50. However, the Curie temperature T C (for x = 50) is relatively low (93 °C), thus restricting its applications. We report a method to increase the T C of the lead-free system BZT– x BCT, that is, increasing the T C of both tetragonal and rhombohedral terminals. The modified system Ba(Zr 0.15 Ti 0.85 )O 3 – x (Ba 0.8 Ca 0.2 )TiO 3 showed a higher T C of 114 °C at x = 53. We also found that both d 33 and ε 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 .