Effect of thermal-cycling on the piezoelectricity of 0.5Ba(Zr_0.2Ti_0.8)O₃-0.5(Ba_0.7Ca_0.3)TiO₃ Pb-free piezoceramic

The reliability of piezoelectricity under thermal-cycling is an important consideration for the practical application of Pb-free piezoelectric materials. In this paper, we investigated the effect of thermal-cycling on the piezoelectricity of 0.5Ba(Zr_0.2Ti_0.8)O₃-0.5(Ba_0.7Ca_0.3)TiO₃ (BZT-BCT) Pb-free piezoceramic. The results show that, in BZT-BCT, the tetragonal-orthorhombic (T-O) transition causes a strong piezoelectricity degradation (∼40% reduction after 60 thermal cycles between −40 °C and 50 °C), whereas the orthorhombic-rhombohedral (O-R) transition only leads to negligible degradation during the thermal-cycling test, indicating a weak depoling effect. The comparative studies made between BZT-BCT and BaTiO₃ (BT) reveal that the weak depoling effect results from the diffuseness of the O-R transition in BZT-BCT and weak domain pattern change across the transition. Our work implies that Pb-free piezoelectrics with good thermal-cycling stability can be achieved through engineering the normal ferroelectric-to-ferroelectric transition to a diffused one, which may help to design new Pb-free piezoelectric materials with good thermal-cycling stability.