Phase coexistence and evolution in sol-gel derived BY-PT-PZ ceramics with significantly enhanced piezoelectricity and high temperature stability

In this study, high Curie Temperature ( T c ) perovskite ceramics of optimized composition 0.55(0.1BiYbO 3 -0.9PbTiO 3 )-0.45PbZrO 3 with unique double orthorhombic main phases were prepared by a modified sol-gel method. Compared to the usual solid-state prepared sample, the sol-gel derived sample has a 1.6 times higher d 33 of 325 pC/N, a 2.4 times higher remnant polarization, and a much better high temperature stability with similar depolarization temperature ( T d ) and T c . Comprehensive analysis of the xerogel prepared over a wide calcination temperature ( T cal ) range of 300–1000 °C revealed that perovskite structure appeared at only 400 °C and it became the main phase above 500 °C. Comparison of XRD refinement results showed that calcination and sintering induced subtle and continuous phase transition, namely, the 400–900 °C calcined powders with coexisted tetragonal ( P4mm ) and orthorhombic ( Pbam ) phase changed to a rather stable double orthorhombic ( Pmmm and Pbam ) main phase in all the differently sintered ceramics, as similar to the 1000 °C calcined powders. The stable phase coexistence well explains the enhanced performance. The results also demonstrate that optimized sol-gel processing can provide high T c ceramics with desirable multi-phase structure and significantly enhanced performance at a lower temperature.