Ultrahigh thermal stability of lead-free Bi0.5Na0.5TiO3-Bi0.5K0.5TiO3-BaTiO3 ternary piezoceramics upon quenching treatment

The Bi0.5Na0.5TiO3-based system is one of the most competitive candidates for lead-free piezoelectric materials. However, the relatively low thermal depolarization temperature (Td) hinders the practical application of the materials, making effectively improving Td an urgent challenge to be overcome. Herein, excellent thermal stability with ultrahigh Td value (251 degrees C) is obtained in Mn-doped 0.79Bi0.5Na0.5TiO3-0.14Bi0.5K0.5TiO3-0.07BaTiO3 (79BNT-14BKT-7BT:Mn) ternary ceramics by quenching strategy. It is found that the quenching treatment increases the phase proportion and enhances the lattice distortion of tetragonal structure. By utilizing piezoelectric force microscopy (PFM) and autocorrelation function method, it is revealed that the quenching process can induce an increase in the length of correlation polarization, ferroelectric long-range ordering and domain size. The domain switching is significantly suppressed, which contributes to the improvement of Td. This study provides a feasible avenue to achieve BNT-based piezoelectric ceramics with high thermal stability and facilitates their development and application.