Enhancement of piezoelectric performance in (Bi1/2Na1/2)TiO3-based system through single-crystallization

(Bi1/2Na1/2)TiO3-based ceramics are prominent candidates for lead-free piezoelectric applications; however, they are hampered by low piezoelectric coefficients (-200 pC/N) and low depolarization temperatures (-100 degrees C). Herein, we present a strategy for enhancing the comprehensive piezoelectric performance of these ceramics through single-crystallization. High-quality 0.85(Bi1/2Na1/2)TiO3-0.11(Bi1/2K1/2)TiO3-0.04BaTiO3 (BNT-11BKT4BT) single crystals were synthesized using a flux growth method. These crystals exhibit significantly enhanced piezoelectric coefficients (-360 pC/N) and elevated depolarization temperatures (-220 degrees C) compared to random ceramics with equivalent composition. The observed increase in depolarization temperature by 100 degrees C in single crystals, attributed to an elevated c/a ratio (1.014 versus 1.005 in random ceramics). Notably, the piezoelectric coefficient surpasses 1000 pC/N at 210 degrees C, a phenomenon linked to the flattening of the free energy near the tetragonal-pseudocubic phase transition point. Furthermore, the polarization and electrostrain demonstrate remarkable temperature stability, owing to the improved depolarization temperature. This study elucidates a pathway towards advancing the comprehensive piezoelectric performance of (Bi1/2Na1/2)TiO3-based materials, providing valuable insights for future research and development in the field.