Top-seeded solution growth and properties of K_1-xNa_xNbO₃ crystals

A series of large-sized (maximum 16 × 16 × 20 mm³), high-quality K_1-xNa_xNbO₃ (x = 0.118, 0.378, 0.462, 0.545, and 0.666) single crystals were successfully cultivated using the top-seeded solution growth method. The crystallization and structures of the K_1-xNa_xNbO₃ single crystals were studied using first-principles calculations and X-ray diffraction, respectively. The segregation of the K_1-xNa_xNbO₃ single crystals was investigated, which enabled precise control of the individual components of the crystals during growth. Excellent properties were obtained without annealing, including a low dielectric loss (minimum 0.2%), a saturated hysteresis loop with a low coercive field E_c, a large piezoelectric coefficient d₃₃ (d₃₃ = 161 pC/N when x = 0.378), and a low leakage current density J (10^-6 A/cm²). These results indicated that the K_1-xNa_xNbO₃ (x = 0.118, 0.378, 0.462, 0.545, and 0.666) crystals can be used as a high-quality, lead-free piezoelectric material.