Growth and electrical properties of Na0.5Bi0.5TiO3-K0.5Bi0.5TiO3 lead-free single crystals by the TSSG method

A series of NBT-KBT lead-free crystals with dimensions of Φ 35×10 mm were successfully grown by the TSSG method. The as-grown crystals possess rhombohedral perovskite structure at room temperature. The curves ε(T) for all crystals show two abnormal dielectric peaks. The depolarization temperatures Td derived from the first peak of curves tan δ(T) vary with the KBT content, which are 130, 150, 140, and 115 °C respectively, for (100−x)NBT−xKBT (x=5, 8, 12, 15) crystals, being well consistent with the Td obtained from the temperature dependence of kt. A notable thermal hysteresis, ΔT≈35 °C, for ferroelectric-antiferroelectric phase transition was also disclosed for 92NBT-8KBT crystal. The investigation of orientation dependence for electrical properties disclosed the dielectric parameters show weak anisotropy. The piezoelectric constants (d33) are 147, 175, 205, 238 pC/N and the values of kt are 38%, 52%, 52%, 54%, respectively for (100−x)NBT−xKBT (x=5, 8, 12, 15) crystals.