Enhanced electromechanical properties and temperature stability of textured (K_0.5Na_0.5)NbO₃-based piezoelectric ceramics

In this work, we report the electromechanical properties of 〈00l〉_C-textured (K_0.5Na_0.5) _0.98Li_0.02NbO₃ (KNLN) and (K _0.5Na_0.5)(Nb_0.85Ta_0.15)O ₃ (KNNT) ceramics produced by templated grain growth. Both materials show high texture quality (F_00l=98% and full-width at half-maximum [FWHM]=8.4° for KNLN, F_00l=99%, and FWHM=7.6° for KNNT) and enhanced piezoelectric response compared with randomly oriented ceramics. However, textured KNLN shows higher piezoelectric properties (d₃₃=192 pC/N, k_p=0.63, k₃₁=0.39, d₃₁=-73 pC/N, d ₃₃^*=208 pC/N) and higher phase transition temperatures (T_o-t=155°C, T_c=439°C) than textured KNNT. The enhanced room-temperature piezoelectric properties are associated with low-strain hysteresis (4.0%), suggesting that 〈00l〉_C textured and poled orthorhombic KNLN may exhibit domain engineering character. The piezoelectric performance of textured KNLN with T_o-t=155°C is high and stable over a wide temperature range (-60°-100°C), strongly favoring use of this material in device applications compared with the modified KNN-based materials with a T_o-t near room temperature.