Thermal stability of self-polarization in a (K,Na)NbO₃ film prepared by the hydrothermal method

Herein, the systematic change in self-polarization behavior against post-heat treatment after film deposition was investigated to understand origin of hydrothermally prepared (KxNa1−x)NbO3 films with x = 0.88 at 240 °C below Curie temperature. The transverse piezoelectric constant, e31,f, evaluated by cantilever method. as-prepared and heat-treated 300 had an almost perfectly self-polarized state showed e31,f ∼−5.0 C m−2 without applying electric field as a poling treatment. Also, response shows good linearity asymmetric butterfly curves, showing imprint characteristics. states were maintained until heat above Moreover, successfully deposited on post-heat-treated state. This result suggests that is generated regardless polarized underlying layer hydrothermal synthesis which temperature