Synthesis, piezoelectric property and domain behaviour of the vertically aligned K_1−xNa_xNbO₃ nanowire with a morphotropic phase boundary

In this paper, vertically aligned K_1−xNa_xNbO₃(KNN) nanowires were synthesized by the hydrothermal method using KNN gel powders as precursors at 190 °C and 220 °C. Orthorhombic KNN nanowires and perovskite KNN nanowires with a morphotropic phase boundary (MPB) between rhombohedral and tetragonal forms were characterized by X-ray diffraction, SEM and TEM. The domain behaviour, ferroelectric property and the effective piezoelectric coefficient d₃₃ of the two crystal structures of the KNN nanowires were investigated. The d₃₃ of the KNN nanowires reacting at 190 °C and 220 °C were 26.37 pm V⁻¹ and 28.93 pm V⁻¹, respectively. Domain switching was observed in a KNN nanowire prepolarized at +8 Volts using piezoresponse force microscopy (PFM).