Hydrothermal preparation and characterization of sheet-like (K_xNa_1-x)NbO₃ perovskites

(K_xNa_1-x)NbO₃ (KNN) powders with sheet-like morphologies were successfully prepared by the hydrothermal synthesis route combined with subsequent heat-treatment processes. When the heat-treated temperature was 600 °C, the (K_xNa_1-x) NbO₃ (0.6≤x≤0.7) perovskite sheets were obtained in the KNN powders. The surface morphology and crystal structure of the KNN sheets were investigated by scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM), respectively. The KNN sheets were in a well-defined hexagonal shape with a thickness of about 100-200 nm and a diameter of 1.5-3 μm. The chemical structure of the KNN sheets was analyzed using Fourier Transform infrared spectroscopy (FTIR) and Raman spectroscopy. A growth mechanism for the sheet-like microstructures was discussed.