Synthesis of (K,Na)NbO3 particles by traditional hydrothermal method and high-temperature mixing method under hydrothermal�Csolvothermal conditions

Pure (K,Na)NbO₃ (KNN) powders have been successfully prepared by using traditional hydrothermal method and high-temperature mixing method (HTMM) under solvothermal and hydrothermal conditions. The products were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) to show the change of phase, morphology, and size of the as-prepared particles with the alkalinity of the starting solution. Compared with the traditional hydrothermal method, smaller particles with higher phase purity are prepared using HTMM under hydrothermal conditions. It is found that the alkalinity has significant effects on the crystal size. The KNN grain size first increases and then decreases with increasing alkalinity. Typical samples solvothermally synthesized in a mixed solvent with isopropanol/deionized water ratio of 50/50 by volume were made of well-crystallized single-crystalline nanoparticles with size of about 500 nm.