Modified hydrothermal synthesis and structural characterization of monoclinic (K_xNa_1-x)NbO₃ (0.05≤x≤0.15) rods

Monoclinic (K_xNa_1-x)NbO₃ (0.05≤x≤0.15) rods were prepared successfully by the hydrothermal synthesis method combined with dissolution-precipitation and subsequent heat-treatment processes. At first, the primary precipitate of the niobate precursor was obtained using Nb₂O₅, KOH and NaOH as the initial reactants, and deionized water as the solvent for the hydrothermal synthesis. Interestingly, when the obtained precipitate was dissolved in 90 °C of deionized water and then the solution kept standing till ambient temperature, the secondary precipitate of rod-like niobate (K_xNa_6-x)H₂Nb₆O₁₉·2H₂O was formed. After centrifugation, washing, and the subsequent heat treatment of the secondary precipitate sample, the (K_xNa_1-x)NbO₃ rods of 1-60 μm in length and 1-5 μm in width were finally prepared. The surface morphology and phase structure of the prouducts were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively, and the chemical composition of the prouducts were identified by means of energy-dispersive X-ray spectroscopy(EDS). Furthermore, fourier transform infrared spectroscopy (FT-IR) and high-resolution transmission electron microscopy (HRTEM) were employed to investigate the fine structures of the prouducts. This research provides a new approach for the preparation of one-dimensional (K_xNa_1-x)NbO₃ material and template grains for the fabrication of lead-free textured alkali niobate piezoelectric ceramics.