Modified hydrothermal synthesis and structural characterization of monoclinic (KxNa1−x)NbO3 (0.05≤x≤0.15) rods

Monoclinic (KxNa1−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 (KxNa6−x)H2Nb6O19·2H2O was formed. After centrifugation, washing, and the subsequent heat treatment of the secondary precipitate sample, the (KxNa1−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 (KxNa1−x)NbO3 material and template grains for the fabrication of lead-free textured alkali niobate piezoelectric ceramics.