Nondoped Potassium Niobate Ceramics Synthesized by Hydrothermal Method with Optimum Temperature Condition

Nondoped potassium niobate (KNbO 3 ) ceramics were synthesized with fine powders obtained by a hydrothermal method. The hydrothermal method employs a chemical reaction in a solution. Low reaction temperature and self-assembly growth resulted in high-quality KNbO 3 powders. In this study, various temperature conditions from 180 to 230 °C were examined for high-performance KNbO 3 ceramics. After sintering at 1030 °C using hydrothermally crystal powders under respective conditions, the dielectric loss and permittivity of each ceramic were measured. As a result, the suitable temperature condition of the hydrothermal synthesis for piezoceramics was 210 °C. With admittance measurements, the piezoelectric performance of fabricated KNbO 3 ceramics was confirmed. From the resonance frequency response corresponding to the radial vibration and thickness vibration modes, the coupling factors k r and k t and the piezoelectric constants d 31 and d 33 were measured to be 0.14 and 0.26, and -28 and 55 pm/V, respectively.