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

摘要

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℃ were examined for high-performance KNbO_3 ceramics. After sintering at 1030℃ 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℃. 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.