Properties of NaNbO3 powders and ceramics prepared by hydrothermal reaction

NaNbO3 (NN) powders were synthesized by hydrothermal (HT) and conventional solid-state (CMO) methods, the obtained fine powders were used to prepare ceramics through conventional sintering process. The effect of preparation methods on the phase structure, morphology, and microstructure were investigated. Electric and piezoelectric properties of NN ceramics were measured. Fine NN powders with smaller sizes and high crystallinity were obtained under suitable hydrothermal conditions (200 °C, 2.64 M NaOH concentration and heat preservation for 24 h). The different fingerprints of Raman spectra of samples could be attributed to the different phase structure of NN powders prepared by HT (O3 orthorhombic phase) and CMO (O1 orthorhombic phase) methods. In addition, the results illustrated that the sintering temperature of HT-synthesized ceramics was lower and compactness was better than that of CMO-synthesized ceramics. Notably, the HT-synthesized ceramics obtained better electrical properties than that of CMO-synthesized ceramics, which were as follows: d33 = 41 pC N−1, Kp = 0.30, ɛm = 1565 (1 kHz) and Tc = 378 °C.