NaNbO 3 nanoparticles: Rapid mechanochemical synthesis and high densification behavior

Abstract Sodium niobate (NaNbO 3 ) is an important lead-free electronic ceramic, but it is difficult to obtain high sintering densification due to the strong volatility of alkali metal elements. Reducing particle size of the precursor powder is believed to be an effective method to improve sintering activity, further to achieve high densification. In this work, pure perovskite NaNbO 3 nanoparticles with mean size of 15 nm have been synthesized by a facile one-step route using the mechanochemical method. The evolution of crystal structure and morphology of the particles milled for different times were investigated, and a transformation mechanism has been proposed to elucidate the formation processes of NaNbO 3 nanoparticles. Furthermore, high-density (98%) NaNbO 3 ceramics were successfully prepared from nanoparticle compact without any sintering additives. In addition to the Curie temperature of 360 °C, a diffuse dielectric peak ∼100 °C has been observed, evidencing an intrinsic P-Q phase transition. After the polarizing treatment, the obtained NaNbO 3 ceramic exhibited a high piezoelectric coefficient, d 33  = 37 pC/N.