Excellent piezoelectric performance of KNNS-based lead-free piezoelectric ceramics through powder pretreatment by hydrothermal method

Abstract In the work, effects of BiFeO3 superfine particles synthesized by the hydrothermal method (PPH) on microstructure and electrical properties of potassium-sodium niobate (KNN) lead-free piezoelectric ceramic were investigated. The optimized piezoelectric properties of d33~220 pC/N, d*33~534.5 pm/V and kp ~0.46 were obtained in 0.993(K,Na)NbO3-0.007BiFeO3 piezoceramics. The mechanism of the significant property enhancement was elaborated here. The results suggested that the proportion of T phase probably had a positive effect on the enhancement. Nanodomains and abundant 180° domain walls also played indispensable roles in such enhancement. What's more, a comparison of the energy band structures of the ceramic by PPH and the one by conventional solid-reaction method (CSR), indicated that the Schottky barrier was generated in the interface of KNNS and BF for the ceramic by PPH, which facilitated the motions of the domains and domain walls, and therefore results in superior piezoelectric properties to the one by CSR (d33~161 pC/N and kp~0.39).