SHU Kaizheng, YI Wenbin, JIANG Xiangping, CHEN Chao, TU Na, LI Xiaohong

(Jiangxi Key Laboratory of Advanced Ceramic Materials, School of Materials Science and Engineering, Jingdezhen Ceramic Institute, Jingdezhen Jiangxi 333001 China)

Abstract:In this paper, (1-x)K0.5Na0.5NbO3-x (Na0.8K0.2)0.5Bi0.5TiO3 (x=0-5%) lead-free piezoelectric ceramics were synthesized by solid-state reaction method. The effects of the content of (Na0.8K0.2)0.5Bi0.5TiO3 on the phase, microstructure, dielectric and piezoelectric properties of the samples were investigated. The results show that all samples possess perovskite structure.With the increasing amount of (Na0.8K0.2)0.5Bi0.5TiO3, the phase structure of the samples at room temperature changes from orthorhombic symmetry to tetragonal symmetry and both the piezoelectric constant d33 and planar coupling factor kp of the samples increase first and then decrease while Curie temperature decreases gradually. A polymorphic phase transition(PPT) from orthorhombic to tetragonal symmetry occurs in the composition range of 2%≤x≤3% in this system and the ceramic sample in the composition of x=3% owns peak piezoelectric properties (d33=189pC/N, kp=41%, Qm=96, tanδ=0.028).

Key words:lead-free piezoelectric; sodium potassium niobate (KNN); polymorphic phase transition (PPT); piezoelectric properties