The Investigation Of Doping In KNN-based Lead-free Piezoelectric Ceramics

Potassium sodium niobate-based ceramics is considered as one of the most attractive lead-free piezoelectric ceramics. The influence of doping Ca(Mg1/3Nb2/3)O3 (CMN), Ca(Zn1/3Nb2/3)O3 (CZN) and CaTiO3 (CT) on the phase structure, microstructure and phase transition temperature of monoclinic (Ko.48Nao.52)Nb03 (KNN) ceramics were investigated respectively. It is found that grain growth is inhibited because of doping CMN, CZN or CT. And the doping CMN or CZN has little effects on the phase structure and the monoclinic-tetragonal transition temperature (TM-T) of KNN-based ceramics. Moreover, doping CMN can hardly change the tetragonal-cubic transition temperature of (TT-C) while doping CZN can decrease TT-C obviously. In addition, TM-T and TT-C decline linearly with doping CT. The morphotropic phase boundary with two phases (R-T) coexistence can be obtained by doping rhombohedra (R) structure (Bi1/2Na1/2)TiO3 in the tetragonal structure 0.93(Ko.48Nao.52)Nb03-0.07CaTi03. It provides a new idea for developing high properties of KNN-based lead-free piezoelectric ceramics.