Effect of Mn-Doping on the Piezoelectric Properties of (K0.5Na0.5)(Nb0.67Ta0.33)O3 Lead-Free Ceramics

The piezoelectric properties of 100(K0.5Na0.5)(Nb0.67Ta0.33)O3–x1/3Mn3O4 (abbreviated as KNNT–xMn) lead-free piezoelectric ceramics were investigated as a function of x. These ceramics were fabricated by conventional ceramics processing with K4.1CuTa7.7O22.3 (KCT) and ZnO as sintering aids. Mn-doping was found to decrease the phase transition temperature from tetragonal to orthorhombic (TO–T) near room temperature and clearly increase the d33 value. A high d33 value of 240 pC/N was obtained at x = 1.4. Values of kp and Qm kept were also maintained at over 0.40 and 280, respectively in the range of x = 0–2.0.