BiFeO₃-doped (Na_0.5K_0.5)NbO₃ lead-free piezoelectric ceramics

Lead-free piezoelectric ceramics (1-x)(Na_0.5K_0.5)NbO₃-xBiFeO₃ (x=0∼0.07) were synthesized by the solid-state reaction. Differential scanning calorimetry (DSC) measurements revealed that an increase in the amount of BiFeO₃ dopant resulted in a decrease in the orthorhombic-tetragonal and tetragonal-cubic phase transition temperature of the material. One percent BiFeO₃ additive suppressed grain growth, which not only benefits the sintering of ceramics but also enhances the piezoelectric and ferroelectric properties, where d₃₃=145pC/N, k_p=0.31, Q_m=80, P_r=11.3 μC cm^-2 and E_c=16.5 kV cm^-1. As x_BF>0.01, both piezoelectric and ferroelectric properties decreased rapidly with an increasing amount of dopant.