Piezoelectric properties of (Li, Ag) modified (Na0.50K0.50)NbO3 lead-free ceramics with high Curie temperature

Lead-free piezoelectric ceramics (1 − x)[(Na0.4725K0.4725)Li0.055]NbO3–x(Ag0.5Li0.5)NbO3 [(1 − x)KNNL–xALN] have been prepared by the conventional mixed oxide method. The ceramics show good piezoelectric and ferroelectric properties. Effect of the amount of (Ag0.5Li0.5)NbO3 (ALN) on the phase structure, microstructure, piezoelectric and ferroelectric properties of (1 − x)KNNL–xALN ceramics were systematically investigated. It is found that the samples with 1 mol% ALN exhibit good piezoelectric and ferroelectric properties, and high Curie temperature. For (1 − x)KNNL–xALN (x = 0.01) ceramics, the piezoelectric constant d33 and Curie temperature Tc reach 220 pC/N and 476 °C, respectively; the electromechanical coupling coefficient of the planar mode kp reaches 37%; the remnant polarization (Pr) is 22.4 μC/cm2 with a coercive field (Ec) of 11.3 kV/cm. These results show that the (1 − x)KNNL–xALN is a promising candidate for high temperature lead-free piezoelectric ceramics.