Recent study progresses of (K,Na)NbO3-based lead-free piezoelectric ceramics

This paper outlines our recent study progresses on (K,Na)NbO 3 -based lead-free piezoelectric ceramics. It has been found in (K x Na 1-x )NbO 3 ceramics that piezoelectric properties are almost irrelevant to the K/Na ratio within x=0.40 ∼ 0.60 and orthorhombic phase possesses the much better piezoelectric temperature stability than tetragonal phase. Similar phenomena are also observed in some (K,Na,Li)(Nb,Ta)O 3 ceramics, of which (K 0.55 Na 0.45 ) 0.965 Li 0.035 Nb 0.80 Ta 0.20 O 3 ceramic shows particularly an outstanding piezoelectric performance with the piezoelectric properties of d 33 =262 pC/N, kp=0.53 and k 33 =0.63 at room temperature and the weak temperature dependence of electromechanical coupling coefficients in the common usage temperature range. Furthermore, we have successfully obtained a remarkably high d 33 value of 413 pC/N in (K 0.45 Na 0.55 ) 0.98 Li 0.02 (Nb 0.77 Ta 0.18 Sb 0.05 )O 3 ceramic through the conventional solid state reaction process.