High Performance Lead-free Piezoelectric Ceramics in the (K,Na)NbO₃-LiTaO₃ Solid Solution System

A new solid solution system, namely {(K 0.5 Na 0.5 ) 1− x Li x }(Nb 1− y Ta y )O 3 , with full density, a large piezoelectric constant and high stability has been developed. The system has a morphotropic phase boundary (MPB) between orthorhombic and tetragonal. The MPB gives the largest piezoelectric d constant at {(K 0.5 Na 0.5 ) 0.97 Li 0.03 }(Nb 0.8 Ta 0.2 )O 3 , which exhibits a piezoelectric actuator constant d 33 of 230 pm/V, 2.34 times that of pure (K 0.5 Na 0.5 )NbO 3 (KNN). Also, it gives a piezoelectric coupling Kp value (0.505), a dielectric constant (1256), and an elastic compliance (10.9 TPa−1 ) 1.51, 2.93, and 1.14 times those of pure KNN, respectively. The long-term stability of the dielectric loss was demonstrated to be far superior to that of pure KNN.