Enhancing piezoelectric d33 coefficient in Li∕Ta-codoped lead-free (Na,K)NbO3 ceramics by compensating Na and K at a fixed ratio

Lead-free alkali niobate piezoelectric ceramics with nominal compositions [(Na0.535K0.480)0.942+xLi0.058](Nb0.90Ta0.10)O3 compensated with Na and K at a fixed and optimized ratio of 0.535:0.480 were prepared by normal sintering. The electrical properties were investigated with a special emphasis on the influence of compensating amount x of Na0.535K0.480. A phase transition from tetragonal to orthorhombic was observed as x was increased from 0 to 0.024, resulting in enhanced piezoelectric coefficient and planar electromechanical coupling coefficient from 216 and 38.1% to 268pC∕N and 46.2%, respectively. Our results indicate the importance of elaborate compositional control for enhancing piezoelectric properties in niobate-based ceramics.