Influence of Bi-perovskites on the piezoelectric properties of (K0.5Na0.5)NbO3-based lead free ceramics

Bi-perovskites, such as BiFeO3 (BF), BiInO3 (BI) and BiScO3 (BS), were added to (Li0.04K0.52Na0.44)(Nb0.84Ta0.1Sb0.06)O3 (LF4) to improve the piezoelectric properties of lead-free piezoelectric ceramics. The addition of Bi-perovskites up to 0.6 mol% did not depress the sinterbility of ceramics and the relative densities above 96% could be achieved by a powders-solid state reaction process. The c/a ratio of the tetragonal lattice of the LF4 ceramics was monotonously reduced with the amount of the BF added. The electrical insulation of the LF4 was improved with the addition BF, making the poling procedure under high electric fields become easy. The addition of BF was also effective to enhance the remnant polarization of the LF4 and the piezoelectric d33 constant of 358 pm/V was obtained by the addition of 0.4 mol% BiFeO3. However, the enhancement of the remnant polarization was not observed when the BI and BS were added to the LF4.