Enhanced piezoelectric performance and thermal stability of alkali niobate-based ceramics

In this study, 0.5 wt% MnO2 doped (0.99-x)(K0.5Na0.5)(Nb0.965Sb0.035)O-3-0.01CaZrO(3)-x(Bi0.5K0.5)(Hf0.98Ti0.02) O-3 [abbreviated as (0.99-x)KNNS-0.01CZ-xBKHT, x = 0.01, 0.02, 0.03, 0.04, 0.05, 0.06] lead-free piezoelectric ceramics were fabricated by traditional solid-state reaction method. The microstructure, phase transformation, electromechanical properties and the thermal stability of the ceramics were systematically studied. Resulting from the R-T phase coexisting, a large piezoelectric coefficient (d(33) similar to 425 pC/N), planar electromechanical coupling factor (k(p) similar to 49%) were achieved in the ceramics with x = 0.04. Furthermore, the specimens with x = 0.04 also exhibit excellent temperature stability for d(33) which was manifested by the less than 10% variation of d(33) values when the annealing temperature increase from 25 degrees C to 100 degrees C. The good comprehensive properties indicate that MnO2 doped (0.99-x)KNNS-0.01CZ-xBKHT ceramics are promising candidates for practical application to eliminate the Pb-based piezoelectric ceramics from the market.