Ultrahigh electric‐field‐induced strain in KNN‐based piezoelectric ceramics sintered in reducing atmosphere.

With the goals of sustainable development adopted by more and more nations, the lead‐free trend of multilayer ceramic actuators has become a widely recognized consensus. Sintering in a reducing atmosphere is a necessary approach for preparing lead‐free ceramics co‐fired with low‐cost nickel internal electrodes. Herein, (1 − x)K0.48Na0.52Nb0.96Ta0.04O3–xSr(Zr0.5Ti0.5)O3 + 0.03ZrO2 + 0.08MnO2 (KNNT‐SZT) ceramics were sintered in a reducing atmosphere using a solid‐state reaction. The Sr(Zr0.5Ti0.5)O3 (SZT) dopant decreased the Curie temperature TC and the O–T phase transition temperature. The enhanced diffuseness of the ferroelectric phase transition of KNNT‐SZT ceramics is attributed to the element doping and the locally inhomogeneous microstructure. High inverse piezoelectric coefficients d33* of 883 and 787 pm/V were obtained for the 8‐ and 9‐mol% SZT‐doped samples, respectively. These results were attributed to the synergistic effect of ferroelectric domains with different sizes. The diffused O–T phase transition significantly improved the piezoelectric temperature stability of the 9‐mol% SZT‐doped sample, whose electric‐field‐induced strain decreased by <10% from room temperature (25°C) to 115°C. The cyclic fatigue test showed that >98% of the initial d33* was retained after 106 cycles of unipolar electrical loading. The KNNT‐SZT ceramics sintered in a reducing atmosphere possessed excellent inverse piezoelectric properties and are expected to be applied in the field of multilayer ceramic piezoelectric actuators with base metal internal electrodes. [ABSTRACT FROM AUTHOR]