Exceptional electrostrain with minimal hysteresis and superior temperature stability under low electric field in KNN-based lead-free piezoceramics
Huan Liu, Yijin Hao, Ziqi Yang, Tianyi Feng, Bin Su, Xin Zhang, Mengping Xue, Boping Zhang, Jing‐Feng Li
Abstract
Over the past two decades, (K<sub>0.5</sub>Na<sub>0.5</sub>)NbO<sub>3</sub> (KNN)-based lead-free piezoelectric ceramics have made significant progress. However, attaining a high electrostrain with remarkable temperature stability and minimal hysteresis under low electric fields has remained a significant challenge. To address this long-standing issue, we have employed a collaborative approach that combines defect engineering, phase engineering, and relaxation engineering. The LKNNS-6BZH ceramic, when sintered at <i>T</i><sub>sint</sub> = 1170 ℃, demonstrates an impressive electrostrain with a <inline-formula id="M1"> <math id="mathml_M1" display="inline" overflow="scroll"><msubsup><mrow class="MJX-TeXAtom-ORD"><mi>d</mi></mrow><mrow class="MJX-TeXAtom-ORD"><mn>33</mn></mrow><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><mo>∗</mo></mrow></mrow></msubsup></math></inline-formula> value of 0.276% and 1379 pm·V<sup>–1</sup> under 20 kV·cm<sup>–1</sup>, which is comparable to or even surpasses that of other lead-free and Pb(Zr,Ti)O<sub>3</sub> ceramics. Importantly, the electrostrain performance of this ceramic remains stable up to a temperature of 125 ℃, with the lowest hysteresis observed at 9.73% under 40 kV·cm<sup>–1</sup>. These excellent overall performances are attributed to the presence of defect dipoles involving <inline-formula id="M2"> <math id="mathml_M2" display="inline" overflow="scroll"><msubsup><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><mi mathvariant="normal">V</mi></mrow></mrow><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><mi mathvariant="normal">A</mi></mrow></mrow><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><msup><mi></mi><mo>′</mo></msup></mrow></mrow></msubsup><mtext>–</mtext><msubsup><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><mi mathvariant="normal">V</mi></mrow></mrow><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><mi mathvariant="normal">O</mi></mrow></mrow><mrow class="MJX-TeXAtom-ORD"><mtext>∙∙</mtext></mrow></msubsup></math></inline-formula> and <inline-formula id="M3"> <math id="mathml_M3" display="inline" overflow="scroll"><msubsup><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><mi mathvariant="normal">B</mi></mrow></mrow><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><mi mathvariant="normal">N</mi><mi mathvariant="normal">b</mi></mrow></mrow><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><msup><mi></mi><mo>′</mo></msup></mrow></mrow></msubsup><mtext>–</mtext><msubsup><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><mi mathvariant="normal">V</mi></mrow></mrow><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><mi mathvariant="normal">O</mi></mrow></mrow><mrow class="MJX-TeXAtom-ORD"><mtext>∙∙</mtext></mrow></msubsup></math></inline-formula>, the coexistence of R–O–T multiphase, and the tuning of the trade-off between long-range ordering and local heterogeneity. This work provides a lead-free alternative for piezoelectric actuators and a paradigm for designing piezoelectric materials with outstanding comprehensive performance under low electric fields.