Simultaneous realization of giant d33, large kp, and high Qm from periodic interface strain generated by co-doping strategy

Abstract

However, achieving a well-balanced performance in environment-friendly lead-free piezoelectrics remains challenging as they still fall short of their lead-based counterparts owing to the unclear promotional origins of doping modification. We propose an ion co-doping strategy that simultaneously optimizes the piezoelectricity, electromechanical performance, mechanical quality factor, and electrical anti-fatigue in KTa_1−xNb_xO₃ (KTN) single crystals. Further, the mechanism underlying the enhancement of these properties is elucidated. Microscopic and mesoscopic evidence demonstrate a more uniform order parameter induced by the co-doping defect structures, thereby yielding hierarchical domains and ordered lattice planes. At the atomic scale, the periodic interface strain induced by Mn and Fe co-doping orders the atomic arrangements, thereby stabilizing the polarization and domain states. Thus, the advantageous functions of both Mn and Fe ions are maintained. The superior overall properties of the co-doped KTN reach the level of lead-based single crystals. This work provides valuable insights into achieving piezoelectrics with excellent comprehensive performances using a co-doping strategy, while also advancing the understanding of how defect structures improve piezoelectric properties.