High‐Performance Lead‐Free Ceramics With Simultaneously High Piezoelectricity and High Mechanical Quality Factor

Abstract Piezoelectric materials with a high piezoelectric coefficient ( d 33 ) and high mechanical quality factor ( Q m ) are vital for advanced high‐power applications. However, achieving this combination is challenging, particularly for lead‐free piezoelectrics, because a high d 33 value relies on mobile domain walls, which increase dissipative losses and reduce Q m . In this study, this longstanding trade‐off is overcome by introducing defect dipoles (via Mn doping) into the quadruple point (QP) composition of the lead‐free Ba(Sn, Ti)O 3 system. The resultant 0.5%Mn‐doped Ba(Sn 0.11 Ti 0.89 )O 3 (BST‐0.5%Mn) ceramic exhibits a high d 33 value of 710 pC/N and high Q m value of 929, while the BST‐1%Mn ceramic achieves a d 33 value of 614 pC/N and Q m value of 1138. These values represent a 10‐fold increase in Q m and 1.6‐fold increase in d 33 for BST‐0.5%Mn, compared to those for undoped BST. High‐resolution scanning transmission electron microscopy and phase‐field simulations reveal that the enhanced d 33 and Q m are attributable to the coexistence of multiple phases of QPs with symmetry‐conforming defect dipoles, challenging the long‐held notion of physical incompatibility between high d 33 and high Q m . These findings offer a pathway for designing eco‐friendly piezoelectric materials with unprecedented performance, paving the way for sustainable and efficient high‐power applications.