Simultaneous Enhancement of Piezoelectricity and Mechanical Quality Factor in Hard‐Type KNN‐Based Lead‐Free Ceramics via Hierarchical Domain Architecture

• Published in: Advanced functional materials Vol. 35; no. 30
• Main Authors: Feng, Tianyi, Yang, Ziqi, Liu, Huan, Huang, Haofeng, Hu, Jinhao, Zhu, Li‐Feng, Zhang, Bo‐Ping, Li, Jing‐Feng
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc 24.07.2025
• Subjects: Domain walls; Ferroelectric domains; Ferroelectricity; hierarchical domain architecture; lead‐free piezoelectric ceramics; mechanical quality factor; Piezoelectric ceramics; Piezoelectricity; potassium sodium niobate; Q factors; Thermal stability
• ISSN: 1616-301X; 1616-3028
• DOI: 10.1002/adfm.202425699

High mechanical quality factor (Qm) and low mechanical loss are crucial for the performance of piezoelectric materials in high‐power applications. Although potassium sodium niobate (KNN) based ceramics are promising candidates for lead‐free piezoelectric materials due to their favorable piezoelectric performance and environmental benefits, they traditionally face a trade‐off between high piezoelectric coefficient (d33) and Qm. To address this long‐standing issue, a multivalent acceptor codoping strategy is presented that innovatively induces hierarchical domain structure in hard‐type KNN‐based piezoceramics, significantly increasing domain wall density and pinning strength while maintaining well‐ordered ferroelectric domain structure, thereby achieving a simultaneous enhancement of Qm, d33 and thermal stability. The optimized composition possesses a high Qm up to 948 with a d33 of 132 pC/N, representing improvements of 80% and 25% compared to Cu‐doped samples, and maintaining outstanding performance with Qm > 800, d33 > 130 pC/N across a broad temperature range of 25–175 °C. Furthermore, our sample retained high Qm performance under high‐power conditions, outperforming several commercial lead‐based ceramics. These results provide new insights into the defect‐domain interaction of hard‐type KNN‐based ceramics and demonstrate their potential for lead‐free high‐power piezoelectric applications. Hard‐type KNN‐based lead‐free ceramics simultaneously exhibit an outstanding d33, Qm, and temperature stability in the range of 25–175 °C by introducing a multivalent acceptor codoping strategy to induce the hierarchical domain structure. This performance is attributed to the integration of increased domain wall density, strengthened pinning effects, and maintaining well‐ordered ferroelectric domain structures.