Simultaneous Enhancement of Piezoelectricity and Temperature Stability in KNN‐Based Lead‐Free Ceramics Via Layered Distribution of Dopants

• Published in: Advanced functional materials 2022-08, Vol.32 (34), p.n/a
• Main Authors: Song, Aizhen, Liu, Yixuan, Feng, Tianyi, Li, Haitao, Zhang, Yuanyuan, Wang, Xuping, Liu, Lisha, Zhang, Bo‐Ping, Li, Jing‐Feng
• Format: Article
• Language: English
• Subjects: Blocking; Ceramics; Dopants; dopant‐graded ceramics; KNN‐based ceramics; Materials science; Phase transitions; piezoelectric performance; Piezoelectricity; Stability; temperature stability
• ISSN: 1616-301X; 1616-3028
• DOI: 10.1002/adfm.202204385

The past two decades have seen a great enhancement of piezoelectric coefficients (d33) to higher than 570 pC/N in (K, Na)NbO3 (KNN) piezoelectrics, but one notoriously unresolved issue is their severe temperature instability, obstructing them toward practical applications. The present work demonstrates a facile approach to overcome this problem by introducing a layered distribution of key dopants (Li and Sb) in a monolithic ceramic, featuring stepwise varied polymorphic phase transition (PPT) temperatures along the thickness direction. The dopant‐graded ceramic exhibits an outstanding d33 of 508 pC/N and a very large piezoelectric strain (Suni, of 0.18%). More importantly, an excellent temperature stability (d33 variation within 13% over the temperature range of 25–150 °C) is achieved, which is superior to that of most state‐of‐art KNN counterparts. These are attributed to the construction of spatially diffused PPT in combination with enhanced polarization, permittivity, and piezoresponse through interfacial effect, including the Maxwell–Wagner effect and intergranular stress by gradient doping. The results offer an alternative strategy for designing high‐performance piezoelectric materials with desirable temperature reliability. KNN‐based lead‐free ceramics exhibit simultaneously an outstanding d33 and temperature stability in the range of 25–150 °C by introducing a layered distribution of key dopants in a monolithic ceramic with stepwise varied polymeric phase transition (PPT) temperatures along the thickness direction. These are attributed to the construction of spatially diffused PPTs in combination with the Maxwell–Wagner effect and intergranular stress.