High Temperature‐Insensitive Electrostrain Obtained in (K, Na)NbO3‐Based Lead‐Free Piezoceramics

• Published in: Small (Weinheim an der Bergstrasse, Germany) Vol. 20; no. 51; pp. e2407848 - n/a
• Main Authors: Liu, Huan, Yang, Ziqi, Su, Bin, Hao, Yijin, Feng, Tian‐Yi, Zhang, Bo‐Ping, Li, Jing‐Feng
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 01.12.2024
• Subjects: Actuators; defect engineering; Defects; Dipole moments; Domains; Electric fields; electrostrain; hierarchical domain configurations; High temperature; lead‐free piezoelectric; Niobates; Piezoelectric ceramics; Piezoelectricity; potassium‐sodium niobate; Room temperature; Stability; Temperature; temperature stability
• ISSN: 1613-6810; 1613-6829; 1613-6829
• DOI: 10.1002/smll.202407848

Over the last decades, notable progress is achieved in (K, Na)NbO3 (KNN)‐based lead‐free piezoceramics. However, more studies are conducted to increase its piezoelectric charge coefficient (d33). For actuator applications, piezoceramics need high electric‐field induced strain under low electric fields while maintaining exceptional temperature stability across a wide temperature range. In this study, this work developes Li/Sb‐codoped KNN (LKNNS) ceramics with high electrostrain by defect engineering and domain engineering. A remarkable strain of 0.43%, along with a giant d33* value of 2177 pm V−1, is attained in the LKNNS ceramic at 20 kV cm−1. The ceramic exhibits a minimal performance decrease of less than 15% over a temperature range from room temperature to 150 °C. The exceptional strain is attributed to the presence of A‐site vacancy‐oxygen vacancy (VA′−VO••${\mathrm{V}}_{\mathrm{A}}^{{\prime}}{\mathrm{ - V}}_{\mathrm{O}}^{{\mathrm{ \bullet \bullet }}}$) defect dipoles and the increase in nano‐domains. The hierarchical domain configuration and VA′−VO••${\mathrm{V}}_{\mathrm{A}}^{{\prime}}{\mathrm{ - V}}_{\mathrm{O}}^{{\mathrm{ \bullet \bullet }}}$ defect dipoles impede the switched domains from reverting to their original state as temperature increases, furthermore, the elongated dipole moments of VA′−VO••${\mathrm{V}}_{\mathrm{A}}^{{\prime}}{\mathrm{ - V}}_{\mathrm{O}}^{{\mathrm{ \bullet \bullet }}}$ caused by rising temperatures compensate for strain reduction results in exceptional temperature stability. This study provides a model for designing piezoelectric materials with exceptional overall performance under low electric fields and across a wide temperature range. By combining defect engineering and domain engineering, Li/Sb‐codoped (K, Na)NbO3 (KNN) ceramics achieve exceptional electrostrain and superior temperature stability under low electric fields. This work provides an effective strategy for designing KNN‐based materials suitable for high‐displacement piezoelectric actuators across a wide temperature range.