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

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 ( $$ ) defect dipoles and the increase in nano-domains. The hierarchical domain configuration and $$ defect dipoles impede the switched domains from reverting to their original state as temperature increases, furthermore, the elongated dipole moments of $$ 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.