(K,Na)NbO 3 ‐based relaxor ferroelectric thin film for energy storage

Abstract Ferroelectric energy storage research is a hot topic of today. Based on the requirements of microdevice development and environmental protection, it has become a challenge to develop high‐performance lead‐free ferroelectric films for energy storage. In this study, a lead‐free 0.95(K 0.49 Na 0.49 Li 0.02 )(Nb 0.8 Ta 0.2 )O 3 –0.05CaZrO 3 (KNNLT‐CZ) film was epitaxially grown on Nb:SrTiO 3 (001) substrate by pulsed laser deposition. The film exhibits relaxor ferroelectric characteristics and possesses an excellent energy storage density ( W tot ) of 33.26 J/cm 3 and recoverable energy storage density ( W rec ) of 25.13 J/cm 3 ; the energy storage efficiency exceeds 75% with a maximum of 93.8%. Furthermore, the film maintains stable performance within a temperature range of 25°C–175°C and a frequency range of 1–10 kHz, and shows a high fatigue resistance after 10 6 cycles. Transmission electron microscopy (TEM) image proves the existence of polar nano‐domains in the film, which are unique to relaxor ferroelectrics. This study presents that KNN‐based films are expected to be candidates for future lead‐free energy storage.