Large Electrocaloric Effect in Nanostructure-Engineered (Bi, Na)TiO3‑Based Thin Films

• Published in: ACS applied materials & interfaces 2022-11, Vol.14 (47), p.53048-53056
• Main Authors: Sun, Yunlong, Chen, Zibin, Luo, Hao, Liang, Jun, Chang, Shery L. Y., Wang, Danyang
• Format: Article
• Language: English
• Subjects: Functional Inorganic Materials and Devices
• ISSN: 1944-8244; 1944-8252
• DOI: 10.1021/acsami.2c14831

Although the solid-state cooling technology based on electrocaloric response has been considered a promising refrigeration solution for microdevices, the mediocre dipolar entropy change ΔS impedes its practical applications. In this work, ΔS of a conventional ferroelectric thin film, namely, 0.94­(Bi0.5Na0.5)­TiO3-0.06BaTiO3 (BNBT), was greatly improved through engineering the nanodomain structures. The number of zero-field polar states and saturation polarization were greatly increased concomitant with a weakened strength of polar correlation in the thin films, owing to the local stabilization of strongly tetragonally distorted nanoclusters (tetragonality of ∼1.25) by modulating the growth conditions during the thin film deposition process. Consequently, a giant ΔS value of ∼ –48.5 J K–1 kg–1 (corresponding to ΔT = ∼27.3 K) and a wide window of operating temperature (>70 °C) were obtained near room temperature under a moderate electric field of 1330 kV cm–1. Moreover, our engineered BNBT thin film exhibits decent fatigue endurance; i.e., a substantial electrocaloric effect over a broad span of temperature can be sustained after 5 × 107 cyclic loading of the electric field. This work provides a universal design strategy for significantly improving the close-to-room-temperature electrocaloric performance of Bi-based ferroelectric thin films without the need of compositional or architectural complexity.