Enhanced electrocaloric effect in (Bi0.5Na0.5)TiO3-6BaTiO3 based relaxor ferroelectric nanocomposites by regulating Joule heating

Abstract

Recently, electrocaloric effect (ECE)-based cooling technology has attracted a great deal of research attention. With a relatively high energy conversion efficiency (∼70 %) and no generating greenhouse gases, ECE-based cooling technology is suitable for use in the next generation of solid-state cooling devices. In this investigation, the PMMA layer was coated on the surface of (Bi0.5Na0.5)TiO3-6BaTiO3-1.5 %BiCoO3 (BNBT-BCO) nanofillers to reduce the Joule heat of BNBT-BCO/terpolymer (P(VDF-TrFE-CFE)) nanocomposite. From the ECE measurement result, the adiabatic temperature change (ΔT) of the BNBT-BCO@P/T-15 nanocomposite film reached 10.33 °C under 90 MV/m, which is 25 % higher than that of the BNBT-BCO/T-15 nanocomposite film (no PMMA coating, ∼8.29 °C) under the same electric field. In addition, the ΔT of the BNBT-BCO@P/T-15 nanocomposite film reached 17.52 °C under 150 MV/m at room temperature. This value is approximately 60 % higher than that of the pristine terpolymer films (ΔT ∼ 10.84 °C) and 17.4 % higher than that of BNBT-BCO@P/T-20 nanocomposite film (ΔT ∼ 14.92 °C). This work creates a new approach to using the surface coating on ceramic nanoparticles to reduce the Joule heat of the nanocomposites and improving the adiabatic temperature change (ΔT) and efficiency of ECE devices.