Giant room-temperature electrocaloric effect within wide temperature span in Sn-doped Ba0.85Ca0.15Zr0.1Ti0.9O3 lead-free thin films

Abstract

The electrocaloric (EC) effect cooling technique of environmentally friendly lead-free thin film materials driven by electric fields has recently gained tremendous attention due to the urgent demand for microelectronic and integrated circuit refrigeration devices. However, the widespread use of lead-free materials in EC devices is seriously hindered due to the small electrocaloric temperature change (ΔT) within a narrow operation temperature span (Tspan) near room temperature. Here, lead-free Ba0.85Ca0.15Zr0.1Ti0.9-xSnxO3 (BCZT-xSn, 0 ≤ x ≤ 0.03) thin films were prepared on substrates (Pt/Ti/SiO2/Si) via a sol-gel route. The BCZT-0.02Sn thin film presents an excellent EC effect (ΔT = 32.74 K, ΔS = 37.18 J kg−1 K−1) and large EC strength (ΔT/ΔE = 0.033 K cm kV−1, ΔS/ΔE = 0.037 J cm K−1 kg−1 kV−1) over a wide Tspan (∼26 K) under 1000 kV cm−1 near room temperature. The giant ΔT is mainly attributed to the emergence of an intermediate O phase and the formation of a multiphase (R, O and T phases) coexistence structure at room temperature, while the diffuse phase transition behavior is responsible for the wide Tspan. Our study provides a new idea for developing environment-friendly EC materials with an excellent room-temperature ΔT over a broad operational temperature region.