We report the giant electrocaloric effect (ECE) of BaZr0.2Ti0.8O3 (BZT) thick film near room temperature. The BZT thick film was fabricated by the tape casting method with the thickness of 12.0 μm. Due to the near invariant critical point composition, relaxor behavior, and the stress generated between the film and the substrate, the thick film exhibits a large adiabatic temperature drop ΔT = −7 °C under 19.5 MV/m electric field, large EC coefficient ΔT/ΔE = 0.50 x 10−6 K • m • V−1, ΔS/ΔE = 0.88 x 10−6 J • m • kg−1 • K−1 • V−1 over a wide temperature range near room temperature, where ΔS is the isothermal entropy change and ΔE is the applied field. These high EC properties and possibility of fabrication of the EC ceramics into multilayer ceramic capacitor configuration provide solution for the application of the EC material for practical cooling device applications.

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The relaxor ferroelectric materials, because of their large and reversible electric fi eld induced polarization, have been demonstrated to possess giant electrocaloric effect (ECE) over a broad temperature range, which are attractive for refrigeration with high energy effi ciency and environmental friendliness. However, high electric fi elds are required to generate the giant ECE in these materials, posing challenge for these materials in practical cooling devices which also require high reliability and low cost. Here, a general approach is reported, for example, establishing an internal bias fi eld in these relaxor ferroelectric polymers, to signifi cantly improve ECE which can be induced at low electric fi elds. It is demonstrated that in a polymer blend (nanocomposite) with a properly controlled normal ferroelectric in nanophase dispersion in the relaxor polymer matrix, the charge neutrality in the blends can cause an internal biasing fi eld, leading to more than 45% enhancement in the ECE at low electric fi eld (≈50 MV m −1 ). This internal biasing approach provides a universal strategy to enhance other low fi eld responses such as the electromechanical response in relaxor ferroelectrics.

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