Peng, BiaolinZhang, QiGang, BaiLeighton, Glenn J. T.Shaw, ChristopherMilne, Steven J.Zou, BingsuoSun, WenhongHuang, HaitaoWang, Zhonglin2019-06-192019-06-192019-05-02Peng B, Zhang Q, Gang B, et al., (2019) Phase-transition induced giant negative electrocaloric effect in a lead-free relaxor ferroelectric thin film. Energy and Environmental Science, Volume 12, Issue 5, May 2019, pp. 1708-17171754-5692https://doi.org/10.1039/c9ee00269chttps://dspace.lib.cranfield.ac.uk/handle/1826/14251Ferroelectric/antiferroelectric thin/thick films with large positive or negative electrocaloric (EC) effects could be very useful in designing commercial refrigeration devices. Here, a giant negative EC effect (maximum ΔT ∼ −42.5 K with ΔS ∼ −29.3 J K−1 kg−1) comparable to the best positive EC effects reported so far is demonstrated for 0.5(Ba0.8Ca0.2)TiO3–0.5Bi(Mg0.5Ti0.5)O3 (BCT–BMT) lead-free relaxor ferroelectric thin films prepared on Pt(111)/TiOx/SiO2/Si substrates using a sol–gel method. An electric-field induced structural phase transition (nanoscale tetragonal and orthorhombic to rhombohedral) along the out-of-plane [111] direction plays a very key role in developing the giant negative EC effect. This breakthrough will pave the way for practical applications of next-generation refrigeration devices with high cooling efficiency in one cycle by ingeniously utilizing and combining both the giant negative and positive EC effects. Moreover, a large energy density of 51.7 J cm−3 with a high power density of 1.15 × 1010 W kg−1 at room temperature is also achieved in the thin film, indicating that it is also an attractive multifunctional material for energy storage.enAttribution-NonCommercial 4.0 Internationalhttp://creativecommons.org/licenses/by-nc/4.0/Article23682745