Electric‐Field‐Driven Caloric Effects in Ferroelectric Materials for Solid‐State Refrigeration

Abstract

AbstractFerroelectrics have long been investigated for electrocaloric cooling applications, and recent studies have hinted that these materials possess huge potential for multiple caloric possibilities. These caloric effects are manifested as a response to multiple physical impetus. The present work evaluates the electrocaloric effect (ECE) and inverse piezocaloric (iPC) effect in various ferroelectric materials. Here, three different ferroelectric materials, namely, single crystal 0.65(PbMg1/3Nb2/3)O3–0.35PbTiO3 (PMN–0.35PT), polycrystalline lanthanum‐doped lead zirconate titanate [PLZT(8/65/35)], and (Ba0.865Ca0.135)(Zr0.11Ti0.89)O3 (BCZTO) ceramics are considered for ECE and iPC investigations. The results were obtained using modified Maxwell's relations in conjunction with independent experimental data. It was observed that PMN–35PT possesses significantly high potential for ECE (ΔTEC=0.78 K), for an applied electric field of 2.75 MV m−1 at 418 K. PLZT and BCZTO have ΔTEC values of 0.45 and 0.49 K at 383 K (1 MV m−1) and 353 K (3 MV m−1), respectively. As the selected compositions are relaxors, ΔTEC is observed in a wide operating temperature range. Finally, a new component of electric‐field‐driven caloric effect (iPC effect) has been reported for all compositions. PMN–35PT and PLZT exhibit ΔTiPC values of 0.29 K (425 K) and 0.49 K (383 K) under applied electric fields of 2.75 and 1 MV m−1, respectively. However, BCZTO demonstrates a stress‐biased =0.35 K at 298 K for a 3 MV m−1 electric field. This new way of estimating the caloric effect can be employed for materials having higher strain. Moreover, the iPC and ECE effects are manifested simultaneously in the material; therefore it is very difficult to determine, theoretically, which effect ultimately dominates.