Electrocaloric Effect of Lead Magnesium Niobate-lead Titanate (PMN-PT) Ceramics

Electrocaloric refrigeration technology has emerged as a research hotspot in solid-state cooling due to its advantages of high energy efficiency, miniaturization potential and environmental friendliness. However, achieving a large adiabatic temperature change (ΔT) and a wide operation temperature (Tspan) under low electric fields remains challenging. In this study, a new type of ceramics, (1-x )Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-PT, x=0.08, 0.10, 0.12, 0.14) ferroelectric relaxor with different PT contents, was synthesized via a conventional solid-state reaction method. The influence of PT concentration on their electrocaloric performance was investigated. Results indicate that increasing PT content weakens their relaxor characteristics, reduces their dielectric frequency dispersion, and drives their relaxor ferroelectric behavior toward normal ferroelectric. Notably, the 0.88PMN-0.12PT ceramic exhibits outstanding electrocaloric properties under a low electric field of 50 kV/cm, achieving a maximum ΔT of 1.60 K, with ΔT exceeding 0.5 K across a broad temperature range of 30-180 ℃. Piezoresponse force microscopy (PFM) reveals its uniformly distributed long-range ferroelectric domain structure. The electrocaloric effect originates from entropy changes induced by transition of ferroelectric domains from an ordered to a disordered state during electric field unloading. By integrating dielectric, ferroelectric and domain structure analyses, the diffuse phase transition of relaxor ferroelectrics is correlated to their wide-temperature-range electrocaloric performance. This study provides theoretical guidance for designing lead-based electrocaloric materials compatible with low-field driving and wide temperature ranges, which has potential for applications in solid-state refrigeration devices.