Room‐Temperature Symmetric Giant Positive and Negative Electrocaloric Effect in PbMg_0.5W_0.5O₃ Antiferroelectric Ceramic

Abstract

As an emerging solid‐state refrigeration technology with zero‐emission and high energy conversion efficiency, there is a compelling need for ferroelectric materials with giant electrocaloric effects (ECEs) at room temperature suitable for refrigeration applications. The complex perovskite antiferroelectric (AFE), PbMg0.5W0.5O3, containing non‐equivalent B‐site ions with a symmetric giant positive and negative ECE near room temperature is presented. At the Curie temperature of 36 °C, the first‐order AFE–paraelectric phase transition gives rise to a large enthalpy change of 3.92 J g−1, more than four times that of BaTiO3. This leads to a significant ECE under the influence of an electric field. The direct electrocaloric characterization shows that the adiabatic temperature change, ΔT, exhibits symmetric peaks with a giant positive maximum of 1.79 K (ΔS = 1.68 J kg−1 K−1) at 36 °C and a negative maximum of −2.02 K (ΔS = −1.93 J kg−1 K−1) at 34 °C. The ultrahigh magnitude of ΔT near room temperature makes PbMg0.5W0.5O3 a superior electrocaloric material far beyond traditional PbZrO3‐based AFEs. The coexistence of symmetric giant positive and negative ΔT to further improve cooling efficiency is expected. In addition, the good reversibility and negligible leakage current should pave the way for practical applications.

Phase-pure antiferroelectric AgNbO3 films on Si substrates: chemical solution deposition and phase transitions

“…Antiferroelectric (AFE) materials have attracted resurgent interest owing to promising applications in a number of energyefficient technologies, including transducers, electrocaloric solid-state cooling, and pulsed power capacitors. [1][2][3][4][5] However, most known antiferroelectrics involve lead. As one of the few notable lead-free antiferroelectric families, AgNbO 3 -based compounds have aroused enormous interest in dielectric energy storage as well as other applications, such as photocatalysis and microwave devices.…”

Novel Fluorite‐Structured Materials for Solid‐State Refrigeration

“…an AFE PbMg 0.5 W 0.5 O 3 ceramic. [92] The maximum positive ΔT (1.79 K) and ΔS (1.68 J K −1 kg −1 ) were observed at 309 K, while a negative ΔT (2.02 K) and ΔS (1.93 J K −1 kg −1 ) were observed at 307 K.…”

Large conventional and inverse electrocaloric effects in PbMg0.5W0.5O3 multilayer capacitors above and below the Néel temperature

“…Unlike FE materials, AF materials can show field-driven phase transitions both b) paraelectric (PE) phases at zero field, after [24], drawn using VESTA software [27]. (c) Crudely sketched temperature-field (T-E) phase diagram based on [23] (solid lines) and selected data from figure 4(c) (dashed lines). The high-field region is labeled FE (ferroelectric) after [23], but some parts are not fully transformed.…”