Li Maofan, Han Shiguo, Liu Yi, Luo Junhua, Hong Maochun, Sun Zhihua
State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002, China.
Fujian Science & Technology Innovation Laboratory for Optoelectronic Information of China, Fuzhou, Fujian 350108, China.
J Am Chem Soc. 2020 Dec 9;142(49):20744-20751. doi: 10.1021/jacs.0c09601. Epub 2020 Nov 23.
Antiferroelectric materials, characterized by an antiparallel array of adjacent dipoles, are holding a bright future for solid-state refrigeration based on their electrocaloric (EC) effects. Despite great advances of inorganic oxides and some organic soft polymers, their EC effects are achieved under quite high electric fields that result in too low EC strengths for practical application. Currently, it is a challenge to exploit soft antiferroelectric with strong EC strengths. Here, by the mixed-cation alloying, we present a new perovskite-type soft antiferroelectric, (isopentylammonium)CsPbBr (), which incorporates both an organic spacing cation and an inorganic perovskitizer Cs moiety. Remarkably, the synergic cooperativity between the reorientation of the organic spacer and atomic displacement of Cs cation triggers its multiple ferroelectric-antiferroelectric-paraelectric phase transitions at 321 and 350 K. Their natural polarization vs electric field hysteresis loops are characterized to confirm ferroelectric and antiferroelectric orders of , respectively. It is emphasized that, under a low electric field of 13 kV/cm, the antipolar dipole realignment in endows a giant near-room-temperature EC strength (Δ/Δ) of 15.4 K m MV at antiferroelectric phase. This merit is on par with the record-high value of BaTiO (∼16 K m/MV) but far beyond the state-of-the-art soft polymers. The underlying EC mechanism for is ascribed to the extremely low critical field to switch dipoles, involving the reorientation of the organic spacer and the shift of the Cs cation. Besides, notable EC entropy change (∼4.1 J K kg) and temperature change (∼2 K) reveal potentials of for solid-state refrigeration. As far as we know, this discovery of near-room-temperature EC strengths is unprecedented in the hybrid perovskite family, which sheds light on the exploration of new soft antiferroelectrics toward high-efficiency refrigeration devices.
反铁电材料具有相邻偶极子的反平行排列特性，基于其电热效应，在固态制冷领域有着光明的前景。尽管无机氧化物和一些有机软聚合物取得了巨大进展，但它们的电热效应是在相当高的电场下实现的，导致实际应用中的电热强度过低。目前，开发具有强电热强度的软反铁电材料是一项挑战。在此，通过混合阳离子合金化，我们展示了一种新型钙钛矿型软反铁电材料，（异戊基铵）CsPbBr（ ），它同时包含有机间隔阳离子和无机钙钛矿化剂Cs部分。值得注意的是，有机间隔基的重新取向与Cs阳离子的原子位移之间的协同合作引发了其在321 K和350 K处的多个铁电 - 反铁电 - 顺电相变。对它们的自然极化与电场滞后回线进行了表征，分别确认了 的铁电和反铁电有序状态。需要强调的是，在13 kV/cm的低电场下， 中的反极偶极子重新排列在反铁电相时赋予了15.4 K m MV的巨大近室温电热强度（Δ /Δ ）。这一优点与BaTiO 的创纪录高值（约16 K m/MV）相当，但远远超过了目前最先进的软聚合物。 的潜在电热机制归因于切换偶极子的极低临界场，涉及有机间隔基的重新取向和Cs阳离子的位移。此外，显著的电热熵变（约4.1 J K kg ）和温度变化（约2 K）揭示了 在固态制冷方面的潜力。据我们所知，这种近室温电热强度的发现在混合钙钛矿家族中是前所未有的，这为探索用于高效制冷设备的新型软反铁电材料提供了线索。
