稀土RE2T2X材料相变调控与磁制冷性能优化

基于磁热效应的磁制冷技术因其具有绿色环保、高效节能等优点有望成为替代气体压缩制冷的新技术之一。磁热效应由磁场与磁亚晶格耦合而生，其大小与材料磁相变密切相关。开发出可用于不同温区的高性能磁制冷用工质材料依然是该领域的研究热点也是难点。本项目在前期研究的基础上，拟选择具有多样晶体结构和丰富物理特性的稀土RE2T2X（RE = Gd-Tm; T= Fe, Co, Ni, Cu, Zn; X = Ga, In, Sn, Cd）材料为研究对象，通过对不同外部参数（温度、磁场、物理/化学压力等）下晶体结构和宏观物性的系统表征与分析，结合第一性原理计算，较全面、立体地阐明稀土4f电子、过渡金属3d电子及4f-3d电子耦合对RE2T2X材料的磁相变及磁制冷等功能特性的贡献及影响规律，并揭示其物理机制。建立有效调控该类材料磁相变的理论模型，为获得高性能低温磁制冷材料提供思路和方法。

The magnetic refrigeration (MR) technology based on magnetocaloric effect (MCE) was considered as a promising alternative technology to the present well commercialized gas compression/expansion technology due to its advantages of high energy-efficiency and environment friendly. The MCE is a thermodynamic response of the coupling effect between the magnetic sub-lattice(s) with applied magnetic fields, which strongly depends on the corresponding magnetic phase transition. Exploiting of high performance MR materials for different working temperature regions is still a hot and difficult point in this field. Based on our primary investigations, the rare earth-based RE2T2X (RE = Gd-Tm; T= Fe, Co, Ni, Cu and Zn; X = Ga, In, Sn and Cd) compounds with various crystal structures and abundant physical properties have been taken as the main research subject in the present project. The crystal structures and macro physical properties will be determined and analyzed systematically under different external conditions (temperature, magnetic field, physical/chemical pressure, etc.). The effect of rare-earth 4f electrons, transition-metal 3d electrons as well as the coupling of 4f-3d electrons on the magnetic properties and MCE performances will be clarified based on the experimental results and the first principle calculation, and then the related physical mechanism will be clarified. A theoretical model is expected to be established for regulating and controlling the magnetic phase transition of RE2T2X-type compounds. The present project could provide some new valuable experimental data and theory basis for synthesis and design high performance cryogenic MR materials.