金属间化合物体系外场驱动的多卡效应和相关科学问题研究

Environmentally friendly magnetic/mechanical/electric refrigeration technique based on magnetocaloric/barocaloric/electrocaloric effect has an extensive future. Searching the method to manipulate multicaloric effect and coupling-caloric effect induced by multiple physical fields opens a new direction for developing solid-state refrigeration technique. In the present proposal, our research will focus on the multicaloric effect and coupling-caloric effect induced by multifield in intermetallic compounds with strong magnetic volume effect, particularly for the novel LaFeSi-based magnetocaloric materials. The characters of strain field introduced by hydrostatic pressure and film technology are quite different, thus the effect on the magnetic volume effect and caloric effect should be also different. Coupling-caloric effect is a new concept for cooling raised in this project. Through extensively study on the effect of the introduction of pressure in a magnetization/polarization process and the application of magnetic/electric field in a pressure process on magnetic/electric volume effect, ferromagnetic/ferroelectric coupling, magnetization/polarization process, itinerant electron metamagnetic transition, we hope to distinguish the difference between multicaloric effect and coupling-caloric effect and understand the relative physics behind. Through our effort in this project, we are able to: (1)enrich and develop the theory and the experimental methodology for studying solid-state multicaloric effect and coupling-caloric effect, (2) understand the different behaviours and relative physics of multicaloric effect and coupling-caloric effect in different systems, (3) obtain multi-field-controlled means on tuning multicaloric effect in ferromagnetic/ferroelectric systems so as to reduce the working magnetic/mechanical/electric field for the novel magnetocaloric/ barocaloric/electrocaloric materials and eventually increase refrigeration efficiency, and (4) design and explore novel solid-state refrigerants working under hybrid cooling condition by applying magnetic, electric field and pressure.

基于磁/压/电热效应的绿色环保固态制冷技术应用前景广阔，寻找具有多源热效应的综合物理场调控手段是固态制冷研究的新方向。本项目重点研究具有显著磁晶耦合的金属间化合物（特别是具有自主知识产权LaFeSi基新型巨磁热材料）多场诱发的多卡和耦合热效应。薄膜技术、静水压引入的应变场特点不同，对磁晶耦合、热效应影响也不同。多场耦合热效应是本项目提出的全新概念。深入研究磁化/电极化过程中压力的引入、压力过程中磁场/电场的引入对磁晶/电极化-结构耦合、铁磁/铁电交换作用的影响，认识多场诱导的多卡、耦合热效应的规律和物理机理并发展先进表征手段是固态热效应新课题。通过本项研究（1）丰富和发展固态多卡和耦合热效应理论和实验研究方法；（2）认识不同体系多卡和耦合热效应特点和机理；（3）获得多卡效应的多场调控手段，降低现有新型巨热材料所需工作磁场/应力场/电场；（4）设计新型固态磁/电/压力混合致冷材料并寻求应用。

基于磁/压/电热效应的绿色环保固态制冷技术应用前景广阔。本项目研究了多种材料体系的磁热、压热和弹热效应，揭示了多场调控卡效应的基本规律和本质，为卡效应材料的制冷应用提供了重要材料基础。主要包括：.1)首次利用电场调控的应力记忆效应实现了对FeRh/PMN-PT磁热材料滞后损耗的非易失性调控。-6 kV/cm脉冲电场使磁滞后损耗降低56%左右。我们创新性地提出的制冷循环与应变记忆效应相结合的新方法，有效解决了样机设计中遇到的双场循环瓶颈问题。.2)在具有自主知识产权的巨磁热La(Fe0.92Co0.08)11.9Si1.1获得静水压大幅增强的磁热和压热效应，11.3kbar压力使磁热熵变增大到2倍，9kbar压力使压热熵变增大到3倍。结合中子衍射和第一性原理计算从原子尺度揭示了机理。.3)在实验测量基础上首次利用热力学解析方法研究了Ni50Mn35In15在磁场和静水压下的耦合卡效应。揭示了压力通过增强磁-结构耦合强度使磁熵变增强的规律。.4)将磁制冷材料薄膜化是制冷器件微型化的发展趋势。成功地制备出具有良好外延/取向的FeRh/PMN-PT薄膜。实现了电场对磁热性能和相变温区的动态调控。制冷温区由34K(327K-361K)拓宽至60K(327K-387K)。在此基础上设计了电场磁场双场激励的AMR循环。.5)创新性地发现了以新戊二醇（NPG）为代表一系列塑晶材料的庞压热效应，熵变(687 J kg-1K-1)高出传统固态制冷材料一个数量级。在原子尺度揭示了这一效应的本质来源是压力对分子取向无序的抑制。.6)对一级磁相变Heusler型合金的应力诱发磁结构相变及其弹热效应开展了系统研究，取得系列创新性成果。搭建了一台将超导磁体与力学试验机相结合的多卡效应表征设备，实现了强磁场环境下直接测量弹热温变。..共发表SCI论文80篇，其中Nature 1篇，Nano energy 2篇，Mater.Horiz. 1篇，Acta Mater.5篇, Chem. Mater.1篇, ACS-Appl.Mater.Interfaces 2篇，Nano Letters 1篇，Nanoscale 2篇, Script Mater. 11篇，APL/APL Mater. 12篇，Phys.Rev.B 3篇；获发明专利授权 19 项；国际国内邀请报告41次；培养博士硕士研究生20名。