Synthesis, structure and properties of responsive solid-state materials

在恒定或可变的外力或电场作用下，反应性材料表现出独特的物理反应。将这种物理反应与固态相的杰出机械性能相结合，可以产生在工业和消费层面都有应用的功能材料。研究将集中在两个领域的响应固态材料：磁热电相和热电相。当磁场变化时，磁热材料通过改变其温度做出反应，可以用于磁冷却，这比传统的蒸汽循环制冷效率更高。热电材料在受到温度梯度作用时产生电压，或在电流通过时进行冷却/加热。目前，热电材料被用于深空任务的发电、远程气象和导航系统，以及电子设备和汽车座椅的冷却。由于一半的能量以废热的形式损失，研究工作开始集中于通过热电发电机回收其中的一些能量，特别是在汽车和烤箱中。提出的研究的短期目标将是发现和表征新的，高性能的热电和磁热材料。从长远来看，我们的目标是更深入地了解这些类型的材料中的成分-结构-性能关系，并将所获得的知识用于快速和有针对性的新材料设计。在热电材料中，我们将重点合成一般分子式为Lnm(Sb,Bi)nOm的类镧（Ln）锑化物和类铋亚氧化物。这些相可以归类为“电子-晶体声子-玻璃”材料，因为它们是良好的导电体，而它们的导热系数很低，接近非晶材料的导热系数。一些Lnm(Sb,Bi)nOm材料显示出新的电荷传输机制，我们希望利用这些机制来优化其热电性能。Lnm(Sb,Bi)nOm亚氧化物的研究是由我们小组发起的，我们希望在这一领域保持领先地位。在磁热场中，我们将有针对性地合成新的极性金属间材料，其中铁磁有序耦合到室温或接近室温的结构转变。我们提出利用价电子浓度和尺寸效应来调整新型磁热材料的结构和磁性能。这些方法是我们小组首创的，我们将应用它们来制备新的高性能相。

Responsive materials exhibit unique physical responses under constant or variable applied forces or fields. Combination of such physical responses with outstanding mechanical properties of solid-state phases yields functional materials that find applications both at the industrial and consumer levels. The research will focus on two areas of responsive solid-state materials: magnetocaloric and thermoelectric phases. Magnetocaloric materials respond by changing their temperature when the magnetic field is varied and can be used for magnetic cooling, which offers better efficiency than conventional vapour-cycle refrigeration. Thermoelectric materials generate voltage when subject to a temperature gradient or perform cooling/heating when current is passed through them. Currently, thermoelectric materials are used for power generation in deep-space mission, remote weather and navigation systems and for cooling in electronic devices and car seats. And since half of the energy is lost as a waste heat, research efforts start to focus on recovering some of this energy, especially in cars and ovens, through thermoelectric generators.The short term goals of the proposed research will be discovery and characterization of novel, high-performance thermoelectric and magnetocaloric materials. In the long run, we aim to develop a deeper understanding of the composition-structure-property relationship in these types of materials, and to use the obtained knowledge for the rapid and targeted design of new materials.Among the thermoelectric materials, we will focus on the synthesis of lanthanoid (Ln) antimonide and bismuthide suboxides with the general formula Lnm(Sb,Bi)nOm. These phases may be classified as "electron-crystal phonon-glass" materials, as they are good electrical conductors, while their thermal conductivity is very low and is approaching that of amorphous materials. Some of the Lnm(Sb,Bi)nOm materials display novel charge transport mechanisms and we want to use these mechanisms to optimize their thermoelectric properties. The research on the Lnm(Sb,Bi)nOm suboxides was initiated in our group and we would like to maintain our leading role in this area.In the magnetocaloric field, we will pursue targeted synthesis of new polar intermetallic materials, in which a ferromagnetic ordering is coupled to a structural transition at or near room temperature. We proposed to utilize the valence electron concentration and size effects to tune structural and magnetic properties of new magnetocaloric materials. These approaches were pioneered in our group and we will apply them to prepare novel high-performance phases.