EAGER: CRYO: Development of Novel Ce1-xLaxB6 Thermoelectric Nanocomposites for Cryogenic Cooling

该项目由化学、生物工程、环境和交通系统部、土木工程、机械和制造创新部以及材料研究部联合支持。能够在超低温1开尔文下工作的制冷机需要运行量子设备。热电冰箱是一种固态热泵，它使用电子作为热载体，从制冷负荷中提取热量，与替代制冷技术相比，它们往往具有实质性的优势。热电冰箱的一些更显著的特点包括没有移动部件，体积和重量小，精确的温度控制，电气上的“安静”操作，以及环保。然而，现有的热电材料在低温制冷中并不是很有效。正常金属的热电冷却在任何温度下都很弱。半导体在室温下是理想的热电材料，但在超低温时会变成电绝缘体。这个早期概念探索性研究奖助金(AGER)项目的总体愿景是开发一种能够在超低温下制冷的热电材料，1开尔文。该项目的更广泛影响包括将其融入马里兰大学的教育活动，扩大代表不足的群体在研究中的参与，以促进多样性、公平性和包容性，以及K-12计划。该研究计划寻求开发实现超低温制冷所需的新型CE1-xLaxB6热电材料(开尔文1)。在这项工作中，我们将探索在CeB6中掺入非磁性的La，以降低电子输运中从近藤效应区到费米液区的转变温度，从而使其热电峰值温度移动1开尔文。此外，纳米复合技术将被用来通过降低单晶CeB6的声子导热系数同时保持其电子迁移率来提高单晶CeB6的优值系数。采用马里兰大学最近开发的快速高温烧结方法，制备了不同掺杂的Ce1-xLaxB6热电纳米复合材料。为了实现这些技术目标，我们制定了一系列相关的工作：1)Ce1-xLaxB6纳米复合材料的制备和优化；2)Ce1-xLaxB6纳米复合材料的微观结构和成分表征；3)Ce1-xLaxB6纳米复合材料的热电性能表征；以及4)Ce1-xLaxB6纳米复合材料的热电性能模拟。热电材料中的关键元素是Ce和La，它们在地球上的含量与许多常见的工业金属一样丰富，如铜和铬。这项研究是雄心勃勃的高风险-高回报议程中必要的第一个探索阶段。这种在低温下潜在改变游戏规则的制冷技术的开发对量子设备的进步至关重要。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

This project is jointly supported by the Division of Chemical, Bioengineering, Environmental and Transport Systems, the Division of Civil, Mechanical and Manufacturing Innovation, and the Division of Materials Research.Refrigerators that can function at ultra-low temperatures, 1 Kelvin, are required to operate quantum-enabled devices. Thermoelectric refrigerators are solid-state heat pumps that use electrons as heat carriers to extract heat from the cooling load, and they often provide substantial advantages over alternative refrigeration technologies. Some of the more significant features of thermoelectric refrigerators include no moving parts, small size and weight, precise temperature control, electrically “quiet” operation, and environmentally friendly. However, the existing thermoelectric materials are not effective at cryogenic refrigeration. The thermoelectric cooling in normal metals is weak at any temperature. Semiconductors are ideal thermoelectric materials around room temperatures, but turn into electrical insulator at ultra-low temperatures. The overarching vision of this EArly-concept Grant for Exploratory Research (EAGER) project is to develop a thermoelectric material that can enable refrigeration at ultra-low temperatures, 1 Kelvin. The broader impacts of this project include its integration into educational activities at University of Maryland, broadening the participation of under-represented groups in research to foster diversity, equity, and inclusion, and K-12 outreach.This research program seeks to develop novel Ce1-xLaxB6 thermoelectric materials needed to enable ultra-low temperature refrigeration (1 Kelvin). In this effort, the doping of non-magnetic lanthanum (La) in CeB6 will be explored to lower the temperature of transition from the Kondo effect region to Fermi liquid region in electron transport, and therefore to shift its peak thermoelectric temperature 1 Kelvin. In addition, the nanocomposite technology will be employed to enhance the figure-of-merit of the single crystalline CeB6 by reducing its phonon thermal conductivity while preserving its electron mobility. The rapid, high temperature sintering method recently developed at the University of Maryland will be adopted to manufacture the Ce1-xLaxB6 thermoelectric nanocomposites with various doping. To achieve the technical objectives, a series of interrelated tasks is formulated: 1) Manufacturing and optimization of Ce1-xLaxB6 nanocomposites; 2) Microstructure and composition characterization of Ce1-xLaxB6 nanocomposites; 3) Thermoelectric property characterization of Ce1-xLaxB6 nanocomposites; and 4) Thermoelectric property modeling of Ce1-xLaxB6 nanocomposites. The key elements in the thermoelectric materials are Cerium and Lanthanum, which are as abundant on Earth as many familiar industrial metals, such as copper and chromium. The research is a necessary first exploratory stage in an overall ambitious high-risk-high-payoff agenda. The development of this potential game-changing refrigeration technology at cryogenic temperatures is critical for the advancement of quantum devices.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.