Synthesis and Properties of Quasicrystalline and Crystalline Intermetallic Compounds with Bandgap

本文提出对金属间合金的电子性质进行全面的研究，目的是了解近年来在某些准晶合金中观察到的绝缘态、金属-绝缘体跃迁和强电子各向异性的性质，并探讨原子尺度上的有序和化学在金属间化合物中电子传递和带隙形成中的作用。该项目的副产品将是确定用于高温应用的新型热电材料。该项目是一个广泛合作的项目，涉及多个领域的专家来研究结构-化学-性质关系。首席研究员将进行合金的合成和结构表征、电导率、比热、霍尔效应和热功率的测量。其他合作者将利用光学导电性、x射线光谱学、电子隧穿和核磁共振来探测电子结构。结构对性能的影响将通过先进的电子显微镜和核磁共振技术来研究。物理学家和材料科学家对不寻常的晶体结构感兴趣，因为固体中不寻常的原子排列为理解自然界的组织和秩序提供了新的挑战。同样重要的是，不同寻常的物理性质有望在新材料中看到。我们的研究项目侧重于全面研究和进一步探索金属合金的电子性能，包括那些表现出非晶结构的合金，即准晶体。该项目是一个广泛合作的项目，涉及世界各地的几个小组，为各种实验测量做出贡献。已经证明，一些以金属为基础的合金化合物可以变成非金属，其中一些甚至表现出类似于在硅和锗等半导体中观察到的电子现象。结果表明，新合金具有良好的热电材料潜力。* * *

9700584 Poon A comprehensive study of electronic properties in intermetallic alloys is proposed, the goals are to understand the nature of the insulating state, the metal- insulator transition and the strong electronic anisotropy recently observed in some quasicrystalline alloys as well as to explore the roles of atomic-scale order and chemistry in electron transport and bandgap formation in inermetallic compounds. The spin-off of the project will be to identify new thermoelectric materials for high-temperature applications. The project is a widely collaborative one, it involves experts from several areas to study structure- chemistry-property relationships. The principal investigator will carry out synthesis and structural characterization of alloys, measurements of conductivity, specific heat, Hall effect, and thermopower. Other collaborators will utilize optical conductivity, x-ray spectroscopy, electron tunneling, and nuclear magnetic resonance to probe electronic structure. Effects of structure on properties will be studied by advanced electron microscopy and nuclear magnetic resonance techniques. %%% Physicists and materials scientists are interested in unusual crystal structures because unusual atomic arrangements in solids provide new challenges for understanding organization and order in nature. Equally important, unusual physical properties are expected to be seen in novel materials. Our research project focuses on comprehensive study and further exploration of electronic properties of metallic alloys including those that exhibit noncrystalline structures, known as quasicrystals. The project is a widely collaborative one, involving several groups world-wide to contribute to a variety of experimental measurements. It has been shown that some of the titled alloy compounds based on metals can become nonmetals, several of them even exhibit electronic phenomena similar to those observed in semiconductors such as silicon and germanium. The re are indications that the new alloys are potentially good thermoelectric materials. ***