Mixed Molten Metals as Solvents for Materials Synthesis

非技术摘要本研究项目探索通过使用熔融金属作为溶剂进行反应来合成新的半导体和磁性材料。金属助熔剂中的合成允许在溶液中进行反应;这种液态方法可以使晶体生长和形成不寻常的新化合物。在这项工作中发现的新材料可能具有有用的磁性和电子特性，它们的研究有助于增加对磁性合金，太阳能电池材料和储氢合金性质的理解。这个跨学科的研究项目教育本科生和研究生研究人员在材料化学。 这项工作涉及与各个领域（如化学、物理和工程）的科学家合作，以及使用国家实验室（如橡树岭国家实验室和国家高磁场实验室）的先进设施。这使得学生参与者能够理解现代科学日益复杂和协作的本质。技术摘要来自材料研究部固态和材料化学计划的支持使研究团队能够探索两个领域：在镧系元素/过渡金属（Ln/T）共晶助熔剂中合成磁性合金，以及在富含碱土金属（AE）的助熔剂混合物中合成轻质复合盐状化合物。这些反应的产物通过X射线衍射、磁化率测量、输运测量、能带结构计算和其他技术来表征。研究了反应性、常见结构构建块和结构-性能关系的趋势。 Ln/T磁通合成产生新的化合物的磁性源于镧系元素和过渡金属元素。产品结构通常包含过渡金属的簇或层;这些构建块的磁性行为将揭示磁矩如何随着过渡金属簇大小的增加而发展。可能出现的磁行为包括磁有序、自旋玻璃行为、超导性、磁阻、混合价态和重费米子行为。使用钙、锶或钡的富碱土熔剂混合物将强烈还原大多数主族元素以形成新的Zintl相和复盐。这些包括新的金属氢化物和亚氢化物相，这可能是感兴趣的氢存储。使用富含镁的焊剂产生更多的边界产品，这些产品不表现出完全的电荷转移，并且通常是半金属的;它们可能具有作为热电材料的潜在用途，或者可能显示金属到绝缘体的转变。

Non- Technical AbstractThis research project explores the synthesis of new semiconductors and magnetic materials by carrying out reactions using molten metals as solvents. Synthesis in metal flux allows reactions to take place in a solution; this liquid state method enables crystal growth and the formation of unusual new compounds. The new materials discovered in this work may possess useful magnetic and electronic properties, and their study contributes to increasing understanding of the nature of magnetic alloys, solar cell materials, and hydrogen storage alloys. This interdisciplinary research project educates undergraduate and graduate student researchers in materials chemistry. The work involves collaboration with scientists in a variety of areas (such as chemistry, physics, and engineering), as well as the use of advanced facilities at national labs such as Oak Ridge National Laboratory and the National High Magnetic Field Laboratory. This allows the student participants to understand the increasingly complex and collaborative nature of modern science.Technical AbstractSupport from the Solid State and Materials Chemistry program in the Division of Materials Research allows the research team to explore two areas: the synthesis of magnetic alloys in lanthanide/transition metal (Ln/T) eutectic fluxes, and the synthesis of lightweight complex salt-like compounds in alkaline earth-rich (AE) flux mixtures. Products of these reactions are characterized by X-ray diffraction, magnetic susceptibility measurements, transport measurements, band structure calculations, and other techniques. Trends in reactivity, common structural building blocks, and structure-property relationships are investigated. The Ln/T flux syntheses yield new compounds with magnetic properties stemming from both the lanthanide and the transition metal element. Product structures often contain clusters or layers of transition metals; the magnetic behavior of these building blocks will shed light on how magnetic moments develop as transition metal clusters increase in size. Magnetic behavior that may arise includes magnetic ordering, spin glass behavior, superconductivity, magnetoresistance, mixed valence and heavy fermion behavior. Alkaline earth-rich flux mixtures using calcium, strontium, or barium will strongly reduce most main group elements to form new Zintl phases and complex salts. These include new metal hydride and subhydride phases which may be of interest for hydrogen storage. Using magnesium-rich fluxes yields more borderline products which do not exhibit complete charge transfer and are often semimetallic; they may be of potential use as thermoelectric materials, or may show metal-to-insulator transitions.