Mixed Molten Metals as Solvents for Materials Synthesis

摘要本课题以熔融金属为溶剂进行反应，探索合成新型半导体和磁性材料。在金属熔剂中合成允许在溶液中发生反应；这种液态方法使晶体生长和不寻常的新化合物的形成成为可能。这项工作中发现的新材料可能具有有用的磁性和电子学性质，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认识。这个跨学科的研究项目培养本科和研究生的材料化学研究人员。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，以及使用橡树岭国家实验室和国家强磁场实验室等国家实验室的先进设备。这使学生参与者能够理解现代科学日益复杂和协作的本质。技术摘要材料研究部固态与材料化学项目的支持，使研究团队能够探索两个领域：在镧系/过渡金属（Ln/T）共晶通量中合成磁性合金，以及在富碱土（AE）通量混合物中合成轻质复杂盐类化合物。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-性质关系的发展趋势。Ln/T助熔剂合成的新化合物具有镧系元素和过渡金属元素的磁性。产品结构通常包含过渡金属簇或层；这些构建块的磁性行为将揭示磁矩是如何随着过渡金属簇尺寸的增加而发展的。可能出现的磁性行为包括磁有序、自旋玻璃行为、超导性、磁电阻、混合价态和重费米子行为。使用钙、锶或钡的富碱土助熔剂混合物会强烈还原大多数主族元素，形成新的锌相和络合盐。这些包括可能对储氢感兴趣的新的金属氢化物和亚氢化物相。使用富镁助焊剂产生更多的边缘产品，不表现出完全的电荷转移，往往是半金属的；它们可能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.