Mixed metal melts as solvents for materials synthesis

技术摘要：本研究得到了美国国家科学基金会材料研究部固态与材料化学项目的支持。本项目将研究由两种元素组成的金属助熔剂合成新的金属间化合物、锌相和络合盐。在金属助熔剂中合成允许在熔融溶液中发生反应；这种液态方法使晶体生长和形成不寻常的新亚稳相。结合两种不同的金属作为混合溶剂，由于共晶的形成，可以降低反应温度，并提高更大范围反应物的溶解度。将探索两个领域：在镧系/过渡金属（Ln/T）共晶熔剂中磁性金属间相的合成，以及在富碱土（AE）熔剂混合物中轻质Zintl相和复杂的盐类化合物的合成。利用镧系元素和过渡金属元素的磁矩，可以合成具有复杂晶体结构和磁性质的新化合物。可能出现的磁性行为包括磁有序、自旋玻璃行为、超导性、磁电阻行为、混合价态和重费米子行为。在富含碱土的助熔剂中发生反应，根据所用助熔剂金属的不同，将产生种类繁多的材料。富含高正电性Ca、Sr或Ba的助熔剂会强烈还原主族元素，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复杂氢化物相。使用富镁焊剂将产生更多的边缘产品，这些产品不表现出完全的电荷转移，结果可能显示金属到绝缘体的转变。非技术摘要：美国国家科学基金会材料研究部的固态和材料化学项目支持探索可能导致发现具有有用性质的新化合物的不寻常合成方法。金属助熔剂技术使用熔融金属作为溶剂，用于合金和金属间化合物的合成和晶体生长。磁性化合物是通过在两种磁性金属（镧系金属和过渡金属）的通量混合物中进行各种元素的反应来寻找的。用于储氢和潜在航空航天应用的轻质合金正在从由诸如Li， Mg和Ca等轻质金属组成的助熔剂混合物中的元素的反应中寻找。助熔剂生长通常产生大晶体形式的产品；这允许使用大量的表征技术，这将导致更好地理解如何从化合物的结构和组成中获得磁性和电子性质。这项研究将培养材料化学方面的本科生、研究生和博士后研究人员，这将加强佛罗里达州立大学材料科学的发展计划。这个高度跨学科的项目涉及与各个领域（如化学、物理和工程）的科学家合作；这将使参与者了解现代科学日益复杂的本质。

TECHNICAL SUMMARY:This research is supported by the Solid State and Materials Chemistry program of the NSF Division of Materials Research. This project will investigate the synthesis of new intermetallics, Zintl phases, and complex salts from metal fluxes comprised of two elements. Synthesis in metal flux allows reactions to take place in a molten solution; this liquid state method enables crystal growth and the formation of unusual new metastable phases. Combining two different metals to act as a mixed solvent allows for lower reaction temperatures due to eutectic formation, and improved solubility of a wider range of reactants. Two areas will be explored: the synthesis of magnetic intermetallic phases in lanthanide/transition metal (Ln/T) eutectic fluxes, and the synthesis of lightweight Zintl phases and complex salt-like compounds in alkaline earth-rich (AE) flux mixtures. The Ln/T flux syntheses will yield new compounds with complex crystal structures and magnetic properties stemming from magnetic moments of both the lanthanide and the transition metal element. Possible magnetic behavior that may arise includes magnetic ordering, spin glass behavior, superconductivity, magnetoresistive behavior, mixed valence and heavy fermion behavior. Reactions in alkaline earth rich fluxes will produce a wide range of classes of materials, depending on the flux metals used. Fluxes rich in highly electropositive Ca, Sr, or Ba will strongly reduce main group elements to form new Zintl phases and complex salts. These include new complex hydride phases which may be of interest for hydrogen storage. Using Mg-rich fluxes will yield more borderline products which do not exhibit complete charge transfer and may as a result show metal-to-insulator transitions. NON-TECHNICAL SUMMARY:The Solid State and Materials Chemistry program of the NSF Division of Materials Research supports exploration of unusual synthetic methods which may lead to discovery of new compounds with useful properties. The metal flux technique uses molten metals as solvents for synthesis and crystal growth of alloys and intermetallics. Magnetic compounds are being sought by carrying out reactions of a variety of elements in flux mixtures of two magnetic metals (a lanthanide metal and a transition metal). Light weight alloys for hydrogen storage and potential aerospace applications are being sought from reactions of elements in flux mixtures comprised of lightweight metals such as Li, Mg, and Ca. Flux growth often yields products in the form of large crystals; this allows for use of a large suite of characterization techniques which will lead to a better understanding of how magnetic and electronic properties are derived from the structure and composition of the compounds. This research will educate undergraduate, graduate and postdoctoral researchers in materials chemistry, which will strengthen the developing program in materials science at Florida State University. This highly interdisciplinary project involves collaboration with scientists in a variety of areas (such as chemistry, physics, and engineering); this will allow the participants to understand the increasingly complex nature of modern science.