Solid State Chalcogenides From Intermediate Temperatures. Exploratory Synthesis in Molten Salts

摘要本研究以熔融多硫系盐为反应介质，探索在中低温（200-500℃）下合成新型硫系材料。各种A2QX盐（A=碱阳离子，Q=S, Se, Te）将用于与晚期过渡金属和主族元素的反应。重点将放在第四相的稳定。本阶段将探索三种季系化合物。一种是混合金属体系A/M/M′/Q （M=晚期过渡金属，M′=镧系元素、锕系元素）。第二种是混合硫系统A/M/S/Te。合成方法将使用二元合金化合物作为起始材料和混合助熔剂，如混合A2TexSy。第三类涉及在材料合成中使用硫代和硒代磷酸盐助熔剂。这些助熔剂是新的，旨在产生含有PxQy n-多阴离子（其中Q=S, Se）的新型硫代磷酸盐和硒代磷酸盐固体。新化合物的物理性质，如光谱、热、磁等，将作为温度的函数进行研究。为了探测不寻常的电子现象，新化合物的电荷输运特性将通过单晶上的变温四探针电阻率和热电功率（Seebeck）测量来详细研究。这项研究涉及新的方法来发现具有各种技术上重要性质的新型固态材料。将进一步研究有前途的材料，并对其应用潜力进行评估。本提案的主题是使用熔盐作为溶剂进行反应。熔盐用于高温单晶生长已有100多年的历史。虽然许多盐是高熔点，但二元盐和多原子盐的共晶组合的熔点通常远低于经典固态合成的温度，这使得它们在中间温度下探索新化学成为可能。在某些情况下，这些盐不仅充当溶剂，而且充当反应物，提供可纳入最终产品的物质。这些研究很重要，因为多硫化物配体被认为存在于金属硫化物催化剂的表面，与原油加氢脱硫有关。多硫系玻璃也是非线性光学、红外波导、光开关和光信息存储的重要材料，但由于化合物的无定形性质，其结构/性能关系尚未得到很好的确定。

Abstract 9527347 Kanatzidis This research is concerned with the use of molten polychalcogenide salts as reactive media to explore the synthesis of new chalcogenide materials at low and intermediate temperatures (200-500 C). Various A2QX salts (A=alkali cation, Q=S, Se, Te) will be used in reactions with late transition metals and main-group elements. Emphasis will be given in the stabilization of quaternary phases. Three kinds of quaternary compounds will be explored in this stage. One kind involves the mixed-metal system A/M/M'/Q (M=late transition metal, M'=lanthanide, actinide). The second involves the mixed-chalcogen system A/M/S/Te. The synthetic approach will use binary alloy compounds as starting materials and mixed fluxes such as mixed A2TexSy. The third kind involves the use of the thio- and seleno-phosphate fluxes in materials synthesis. These fluxes are new and are designed to yield novel thiophosphate and selenophosphate solids containing the PxQy n- polyanions (where Q=S, Se). The physical properties of the new compounds, such as spectroscopic, thermal and magnetic will be studied as a function of temperature. In order to probe for unusual electronic phenomena, the charge transport properties of the new compounds will be studied in detail via variable temperature four-probe resistivity and thermoelectric power (Seebeck) measurements on single crystals. %%% This research is concerned with new methodologies to discover new solid state materials having various technologically important properties. Promising materials will be studied further and their potential for applications will be evaluated. The subject of this proposal is performing reactions using molten salts as solvents. Molten salts have been employed for well over 100 years for high- temperature single crystal growth. Although many salts are high melting species, eutectic combinations of binary salts and salts of polyatomic species often have melting points well below the te mperatures of classical solid-state synthesis, making possible their use in the exploration of new chemistry at intermediate temperatures. In some cases, such salts act not only as solvents, but also as reactants, providing species which can be incorporated into the final product. Such studies are important because polysulfide ligands have been implicated in the hydrodesulfurization of crude oil, where they are thought to be present at the surface of metal sulfide catalysts. Polychalcogenide glasses also are important as materials for non-linear optics, IR wave guides, optical switching, and optical information storage, but the structure/property relationships have not been well determined due to the amorphous nature of the compounds.