Exploratory Synthesis of Inorganic Solids Containing Nanosize Transition-Metal-Oxide Frameworks

摘要：本研究的目的是探索一类包含纳米级过渡金属-氧化物框架的新型扩展固体，并研究氧化桥接过渡金属（TM）磁中心在受限晶格中的离域电子行为。预期的结构由tm -氧化物链（线）、层（片）和低聚物（点）组成，它们被封闭壳、非磁性氧离子（即硅酸盐、磷酸盐和砷酸盐）在结构上分离并在电子上隔离。探索性合成的努力将集中在(1)含有金红石和钙钛矿框架的片和线的同源系列和(2)含有纳米级晚期TM氧化物框架的硅酸盐化合物。熔融盐法，使用碱和/或碱土金属卤化物，将被采用，因为这是一种成熟的技术，用于这些难熔氧化物的晶体生长。化合物表征将直接用于理解键强度、自旋-自旋和自旋-晶格相互作用、能带结构以及与有限tm -氧化物结构相关的金属性质的开始。这项研究具有重要意义，因为预期的具有不同长度和几何形状的tm氧化物碎片将为研究有限空间中离域电子的行为提供一个结构模型库。此外，含有有限结构的tm -氧化物框架的化合物可能具有新的电子和/或磁性能，这与扩展氧化物的性质不相容，并且将具有科学和技术上的兴趣。最后，本提案中概述的研究将为继续推进具有电子和磁性重要性的材料技术提供宝贵的基础知识。最近技术的进步和对器件应用中新材料的需求推动了固态科学的快速发展。了解控制材料性能的基本参数在这门多学科科学的每个领域都起着至关重要的作用，包括固态化学和物理，以及电气和材料科学工程等跨学科领域。固态化学是研究具有扩展结构的材料的合成及其相关性质的学科。这些固体结构的多样性和复杂性，以及对影响和控制结构和物理性质的因素的评估，是使固态化学成为一个动态研究领域的要素。因此，试图修改已知结构和探索具有新特性的新结构的目的是揭示可用于微调物理特性并最终合成所需材料的参数。目前，预测扩展固体的组成和结构的能力尚不可能实现，而导致固态科学取得里程碑式进展的合成发现几乎总是通过探索性合成而不是通过设计取得的。本提案中概述的研究将为继续推进具有电子和磁性重要性的材料技术提供宝贵的基础知识。目的是探索包含纳米级过渡金属氧化物框架的新型扩展固体。

Abstract 9612148 Hwu The aim of this research is to explore a new class of extended solids that contain nanosize, transition-metal-oxide frameworks and to investigate the behavior of the delocalized electrons of oxide-bridged, transition-metal (TM) magnetic centers in a confined lattice. The anticipated structures consist of TM-oxide chains (wires), layers (sheets) and oligomers (dots) that are structurally separated and electronically isolated by closed-shell, non-magnetic oxyanions, i.e., silicates, phosphates and arsenates. Efforts in exploratory synthesis will focus on (1) homologous series containing sheets and wires of rutile and perovskite frameworks and (2) silicate compounds containing nanosize frameworks of late TM oxides. Molten-salt methods, using alkali and/or alkaline-earth metal halides, will be employed, since it is a proven technique for the crystal growth of these refractory oxides. Compound characterizations will be directed toward understanding the bond strength, spin-spin and spin-lattice interactions, band structures, and the onset of metallic properties associated with finite TM-oxide structures. This proposed research is significant because the anticipated TM-oxide fragments with different lengths and geometries will provide a library of structural models for studying the behavior of the delocalized electrons in a confined space. Also, compounds containing TM-oxide frameworks with finite structures may possess novel electronic and/or magnetic properties, which are incompatible with the properties of extended oxides and will be of both scientific and technological interest. Finally, the research outlined in this proposal will provide invaluable fundamental knowledge necessary to continue advancing technology for materials that are of electronic and magnetic importance. %%% Recent advances in technology and the need for new materials in device applications have driven the rapid growth of solid-state science. Understanding fundamen tal parameters that govern the performance of a material has played a crucial role in every area of this multi-disciplinary science, which includes solid-state chemistry and physics, as well as interdisciplinary areas such as electrical and materials science engineering. Solid-state chemistry is concerned with the synthesis of materials with extended structures and their related properties. The variety and complexity of these solids' structures, and the evaluation of the factors that influence and control structural and physical properties, are the elements that have made solid-state chemistry a dynamic area of study. As a result, attempts to modify known structures and explore new ones with novel properties are made with the aim of revealing parameters that may be used to fine tune the physical properties and to ultimately synthesize the desired materials. Currently, the ability to predict the composition and structure for extended solids is not yet possible and synthetic discoveries that have led to landmark advances in solid-state science have nearly always been made through exploratory synthesis, rather than by design. The research outlined in this proposal will provide invaluable fundamental knowledge necessary to continue advancing technology for materials that are of electronic and magnetic importance. The aim is to explore new class of extended solids that contain nanosize, transition-metal-oxide frameworks.