Novel Strongly Correlated-Electron Materials with Rock-Salt Related Structures

技术总结在美国国家科学基金会材料研究部固态和材料化学计划的支持下，拟议的研究重点是过渡金属氧化物AMO2(A=碱金属，M=3D金属)具有CdI2类型的层。AMO2相表现出许多不同的物理性质，包括几何受挫磁性、自旋、电荷和轨道有序性、热电性和非传统超导电性。在所有已知的AMO2相中，过渡金属只处于3+或3+/4+氧化态。β-NaFe_2O_3是唯一已知的具有层状岩盐相关结构和双层过渡金属-氧块的化合物。该方案的主要组成部分是合成、晶体结构和物理性质研究：(1)具有CdI2型层状结构的新型层状相，M处于唯一低的(对于这种相)2+/3+混合价氧化态；(2)新的n=2和n=3的层状岩盐相关同系物。据设想，实施所述的提议目标不仅将导致新的强关联电子氧化物，而且还将为制备高度不寻常的相以及导致对关联电子行为的新的基本见解提供新的合成方法，从而导致发现具有潜在有用的热电和/或磁性的化合物。非技术概述在一类特殊的金属化合物中，电子-电子相互作用导致各种物理性质，从基本和技术角度来看都很重要。这些所谓的强关联电子材料的性质取决于晶体结构的细节，以及过渡金属的氧化和自旋态。在这项提案中开发的新的合成方法将使以可预测的方式制备强关联的电子材料成为可能。对结构-性质关系的研究将提供对相关电子行为的深刻见解，并使能够通过温度梯度将热转换为电能的新材料(热电材料)以及具有有趣的磁性的化合物的设计原则得以发展。研究生和本科生将接受无机合成、电化学、结晶学、磁学和各种表征技术方面的培训。国际化学联合会将领导组织中西部本科生化学研究研讨会。这一研讨会由PI带头，目标是从本科生到研究生的过渡，旨在增加国内申请研究生项目的人数。

TECHNICAL SUMMARYWith support from the Solid-State and Materials Chemistry Program in the NSF Division of Materials Research, the proposed research focuses on transition metal oxides AMO2 (A = alkali metal, M = 3d metal) with CdI2-type layers. AMO2 phases demonstrate a large variety of physical properties, including geometrically frustrated magnetism, spin, charge and orbital ordering, thermoelectricity, and nonconventional superconductivity. In all known AMO2 phases, transition metals are only in the 3+ or 3+/4+ oxidation states. Beta-NaFe2O3 is the only known compound with a layered rock-salt related structure and double layer transition metal-oxygen block. The main components of this proposal are synthesis, crystal structure and physical properties investigation: (1) of novel layered phases with CdI2-type layers and M in uniquely low (for such phases) 2+/3+ mixed valent oxidation states and (2) of new n = 2 and n = 3 members of the layered rock-salt related homologue. It is envisioned that implementation of the stated proposal objectives will not only result in novel strongly correlated-electron oxides, but also provide new synthetic methodologies for the preparation of highly unusual phases as well as result in new fundamental insights into correlated-electron behavior, leading to the discovery of compounds with potentially useful thermoelectric and/or magnetic properties. NON-TECHNICAL SUMMARY In a special class of metal compounds electron - electron interaction results in a variety of physical properties important from fundamental and technological points of view. Properties of these so called strongly correlated-electronic materials depend on details of crystal structure, as well as on transition metal oxidation and spin states. New synthetic methodology developed in this proposal will enable preparation of strongly correlated-electronic materials in a predictable way. Investigation of structure-property relationships will provide deep insights into correlated-electron behavior and enable development of design principles for new materials capable of converting heat via a temperature gradient into electric energy (thermoelectric materials), as well as compounds with interesting magnetic properties. Graduate and undergraduate students will be trained in the areas of inorganic synthesis, electrochemistry, crystallography, magnetism, and various characterization techniques. The PI will lead the organization of the Midwestern Symposium on Undergraduate Research in Chemistry. This symposium, spearheaded by the PI targets the undergraduate to graduate school transition and is designed to increase the number of domestic applicants to graduate programs.