Ordered States in Oxides

氧化物的有序态

基本信息

批准号：
EP/F02083X/1
负责人：
J Attfield
金额：
$ 17.15万
依托单位：
University of Edinburgh
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2008
资助国家：
英国
起止时间：
2008 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=EP%2FF02083X%2F1
关键词：
Ordered States Oxides

项目摘要

The electronic properties of transition metal oxides continue to drive many fields, from fundamental condensed matter physics and solid state chemistry to materials science and engineering applications. High temperature superconductivity (HTSC) in copper oxides and colossal magnetoresistances (CMR) in manganite perovskites are two particularly important phenomena that have led to many other perovskite oxides being widely studied for their electronic properties.Knowledge of structure is always important for understanding materials properties. Transition metal oxide structures are often based on simple high symmetry structures e.g. perovskite, spinel, but the above orderings lower symmetry leading to slight lattice distortions and superstructures. It has become clear that much subtle but important information can be gained from high resolution powder diffraction studies. Powder diffraction is needed partly because many of these materials are difficult to crystallise, but more fundamentally, the distortions lead to severe (micro)twinning in crystals that makes conventional single crystal structure determinations difficult (e.g. in the case of Fe3O4).Powder diffraction is a simple technique but remains one of the most popular in the synchrotron X-ray and neutron user communities. A variety of instruments are now available at ISIS, ILL, ESRF and (in the future) Diamond. These are applied to many problems in chemistry, physics, materials science, engineering and geosciences. To make the best use of available facilities, as well as providing a broad training in leading powder diffraction techniques, this project will study several materials using a range of instruments.The structures and magnetic order in high pressure Cr, Ru and Bi-based perovskites will be investigated. These materials will be synthesised using a recently commissioned Walker press. The complex superstructures associated with charge, spin and orbital order in RBaMn2O6 manganites will also be studied. Charge ordering in magnetite (Fe3O4) is a classic and long running problem. We aim to improve on a previous structural model through further high resolution powder diffraction study, and analysing data from heavily twinned microcrystals. Further aspects of the student training will be through attending workshops in Grenoble (HERCULES) and ISIS, and by 3 month visits to each centre.

过渡金属氧化物的电子特性继续推动着许多领域的发展，从基础凝聚态物理和固态化学到材料科学和工程应用。铜氧化物中的高温超导性 (HTSC) 和亚锰矿钙钛矿中的巨磁阻 (CMR) 是两个特别重要的现象，导致许多其他钙钛矿氧化物的电子特性得到广泛研究。结构知识对于理解材料特性始终很重要。过渡金属氧化物结构通常基于简单的高对称性结构，例如钙钛矿、尖晶石，但上述排序降低了对称性，导致轻微的晶格畸变和超结构。很明显，可以从高分辨率粉末衍射研究中获得许多微妙但重要的信息。需要粉末衍射的部分原因是许多这些材料难以结晶，但更根本的是，扭曲导致晶体中严重的（微）孪生，这使得传统的单晶结构测定变得困难（例如，在 Fe3O4 的情况下）。粉末衍射是这是一种简单的技术，但仍然是同步加速器 X 射线和中子用户社区中最受欢迎的技术之一。 ISIS、ILL、ESRF 和（未来）Diamond 现已提供各种仪器。这些应用于化学、物理、材料科学、工程和地球科学的许多问题。为了充分利用现有设施，并提供领先粉末衍射技术的广泛培训，该项目将使用一系列仪器研究多种材料。高压 Cr、Ru 和 Bi 基钙钛矿的结构和磁序将被调查。这些材料将使用最近投入使用的沃克压机进行合成。还将研究 RBaMn2O6 锰氧化物中与电荷、自旋和轨道顺序相关的复杂超结构。磁铁矿 (Fe3O4) 中的电荷排序是一个经典且长期存在的问题。我们的目标是通过进一步的高分辨率粉末衍射研究和分析来自重孪晶微晶的数据来改进以前的结构模型。学生培训的其他方面将通过参加格勒诺布尔 (HERCULES) 和 ISIS 的研讨会以及对每个中心进行 3 个月的访问来进行。