Designing Oxide Ion Conductors: Synthetic Routes and Structure-Property Relationships

氧化物离子导体是许多重要技术应用的关键部件，包括氧传感器和泵、氧分离膜和固体氧化物燃料电池。在第一种情况下，它们可以用于汽车排气系统，以监测氧分压，帮助保持最佳的发动机性能，以减少烟雾排放。在后一种情况下，它们作为电解质运输O2-与氢等燃料发生反应，直接、清洁、高效地将化学能转化为电能。更好地理解为什么氧化物离子导体表现出这种不寻常和高度可开发的行为，并更全面地了解其起源和机制，可以为所描述的应用带来新的更好的材料。这将产生重大的技术和环境影响。由于原子或离子占据晶格内特定的固定位置，结晶固体通常被认为是具有长程三维原子顺序的材料。氧化物离子导体的关键要求是它们也有可移动的原子。这是我们需要设计到材料中的特性。该提案提供了一个工作计划，其重点是发现和表征新的氧化物离子导体，目的是建立这类材料的成分-结构-性能关系。将研究三种不同的合成线，包括一系列低温和传统的固态技术。在很大程度上，合成靶点的选择受到氧化离子导电材料中晶体化学的现有知识的影响，其中一些知识来自于PI最近的研究。具体来说，包含阳离子配位多面体的复杂扩展固体，可以支持可变配位数和几何形状，本质上具有为氧化物离子提供传导途径的系统，这一想法将被探索。所制备的所有化合物将使用各种技术进行表征，包括原位变温粉末x射线和中子衍射、阻抗谱、电子显微镜、固态核磁共振和单晶衍射（如适用），以及一些辅助技术。一些目标化合物类别预计将采用非常复杂的晶体结构，这些挑战将通过应用和进一步发展一些最先进和最强大的衍射数据分析方法来解决，例如模拟退火和电荷翻转。计算方法（DFT和MD）的互补使用，包括与格勒诺布尔朗格万研究所计算组组长Mark Johnson教授的合作和互访，将是该项目的重要组成部分。

Oxide ion conductors are key components in a number of technologically important applications, including oxygen sensors and pumps, membranes for oxygen separation and solid oxide fuel cells. In the first case, they can be used in car exhaust systems to monitor oxygen partial pressures, helping maintain optimum engine performance in order to lower smoke emissions. In the latter case, they act as electrolytes transporting O2- to react with a fuel such as H2 in the direct, clean and highly efficient conversion of chemical to electrical energy. A better understanding of why oxide ion conductors show this unusual and highly exploitable behaviour, and a fuller insight into its origins and mechanisms, can lead to new and better materials for the applications described. This would have significant technological and environmental impact.Crystalline solids are usually thought of as materials with long-range three dimensional order of atoms, due to atoms or ions occupying specific fixed sites within a crystal lattice. The key requirement for oxide ion conductors is that they also have mobile atoms. This is the feature that we need to design into the materials. This proposal offers a programme of work which focuses on discovery and characterisation of new oxide ion conductors, with the aim of establishing composition-structure-property relationships in this class of materials. Three different synthetic strands will be pursued, which include a range of low-temperature and conventional solid state techniques. To a large extent, the choice of synthetic targets has been informed by the existing knowledge of crystal chemistry in oxide ion conducting materials, including some which originated from the PI's recent research. Specifically, the idea that complex extended solids containing coordination polyhedra of cations which can support variable coordination numbers and geometries essentially have a system which provides a conduction pathway for oxide ions will be explored. All compounds prepared will be characterised using a variety of techniques, including in-situ variable temperature powder X-ray and neutron diffraction, impedance spectroscopy, electron microscopy, solid state NMR and single crystal diffraction (where appropriate), as well as a number of auxiliary techniques. Some of the target compound classes are expected to adopt very complex crystal structures and these challenges will be tackled by application and further development of some of the most advanced and powerful methodologies for diffraction data analysis, such as simulated annealing and charge flipping. Complementary use of computational methods (DFT and MD), involving collaboration and exchanges of visits with Prof. Mark Johnson, Head of the Computational Group at Institut Laue Langevin in Grenoble, will be an important component of this project.