同步辐射研究钙钛矿型混合导体的局域结构与性能调控机制

Solid oxide fuel cells (SOFC) and dense ceramic oxygen separation membranes hold promising potentials in many important fields, such as clean energy and pure oxygen production. However, the development of these techniques is currently greatly limited, due to the fact that the properties such as oxygen transport and carbon dioxide tolerance of the key materials, perovskite-type mixed conductors, can't meet the requirements for practical applications. In order to guide design of new materials, a more in-depth understanding towards the mechanism of property tuning is crucial, which is associated with changes in the local structures as a result of composition variation. Stemming from such consideration, the present proposal employs synchrotron radiation X-ray absorption fine structure spectroscopy (XAFS) to study the local structures of typical perovskites. The coordination environment such as coordination distance and numbers as well as oxidation states will be obtained for the metal ions, and variation of these parameters with composition, temperature, and atmosphere will be studied, in order to explore the interaction among the metal ions and how the local structures change with composition. Subsequently, the oxygen transport property and chemical stability of the materials will be characterized to shed more light on the relationship among these key properties, composition, and local structures. The microscopic mechanism of property tuning will be then discussed. Further, we will attempt to optimize the materials system and composition by selective doping and introducing A-site metal deficiency. Through the implementation of the project, we seek to gain more insight into the composition-structure-property relationship for perovskites, and provide important research basis and useful theoretical guidance for developing high performance perovskite mixed conductors that fulfill the practical requirements for SOFC and oxygen separation membrans.

固体氧化物燃料电池（SOFC）和致密陶瓷透氧膜在清洁能源和纯氧生产等重要领域有着良好的应用前景。然而，由于现有的关键材料——钙钛矿混合导体在氧输运和耐二氧化碳腐蚀等性能上不能满足实用要求，这些技术的发展受到了严重限制。为指导设计新型钙钛矿，需要在现有研究基础上加深对材料中组成的变化通过改变局域结构来调控材料性能的机制的理解。因此，本项目利用上海光源的同步辐射XAFS手段，测量典型钙钛矿中金属离子的配位距离、配位数和价态等结构参数，并原位考察温度、气氛等因素的影响，研究金属离子的相互作用和局域结构的变化规律；进一步结合氧输运性能和化学稳定性表征，研究这些关键性能随组成和局域结构的变化，探讨性能调控的微观机制；基于以上研究，通过掺杂和A位金属缺量来优化体系和组成。项目的实施将可加深对钙钛矿的组成-结构-性能关系的理解，为研制符合实用要求的高性能钙钛矿混合导体提供重要研究基础和理论依据。

具有氧离子和电子混合导电能力的钙钛矿结构金属氧化物在固体氧化物燃料电池、氧分离膜和气体传感器等领域有着良好的应用前景。然而，现有材料不能兼备高氧输运性能和长期稳定性，其应用受到了严重限制，亟待发展新型材料。目前人们对钙钛矿混合导体的组成-结构-性能关系还不甚了解，材料的研制仍主要凭经验和采用试错法。为突破这一瓶颈，本项目借助于同步辐射X射线吸收谱学（XAFS）这一强有力的手段，研究了典型钙钛矿的局域结构随金属离子组成的变化，探讨了氧输运性能和化学稳定性的微观调控机制。项目首先采用XAFS系统表征了Sb掺杂的SrFeO3-δ中金属离子价态、配位数和键长等结构参数，考察了CO2和O2在材料上的吸附/脱附行为，测量了氧渗透性能，结合DFT理论计算获得不同组成下的氧空位形成能量，阐述了局域结构和性能的关系，优化了材料组成。在此基础上，进一步采用La3+、Ba2+、Nb5+、Sn4+、Al3+、Ti4+、Sb5+、Zn2+等不同金属离子，分别对SrFeO3钙钛矿的A和B位进行掺杂，通过XAFS测试，结合离子价态、半径、金属-氧键能、离子势等方面的变化，分析了不同结构参数之间的相互关系。另外，作为项目研究的延伸，发展了一种制备三层非对称结构高效氧分离膜的方法，并研制了基于La0.8Sr0.2Cr0.5Fe0.5O3-δ等钙钛矿的高性能气体传感器。通过本项目的实施，加深了对钙钛矿的组成-结构-性能关系的理解，有助于指导新型混合导体材料的设计。已发表标注的SCI期刊论文7篇，中国发明专利授权和申请各1项，培养毕业博士和硕士研究生共3人。