Ruddlesden-Popper型层状钙钛矿的离子束辐照效应及机理研究

Perovskites are important phase for immobilization of high level nuclear wastes. Ruddlesden-Popper (RP) phases are the nonstoichiometric derivatives of perovskites and exhibit novel radiation behavior due to the layered structure, which may provide new insights into the enhancement of radiation tolerance of complex oxides. However, the related physical mechanisms are not fully understood at present. In this project, 400 keV Ne2+ and 1 MeV Xe4+ ion irradiations will be performed on synthesized samples of selected An+1TinO3n+1 (A = Sr, Ca; n = 1-3, ∞) compositions at both room and high temperatures, to investigate the radiation-induced structural evolutions of RP phases, such as amorphization, volume changes and phase transformation, as well as the microscopic mechanisms. The role of layered structure (i.e., the number of n), ion beam species and temperature on the radiation effects of RP phases. Based on the first principles calculations, the structural parameters, densities of electronic densities, charge densities and defect formation energies will be computed. To facilitate a good combination of experimental and theoretical investigation, further correlations between the radiation behavior of RP phases with their structures, defect energetics and chemical bonding properties will be performed. This project will lead to improvements in the understanding of radiation effects in nonstoichiometric RP layered perovskite oxides and will provide the underpinning science and new avenues for developing improved radiation resistant oxide ceramics.

钙钛矿是固化高放废物的重要矿相。作为钙钛矿的非化学计量衍生物，Ruddlesden-Popper (RP)相因具有特殊的层状结构而表现出不同的辐照行为，可为提高氧化物的抗辐照性能开辟新路径，然而相关物理机制尚不明确。本项目拟在制备出RP相An+1TinO3n+1 (A=Sr, Ca; n=1-3, ∞)样品的基础上，采用400 keV Ne、1 MeV Xe对其进行室温和高温辐照，研究RP相在离子束辐照下的结构变化（如非晶化、体积变化、晶相转变）及规律，明确层状结构（n值）的影响；研究离子束种类以及温度对RP相辐照效应的影响。通过第一性原理对RP相的结构参数、电子态密度、电荷密度和缺陷形成能进行计算，并建立RP相的辐照效应与结构、缺陷和化学键等性质之间的关联，实现实验与理论相结合。本项目的研究将深化对非化学计量RP层状钙钛矿的辐照效应及物理机制的理解，为开发抗辐照损伤的氧化物提供有效参考。

钙钛矿一直是材料学的研究热点，由于其优异的物理化学性能，钙钛矿在高放废物固化、太阳能电池等领域具有重要应用前景。本项目主要基于放射性核素90Sr固化的应用，对Ruddlesden-Popper型层状钙钛矿Sr1+nTinO3n+1 (n=1-3, ∞)系列进行了系统性研究。通过高温固相反应法制备了Sr1+nTinO3n+1 (n=1-3, ∞)样品，采用X射线衍射、拉曼散射、扫描电子显微镜、透射电子显微镜等等技术对其结构进行表征，确定了Sr1+nTinO3n+1 (n=1-3, ∞)的晶胞结构信息。依托于中国科学院近代物理研究所320 kV高电荷态离子综合研究平台，采用3 MeV Xe离子和400 keV Ne离子对所制备Sr1+nTinO3n+1 (n=1-3, ∞)系列样品进行辐照，研究其在辐照环境下的结构演变过程，包括晶格肿胀、晶相转变、非晶化等过程，明确了层状结构（n值）与Sr1+nTinO3n+1 (n=1-3, ∞)抗辐照性能之间的关联与内在机制。同时，研究了离子束种类（能量和质量）与环境温度对Sr1+nTinO3n+1 (n=1-3, ∞)辐照行为的影响。通过第一性原理，对Sr1+nTinO3n+1 (n=1-3, ∞)的化学势、点缺陷形成能、耦合缺陷形成能、电子结构等性质进行了计算。借助理论计算结果，对Sr1+nTinO3n+1 (n=1-3, ∞)的辐照行为进行了深入探索。本项目的研究工作对Ruddlesden-Popper型层状钙钛矿作为高放射性废物核素的固化基材候选材料进行了评估，相关研究成果也为设计研发先进抗辐照陶瓷材料提供数据基础。同时，作为项目扩展部分，利用135 keV Fe离子对RP相Sr1+nTinO3n+1 (n=1-3, ∞)样品进行辐照掺杂，并对其带隙进行研究，为其更好地应用于太阳能电池提供了新的思路。