1111体系双掺杂铁基超导体的固相反应过程的结构研究

The current investigations of the iron-based superconductors are mainly focusing in the field of solid state physics. The interactions of the atoms, the ions and the electrons of the superconductors, the superconducting structures, the superconducting mechanisms are intensely studied. From solid state chemistry point of view, it is also important to investigate the chemical reaction process of the iron-based superconductors. The chemical reaction process includes the chemical synthetic methods, the reaction mechanisms, the crystal growths, the chemical compositions and the crystal strucutures. All these investigations will assist and drive the work of solid state physicists.This proposal targets at the structural design, the synthesis, the properties and the strcutural study of the 1111 iron-based superconductors. Co-doping method will be employed to synthesize the 1111 superconductors. The cations differing with the rare earth cations in atomic size and F- ion will be chosen to introduce into the Ln-O layer. Therefore, the charge carrier density and the structural distortion will be increased to a larger extent. The dependences of the physical properties to the structural parameters are more precise. The solid state reaction processes are studied by using electron microscope technique, assisted by XRD and XPS. The tendency of the structural parameters, the valent state of Fe, the grain boundary and the interface, the distribution of the doping atoms and the vacancies/nonvacancies will be extensively and deeply studied by using the above mentioned methods. We try to experimentally clarify the fundamental science of the solid state reactions, try to improve the physical property of the iron-based superconductors.

目前铁基超导体主要由物理学家围绕新材料和新制备来研究其物性与超导机理，然而1111复杂体系的掺杂缺陷-超导性能的关系仍不清楚。完全有必要从固体化学家的角度，通过化学反应过程、化学组成分布、晶体结构与微结构的研究，深入研究超导机理。本课题拟围绕1111体系双掺杂铁基超导体的结构设计、制备、性质和结构研究开展系统工作。选取离子半径与稀土离子相差较大的阳离子与氟离子配对，固相反应制备1111体系超导体。扩大载流子浓度范围和所引起的结构畸变的程度，使载流子浓度、结构参数对电磁性质的影响趋势更加显著。利用电子显微分析技术并结合XRD和XPS等手段，研究反应过程中基本结构参数的变化趋势，元素价态与化学键状态，研究晶界、相界内的掺杂原子的分布，缺陷区/无缺陷区的分布等局域结构特点。力求在原子分辨率层次对超导体的固相反应过程的基本问题给出可靠的实验结果，力求优化合成条件来提高其超导性质。

目前铁基超导体的研究热点集中在物性与超导机理，而1111复杂体系的掺杂缺陷与超导性能的关系仍不清楚，有必要从固体化学的角度，通过化学反应过程、化学组成分布、晶体结构与微结构的研究，深入研究两者的关系。本课题拟围绕1111体系双掺杂铁基超导体的结构设计、制备、性质和结构研究开展系统工作。选取离子半径与稀土离子相差较大的阳离子与氟离子配对，固相反应制备1111体系超导体。扩大载流子浓度范围和所引起的结构畸变的程度，使载流子浓度、结构参数对电磁性质的影响趋势更加显著。利用电子显微分析技术并结合XRD和XPS等手段，研究反应过程中基本结构参数的变化趋势，元素价态与化学键状态，研究晶界、相界内的掺杂原子的分布，缺陷区/无缺陷区的分布等局域结构特点。力求在原子分辨率层次对超导体的固相反应过程的基本问题给出可靠的实验结果，力求优化合成条件来提高其超导性质。用高分辨电镜技术研究了趋磁细菌中磁小体的进化过程，发现多种三价铁的氧化物作为磁小体的中间体。