掺杂赤铁矿（α-Fe2O3）纳米晶高压下的结构转变与物性研究

Introducing of dopants into the hematite (α-Fe2O3) nanocrystals would give rise to changing of the morphology and structure and the emergence of various defects, and bring about inestimable phenomena at high pressure conditions, which will be very different from those for pure α-Fe2O3 nanocrystals or bulk hematite. High pressure could lead to the distortion of crystal structure and change of symmetry and even modification of properties. To further study the modifications of doped α-Fe2O3 nanocrystals under high pressure is helpful to get some materials with special functions and applications. In this project, the transition metals (Mn, Ti) doped α-Fe2O3 nanocrystals are selected as targets, we firstly plan to prepare various metal atoms doped α-Fe2O3 nanocrystals with controllable concentration of dopants and shape and size of nanocrystals, by using special reactive colloids produced by Laser Ablation in Liquids (LAL) technology that developed in our group. Our next attentions of the project are focused on analyzing the structure and property change rule of doped and undoped α-Fe2O3 nanocrystals under high pressure, understanding the internal connection of shape, size and inner defects of nanocrystals with the high-pressure phase transition, studying the role of dopants for properties change of the nanocrystals under high pressure and tuning the structure and property of doped α-Fe2O3 nanocrystals through high pressure conditions. The success of this project, will not only provide technological guide and substantial materials for revealing the changing rule of structure and property of nanocrystals at high pressure, but also supply scientific foundation for further understanding the high-pressure phase transition processes of Fe2O3 nanocrystals materials.

对于赤铁矿（α-Fe2O3）纳米晶，掺杂不仅能引起其形貌结构发生变化，掺杂离子也导致晶体中新缺陷的形成。形貌结构、缺陷是影响纳米晶高压结构转变行为的重要因素，因而掺杂纳米晶高压相变过程可能显著区别于相应未掺杂和体相材料，研究掺杂赤铁矿纳米晶在高压下结构性能转变对于开拓Fe2O3材料新的功能与应用具有重要意义。鉴于此，项目拟以过渡族金属Mn、Ti掺杂的α-Fe2O3纳米晶为研究对象，利用液相激光熔蚀技术获取高活性胶体作为掺杂前驱体，制备杂质浓度和形貌尺寸可调的掺杂纳米晶，揭示赤铁矿纳米晶及其掺杂体系在高压下结构和性质变化规律，分析纳米晶形貌结构和内部缺陷与高压相变过程内在关联，研究杂质对α-Fe2O3纳米晶高压相物性的作用机制，依赖高压手段调控掺杂α-Fe2O3纳米晶结构与性质。项目的实施将为掺杂纳米晶高压相变研究提供技术途径与材料基础，也为深入理解赤铁矿纳米晶高压相变过程提供科学依据。

赤铁矿（α-Fe2O3）纳米晶在高压下的结构转变行为与形貌结构和内部缺陷密切相关。高效的掺杂技术不仅可以改变α-Fe2O3纳米晶的形貌尺寸，也能形成新的缺陷。本项目通过液相激光溶蚀技术制备高活性的胶体纳米颗粒作为掺杂前驱体，成功实现Mn、Si、Sn等元素对α-Fe2O3纳米晶的高效掺杂，不仅改变了氧化铁纳米晶的形貌尺寸，更形成了不同的晶格缺陷。通过压力下的原位拉曼光谱分析，纯相α-Fe2O3纳米晶和掺杂的α-Fe2O3纳米晶随压力上升会出现不同的拉曼峰，说明两种体系的结构演变有不同的趋势。其中，Si掺杂的α-Fe2O3纳米晶在较低压力下即可直接转变为钙钛矿相，这一结果预示着掺杂体系的相变路径极有可能不同于纯相体系，在进一步排除纳米结构形貌和尺寸的影响之后，我们认为是掺杂引起氧化铁晶面原子的重新排列导致了上述结果。同时，我们在常压条件下对不同氧化铁进行了电学性质研究，为了进一步分析掺杂α-Fe2O3纳米晶在高压下的物性变化提供了直接的数据参考。针对纳米材料的形貌结构影响，我们选择纯相的单晶Se纳米带作为研究对象，以规避材质和缺陷影响，研究其高压相变过程中的关键性因素。结果表明，尺寸引起的表面能上升和形貌结构引起的结构坍能够对相变过程的难易程度产生直接影响，而一维纳米结构较纳米晶颗粒更需要考虑后者的影响，较小的纳米晶颗粒则更多考虑前者的影响。本项目不仅成功实现了多种高效掺杂α-Fe2O3纳米晶的普适性方法，也对比分析了纳米材料形貌结构、内部缺陷对高压相变过程的影响。本项目为掺杂纳米晶高压相变研究提供技术途径与材料基础，也为深入理解赤铁矿纳米晶高压相变过程提供科学依据。