稀土全掺CaF2晶体热-力耦合深紫外激光剥蚀行为调控及在萤石地球化学中的应用研究

因高度符合基体匹配和元素均一的要求，稀土全掺CaF2单晶在萤石激光剥蚀-电感耦合等离子质谱（LA-ICP-MS）校正标准应用中具有巨大优势。本项目创新性开展稀土全掺CaF2单晶的设计、生长和激光剥蚀行为系统研究，重点解决CaF2晶体因深紫外高透光性导致的193 nm激光剥蚀信号弱且不规则的关键科学问题。项目从CaF2单晶结构出发，基于晶体物化性能调控理论分析，优化晶体掺杂组分；采用坩埚下降法进行晶体生长，通过温场和生长参数优化，获得高质量单晶，并重点考察晶体中稀土元素均一性；测试晶体物化和光谱性能，开展激光剥蚀线扫描，建立晶体表面激光热力耦合模型，从而揭示激光信号、元素共掺及表面处理技术调控激光剥蚀行为的内在机理；在此基础上，制备系列CaF2校正标样，并建立萤石稀土元素LA-ICP-MS微区分析方法。项目实施将拓展CaF2单晶应用，并为CaF2单晶在萤石稀土元素地球化学中的应用奠定基础。

Due to highly meet the requirements of matrix matching and homogenously distribution, all-rare-earths co-doped CaF2 (REs: CaF2) crystal shows prominent advantage in calibration standard for fluorite LA-ICP-MS technique. In this project, the design, growth and laser ablation operation of all-rare-earths co-doped CaF2 crystal will be creatively be systematic studied with special emphasis on the weak and irregular ablation operation under 193 nm deep UV laser resulting from the high transmission of deep UV light. Based on the local structure, the components of dopants will be optimized based on the theoretical calculations of physical and chemical properties. High-quality REs: CaF2 crystal will be grown by the Bridgman method with the defect analysis and technics parameter optimization. The homogenously distribution of rare earths will be particularly studied in detail. The physical properties of the as-grown crystal will be test. The morphology of laser ablation pits will be studied in detail. The dependence of the laser ablation operation on laser signal, trace metal element co-doping and surface treatment technology will be revealed with a thermo-mechanical coupling model under deep UV lasering in CaF2 crystal. As a result, a design method of REs: CaF2 calibration standard will be summarized. On this basic, an analytical method for accurate determiniaiton of REs concentration in fluorite by LA-ICP-MS will be developed using the as-grown REs: CaF2 crystal calibration standards. The implementation of this project will greatly extend the applied realms of CaF2 crystal, and lay the foundation for the application of CaF2 crystal in rare earth Elements geochemical research of fluorite.