稀土体相掺杂氟化物纳米晶的制备、性能优化及应用研究

Inorganic liquid laser medium is one of best candidate for high power laser. The colloidal solution of fluoride nanocrystals doped with rare earth ions (REs) systhesized by solvo-thermal route had been published in the past several years. However, the optical gain of these colloidal solutions is much lower than the level of application. New synthesis method of colloidal solution of fluoride nanocrystals with REs is proposed in this application. The fluoride nanocrystals doped with REs are extracted from oxyfluoride glass ceramics with REs by wet chemical etching technology. The colloidal solution of fluoride nanocrystals doped with REs in some solvents and the colloidal solution of capped nanocrystals will be obtained. .The fluoride nanocrystals with REs were embedded in the oxide glass matrix in the oxyfluoride glass ceramics with REs. REs could distributed well in the fluoride nanocrystals by substituting for cation or interspacing at the center of anion ions, which are binded by oxide glass net, when the oxyfluoride glass ceramics were prepared at the high temperature. The fluoride nanocrystals with REs well-distributed have high fluorescent efficiency because of the clusters and concentration quenching of REs could be broken. This is one of new ideas in this proposal. .The oxide matrix of oxyfluoride glass ceramics with REs is etched off by wet chemical etching and fluoride nanocrystals with REs are kept in the colloidal solution. The colloidal solution of fluoride nanocrystals with REs is washed and neutralized and then we get the colloidal solution of fluoride nanocrystals with REs well- distributed. The size of the nanocrystals is limited in one hundred nanometers. So the colloidal solution of nanocrystals will be transparent. This is the another new ideas in the proposal..Two technologies could increase the fluorescent efficiency of the colloidal solution. First, the solvents are chosen according to the vibration energy, which are far from the energy levels of REs. There are no resonant energy transfer between REs and solvent molecular. Second, the fluoride nanocrystals are capped by inorganic components, such as SiO2 and TiO2. The energy transfer between REs and solvent molecular is blocked. .In this proposal, two steps should be done in order to obtain colloidal solution with high fluorescent efficiency. First, the REs should be distributed well in the fluoride nanocrystals during preparing oxyfluoride glass ceramics; Second, the nanocrystals should be soluted in the solvent with special vibration energy or the nanocrystals are capped by inorganic component after wet chmical etching. The scattering of laser could be omitted when the size of nanocrystals is small enough and the colloidal solution is transparent. The optical gain of colloidal solution of fluoride nanocrystals with REs well-distributed will be investigated systematically for using into the inorganic liquid laser medium.

无机液体激光介质是高能激光器的首选材料，目前已有水相法合成稀土掺杂氟化物纳米溶胶激光介质的报导，但激光增益远低于实际需求。本项目提出在稀土氟氧化物玻璃体系中用热诱导技术制备玻璃陶瓷（掺稀土氟化物纳米晶镶嵌于氧化物玻璃基质中的透明材料），通过条件控制使稀土体相掺杂于氟化物纳米晶中。然后用湿法腐蚀技术溶掉氟化物纳米晶周围的氧化物玻璃基质，洗涤中和后获得稀土体相掺杂的氟化物纳米晶溶胶。项目的创新点之一是利用高温条件和氧化物玻璃网格束缚使稀土离子占据氟化物阳离子格位或间隙于阴离子构成的亚晶格体心格位实现体相掺杂。创新点之二是用氢氟酸洗去氟化物纳米晶周围的氧化物玻璃基质，获得稀土离子体相掺杂的高发光效率氟化物纳米晶溶胶。针对Nd和Yb离子，选择具有合适振动能的溶剂和对氟化物纳米晶进行包覆抑制稀土激发能的无辐射损耗，进一步提高稀土氟化物纳米晶溶胶的发光效率，探索该溶胶用于无机液体激光介质的可行性。

针对高能激光器对无机液体激光介质的需求，本申请提出用热诱导湿法腐蚀技术制备稀土离子体相掺杂的氟化物纳米晶溶胶，取得系列研究成果。实现了稀土离子在氟化物纳米晶中的体相掺杂并提出稀土离子占位和电荷补偿的结构模型。研究意义在于提出了一种有效提高稀土发光效率的科学途径，并在其他材料体系中得到验证，高效发光的稀土离子体相掺杂纳米晶材料未来可以在纳米尺度区域应用；用两种方案进一步提高稀土离子发光效率，一是通过碱金属离子的共掺杂实现了对体相掺杂稀土离子配位环境和电荷补偿方式的调控，二是通过过渡族金属离子的共掺杂实现对能带结构的调控和激发态能量传输过程的调控，为高发光效率材料设计提供理论依据；利用湿法腐蚀技术提取出稀土离子掺杂纳米晶颗粒，采用不同包覆技术确保纳米晶的分散性，同时保持稀土离子掺杂氟化物纳米晶的结构和荧光性质的继承性，至此，我们解决了申请中提出的所有关键科学问题，获得了高分散性、高透明度和高发光效率的稀土离子体相掺杂氟化物纳米晶溶胶。用制备的稀土离子掺杂氟化物纳米晶溶胶为激光介质，尝试研制自循环可降温无机液体激光器。但在实验中发现，我们设计的可循环液体激光器尚未有效解决散热问题，激光介质升温的主要原因是目前使用的微型泵流速太慢和980nm激光激发时水的自吸收效应，技术改进仍在进行中。研究还发现溶胶温度升高时，荧光光谱发生变化，这直接影响未来激光器激光输出稳定性，散热是大功率液体激光器必须解决的问题。随后对荧光随温度变化的问题做了深入研究，在稀土离子掺杂氟化物上转换荧光温度传感方面完成了一系列卓有成效的结果，分别研究了热耦合对荧光强度比型、非热耦合对荧光强度比型和荧光寿命型上转换发光的荧光温度传感特性，通过晶体场调控和能带调控有效提高了荧光温度传感灵敏度。从系列研究成果可以看出，稀土离子掺杂的氟氧化物玻璃陶瓷具有较高的荧光温度传感灵敏度，在非接触式温度检测中将发挥重要作用。