硬脂酸盐熔融法制备高活性Yb:YAG纳米粉体及透明陶瓷的研究

Yb:YAG transparent ceramic laser has broad application prospects in military and civil fields. Because of Yb3+ ions high doped concentration, high quantum theory efficiency and perfect matching with InGaAs diode, making Yb:YAG transparent ceramics become the focus of research at home and abroad. The light scattering caused by pore in the ceramic is the main factor that affects the laser output power. Therefore, decreasing the porosity is the key to the preparation of Yb:YAG transparent ceramics. In this project, a stearate melting method was introduced to synthesize Yb:YAG nanopowders and has many advantages. First, the melting points of stearate are low and similar. It can guarantee homogeneous mixing of cations at atomic level through direct stirring of the mixed melts. Second, absorption of water is not observed on the surface of stearate, avoiding the particle aggregation due to surface tension and capillarity force between particles. Furthermore, stearate can be directly weighed without considering the absorbed water and crystalline water, guaranteeing an accurate control of cationic stoichiometry. So well dispersed and micro-uniformity Yb:YAG nanopowders can be produced by the stearate melting method. The compact body with small size and distribution of pores was prepared by pressing and forming using no agglomeration and high sintering activity Yb:YAG powders. The compact body can be prepared Yb:YAG laser transparent ceramics with high optical quality by vacuum sintering technology. The effect mechanism of powder dispersion, powder sintering activity, reducing porosity and scattering loss were studied in order to provide a theoretical foundation for improving the laser performance of the laser transparent ceramics.

Yb:YAG透明陶瓷激光器在军事和民用领域有广阔的应用前景。因Yb3+掺杂浓度高、理论量子效率高及完美地与InGaAs二极管匹配等优势，使Yb:YAG透明陶瓷成为国内外研究的重点。陶瓷中气孔引起的光散射是影响激光输出功率的主要因素，因此，降低气孔率是制备透明陶瓷的关键。本项目采用硬脂酸盐熔融法制备Yb:YAG纳米粉体，所用原料硬脂酸盐熔点低且相似，直接加热熔融后搅拌即可达到原子级别的混合；硬脂酸盐不吸附水，减轻了粉体干燥时表面水及结构水引起的表面张力和毛细管力；硬脂酸盐可直接称量，确保了阳离子精确的化学计量比。因此该方法制备的Yb:YAG纳米粉体分散性好、微观均匀。将无团聚、烧结活性高的粉体经压制成型制备气孔尺寸小且气孔分布均匀的坯体，再经真空烧结技术获得高光学质量Yb:YAG透明陶瓷。研究粉体烧结活性及降低气孔含量、降低散射损耗的影响机制，为提高透明陶瓷的激光性能提供理论依据。

钇铝石榴石（YAG）具有优异的光学、力学和热学性能，在红外和可见波段下均有很高的透光率，被用作为激光的基质材料。Yb:YAG透明陶瓷可取代单晶和玻璃激光材料，在军事和民用领域有广阔的应用前景。因Yb3+掺杂浓度高、理论量子效率高、低的量子缺陷及完美地与InGaAs二极管匹配等优势，使Yb:YAG透明陶瓷成为国内外研究的重点。本项目首次提出了合成YAG纳米粉体的硬脂酸盐熔融法，因所用原料硬脂酸盐熔点低且相似，直接加热熔融后搅拌即可达到原子级别的混合；其次，硬脂酸盐不吸附水，减轻了粉体干燥时表面水及结构水引起的表面张力和毛细管力；而且，硬脂酸盐可直接称量，确保了阳离子精确的化学计量比。本项目采用硬脂酸盐熔融法制备了分散性良好、颗粒尺寸分布窄的YAG、Yb:YAG纳米粉体。在1000 ºC温度下煅烧的粉体有较高的烧结活性，颗粒尺寸约为80 nm。粉体经压制成型、1700 ºC真空烧结后，可得到透明的YAG、Yb:YAG陶瓷，表面几乎无气孔和杂质。对陶瓷表面做EDS线扫描分析，各元素不存在浓度梯度及偏析现象，均匀分布在晶粒和晶界上，无富集现象。