高热导率异质复合结构透明陶瓷制备及性能研究

Laser has wide applications in the scientific research, laser weapon, and advanced manufacture fields. However, the temperature of the pumping system increases along with continuous high power laser output, and consequently leads to severe thermal aggregation. Because the pumped-end faces and the center region of the laser material can't be effectively cooled down under limited efficiency of cooling system, thermal effect caused by severe thermal aggregation will reduce the laser quality and optical conversation efficiency. Laser media-YAG/Nd:YAG transparent ceramics with homogeneous composite structure have successfully suppressed the thermal effect on the pumped-end faces, and achieved uniform thermal field distribution. Unfortunately, with the temperature of material goes up along with continuous high power laser output, the difference between thermal conductivities of pure YAG and Nd:YAG decreases rapidly, which will diminish the advantages of this kind of composite structure. In this research, based on the fabrication advantages of ceramics with composite structure and different sintering behaviors of powders synthesized by various processes, the sintering of Y2O3/Nd:YAG ceramic with high thermal conductivity and heterogeneous composite structure can be achieved simultaneously. Optical losses caused by refractive index can be eliminated via using Sc2O3 and La2O3 to control refractive index of the ceramic. The thermal diffusion of different elements in the interface and thermal field distribution of the laser materials are also studied. This project will make profound impact on the research of new heterogeneous composite structure ceramics.

激光在科学研究、激光武器、先进制造等领域有广泛应用前景。然而，在连续高功率激光条件下，泵浦系统温度升高，产生热聚集，受冷却系统设计限制，激光材料泵浦端面和中心区域难以获得有效冷却，热聚集导致热效应的产生，降低输出激光质量和光转换效率。利用同质复合结构YAG/Nd:YAG陶瓷为激光介质，端面热效应得以改善，热场分布更均匀。遗憾的是，在激光连续作用下，材料温度逐渐升高，YAG与Nd:YAG之间热导率差距缩小，该复合结构高导热优势被削弱。本项目利用陶瓷易于制备复合结构的优势，结合不同工艺制备的粉体具有不同烧结性质这一特点，筛选合适陶瓷粉体，实现高热导率异质复合结构Y2O3/Nd:YAG陶瓷中Y2O3和Nd:YAG共烧。利用Sc2O3和La2O3调控陶瓷折射率，消除因折射率突变而产生的光损耗，研究界面区域元素热扩散行为和材料在激光条件下的热场分布。本课题的实施对开展异质复合结构研究具有重要意义。

激光在科学研究、激光武器、先进制造等领域有广泛应用前景，但在连续激光条件下，泵浦系统温度升高，产生热聚集，受冷却系统设计限制，激光材料泵浦端面和中心区域难以获得有效冷却，热聚集导致热效应产生，降低输出激光质量和光转换效率。利用同质复合结构YAG/Nd:YAG 陶瓷为激光介质，端面热效应得以改善，热场分布更均匀。遗憾的是，激光连续作用导致材料温度逐渐升高，YAG 与Nd:YAG 之间热导率差距缩小，该复合结构高导热优势被削弱。本项目利用陶瓷易于制备复合结构的优势，结合不同工艺制备的粉体具有不同烧结性质这一特点，筛选合适陶瓷粉体，制备Y2O3/Nd:YAG 异质复合结构陶瓷材料。.本项目主要研究内容包括四个方面：（一）Y2O3纳米粉体合成与性能研究；（二）Nd:YAG纳米粉体与性能研究；（三）Nd:YAG和YAG/Nd:YAG/YAG透明陶瓷性能研究；（四）Y2O3/Nd:YAG复合结构陶瓷制备与性能研究。.以Y2O3粉体为原料，以La2O3为烧结助剂，1700oC真空烧结20h，制备出Y2O3透明陶瓷，但其透过率曲线最高值仍低于80%，陶瓷内部有少量光散射中心存在（气孔、杂质等）。制备出高质量Nd:YAG和YAG/Nd:YAG/YAG透明陶瓷，光学透过率可与高质量晶体相媲美。尺寸为6×100mm2Nd:YAG陶瓷棒和晶体棒在相同激光条件下，泵浦阈值皆为105W，泵浦功率为1000W，输出功率为425W。YAG/Nd:YAG/YAG复合结构透明陶瓷（两端为14mm纯YAG，中间为54mm1.0 at.%Nd:YAG棒状结构，直径为3mm）。泵浦阈值为23W，泵浦功率为201W，输出功率为20.3W，光转换效率为10.1%，在最高泵浦功率处。.以Y2O3粉体为原料，以0.8 wt.%TEOS和La2O3为烧结助剂，倒入圆柱形磨具中，轻压预成型，再向圆柱形磨具中倒入Nd:YAG粉体，以0.8wt.% TEOS和0.08wt.%MgO为烧结助剂，60Mpa干压成型为Y2O3/Nd:YAG素坯，将预成型好的素坯在250Mpa冷等静压，成型素坯真空烧结后，空气中退火处理，即得Y2O3/Nd:YAG异质复合结构陶瓷材料，材料呈白色不透明状态，对其显微结构进行分析发现Nd:YAG区域存在大量气孔，而Y2O3区域致密化完善。Y2O3和Nd:YAG纳米粉体性质差异导致两种结构陶瓷材