Nd,Y∶SrF_(2)激光晶体的位错缺陷表征及分布研究

Characterization and Distribution of Dislocation Defects of Nd,Y∶SrF_(2)Laser Crystals

氟化物激光晶体Nd,Y∶SrF_(2)(NYSF)具有热导率高、发射光谱宽、发射截面适中等特点,在高功率激光技术领域具有重要应用。激光晶体中的位错是反映其晶格完整性的一类重要的微观晶体缺陷,对晶体材料的力学、光学性能具有重要影响。本文采用坩埚下降法制备了NYSF激光晶体,分析了腐蚀实验条件对位错蚀坑形貌的影响,获得了化学腐蚀法研究NYSF晶体位错缺陷的最佳腐蚀工艺,即浓度为4 mol/L的盐酸溶液作为腐蚀液,腐蚀温度为60℃、腐蚀时间为9~12 min;表征了位错腐蚀坑形态的演变过程,探讨了晶格原子排列对位错蚀坑形态的影响;利用化学腐蚀方法表征了位错缺陷在晶体中的分布规律,即轴向分布为从放肩到尾部先减少后增加,径向分布为从中心到边缘逐步增加;分析了晶体生长条件对位错缺陷形成的影响,提出了位错密度随坩埚下降速率的提高而升高的可能原因。

Combining the advantages of high thermal conductivity,large emission bandwidth and appropriate emission cross-section,the fluorite-type laser crystal Nd,Y∶SrF_(2)(NYSF)has important application in high-power laser techniques.Dislocation in laser crystals is an important category of microscopic defects which implies the integrity of crystalline lattice structure,and influences the mechanical and optical performances of crystals.The NYSF crystals were grown by vertical Bridgman method and the optimized experimental parameters for chemical etching of dislocation defects were obtained by comparing the influence of various etching conditions on the morphology of etch pits in in NYSF crystals.The optimized etching condition are:concentration of 4 mol/L hydrochloric acid solution as a corrosive solution and corrosion temperature of 60℃and corrosion time of 9~12 min.The evolution of dislocation etch pit morphology was studied and the relationship between the lattice structure and the morphology of etch pits was analyzed.The distribution of dislocation defects in NYSF was characterized by chemical etching method.The axial distribution first decreases and then increases from the shouldering to the tail,and the radial distribution gradually increases from the center to the edge.The influence of crystal growth processes on the formation of defects was discussed and the possible reason why dislocation density increases with increasing crucible drop rate was proposed.