新型稀土正磷酸盐晶体Yb:RPO4(R=La, Gd, Y, Lu)的生长机理、光学与热学性能研究

The lanthanide orthophosphates RPO4 (R=La-Lu) are expected to have widely applications in chemical protection, coating materials, radiation protection and other fields. In recent years, American researchers achieved laser output from Nd:LuPO4 crystal, so the rare-earth orthophosphates were also considered as excellent laser host materials. Single crystals with millimeter sizes were obtained using spontaneous nucleation method. But the crystal size and quality can not meet the requirements of research and application. Rare-earth orthophosphates have high melting point and do not melt congruently. Therefore, we plan to deeply study on the physical and chemical properties of RPO4-Pb2P2O7 system and grow crystals by using top seeded flux growth method. By adjusting the component of raw materials and improving growth technology, the evaporation problem of Pb2P2O7 at high temperature will be overcome. Series of Yb:RPO4（R=La, Gd, Y, Lu） crystals with centimeter sizes and high quality will be obtained. The mechanisms of crystal growth and defects formation will be revealed. All of these will establish the theoretical and technical foundation for further application. Moreover, the thermal and optical spectroscopy properties of rare-earth orthophosphates will be measured and the continuous-wave laser output will be realized. A few of laser crystals with important potential application value will be developed. 3-6 pieces of invention patents with independent intellectual property rights will be applied. This work will provide theoretical and experimental basis for the industrialization of this novel important kind of laser crystals.

镧系稀土正磷酸盐RPO4（R=La-Lu）可广泛用于化学防护、涂层和耐辐射材料等领域，美国学者已在Nd:LuPO4晶体中实现了激光输出，证明稀土正磷酸盐单晶还是一类全新的激光基质晶体材料。目前采用的自发成核方法仅能获得毫米级尺寸的单晶，且尺寸和质量都无法满足研究和应用需要，该类材料熔点高，且属非一致熔融化合物，本项目拟通过深入分析RPO4-Pb2P2O7二元体系，采用顶部籽晶助熔剂法生长晶体，调整原料组份，改进生长工艺，克服焦磷酸铅助熔剂易挥发的难题，生长出厘米级尺寸的新型Yb:RPO4（R=La, Gd, Y, Lu）系列高质量晶体，并明确其生长机理和缺陷形成机制，为建立稳定的制备工艺提供科学依据；再通过测试晶体热学和光谱学性能，实现连续波激光输出，进而筛选出有潜在应用价值的新型激光晶体材料，形成3-6件具有自主知识产权的发明专利，为该类稀土正磷酸盐激光材料的实用化提供理论和实验依据。

稀土磷酸盐晶体是一类难熔材料，熔点分布在 2000℃ 左右，多数在接近熔点时仍能保持其化学稳定性，具有优良的高温相稳定性，可用于热绝缘、化学防护、涂层材料等众多领域。美国学者在Nd:LuPO4晶体中实现了激光输出，证明其还是一类全新的激光基质晶体材料，但晶体尺寸和质量一直无法满足研究和应用需要。本项目：①通过添加碱金属氧化物，创新了以Pb2P2O7为助熔剂生长稀土正磷酸盐的工艺方法，发展了新型助熔剂体系，生长出厘米级尺寸的晶体。②测试了片状Yb:LuPO4晶体的偏振吸收和发射谱，利用976 nm的LD作为泵浦源，在2.4W的泵浦功率下，在1039nm处实现了1.6W的连续波激光输出，斜率效率达到75%，证明Yb:LuPO4晶体是一种极具潜质的激光晶体材料。③以Cr4+:YAG晶体作为可饱和吸收体，在棒状Yb:LuPO4晶体实现被动调Q激光输出，在脉冲重复频率为166.7 kHz条件下得到平均输出能量为7.2 W，光-光转换效率及斜率效率分别为38.5%和45%。④生长出厘米级尺寸高质量Yb:YPO4晶体，测试了偏振吸收和发射截面，实现了最高功率达3.62 W的连续波激光输出，光-光转化效率达到36%，证实Yb:YPO4晶体是一种极具潜质的新型激光材料。⑤开展了Yb:LuxY1-xPO4和Yb:LuxY1-xPO4混晶的生长、光谱、热学和激光性能研究，并对Yb3+单掺和Yb3+/Er3+双掺ReCOB晶体进行了一系列实验探索。⑥合成了不同浓度的Y1-x(P0.6V0.4)O4:xEu3+荧光粉，证实VO43-离子团能够增强Eu3+离子的发射强度，是一种极具应用价值的荧光材料。⑦发表研究论文18篇，其中SCI收录15篇，授权国家发明专利4项，申请国家发明专利2项，相关研究成果获山东高等学校优秀科研成果奖2项。这些结果为该类激光材料的实用化提供了重要的理论和实验依据。