Te2HPO7晶体的非线性光学特性研究

采用水热法合成了一种具有非中心对称结构的已知化合物Te2HPO7,并用波长为1064 nm的激光测试了其粉末倍频效应,发现相同颗粒尺寸下其倍频效应近似为KH2PO4的0.27倍,并且满足相位匹配条件.偶极矩计算表明,该化合物倍频效应主要源于含有孤立电子的TeO4多面体非对称单元.另外,本文用高温差示扫描量热法研究了晶体的热稳定性,在紫外-可见-近红外分光光度计上测量了它的透过光谱.     

A Short-wave UV Nonlinear Optical Sulfate of High Thermal Stability

Compared with borates, carbonates, nitrates and phosphates, sulfates have been ignored as nonlinear optical(NLO) materials for a long time. Recently, researchers started to realize sulfates which have the potential as NLO materials, and synthesized some sulfate NLO materials by the water solution method and solvothermal method. However, all these sulfate NLO materials have the same problem of low thermal stability. Here, we synthesized a new Cs4 Mg6(SO4)8, which crystallizes in the orthorhombic space group P212121 with a = 9.102, b = 9.955, c = 16.127 ?, V = 1461.3 ?3, Z = 2, F(000) = 1352, μ = 5.777 mm-1, R = 0.0213 and wR = 0.0480. The single crystal structure can be described as a three-dimensional framework constructed by MgO6 octahedra and SO4 tetrahedra. Relevant optical measurements indicate that Cs4 Mg6(SO4)8 is short-wave ultraviolet transparent and has a moderate second harmonic generation response. Theoretical calculations by the CASTEP package reveal that S–O groups are NLO-active anionic groups. Significantly, Cs4 Mg6(SO4)8 has high thermal stability up to 781 ℃ based on thermal analyses. We believe that our work will provide a new strategy for researchers to develop new sulfate short-wave ultraviolet NLO materials of high thermal stability.     

银簇化合物Ag3B6O10I的合成、晶体结构和双折射性质

通过高温固相合成技术,成功合成了一种新型含银簇卤化硼酸盐Ag₃B₆O₁₀I。该晶体属正交晶系,空间群为Pnma (No. 62)。结构分析表明,该晶体结构中BO₄四面体和BO₃三角形连接形成[B₆O₁₀]^2-并最终相互连接形成三维孔洞结构,Ag₃I三角锥位于孔洞中。这种基于B₆O₁₀基元的含银簇三维孔洞结构为首次报道。热稳定性分析表明Ag₃B₆O₁₀I为非同成分熔融化合物,熔融分解温度为963 K。紫外-可见-近红外漫反射光谱分析显示该晶体光学带隙约为3.1 eV。值得关注的是,Ag₃B₆O₁₀I晶体具有较大的双折射率(0.031@550 nm)。第一性原理理论计算揭示了该晶体的光学特性来源。