碱金属阳离子对[B_3O_7]型非线性光学晶体结晶习性的影响  

The influence of alkali metal ions on crystallization habits of nonlinear optical crystal containing [B_3O_7] groups

作　　者：王迪[1] 张德明[1] 张季[1] 王小飞[1] 张庆礼[1] 万松明[1] 殷绍唐[1] 

机构地区：[1]中国科学院安徽光学精密机械研究所,安徽省光子器件与材料重点实验室,合肥230031

出　　处：《物理学报》2013年第15期179-185,共7页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:50932005;51102239;90922003;51172236)资助的课题~~

摘　　要：本文利用高温拉曼光谱技术和从头计算的方法,研究了LiB3O5和CsB3O5晶体高温熔融体的结构,分析了碱金属阳离子对熔体结构的影响,以及熔体结构的差异与LiB3O5和CsB3O5晶体结晶习性的联系.结果表明:LiB3O5和CsB3O5晶体高温熔融体中的结构基团主要为B37和B36两种不同类型的硼氧六元环;环内B4四面体的数量影响了六元环呼吸振动峰的拉曼频率,随B4四面体数量的增加六元环呼吸振动峰向低频移动;LiB3O5晶体高温熔融体中,B4四面体含量相对较多;然而,离子半径相对较大的Cs+离子却阻碍了熔体中B4四面体的形成,造成CsB3O5晶体高温熔融体中B4/B3比值的降低.结合LiB3O5和CsB3O5晶体生长动力学过程的分析(Wang D,Wan S Metal.2011 Cryst.Eng.Comm.13 5239),阳离子的不同导致高温熔体中B4四面体数量的差异,被认为是影响LiB3O5和CsB3O5晶体结晶习性的重要因素,有效降低高温熔体中B4四面体的数量,将是实现LiB3O5晶体生长的关键条件.LiB3O5 and CsB3O5 are two excellent nonlinear optical borate crystals containing [B3O7] groups. With a difference of aikali metal ions in structure, LiB3O5 and CsB3O5 exhibit different crystallization habits. The former is an incongruent compound, which cannot crystallize from its melt; however, the latter is a congruent compound obtained by cooling its melt directly. In this work, using Raman spectroscopy and ab initio calculation, the structures of LiB3O5 and CsB3O5 melts have been investigated, and then the influence of alkali metal ions on melt structures is discussed, finally, the relationship between crystallization habits of LiB3O5 and CsB3O5 and their melts is proposed. Results suggest that the boron oxide species of LiB3O5 and CsB3O5 melts are in the form of six-membered rings B37 and B36 （ represents a bridging oxygen）; Raman frequency of the symmetric breathing vibration of six-membered rings shifts to low frequency with the addition of B4 tetrahedrons in rings; the relatively large amount of B4 tetrahedrons is found in LiB3O5 melts. However, Cs＋ ions with larger ion radius hinder the formation of B4 tetrahedrons, and then reduc, the B4/B3 ratio of the melt. Finally, considering the growth mechanism of LiB3O5 and CsB3O5 crystals （Wang D, Wan S M et al. 2011 Cryst. Eng. Comm. 13 5239）, we propose that the amount of B4 tetrahedrons in melts, which is influenced by aikali metal ions, determines LiB3O5 and CsB3O5 crystallization habits, therefore, and suggest the reduction of B4 tetrahedrons in melts is an effective way to crystallize LiB3O5 .

关 键 词：硼酸盐晶体 熔体结构 拉曼光谱 结晶习性 

分 类 号：O734[理学—晶体学]