【作者】 夏明军；

【导师】 李如康；

【作者基本信息】 中国科学院研究生院（理化技术研究所） ， 物理化学， 2008， 博士

【摘要】 本论文主要研究了紫外非线性光学晶体的Ca₅（BO₃）₃F（简写为CBF）生长以及Nd³⁺掺杂的生长与光谱性能的研究,并且发现稀土硼酸盐体系新化合物CsLi₂Gd₄（BO₃）₅。1. Ca₅（BO₃）₃F晶体的研究本部分主要是探索新的助熔剂体系生长Ca₅（BO₃）₃F晶体,找到了适合生长Ca₅（BO₃）₃F晶体的几种助熔剂:用Li₂O-B₂O₃-CaF₂-LiF助熔剂能够在较低的生长温度（850°C左右）生长出透明部分较大、质量较高的完整的Ca₅（BO₃）₃F晶体,并且体系的挥发程度较轻。测试了CBF晶体的透过范围,发现该晶体的紫外吸收边在190nm,300-2500nm范围的透过率有80%以上。CBF晶体可能是一种性能优异的紫外非线性光学晶体。2. Nd³⁺掺杂Ca₅（BO₃）₃F晶体的研究利用Li₂O-B₂O₃-CaF₂-LiF助熔剂体系,分别生长出掺杂浓度为1%、2%、4%和6%的Nd:Ca₅（BO₃）₃F晶体。也分别尝试用泡生法和顶部籽晶两种方法来生长Nd:CBF晶体,在晶体的生长过程中发现同样的助熔剂体系生长出的Nd:CBF晶体要比纯的CBF晶体的质量要好,更加完整。使用电感耦合等离子原子发射光谱对两种不同掺杂离子浓度进行分析,Nd:CBF晶体的Nd³⁺离子的分凝系数是65.8%（4%Nd:CBF）和52.8%（2%Nd:CBF）。此外对2%Nd:CBF晶体的透过、荧光光谱等进行了研究。根据J-O理论计算了Nd:CBF晶体中的Nd³⁺离子偶极跃迁的谱线强度S以及唯象强度系数Ωt （t=2,4,6）,它们的值分别是Ω₂ = 5.22×10^-20 cm²,Ω₄ = 1.91×10^-20 cm²和Ω₆ = 1.30×10^-20 cm²。同时计算了⁴F_3/2→⁴I_9/2和⁴F_3/2→⁴I_11/2跃迁几率: 589.0s-1和536.8 s-1,辐射寿命τr=817.6μs。各个发射带的荧光分支比分别为β（877nm）=0.48,β（1051 nm）=0.44,β（1330 nm）=0.076,β（1830 nm）=0.004。通过测量Nd:CBF晶体的荧光光谱和荧光寿命（51.8μs）,计算得到发射截面σ_e （877nm）=0.69×10-19cm²,σ_e （1051nm）=0.63×10^-19cm²,和量子效率η_c=6.3%。由于⁴F_3/2→⁴I_9/2的跃迁几率A_r和发射截面σ_e都比⁴F_3/2→⁴I_11/2稍大,因此在877nm的辐射较强,有利于自倍频产生蓝光。对比于其他自倍频晶体，Nd：CBF晶体的荧光寿命同NGAB晶体差不多，比Nd：GdCOB晶体的发射截面大，同时Nd：CBF晶体也具有较大的倍频系数，因此，Nd：CBF晶体可能是一种潜在的、新型自倍频晶体。3．稀土硼酸盐CsLi₂Gd₄（BO₃）₅化合物CsLi₂Gd₄（BO₃）₅化合物，空间群为P2／n，单胞参数为：a=10．644（2）A，b=6．4661（15）A，c=20．093（4）A，β=105．250（16）。Z=4；它的阴离子结构基团是平面的B03基团，5个不同晶体学位置的Gd原子形成两种类萤石结构的基本框架的Gd-O链，一条是包含Gd2和Gd4的Gd₃O₁₇链，另一条是包含Gd1，Gd3和Gd5的链，其中该链的两端分别与BO₃基团相连形成Gd₅O₂₉（BO₃）₂链。两条Gd-O链通过共享的O原子在ac平面形成二维的[Gd₈O₁₆（BO₃）₂]₁₄-的层状结构，这个层与平面外的BO₃基团在b方向相连形成三维的网络结构。用Rb来替代CsLi₂Gd₄（BO₃）₅晶体中的Cs时，同样能够得到相应的化合物。由于该化合物与CsLi₂Gd₄（BO₃）₅的结构同构，对RbLi₂Gd₄（BO₃）₅指标化，得出单胞参数为a=10．433 A，b=6．325 A，c=19．688 A，β=105．09更多还原

【Abstract】 In this dissertation, the new NLO crystal Ca₅（BO₃）₃F （hereafter, abbreviated as CBF） and Nd³⁺ doped CBF crystal were studied, and a new rare earth borate compound was found. The main work is listed in following:1. Study on Ca₅（BO₃）₃F crystalBecause CBF compound is incongruently melting, we must seek a flux system for growing CBF crystal. A new Li₂O-B₂O₃-CaF₂-LiF flux system was considered to be appropriate for crystal growth through various test growths. The new flux system has many advantages over the other fluxes reported in the literature, such as lower crystal growing temperature and lower volatility. Besides, some transparent CBF crystals were with both Kyropoulos and top seeded solution growth methods.The transmission spectrum was collected in the Lambda 900 UV/VIS/NIR instrument with wavelength ranging from 180 to 3500nm. The crystal shows high transmittance （>80%） in the wavelength range 350-2500nm with a UV transmission cut-off of 190nm.2. Study on Nd:Ca₅（BO₃）₃F crystalSince the crystal structures of CBF and RCOB are nearly identical, Nd³⁺ doped CBF crystals with Nd contents of 1%, 2%, 4% and 6%, were grown for studying their luminescence and potential laser properties. The segregation coefficients of Nd:CBF crystals were found to be 65.8% （4%Nd:CBF） and 52.8% （2%Nd:CBF） using ICP-AES measurements, respectively.The spectra of transmission, absorption and fluorescence were performed in the 2%Nd:CBF crystal. According to J-O theory, the experimental oscillator strength Smea was calculated and the oscillator strength parametersΩt（t=2,4,6） were obtained as follows:Ω₂ = 5.22×10^-20 cm²,?4 = 1.91×10^-20 cm², ?6 = 1.30×10^-20 cm²。The fluorescence branch rations were also obtained:β（877 nm） = 0.48,β（1051 nm） = 0.44,β（1330 nm） = 0.076,β（1830 nm） = 0.004. The radiative lifetime isτ_r = 817.6μs and quantum efficiencyη_c=6.3%. The radiative transition rate and emission cross section for the ⁴F_3/2→⁴I_9/2 and ⁴F_3/2→⁴I_11/2 transiton were 589.0s-1, 536.8 s-1 andσ_e （877nm）=0.69×10^-19cm²,σ_e （1051nm）=0.63×10^-19cm², respectively. Since the radiative transition rate and emission cross section for the ⁴F_3/2→⁴I_9/2 was larger than ⁴F_3/2→⁴I_11/2 transition and its larger second harmonic coefficient, it is hoped Nd:CBF can be a promising material to generate blue laser via self-frequency doubling.3. A new rare earth borate compound CsLi₂Gd₄（BO₃）₅A new rare earth borate compound CsLi₂Gd₄（BO₃）₅ was found. Its space group is P2/n and cell parameters are as following: a=10.644（2） A, b=6.4661（15） A, c=20.093（4） A,β=105.250（16）°, Z=4; The crystal structure features chains of edge and corner-sharing GdOn polyhedra. The GdOn polyhedra yield two types of Gd-O chains. The chain containing Gd1, Gd3 and Gd5 atoms is terminated by two BO3 groups, the other Gd3O7 chain containing Gd2 and Gd4 joins other three-element chains to form infinite zig-zag chain. Both chains can be classified as fluorite-related ribbons, which are common in the other rare earth borate, such as Li₃Gd（BO₃）₂ andLiGd₆O₅（BO₃）₃ compounds. The two chains in CsLi₂Gd₄（BO₃）₅ are interlocked by sharing edges of the GdO polyhedra to form a two dimensional [Gd₈O₁₆（BO₃）₂]^14- layer in the ac plane. The layers are inter-linked by out of plane BO3 group in the b direction into a 3 dimensional network. Both Li atoms are five-coordinated, and the Cs atom is coordinated by seven O atoms and resides in a big basket-like cage.The Rb analogue of the CsLi₂Gd₄（BO₃）₅ compound can also be synthesized by solid-state reaction and its cell parameters are determined as: a=10.433 A, b=6.325 A, c=19.688 A,β=105.09°.更多还原