Growth And Properties Of Nonlinear Optical Crystal Ca₅(BO₃)₃F And Its Nd³⁺ Doped Analog

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 cm²ã€‚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 isÏ„_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°.