|关键词||硼酸盐 磷酸盐 晶体合成 X射线衍射 红外 热重 /差热 紫外 -可见 -近红外漫反射 电子结构|
The research directions are the synthsis of borates crystals, sodium orthophosphate, and the research of the chemical and physical properties of these crystals. This research mainly includes the synthsis of crystals, the optimization of crystal growth, the definition of crystalline structures, optical spectrum such as X-ray diffraction, infrared absorption, UV-Vis-NIR-diffuse reflection, differential thermal analysis and theoretical calculation of electronic structure of the crystals, and so on. In this thesis, a new congruent melting diborate MgSrB2O5 has been synthesized by high temperature solution method from the MgO-SrO-B2O3 system. The large-sized single crystal of known compound Li3B5O8(OH)2 has been synthesized by hydrothermal synthesis from the LiOH-H3BO3-H2O system under more moderate conditions. And a new two-third hydrated sodium dihydrogen phosphate has been synthesized by hydrothermal synthesis from the NaF-NaOH-H3PO4 system, the crystal structure has been determined by sigle crystal X-ray diffraction. The main contents of this paper are as follows: 1. Background and the present situation of linear and nonlinear and optical materials has been summarized. The crystal growth methods, the study and research ideas in the experiments and the thesis were introduced, including the specific apparatus and methods in the process of crystal growth, methods or means and basic theories used in the research, and the roles and significance of them in the experiments and researches, such as powder X-ray diffraction, infrared, ultraviolet - visible - near infrared diffuse reflectance, differential thermal analysis and theoretical calculations, etc. 2. A new congruent melting magnesium strontium diborate MgSrB2O5 was synthesized and studied. The single crystal was grown by high temperature solution method from the MgO-SrO-B2O3 system. The crystal structure was determined by single-crystal X-ray diffraction methods. The compound belongs to monoclinic system, with space group P21/c，a = 6.478(4) ?，b = 5.327(4) ?，c = 12.048(8) ?，β = 102.805(8) °. The crystal structure is composed of isolated B2O5 units and Mg2O10 octahedra. The existence of BO3 groups was confirmed by IR spectrum. Powder sample of MgSrB2O5 was synthesized by high temperature solid-state reaction method and the phase purity of the sample was confirmed by powder XRD and thermal analysis. Differential thermal analysis indicates that the compound is a congruent melting compound, which has advantages in crystals growth, namely, we can grow crystals by melting a stoichiometric mixture of reactant and then cooling down the melt slowly. The diffuse reflectance spectrum shows that its UV cutoff edge is below 190 nm. The first-principles theoretical calculations show that the compound is indirect-gap compound with band gaps of 4.90 eV, which is in good agreement with experimental values. And the birefringence simulated by the DFT method is about 0.08 in the visible region. 3. The large-sized single crystal of known compound Li3B5O8(OH)2, firstly synthesized by the Soviet scientists O. S. Bondareva in 1978, was synthesized by more moderate hydrothermal method. Li3B5O8(OH)2 belongs to tetragonal system，with space group P41212，a = 6.8346 ?，c = 14.5417 ?。Compared to the references, the features of the method in this paper are as following: without mineralizing agent, more simple operation, more moderate temperature, faster growth rate. The existence of BO3 and BO4 groups was confirmed by IR spectrum. The differences of crystal structure between Li3B5O8(OH)2 and other lithium borate, such as Li(B2O3(OH))?H2O, Li(B(OH)4), and Li(H2O)4(B(OH)4)?2H2O, were compared in detail. The powder XRD and UV-Vis-NIR diffuse reflectance spectroscopy of Li(B2O3(OH))?H2O were determined. The diffuse reflectance spectrum shows that its UV cutoff edge is below 190 nm.The thermal stability of the crystal was studied by thermogravimetric and differential thermal analysis. 4. A novel two-third hydrated sodium dihydrogen phosphate crystal of NaH2PO4?(H2O)2/3 was synthesized from the NaF-NaOH-H3PO4 system by hydrothermal method and the crystal structure was determined by single-crystal X-ray diffraction methods. The compound belongs to orthorhombic system, with space group Pbcn，a = 6.8938(9) ?，b = 8.0356(11) ?，c = 22.909(3).
|郭新锋. MgSrB2O5，Li3B5O8(OH)2和NaH2PO4?(H2O)2/3的合成及性能研究[D]. 北京. 中国科学院大学,2014.|
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