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MgSrB2O5,Li3B5O8(OH)2和NaH2PO4?(H2O)2/3的合成及性能研究
郭新锋
学位类型博士
导师潘世烈
2014-05-26
学位授予单位中国科学院大学
学位授予地点北京
学位专业材料物理与化学
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
摘要

本论文的研究方向是合成硼酸盐及磷酸盐晶体,并研究晶体材料的物理和化学性质。涉及的研究内容主要包括:晶体合成及晶体生长条件优化、晶体结构确定、X射线衍射、红外吸收、紫外-可见-近红外漫反射等光谱学性质、差热分析及电子结构等。本论文在研究MgO-SrO-B2O3体系时获得了同成分熔融的新化合物二硼酸镁锶(MgSrB2O5);从LiOH-H3BO3-H2O体系中获得了已知化合物Li3B5O8(OH)2,并优化了晶体生长条件,在温和条件下得到了大尺寸的Li3B5O8(OH)2晶体;在研究NaF-NaOH-H3PO4体系时得到了新型水合磷酸二氢钠NaH2PO4·(H2O)2/3。本文的主要内容如下:
1. 对本领域的研究背景及现状进行了综述,介绍了本论文在实验和研究过程中所用的分析手段、晶体生长方法以及研究思路。详述了所采取的具体晶体合成方法、研究所用的方法或手段、相关理论基础,以及这些研究方法或手段在实验和研究过程中所起的作用和意义,如:单晶X射线衍射、粉末X射线衍射、红外、紫外-可见-近红外漫反射、差热分析和理论计算等。
2.合成并研究了同成分熔融的新化合物二硼酸镁锶(MgSrB2O5),该化合物属于单斜晶系,空间群为P21/c,a = 6.478(4) Å,b = 5.327(4) Å,c = 12.048(8) Å,β = 102.805(8) °。采用高温熔液自发结晶法得到了MgSrB2O5的单晶,并用X射线单晶衍射法确定了其晶体结构。在该化合物的晶体结构中,包含孤立的B2O5、Mg2O10基团。测试了该晶体的红外吸收光谱,并通过红外光谱印证了BO3基团的存在,比较了MgSrB2O5与其它二硼酸盐如Mg2B2O5、Sr2B2O5和SrCdB2O5等在结构上的差别;通过高温固相反应合成了该化合物的纯相,并通过XRD和热重差热分析加以研究和确认;差热分析表明该化合物为同成分熔融化合物,同成分熔融化合物在培养晶体时具有一定优势:可将化学计量比的原料共同熔融,并通过缓慢降温进行自发结晶,从而获得化合物的晶体。因此,同成分熔融化合物的晶体合成较为简单。粉末UV-Vis-NIR漫反射光谱表明,MgSrB2O5晶体的紫外截止边小于190 nm;理论计算结果显示其是一种间接带隙化合物,在可见光区的双折射率约为0.08。
3.通过水热法合成出了Li3B5O8(OH)2晶体,该晶体属四方晶系,空间群为P41212,a= 6.8346 Å,c=14.5417 Å。该晶体由苏联科学家O. S. Bondareva等人于1978年首次合成。本文的合成方法与他们的相比,具有操作简单、无需矿化剂、温度温和和生长速度快等特点。通过红外光谱印证了BO3和BO4基团的存在,对比了该晶体与其他硼酸锂盐如Li(B2O3(OH))·H2O、Li(B(OH)4)和Li(H2O)4[B(OH)4]·2H2O在结构上的差别,并测定了XRD和粉末UV-Vis-NIR漫反射光谱,通过热重-差热手段分析了化合物的热稳定性。
4. 在采用水热合成法研究NaF-NaOH-H3PO4体系时合成了一种新型磷酸二氢钠晶体NaH2PO4·(H2O)2/3,该化合物属于正交晶系,空间群为Pbcn,a= 6.8938(9) Å,b= 8.0356(11) Å,c= 22.909(3) Å。通过X射线单晶衍射确认了该晶体的结构,并将其结构与其它已知磷酸二氢钠(NaH2PO4、NaH2PO4·H2O和NaH2PO4·2H2O)的结构进行了对比。

其他摘要

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).

文献类型学位论文
条目标识符http://ir.xjipc.cas.cn/handle/365002/3400
专题材料物理与化学研究室
作者单位中国科学院新疆理化技术研究所
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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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