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碱金属硼、碳酸盐的合成及光学性质研究
刘琼
学位类型硕士
导师杨志华
2017-05-31
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
关键词碱金属 阳离子替换 晶体结构 第一性原理
摘要

光电功能材料是材料领域研究的热点,在激光,通讯,医疗等方面具有广泛应用。为了满足社会发展的需要,急需探索可在紫外、深紫外区域应用的短紫外截止边的非线性光学材料和较大双折射的双折射率材料。鉴于碱金属、硼氧基团及碳氧基团在紫外区域有较大的透过等优异性能,希望通过复合碱金属和硼氧基团或碳氧基团获得新型的化合物。经过系统的研究,设计合成出四种截止边均短于200 nm的新型紫外/深紫外用光学材料:包括两种倍频效应与磷酸二氢钾(KDP)相当的非线性光学材料K3B3O4(OH)4·2H2O和Rb3B3O4(OH)4·2H2O,两种具有较大双折射率的碳酸盐材料LiRbCO3和LiCsCO3。对这四种新化合物的线性(双折射率)/非线性(倍频效应)与结构内在关联机理进行系统研究。本文是以设计制备紫外/深紫外光电功能材料为主线,通过筛选组合BO3及BO2(OH)2阴离子基团、调控碱金属阳离子等设计策略,合成了四种在紫外/深紫外具有潜在应用非线性光学(双折射率)材料,为性能导向型新材料设计制备提供了新思路。具体研究内容如下:1. 理论计算表明BO3基团有利于大倍频效应、合适双折射率,BO2(OH)2基团更有利于紫外透过,因此通过基团筛选组合设计合成了含B3O4(OH)4基团(两个BO2(OH)2和一个BO3组成)的K3B3O4(OH)4·2H2O和Rb3B3O4(OH)4·2H2O非线性光学材料,并得到了4×2×2 mm3的K3B3O4(OH)4·2H2O单晶。这两种新水合碱金属硼酸盐化合物K3B3O4(OH)4·2H2O和Rb3B3O4(OH)4·2H2O是通过水热法合成的。它们均结晶于正交晶系,Cmc21(No. 36)空间群。它们具有类似的层状结构:基本构筑单元为B3O4(OH)4基团,每个B3O4(OH)4基团由两个BO2(OH)2和一个BO3组成,B3O4(OH)4又通过氢键连成类层状结构,K或Rb原子填充在层内的三维孔道中。通过优化实验条件,得到了尺寸为4×2×2 mm3的K3B3O4(OH)4·2H2O单晶。紫外-可见-近红外漫反射光谱测试表明,K3B3O4(OH)4·2H2O的光学吸收截止边低于190 nm,粉末倍频效应测试表明K3B3O4(OH)4·2H2O为一类相位匹配,倍频效应约为0.8 KDP。第一性原理计算表明,K3B3O4(OH)4·2H2O的非线性光学效应主要来自于BO基团的贡献。另外,在K3B3O4(OH)4·2H2O和Rb3B3O4(OH)4·2H2O结构的基础上,我们通过离子替代获得Cs3B3O4(OH)4·2H2O的晶体结构模拟数据,通过第一性原理计算,研究了阳离子替换对它们线性光学性质的影响:研究发现随着K,Rb,Cs的替换,它们的折射率逐渐增加,双折射逐渐减小。2. 本文通过系统研究阳离子调控致使双折射率绝对值、色散变化的内在规律,指导设计合成了具有较大双折射率的两种新的复合碱金属碳酸盐LiRbCO3和LiCsCO3。这两种新的复合碱金属碳酸盐LiRbCO3和LiCsCO3也是通过水热法合成获得。它们均结晶于单斜晶系,P21/c(No.14)空间群,与已知的LiKCO3同构。在LiRbCO3和LiCsCO3中,CO3基团呈孤立排列,通过Li-O键连接成类波浪状的[LiCO3]∞层,而[LiCO3]∞层又通过Rb-O或Cs-O连接成三维的网状结构。紫外-可见-近红外透过光谱测试表明,LiRbCO3和LiCsCO3具有宽的透光范围,其吸收截止边低于200 nm。第一性原理计算表明,两种化合物在可见光区具有较大的双折射,分别为0.1,0.09。另外,与LiKCO3相结合,系统研究了K,Rb,Cs阳离子替代对于材料光学性质的影响。LiKCO3,LiRbCO3和LiCsCO3的折射率逐渐增大但双折射率逐渐减小。在LiKCO3,LiRbCO3和LiCsCO3体系中,折射率的增大是由于K,Rb,Cs的替换使得动量矩阵元增大,加强了C-O之间的键。而双折射的减小是因为随着K,Rb,Cs替换,材料中碳氧基团的密度减少而导致材料的结构各向异性在变小。

其他摘要

Photoelectric functional materials is one of the hotspots in the field of material, which are widely used in laser, communication and related technologies. In order to meet the demand of the rapid development of the society,we need to design and synthesis new material with relatively large second-order harmonic generation (SHG) reponse or large birefringence which can be used in the ultraviolet/deep-ultraviolet region. Pervious work has proved that the alkali metals, BO groups and CO3 groups would have high transmittance properties in the ultraviolet (UV) region, so we expected to combine them to obtain new photoelectric functional materials which can be used in the UV region. After systematically investigated, we have got four new crystals with short absorption edge: two new alkali metal borates-K3B3O4(OH)4·2H2O and Rb3B3O4(OH)4·2H2O,two new alkali metal carbonates-LiRbCO3 and LiCsCO3. We have performed the general characterizations on their physical and chemical properties and studied the mechanism of action between structure and the optical properties. This work mainly focuses on the design and synthesis of two potential UV nonlinear optics (NLO) crystals- K3B3O4(OH)4·2H2O and Rb3B3O4(OH)4·2H2O as well as two potential birefringence materials- LiRbCO3 and LiCsCO3, which were obtained by the regulation of alkali metal cations and would promote the discovery of other materials.1. It has been proved that the BO3 group is a factor that favors not only large SHG efficiencies but also the moderate birefringence, so we have successfully obtained two new NLO crystals K3B3O4(OH)4·2H2O and Rb3B3O4(OH)4·2H2O. The two potential UV NLO materials were successfully synthesized by hydrothermal methods. The compounds crystalize into the Cmc21 space group, and exhibit isolated [B3O4(OH)4]3- anion groups connected by O-H…O hydrogen bonds. Moreover, we have obtained a crystal sized 4×2×2 mm3 by optimization of reaction conditions. The UV-Vis diffuse reflectance spectrum shows that K3B3O4(OH)4·2H2O has a wide transparency range with an absorption edge below 190 nm. Powder SHG measurements using 1064 nm radiation revealed a moderate efficiency, 0.8×KDP. Additional particle size vs SHG efficiency measurements indicate that K3B3O4(OH)4·2H2O is type I phase-matchable. Our calculated results show that the borate groups determine the NLO properties of K3B3O4(OH)4·2H2O. Moreover, based on the crystal structure of K3B3O4(OH)4·2H2O and Rb3B3O4(OH)4·2H2O, we invented the crystal structure of Cs3B3O4(OH)4·2H2O, and the linear properties of the three crystal were studied by the first principles calculations. 2. It is important to study how to control the birefringence for the optical polar material which need a large birefringence. In this work, we systematically investigated the variation of the chromatic dispersion and birefringence that caused by the atomic transaction. By the hydrothermal method, two new mixed alkali carbonates, LiRbCO3 and LiCsCO3 were synthesized for the first time. Both compounds crystalize into the monoclinic space group P21/n, and exhibit similar wave like [LiCO3]∞ layers connected by Rb-O and Cs-O bonds, respectively. Except for low melt temperature, wide spectral transmittance range, both compounds also have relatively large birefringence which is confirmed by first principles calculations. With the increase of atomic radius of alkali metal, the birefringence is reduced from 0.11 in LiKCO3 to 0.09 in LiCsCO3, while the refractivity is increasing. The increasing refractivity and decreasing birefringence can be interpreted by the enhancement of orbitals hybridization resulting from reduced C-O bond length and weakened structural anisotropy which origin from the decrease of the densities of the COgroups, respectively.

文献类型学位论文
条目标识符http://ir.xjipc.cas.cn/handle/365002/4962
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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刘琼. 碱金属硼、碳酸盐的合成及光学性质研究[D]. 北京. 中国科学院大学,2017.
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