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含孤立B-O基团硼酸盐化合物的合成、结构及性质研究
刘璐
学位类型硕士
导师潘世烈
2015-05-20
学位授予单位中国科学院大学
学位授予地点北京
学位专业材料工程
关键词硼酸盐 晶体结构 孤立b-o基团 光学各向异性
摘要

硼酸盐具有丰富的结构类型和优良的物理化学性能,因此在光学材料领域有广泛的应用。本论文主要基于以下特点探索硼酸盐体系:(1)孤立的硼氧基团共平面、共平行或共轴排列,有益于产生大的光学各向异性,进而产生大的双折射率;(2)引入具有立体活性孤对电子的Pb2+,可产生大的光学各向异性;(3)碱金属、碱土金属无d-d电子跃迁,有利于紫外光的透过;(4)阳离子的数目越多, 更易于产生孤立的B-O 基团。经过系统研究,共得到六种化合物:Pb6Ba2(BO3)5X (X = Cl, Br)、Sr3(BO3)2、Ba2Ca2(B2O5)2、Ca2B2O5和Na3PbB5O10。这六个化合物中都含有孤立的B-O基团(BO3,B2O5,B5O10),并对该六种化合物进行了固相合成、晶体生长、结构解析和性能表征等工作。1.通过高温熔体法获得了两种新化合物Pb6Ba2(BO3)5X (X = Cl, Br),解析了其单晶结构。Pb6Ba2(BO3)5Cl和Pb6Ba2(BO3)5Br是同构化合物,结晶于单斜晶系,空间群C2/m。Pb6Ba2(BO3)5Cl的晶胞参数为:a= 9.3155(7) Å,b= 5.3958(5) Å,c = 17.9757(17) Å,= 101.172(6)º,V= 886.42(13) Å3,Z= 2;Pb6Ba2(BO3)5Br的晶胞参数为:a= 9.306(5) Å,b= 5.388(3) Å,c = 17.994(9) Å,= 101.513(6)º,V = 884.2(8) Å3,Z= 2。化合物是三维网状结构,由[PbBO]层和[PbBOX]层相互交替堆垛,层与层之间通过Ba原子连接而成。基于第一性原理计算表明化合物Pb6Ba2(BO3)5X具有大的双折射率,在532 nm处的双折射率分别是0.1582和0.1810,是潜在的双折射材料。原子切割的结果表明化合物大的双折射率主要是来源于Pb2+阳离子和(BO3)3阴离子基团的协同作用。2.通过高温熔液法首次得到了Sr3(BO3)2晶体,并对结构进行了解析。Sr3(BO3)2晶体属于三方晶系,空间群为Rc。它的晶胞参数为:a= 9.050(6) Å,b= 9.050(6) Å,c = 12.601(8) Å,V= 893.8(10) Å3,Z= 6。晶体结构是由SrO8多面体相互连接形成三维框架,孤立的BO3基团填充其中形成整体结构。有趣的是,孤立的BO3基团在该结构中共平行排列,使得该化合物具有较大的双折射率,第一性原理计算表明在532 nm处的双折射率为0.1216。3.采用高温熔液法在BaO-CaO-B2O3体系得到了两种新的碱土金属硼酸盐Ba2Ca2(B2O5)2和Ca2B2O5。两种化合物的晶体数据及结构如下:(a) Ba2Ca2(B2O5)2结晶于单斜晶系,空间群是P21/c。晶胞参数是a= 6.568(2) Å,b= 20.545(7) Å,c = 8.201(2) Å,= 117.00(2)º,V= 986.0(5) Å3,Z= 4。该晶体的阴离子基团是由两个BO3三角形通过共享O原子形成孤立的B2O5基团。B2O5基团与BaOn (n = 8, 9)多面体、CaO6八面体相互连接形成三维网络结构。紫外-可见-近红外漫反射光谱测试结果表明其紫外截止边低于190 nm。热学性能测试表明Ba2Ca2(B2O5)2为非同成分熔融化合物。(b) Ca2B2O5结晶于单斜晶系,空间群为P21/c,晶胞参数为a=3.5582(5)Å,b= 6.3503(8)Å,c= 19.299(3)Å,β=92.386º,V= 435.70(10) Å3,Z =4。晶体结构是由CaO6和CaO7多面体交替相互连接形成的三维Ca-O框架,孤立的B2O5基团填充到框架中。该化合物具有同质多晶现象,并与已报道的Ca2B2O5化合物进行了结构对比。4. 采用高温熔液法得到新的晶体Na3PbB5O10,属于三斜晶系,空间群是P,晶胞参数是a= 6.568(2) Å,b= 20.545(7) Å,c = 8.201(2) Å,= 69.060(4)º,= 79.231(4)º, = 63.184(4)º,V= 450.98(5) Å3,Z= 2。Na3PbB5O10的晶体结构中包含了一个由B5O10基团和PbO6多面体相互连接形成的二维[PbB5O10]层,层与层之间通过Na原子连接。

其他摘要

Borates have been widely used in the field of optical materials due to their great structural variety and extraordinary physical and chemical properties. In this paper, studies are focused on the systems of transition metal lead borate and alkaline-earth metal borate in consideration of the following points: (1) The coplanar, parallel or coaxial arrangements of B-O groups, specifically, isolated B-O groups such as BO3, B2O5, B5O10 groups, are beneficial to produce large optical anisotropy, and thus generate large birefringence; (2) Inclusion of Pb2+ cationsmay enhance the birefringence due to the optical anisotropy of the stereochemically active lone pairs. (3) There are no d-d electron transitions for alkaline-earth metal cations which is benefit to transmission of ultraviolet light. Therefore, it is expected to obtain new crystals with large birefringence or ultraviolet transmittance from these systems. Through our efforts, six new compounds have been obtained, Pb6Ba2(BO3)5X (X = Cl, Br)、Sr3(BO3)2、Ba2Ca2(B2O5)2、Ca2B2O5 and Na3PbB5O10, respectively. Isolated B-O groups (BO3, B2O5, B5O10) are the sole anion groups in these compounds. The syntheses, crystal structures, spectra properties and thermal stability analyses of these compounds are reported. 1. Single crystals of Pb6Ba2(BO3)5X were grown by the spontaneous crystallization method. And the crystal structures have been determined from single crystal X-ray diffraction data. Pb6Ba2(BO3)5X are isostructural and crystallize in the monoclinicsystem with the space group C2/m. The lattice constants are a = 9.3155(7) ?,b = 5.3958(5) ?,c = 17.9757(17) ?, ?β = 101.172(6) o, V = 886.42(13) ?3, Z = 2 and a = 9.306(5) ?,b = 5.388(3) ?, c = 17.994(9) ?, β = 101.513(6) o, V = 884.2(8) ?3, Z = 2 for Pb6Ba2(BO3)5Cl and Pb6Ba2(BO3)5Br, respectively. They are isostructural and feature 3D frameworks composed of alternate stacking of [PbBO] and [PbBOX] layers which are connected by 10-coordinated Ba atoms along the c direction. First-principles calculations show that both compounds have a large birefringence of 0.1582 and 0.1810 at 532 nm, respectively. The large birefringence originates from the mutual enhancement optical anisotropies of the Pb2+ cations and (BO3)3? groups based on the real-space atom-cutting analysis. 2. The single crystal of Sr3(BO3)2 has been grown by high temperature solution method, and the crystal structure has been solved by single crystal X-ray diffraction. Sr3(BO3)2 crystallizes in the trigonal space group R-3cwith a = 9.050(6) ?,b = 9.050(6) ?,c = 12.601(8) ?,V = 893.8(10) ?3, Z = 6. In this structure, the SrO8 polyhedra connect with each other forming the three-dimensional [SrO3]? framework. The BO3 triangles are filled in the triangular space of the [SrO3]? framework. Interestingly, the configuration of isolated BO3 groups are parallered to each other which makes this compound possess large birefringence. Its birefringence is 0.1216 at 532 nm based on the first principles computations. 3. In the BaO-CaO-B2O3 system, two new alkaline earth metal borates Ba2Ca2(B2O5)2 and Ca2B2O5 were successfully synthesized by high temperature solution method. The crystal data and structural characters of these compounds are as follows: (a) Ba2Ca2(B2O5)2 crystallizes in the monoclinic system with the space group P21/c. Its lattice parameters are a = 6.568(2) ?, b = 20.545(7) ?, c = 8.201(2) ?, β = 117.00(2) o, V = 986.0(5) ?3, Z = 4. In the structure, two BO3 units construct isolated B2O5 group via corner-sharing and the isolated B2O5 groups incorporate with the BaOn (n = 8, 9) polyhedra and CaO6 octahedra giving rise to the 3D network structure. UV-Vis-NIR diffuse reflectance spectroscopy on powder sample indicates that it has a wide transparent region with the UV cut-off edge lower than 190 nm. Thermal analysis reveals that this compound melt incongruently. (b) A new phase of Ca2B2O5 crystallizes in the monoclinic system with the space group P21/c, and the lattice parameters are a = 3.5582(5) ?, b = 6.3503(8) ?,c = 19.299(3) ?,β = 92.386 o, V = 435.70(10) ?3, Z = 4. Its structure features a three-dimensional Ca-O network composed by CaOn (n = 6, 7) polyhedra, where isolated B2O5 groups are filled. We also compared the structure with the known Ca2B2O5. 4.Single crystal of Na3PbB5O10 was grown by the spontaneous crystallization method. It crystallizes in the triclinic space group P with lattice constants a = 6.568(2) ?, b = 20.545(7) ?, c = 8.201(2) ?, α = 69.060(4) o, β = 79.231(4) o, γ = 63.184(4) o, V = 450.98(5) ?3, Z = 2. Its structure features a [PbB5O10]? layer formed by B5O10 groups and PbO6 polyhedra with adjacent layers linked by Na atoms.

文献类型学位论文
条目标识符http://ir.xjipc.cas.cn/handle/365002/4240
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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刘璐. 含孤立B-O基团硼酸盐化合物的合成、结构及性质研究[D]. 北京. 中国科学院大学,2015.
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