| 题名 | 含孤立B-O基团碱金属镁硼酸盐的设计合成及性质研究 |
| 作者 | 王正 |
| 学位类别 | 硕士 |
| 答辩日期 | 2014-05-26 |
| 授予单位 | 中国科学院大学 |
| 授予地点 | 北京 |
| 导师 | 潘世烈 |
| 关键词 | 硼酸盐 晶体结构 高温熔液法 孤立B-O 基团 |
| 学位专业 | 材料工程 |
| 中文摘要 | 本文基于硼酸盐结构的多样性及其在光学材料方面的广泛应用，通过调节阳离子与B原子的比例，系统的对M2O-MgO(F2)/ZnO-B2O3 (M = Li、Rb、Cs)体系进行了探索，得到六种新化合物的单晶：Li0.8Mg2.1B2O5F、RbMgBO3、CsZn4(BO3)3、 Cs4Mg4(BO3)4、Rb18Mg6B29O58F和Cs18Mg6B29O58F。这六个化合物中都含有孤立的B-O基团 （BO3，B2O5，B5O10，B7O14）并对这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研究工作。 1. 通过高温熔液法得到一种新的氟硼酸盐晶体Li0.8Mg2.1B2O5F，该化合物属于单斜晶系，空间群为P21/n (No. 14)，晶胞参数为a = 3.0881(4) ?，b = 13.602(2) ?，c = 9.6563(1) ?，β = 91.744(9)°，V = 405.43(1) ?3，Z = 4。在该化合物中四个MgO5F单链和一个Li/MgO2F4单链共边连接形成一个特殊的沿a方向的Mg-O-F八面体链，相邻的链相互连接形成一个含有 孔洞的三维框架，然后B2O5基团和LiO5链填充到孔洞中形成最终结构。 2. 通过高温熔液法首次获得了一个非中心对称化合物RbMgBO3和两个中心对称化合物CsZn4(BO3)3、Cs4Mg4(BO3)4的晶体。三个化合物 的晶胞参数及结构特征如下： (a) 非中心对称化合物RbMgBO3属于硼酸盐中比较少见的立方晶系，空间群为P213 (No. 198)，晶胞参数为a = 6.942(3) ?，V = 334.5(3) ?3，Z = 4。该化合物中MgO6八面体通过共边连接形成一个具有方形和三角形孔道的三维[MgO3]∞网状结构，三角形孔道被BO3基团填充，方形孔道被铷离子填 充。该化合物中BO3基团有三种取向，呈现非共面排布。 (b) 中心对称化合物硼酸铯锌CsZn4(BO3)3属于单斜晶系，空间群为P2/c (No. 13)，晶胞参数为a = 6.871(7) ?，b = 5.021(5) ?，c = 12.936(13) ?，β = 92.399(11)°，V = 445.9(8) ?3，Z = 2。在该结构中ZnO4四面体通过共顶点连接形成有空隙的二维[Zn4O9]∞层状结构，第一种BO3基团填充其中；层与层之间则是通过第二种BO3基团 和铯离子相连。在该化合物中两种BO3基团分别各自共平面排列，两种BO3基团取向不一致。 (c) 中心对称化合物硼酸铯镁晶体Cs4Mg4(BO3)4属于单斜晶系，空间群为P21/c (No. 14)，晶胞参数为a = 20.217(6) ?，b = 4.8790(12) ?，c = 16.682(4) ?，β = 114.296(2)°，V = 1499.7(7) ?3，Z = 4。在该化合物中MgO4四面体通过共顶点连接形成有空隙的一维[Mg4O15]∞链，两种BO3基团填隙在其中；链与链之间则是通过另外两种BO3基团 和铯离子相连接并沿着b轴方向形成两种孔道，孔道被铯离子填隙。链内和链间的BO3基团分别各自共平面排布，但彼此之间取向近似垂直。 三种化合物中Mg-O和Zn-O形成的骨架对BO3的排布有很重要的影响。低维度的骨架对BO3基团的共平面排布有利。RbMgBO3和 Cs4Mg4(BO3)4有着相同的元素比，但是它们却属于完全不同的空间群，BO3基团的对称操作也有很大区别。 3. 在Rb/Cs2O-MgF2-B2O3体系中，利用高温熔液法首次获得了两个同构的中心对称化合物Rb18Mg6B29O58F和 Cs18Mg6B29O58F，它们均属于单斜晶系，空间群为C2/c (No. 15)。其中Rb18Mg6B29O58F的晶胞参数为a = 11.058(10) ?，b = 19.700(18) ?，c = 31.01(3) ?，β = 90.134(12)°，V = 6754(11) ?3，Z = 4；而Cs18Mg6B29O58F的晶胞参数为a = 11.234(7) ?，b = 20.110(12) ?，c = 32.124(19) ?，β = 90.225(7)°，V = 7257(7) ?3，Z = 4。该同构化合物的晶胞中的B原子多达116个。此外，在该化合物中还存在两种孤立的B-O基团：B5O10基团和B7O14基团，其中B7O14基团仅 在两个化合物中发现过（它们分别是KBa7Mg2B14O28F5化合物和Li4Cs3B7O14化合物）。两种B-O基团通过与MgO4四面体共享氧形 成三维的网络结构，其中铯离子填充在空隙中。M18Mg6B29O58F (M = Rb和Cs)同时含有两种较大的孤立B-O基团（非BO3和BO4基团）在相关的报道中比较少见。 基于碱金属镁硼酸盐的研究，我们可以发现碱金属镁硼酸盐化合物结构丰富多样，而且验证了通过调节阳离子/硼比例，获得含孤立B-O基团的化合物在实验上是 可行的。本文的研究结果可为设计合成新的碱金属镁硼酸盐化合物提供技术借鉴与理论指导。 |
| 英文摘要 | In this thesis, we have studied the systems of M2O-MgO(F2)/ZnO-B2O3 (M = Li, Rb, Cs), and obtained the small crystals of six new compounds: Li0.8Mg2.1B2O5F, RbMgBO3, CsZn4(BO3)3, Cs4Mg4(BO3)4, Rb18Mg6B29O58F and Cs18Mg6B29O58F. All of the compounds contain isolated B-O groups (BO3, B2O5, B5O10, and B7O14). The major work consists of the syntheses, crystal growth, crystal structure determinations and measurements of properties. 1. A new crystal, Li0.8Mg2.1B2O5F, has been grown by high temperature solution method. Li0.8Mg2.1B2O5F crystallizes in monoclinic space group P21/n (No.14) with lattice constants a = 3.0881(4) ?, b = 13.602(2) ?, c = 9.6563(1) ?, β = 91.744(9)°, V = 405.43(1) ?3, Z = 4. In the structure, four [MgO3F]∞ and one [Li/MgO2F2]∞ single chains form a special magnesium-oxygen-fluorine octahedral chain along the a direction, and the adjacent octahedral chains are connected to form a three-dimensional cationic framework containing tunnels. And the tunnel is occupied by the [LiO4]∞ chain and the pairs isolated B2O5 groups. The diffuse-reflectance spectrum show that the ultraviolet cut-off edge for the Li0.8Mg2.1B2O5F crystal is below 190 nm. 2. The single crystals of one noncentrosymmetrical compound, RbMgBO3, and two centrosymmetrical compounds, CsZn4(BO3)3 and Cs4Mg4(BO3)4, were obtained by high temperature solution method for the first time. The lattice parameters and structural features of three compounds are as follows: (a) The noncentrosymmetrical compound RbMgBO3 crystallizes in cubic space group P213 (No. 198) with lattice constants a = 6.942(3) ?，V = 334.5(3) ?3，Z = 4. In this structure, the distorted MgO6 octahedra are connected to form a three-dimensional (3D) [MgO3]∞ framework by corner-sharing. The 3D framework presents two kinds of voids: the triangular one occupied by BO3 groups and the quadrate one occupied by large Rb+ cations. The BO3 groups in RbMgBO3 have three kinds of orientations, and show the non-coplanar configuration. (b) The centrosymmetrical compound, CsZn4(BO3)3, crystallizes in monoclinic space group P2/c (No. 13) with lattice constants a = 6.871(7) ?, b = 5.021(5) ?, c = 12.936(13) ?, β = 92.399(11)°, V = 445.9(8) ?3, Z = 2. The structure of CsZn4(BO3)3 features a 2D infinite [Zn4O9]∞ layer composed of corner sharing distorted ZnO4 tetrahedra with first kind of BO3 groups inserted into the void space, then adjacent [Zn4O9]∞ layers connect into a 3D framework via second kind of BO3 groups and form a tunnel along b direction, and the Cs+ cations reside in the tunnel. The first kind of BO3 groups are coplanar, and the same as the second ones, while the orientations of the two kinds of BO3 groups are different. (c) The centrosymmetrical compound, Cs4Mg4(BO3)4, crystallizes in monoclinic space group P21/c (No. 14), and its lattice constants are a = 20.217(6) ?, b = 4.8790(12) ?, c = 16.682(4) ?, β = 114.296(2)°, V = 1499.7(7) ?3, Z = 4. In the structure, four kinds of MgO4 tetrahedra form a 1D [Mg4O15]∞ infinite chain with two kinds of BO3 groups inserted into the interspaces, then the 1D chains are further connected to form 3D framework by another two kinds of BO3 groups, and two kinds of tunnels are contained alonging b direction with Cs+ cations distributed. The interchain BO3 groups arrange coplanarly and the same as the intrachain ones, however, the orientations of the two kinds of BO3 groups are nearly perpendicular. 3. In the M2O-MgO-B2O3 (M = Rb, Cs) system, two isostructural centrosymmetrical compounds, Rb18Mg6B29O58F and Cs18Mg6B29O58F, were obtained by high temperature solution method. They crystallize in monoclinic space group C2/c (No. 15) with lattice constants a = 11.058(10) ?，b = 19.700(18) ?, c = 31.01(3) ?, β = 90.134(12)°, V = 6754(11) ?3, Z = 4 for Rb18Mg6B29O58F and a = 11.234(7) ?, b = 20.110(12) ?, c = 32.124(19) ?, β = 90.225(7)°, V = 7257(7) ?3, Z = 4 for Cs18Mg6B29O58F. There are 116 B atoms in the unit cell of Rb18Mg6B29O58F and Cs18Mg6B29O58F. In addition, two kinds of isolated B-O groups are included in the two compounds: B5O10 and B7O14 groups, and the B7O14 groups were only found in two borates which are KBa7Mg2B14O28F5 and Li4Cs3B7O14. In the structure, two kinds of the B-O groups connect into 3D framework via MgO4 tetrahedra by sharing terminal oxygens, and the Cs+ cations insert into the tunnels of framework. It is rare that the co-existence of two kinds of big isolated B-O groups (not isolated BO3 and BO4 groups) in one borate. Based on the research of alkalis-magnesium mixed borates, we can find that the alkalis- magnesium mixed borates have a wide variety of chemistry structures, and also verify that it is viable to obtain borates with isolated B-O groups by changing the ratio of cations and boron in experiment. The research results of this thesis can also guide the designing and synthesis of new alkalis-magnesium mixed borates. |
| 公开日期 | 2014-08-05 |
| 内容类型 | 学位论文 |
| 源URL | [http://ir.xjipc.cas.cn/handle/365002/3406]  |
| 专题 | 新疆理化技术研究所_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 |
| 推荐引用方式 GB/T 7714 | 王正. 含孤立B-O基团碱金属镁硼酸盐的设计合成及性质研究[D]. 北京. 中国科学院大学. 2014. |
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