The non-centrosymmetric borate oxides, MBi2B2O7 (M = Ca, Sr)
The non-centrosymmetric borate oxides, MBi2B2O7 (M = Ca, Sr)
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DOI：
10.1016/j.jssc.2006.08.037
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发表时间：
2006-12-01
影响因子：
3.3
通讯作者：
Cranswick, L. M. D.
中科院分区：
文献类型：
--
作者：
Barbier, J.;Cranswick, L. M. D.
本文报道了两种新型非中心对称硼酸盐氧化物MBi_2B_2O_7和MBi_2O（BO_3）（2）（M=Ca，Sr）的合成。它们的晶体结构已被确定从头算和使用粉末中子衍射数据的改进。CaBi 2 B 2 O 7晶体属于正交晶系Pna 2（1）空间群，a = 8.9371（5）埃，B = 5.4771（3）埃，c = 12.5912（7）埃，Z = 4，R-wp = 0.118，chi（2）= 2.30，SrBi 2 B 2 O 7晶体属于六方晶系P6（3）空间群，a = 9.1404（4）埃，c = 13.0808（6）埃，Z = 6，R-wp = 0.115，chi（2）= 4.15。大的位移参数表明存在的无序SrBi 2B 2 O 7也揭示了扩散2 x的超结构反射的电子衍射图案。这两种结构都是由相同的（001）中性层的角共享BO 3三角形和MO 6三角棱镜形成六元环，其中Bi 2 O基团位于。相邻层以交错配置堆叠，并通过弱Bi-O键连接。测量了CaBi_2B_2 O_7（d（eff）= 2d（eff）（KDP））粉末样品的中等二次谐波产生效率。(c)2006年爱思唯尔公司All rights reserved.
Two novel noncentrosymmetric berates oxides, MBi2B2O7 or MBi2O(BO3)(2) (M=Ca, Sr), have been synthesized by solid-state reactions in air at temperatures in the 600-700 degrees C range. Their crystal structures have been determined ab initio and refined using powder neutron diffraction data. CaBi2B2O7 crystallizes in the orthorhombic Pna2(1) space group with a = 8.9371(5)angstrom, b = 5.4771(3)angstrom, c = 12.5912(7) angstrom, Z = 4, R-wp = 0.118, chi(2) = 2.30, SrBi2B2O7 crystallizes in the hexagonal P6(3) space group with a = 9.1404(4) angstrom, c = 13.0808(6) angstrom, Z = 6, R-wp = 0.115, chi(2) = 4.15. Large displacement parameters suggest the presence of disorder in SrBi2B2O7 as also revealed by diffuse 2 x a superstructure reflections in electron diffraction patterns. Both structures are built of identical (001) neutral layers of corner-sharing BO3 triangles and MO6 trigonal prisms forming six-membered rings in which Bi2O groups are located. Adjacent layers are stacked in a staggered configuration and connected through weak Bi-O bonds. A moderate efficiency for second harmonic generation (SHG) has been measured for a powder sample of CaBi2B2O7 (d(eff) = 2d(eff)(KDP)). (c) 2006 Elsevier Inc. All rights reserved.