Crystal structure of synthetic Al4B2O9: A member of the mullite family closely related to boralsilite
Crystal structure of synthetic Al4B2O9: A member of the mullite family closely related to boralsilite
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合成 Al4B2O9 的晶体结构：与硼硅石密切相关的莫来石家族成员
DOI：
10.2138/am.2008.2744
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发表时间：
2008
影响因子：
3.1
通讯作者：
H. Schneider
中科院分区：
文献类型：
--
作者：
R. Fischer;V. Kahlenberg;Dietmar Voll;K. MacKenzie;Mark E. Smith;B. Schnetger;H. Brumsack;H. Schneider
摘要：以Al(NO)3·9H2O和B(OH)3为原料，采用溶胶-凝胶法合成了Al4B2O9晶体结构，并结合11B和27Al MAS NMR谱，采用Rietveld细化和网格搜索分析对其进行了表征。单胞组成为Al32B16O72的硼酸铝与硅被B取代的硼硅石（Al32B12Si4O74）结构和莫来石（Al4+2xSi2-2xO10-x）结构密切相关。Al4B2O9在单斜空间群C2/m中结晶，a = 14.8056(7) Å， b = 5.5413(2) Å， c = 15.0531(6) Å， β = 90.913(2)°，Z = 8。其主要结构单元是与b平行的alo6 -八面体单链，这是莫来石型晶体结构的特征。八面体链由AlO4、AlO5、BO3和BO4基团交联，两个B原子和一个O原子（O5′）在间隙位置上无序。27Al和11B核磁共振研究证实了六重（八面体）、五重和四重（四面体）配位Al（六重：[四重+五重]= ~50%:50%）和三重和四重配位B（~80%:20%）的存在。
Abstract The crystal structure of Al4B2O9, synthesized from Al(NO)3·9H2O and B(OH)3 via a sol-gel process, is studied and characterized by Rietveld refinements and grid search analyses combined with 11B and 27Al MAS NMR spectroscopy. The aluminum borate with a unit-cell composition of Al32B16O72 is closely related to the boralsilite (Al32B12Si4O74) structure with Si replaced by B and to mullite (Al4+2xSi2-2xO10-x). It crystallizes in the monoclinic space group C2/m, a = 14.8056(7) Å, b = 5.5413(2) Å, c = 15.0531(6) Å, β = 90.913(2)°, Z = 8 for Al4B2O9. The main structural units are isolated chains of edge-sharing AlO6-octahedra running parallel to b that is a characteristic feature of the mullite-type crystal structures. The octahedral chains are crosslinked by AlO4, AlO5, BO3, and BO4 groups with two B atoms and one O atom (O5′) disordered on interstitial positions. 27Al and 11B NMR studies confirm the presence of sixfold (octahedral), fivefold, and fourfold (tetrahedral) coordinated Al (sixfold:[fourfold + fivefold] = ~50%:50%) and of threefold and fourfold coordinated B (~80%:20%).