Synthetic tourmaline (olenite) with excess boron replacing silicon in the tetrahedral site: II. Structure analysis
Synthetic tourmaline (olenite) with excess boron replacing silicon in the tetrahedral site: II. Structure analysis
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过量硼取代四面体位点硅的合成电气石（橄榄石）：II。
DOI：
10.1127/0935-1221/2002/0014-0763
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发表时间：
2002
影响因子：
2.1
通讯作者：
W. Schreyer
中科院分区：
文献类型：
--
作者：
B. Marler;Markus Borowski;Ulrich Wodara;W. Schreyer
用Rietveld方法对由0.625 Na 2 O · 4.5 Al 2 O3· 6.0 SiO2· 3.0 B 2 O3+过量H2O在600°C / 25 kbar（样品1）和650°C / 20 kbar（样品2）条件下合成的两个过量硼橄榄石样品进行了结构分析。所研究的电气石具有空间群对称性R3 m，样品1的晶格参数为a = 15.5996（8）A，c = 7.0224（6）A，样品2的晶格参数为a = 15.6329（8）A，c = 7.0365（6）A。29 SiMASNMR谱显示没有八面体Si，因此八面体Y和Z位只被Al 3+占据。样品1和2的平均T-O距离分别为1.573 A和1.590 A，表明B 3+离子（B-O = 1.470 A）在T-位置部分取代了Si 4+离子（Si-O = 1.620 A）。精确的占有因子给出了样品1的Na 0.8 Al 2.9 Al 6 [Si 3.8 B 2.2 O 18 ]（B 3 O 9）（OH，O）4和样品2的Na 0.7 Al 2.9 Al 6 [Si 4.2 B 1.8 O 18 ]（B 3 O 9）（OH，O）4的化学组成，大致证实了样品1的早期化学分析。由B 3+离子部分取代Si 4+离子所产生的电荷差异被质子补偿，导致OH-含量接近4。有趣的是，注意到在较高压力和较低温度下合成的样品1含有较大量的四面体硼。
Two excess-boron olenite samples which had been synthesized from a reaction mixture of 0.625 Na 2 O · 4.5 Al 2 O 3 · 6.0 SiO 2 · 3.0 B 2 O 3 + excess H 2 O at 600°C / 25 kbar (sample 1) and 650°C / 20 kbar (sample 2) were structurally analyzed by a Rietveld refinement. The investigated tourmalines possess space group symmetry R3m with lattice parameters of a = 15.5996(8) A, c = 7.0224(6) A for sample 1 and a = 15.6329(8) A, c = 7.0365(6) A for sample 2. 29 Si MAS NMR spectroscopy showed no octahedral Si, so that the octahedral Y and Z sites are exclusively occupied by Al 3+ ions. The average T-O distances are 1.573 A and 1.590 A for samples 1 and 2, respectively, indicating that B 3+ ions (B-O = 1.470 A) partly replace Si 4+ ions (Si-O = 1.620 A) at the T-position. The refined occupancy factors give a chemical composition of Na 0.8 Al 2.9 Al 6 [Si 3.8 B 2.2 O 18 ](B 3 O 9 )(OH,O) 4 for sample 1 and Na 0.7 Al 2.9 Al 6 [Si 4.2 B 1.8 O 18 ](B 3 O 9 )(OH,O) 4 for sample 2, approximately confirming an earlier chemical analysis of sample 1. The difference in charge which is generated by the partial replacement of Si 4+ ions by B 3+ ions is compensated by protons leading to OH-contents near 4. It is interesting to note that sample 1 synthesized at a higher pressure and lower temperature contains a larger amount of tetrahedral boron.