RIETVELD REFINEMENT OF THE STRUCTURES OF DRY-SYNTHESIZED MFEIIISI2O6 LEUCITES (M=K, RB, CS) BY SYNCHROTRON X-RAY-POWDER DIFFRACTION
RIETVELD REFINEMENT OF THE STRUCTURES OF DRY-SYNTHESIZED MFEIIISI2O6 LEUCITES (M=K, RB, CS) BY SYNCHROTRON X-RAY-POWDER DIFFRACTION
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DOI：
10.1107/s0108270194004014
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发表时间：
1994-10-15
期刊：
影响因子：
--
通讯作者：
HENDERSON, CMB
中科院分区：
文献类型：
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作者：
BELL, AMT;HENDERSON, CMB
对干法合成的MFe（III）Si_2O_6白榴石（M = K，Rb，Cs）的高分辨同步辐射X射线粉末衍射图谱分析表明，含K和Rb的白榴石（硅酸铁钾，KFeSi_2O_6和硅酸铁铷，RbFeSi_2O_6）均具有四斜晶系I_4（1）/a结构，含Cs的白榴石（硅酸铯铁，CsFeSi_2O_6）具有立方晶系I_3BARd结构。 用Rietveld方法对这些材料的结构进行了修正。 在CsFeSi_2O_6白榴石中，Fe（III）和Si由于空间群的限制而在四面体骨架上处于无序状态。 在KFeSi 2 O 6白榴石中，Fe表现出明显的有序性，并集中在T3四面体位置。 RbFeSi 2 O 6白榴石显示出不太明显的T-位点有序性，这反映了它更接近于T位点变得相同的四方-立方相变的事实。
Analyses of high-resolution synchrotron X-ray powder diffraction patterns of dry-synthesized MFe(III)Si2O6 leucites (M = K, Rb, Cs) showed that the K- and Rb-containing leucites (iron potassium silicate, KFeSi2O6, and iron rubidium silicate, RbFeSi2O6) each have a tetragonal I4(1)/a structure and the Cs-containing leucite (caesium iron silicate, CsFeSi2O6) has a cubic Ia3BARd structure. The structures of these materials have been refined by the Rietveld method. In CsFeSi2O6 leucite, Fe(III) and Si are disordered on tetrahedral framework sites as required by space-group constraints. In KFeSi2O6 leucite, Fe shows significant ordering and is concentrated on the T3 tetrahedral site. RbFeSi2O6 leucite shows less pronounced T-site ordering reflecting the fact that it is closer to the tetragonal-cubic phase transition at which the T sites become identical.