کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
75013 | 49106 | 2011 | 10 صفحه PDF | دانلود رایگان |

The hydrothermal synthesis and crystal structures of the aluminogermanate analog of pharmacosiderites with primitive cubic, body-centered cubic and rhombohedral symmetries are described. Under the synthesis conditions studied here, the type of alkali metal cations in the synthesis mixture is the most important factor affecting the crystal symmetry of the pharmacosiderite formed. Rietveld refinements of synchrotron diffraction data confirm the crystal structures of the aluminogermanate pharmacosiderites crystallized. While the presence of Al in both tetrahedral and octahedral positions of the pharmacosiderite framework is evidenced by 27Al MAS NMR spectroscopy, the extent of Al substitution is much higher on octahedral sites. A combination of thermal and high-temperature powder X-ray diffraction analyses demonstrates that the thermal stability and phase transition behavior of germanate-based pharmacosiderites depend on their Al content and type of alkali metal cations.
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► Three aluminogermanate pharmacosiderites with different crystal symmetries are synthesized.
► Their crystal symmetry depends on the type of alkali cations added to the synthesis mixture.
► Their thermal stability depends on their Al content and type of alkali cations.
Journal: Microporous and Mesoporous Materials - Volume 139, Issues 1–3, March 2011, Pages 148–157