Ceramics-Silikáty 20, (2) 97 - 112 (9176) |
|
SYNTHESIS AND CRYSTAL STRUCTURE OF GERMANIUM MULLITE AND CRYSTALLOCHEMICAL PARAMETERS OF D-MULLITES
|
Ďurovič Slavomil 1, Fejdi Pavel 2
|
1 Institute of Inorganic Chemistry of Slovak Academy of Sciences 809 34 Bratislava, Dúbravská cesta 5
2 Department of Mineralogy and Crystallography, Faculty of Natural Sciences, Comenius University, 886 04 Bratislava
|
Single crystals of 1.54/1-germanium mullite were synthetisized from corundum grains and molten GeO₂ at 1600 °C in sealed platinum tubes. An X-ray structure analysis (R = 0.058) revealed that this compound is isostructural with D-(silicon)-mullites; a = 7.650(2), b = 7.779 (2), c = 2.925(2) Å, space group Pbam. There are two formula units Al[Ge2-xAlxO(11-x)/2] (x = 1.26) in the unit cell. The refinement of occupancies of the incompletely filled atomic positions (Al, Ge), Al*, O(3) and O* confirmed their dependence on the chemical composition of given mullite. The substitute tetrahedral position Al* has been found to be occupied by 12.5(3) per cent of aluminum atoms and 0.7(3) per cent of germanium atoms. |
 PDF (1.3 MB) |
|
