β-alumina-14H and β-alumina-21R : two chromic Na2-δ(Al,Mg,Cr)17O25 polysomes observed in slags from the production of low-carbon ferrochromium
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Date
Authors
Hejny, Clivia
Kahlenberg, Volker
Schmidmair, Daniela
Tribus, Martina
De Villiers, J.P.R. (Johan)
Journal Title
Journal ISSN
Volume Title
Publisher
Elsevier
Abstract
The crystal structures of unknown phases found in slags from the production of low-carbon
ferrochromium were studied by powder and single-crystal X-ray diffraction. Two phases of
Na2−δ (Al, Mg, Cr)17O25 composition were found to be composed of an alternating stacking of
a spinel-type and a Na-hosting block. Similar structures are known for β-alumina and β”-
alumina, NaAl11O17. However, the spinel-type block in Na2-δ(Al, Mg, Cr)17O25 is composed
of five cation layers in contrast to three cation layers in the β-alumina spinel-block. The two
new phases, β-alumina-14H, P63/mmc, a=5.6467(2), c=31.9111(12) Å, and β-alumina-21R, R m, a=5.6515(3), c=48.068(3) Å have a 14-layer and 21-layer stacking with a 2 × (cccccch) and a 3 × (ccccccc) repeat sequence of oxygen layers in cubic and hexagonal close packing, respectively.
Description
Keywords
β-alumina, Polysome, Crystal structure
Sustainable Development Goals
Citation
Hejny, C, Kahlenberg, V, Schmidmair, D, Tribus, M & De Villiers, JPR 2016, 'β-alumina-14H and β-alumina-21R : two chromic Na2-δ(Al,Mg,Cr)17O25 polysomes observed in slags from the production of low-carbon ferrochromium', Journal of Solid State Chemistry, vol. 241, pp. 70-78.