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Gesing T.M.,University of Bremen | Uecker R.,Leibnitz Institute For Kristallzuchtung | Zheng W.,Leibnitz Institute For Kristallzuchtung | Buhl J.-C.,Leibniz University of Hanover
Zeitschrift fur Kristallographie - New Crystal Structures | Year: 2010

Al2.90Ca0.45O12Sm 1.59Sr2Ta1.10, tetragonal, I4 (no. 82), a = 5.4174(8) Å, c = 7.643(2) Å, V = 224.3 Å3, Z = 1, Rgt(F) = 0.039, wRref(F 2) = 0.1258 , T = 298 K. © 2014 Oldenbourg Wissenschaftsverlag, München.


Simon U.,TU Berlin | Harth M.,TU Berlin | Arndt S.,Leibnitz Institute For Kristallzuchtung | Berthold A.,TU Berlin | And 4 more authors.
International Journal of Materials Research | Year: 2012

The phase composition and defect structure of the system Li 2O-MgO was investigated in terms of the long term stability of Li/MgO catalysts. The Li content was varied from 0 to 7 mol.%. Pure Li · MgO solid solutions were prepared via a special washing procedure. Li contents below 0.04 wt.% were stabilized within the MgO host lattice, whereas higher Li contents were found to segregate as Li2O and Li2CO 3 phases. The catalytic activity in the oxidative coupling of methane was found to decay for all catalysts over a period of 19 h on stream, accompanied by a loss of Li as LiOH. Li in the Li · MgO solid solution was found to be more stable in the lattice than in the surface region of the solid. However, impedance measurements on transition metal stabilized Li/MgO catalysts indicated that even the Li ions within the Li · MgO solid solution are not sufficiently stabilized. Thus, neither the Li compounds nor the dissolved Li ions within the Li/MgO solution seem to be truly stable at 750°C under catalytic conditions. © 2012 Carl Hanser Verlag GmbH & Co. KG.

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