Crystal structures of two polymorphs of Ca3[Al2N4 |
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Authors: | Ludwig M Jäger J Niewa R Kniep R |
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Institution: | Eduard-Zintl-Institut der Technischen Universit?t, Hochschulstrasse 10, D-64289 Darmstadt, Germany. |
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Abstract: | Green transparent single crystals of alpha-Ca3Al2N4] (monoclinic, P2(1)/c, No. 14, a = 957.2(3) pm, b = 580.2(3) pm, c = 956.3(5) pm, beta = 111.62(3) degrees; Z = 4) were obtained from reactions of mixtures of the representative metals with nitrogen above temperatures of 1000 degrees C. beta-Ca3Al2N4] (monoclinic, C2/c, No. 15, a = 1060.6(2) pm, b = 826.0(2) pm, c = 551.7(1) pm, beta = 92.1(1) degrees; Z = 4) was formed as a byproduct of a reaction of calcium with alumina under nitrogen at T = 930 degrees C in form of colorless crystals. The crystal structures of the two polymorphs contain edge- and corner-sharing AlN4 tetrahedra, leading to different layered anionic partial structures: infinity 2AlN2/2N2/3)2(AlNN2/2N1/3)6/3(12-)] in the alpha-phase and infinity 2Al2N2N4/2(6-)] in the beta-polymorph. |
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