Journal article

Publication year: 1998

Pages: 541-549

Journal: Journal of Inorganic and General Chemistry

Volume number: 624

Issue number: 3

ISSN: 0044-2313

Publisher: Wiley

Abstract: 
The already published, red-transparent, air sensitive, cubic compound Na24In5O15 (a = 1107.7 pm, Z = 2, 3m) is an intermediate oxidation product of the intermetallic phase NaIn. It is reinvestigated with respect to the question whether it contains the tetrahedral polycation [InIn4](6+) or [InIn4](7+). In the latter case the chemical composition would be Na23In5O15 instead of Na24In5O15 and the polycation would be in accordance with the Zintl-Klemm concept. Na24In5O15 is prepared in single phased samples for the first time and investigated by means of the Rietveld refinement technique of X-ray powder data. Based on the results of the Rietveld refinements and new single crystal data in comparison to the published values we note anomalies in the occupancies of the Na positions and a pronounced anisotropy in the thermal parameters of one oxygen position. These investigations together with results obtained by analytical scanning electron microscopy, Extended Huckel and MAPLE calculations give strong evidence for the assumption of [InIn4](7+) instead of [InIn4](6+) and the associated correct composition Na23In5O15. The problems of a reliable characterization of this unique compound are discussed.