A comparative crystal chemical analysis of Ba2CoO4 and BaCoO3

Polycrystalline Ba2CoO4 has been synthesized by the ceramic method. X-ray a nd electron diffraction shows this phase to be monoclinic with a = 5.8878(4 ); b = 7.6158(6); c = 10.3916(8); beta = 90.738(2). This compound is isostr uctural to Ba2TiO4 and the structure has been refined from X-ray powder dif fraction data by using the Rietveld method. High resolution images interpre ted in comparison to simulated images confirm the structure determined by X -ray diffraction. A crystal chemical study based on the cation arrays allow s to establish a new relationship between Ba2CoO4 and 2H-BaCoO3. Moreover, the Ba subarray seems to be related to the structure of elemental Ba. (C) 2 000 Editions scientifiques et medicales Elsevier SAS. All rights reserved.