ON THE CRYSTAL-CHEMISTRY OF THE SILVER MA NGANESE OXOVANADATES AG2BAMNV2O8 AND (AGCA2)MN-2(VO4)(3)

Single crystals of Ag2BaMnV2O8 (I) and (AgCa2)Mn-2(VO4)(3) (II) have b een prepared by reactions of metallic silver and mixtures of MnCO3 . H 2O, V2O5 and I/II: BaCO3/CaCO3. Crystal structure investigations by X- ray methods led to I: trigonal symmetry, C-3i(1)-P (3) over bar, a = 5 .5693(4), c = 7.2706(6) Angstrom, Z = 1 and II: cubic symmetry, O-h(10 )-Ia (3) over bar d, a = 12.6084(9) Angstrom: Z = 8. Despite of differ ent symmetry compound I is strongly related to the monoclinic compound s Ag2SrCuV2O8 and Na2BaCuV2O8, respectively. II belongs to the garnets . Compound I is characterized by [BaO8] nets with incorporated V5+ and Ag+ ions. The [BaO8] nets are connected by Mn2+ ions. A discussion of structural details of I with respect to Ag2SrMnV2O8, Na2BaCuV2O8 and the two modifications of K3Na(CrO4)(2) is given.