Abstract
The title compound, Ag2Zn2Fe(VO4)3, has been synthesized by solid-state reactions and belongs to the alluaudite structure family. In the crystal structure, four sites are positioned at special positions. One silver site is located on an inversion centre (Wyckoff position 4b), and an additional silver site, as well as one zinc and one vanadium site, on twofold rotation axes (4e). One site on a general position is statistically occupied by FeIII and ZnII cations that are octa-hedrally surrounded by O atoms. The three-dimensional framework structure of the title vanadate results from [(Zn,Fe)2O10] units of edge-sharing [(Zn,Fe)O6] octa-hedra that alternate with [ZnO6] octa-hedra so as to form infinite chains parallel to [10]. These chains are linked through VO4 tetra-hedra by sharing vertices, giving rise to layers extending parallel to (010). Such layers are shared by common vanadate tetra-hedra. The resulting three-dimensional framework delimits two types of channels parallel to [001] in which the silver sites are located with four- and sixfold coordination by oxygen.
Highlights
The title compound, Ag2Zn2Fe(VO4)3, has been synthesized by solid-state reactions and belongs to the alluaudite structure family
Four sites are positioned at special positions
One silver site is located on an inversion centre (Wyckoff position 4b), and an additional silver site, as well as one zinc and one vanadium site, on twofold rotation axes (4e)
Summary
The crystal structure of the mineral alluaudite with general formula A(1)A(2)M(1)M(2)2(XO4) was determined nearly fifty years ago by Moore (1971). The synthesis and structural characterization of new alluaudite-type phosphates and vanadates within pseudoternary A2O/MO/P2O5 or pseudo-quaternary A2O/MO/Fe2O3/ P2O5 systems using hydrothermal or solid-state reactions was the focus of our current research. We have succeeded in preparing the first vanadate-based alluaudite-type phase (Na0.70)(Na0.70,Mn0.30)(FeIII,FeII)2FeII(VO4) A second alluaudite-type vanadate with composition Na2(FeIII/CoII)2CoII(VO4) was prepared by Hadouchi et al (2016) shortly afterwards. In this context, the current exploration of A2O/MO/Fe2O3/ V2O5 systems, where A is a monovalent cation and M a divalent cation, led to another vandanate with alluaudite-type structure, namely Ag2Zn2Fe(VO4). Its synthesis and crystal structure are reported in this article
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