Structure and cation distribution of new ternary vanadates FeMg2V3O11 and FeZn2V3O11

FeMg2V3O11 crystals grown from a MgO/Fe2O3/V2O5 melt crystallize in the tri clinic space group P-1 with parameters: a=6.434(1) Angstrom, b=6.806(1) Ang strom, c=10.085(1) Angstrom, alpha=97.44(1)degrees, beta=103.44(1)degrees, gamma=101.56(1)degrees and Z=2. FeZn2V3O11 crystals grown from a ZnO/Fe2O3/ V2O5 melt also crystallize in P-1 with similar parameters: a=6.455(1) Angst rom, b=6.834(1) Angstrom, c=9.988(1) Angstrom, alpha=97.65(1)degrees, beta= 102.61(1)degrees, gamma=101.26(1)degrees and Z=2. Both are isostructural wi th GaZn2V3O11, and susceptibility measurements reveal that all iron is high spin d(5). In FeMg2V3O11, Fe3+ is distributed non-statistically with Mg2on octahedral and bipyramidal sites, in FeZn2V3O11, Fe3+ is found only on t he octahedral sites and Zn2+ exclusively occupies the bipyramidal sites. (C ) 2000 Published by Elsevier Science S.A. All rights reserved.