Crystal Growth of Alkaline Earth Vanadates from Hydroxide Fluxes

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We report the crystal growth and structural characterization of four alkaline earth vanadates synthesized from alkali metal hydroxide flux reactions. The use of molten hydroxides has led to the preparation of the novel hydroxy apatites, A5(VO4)3(OH) (A = Sr, Ba), isolated from mixed NaOH/A(OH)2 (A = Sr, Ba) flux reactions contained in sealed silver tubes. Ba5(VO4)3(OH) and Sr5(VO4)3(OH) crystallize in the hexagonal space group, P63/m with a = 10.4589(2) Å, c = 7.8476(3) Å, V = 743.43(3) Å3 and a = 10.0570(4) Å, c = 7.4349(7) Å, V = 651.24(7) Å3, respectively. The crystal structures consist of isolated VO4tetrahedra separated by layers of Sr/BaOx polyhedra. In addition, we also report the crystal growth of KBaVO4 and Ba3(VO4)2 from hydroxide fluxes.