Crystal growth of alkaline earth vanadates from hydroxide fluxes

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 VO4 tetrahedra separated by layers of Sr/BaOx polyhedra. In addition, we also report the crystal growth of KBaVO4 and Ba3(VO4)2 from hydroxide fluxes.

Graphical abstractThe novel hydroxy apatites, A5(VO4)3OH (A = Sr, Ba), were synthesized from hydroxide flux reactions. The crystal structure consists of A(1)O9 tri-capped trigonal prisms (dark blue), A(2)O7 irregular polyhedra (light blue), and VO4 tetrahedra (orange). Hydrogen and oxygen atoms are represented as green and red spheres, respectively. (For interpretation of the references to color in this text, the reader is referred to the web version of this article.)Figure optionsDownload full-size imageDownload as PowerPoint slide