Synthesis and X-ray crystallographic and IR spectroscopic study of complex alkaline earth zirconium arsenates

Arsenates A0.5Zr2(AsO4)3 (A = Mg, Ca, Sr, Ba), synthesized through sol–gel route with subsequent heat treatment, have been studied by X-ray diffraction, electron probe microanalysis, and IR spectroscopy. Mg0.5Zr2(AsO4)3 crystallizes in the Sc2(WO4)3 structure type (space group P21/n). A0.5Zr2(AsO4)3 (A = Ca, Sr, Ba) crystallize in the NaZr2(PO4)3 structure type (space group $$R\bar 3$$ ). The Ca0.5Zr2(AsO4)3 and Ba0.5Zr2(AsO4)3 structures have been refined by the full-profile analysis. The structure frameworks are composed of ZrO6 octahedra and AsO4 tetrahedra. The alkaline earth metal atoms occupy one of the two extraframework positions inside the structure columns. The internal vibrational frequencies of the AsO4 3- tetrahedron have been assigned. The number of the observed bands corresponds to the number predicted by the factor group analysis of vibrations for space groups $$R\bar 3$$ and P21/n.