Neutron and X-ray diffraction studies on the high temperature phase of Mn3(VO4)2, the new isostructural compound NaMn4(VO4)3 and their mixed crystals NaxMn4.5−x/2(VO4)3 (0≤x≤1)

This paper presents a detailed structure analysis (combined Rietveld analysis of X-ray and neutron powder diffraction data as well as quantum mechanical calculations) of the high temperature phase of Mn3(VO4)2 (space group I4¯2d). Special attention is directed to the analysis of the local coordination around Mn2+ ions or vacancies within a stella quadrangula configuration of anions. Furthermore, the new compound NaMn4(VO4)3 is described as well as a range of mixed crystals between NaMn4(VO4)3 and Mn3(VO4)2 (described by the formula NaxMn4.5-x/2(VO4)3, 0≤x≤1) which were synthesized by a solid state route. All compounds were shown to be isostructural to the high temperature phase Mn3(VO4)2.