Phase Stabilities and Influence on Magnetic and Electrical Properties of the System (Mg _x Mn _4‐x )MnVO ₈

Manganese vanandates have a wide range of interesting material properties, covering magnetic, electrical, and catalytic aspects. Among them, Mn₅VO₈ is a compound containing manganese in both its trivalent as well as divalent oxidation states with ordering of the different manganese species on different crystallographic sites. In this article, we show that the divalent manganese can be replaced by magnesium fully up to a composition of Mg₄MnVO₈. For low magnesium content, this results in a change of symmetry from triclinic to monoclinic, whereas for Mg₄MnVO₈, a trigonal modification can be found in addition to a monoclinic phase. Density Functional Theory based calculations reveal that for magnesium rich compositions, monoclinic and trigonal modifications are energetically similar. Magnetic characterization reveals that the materials are paramagnetic around room temperature. Further, the magnesium substitution results in a strong decrease of electrical conductivity with an increase of the activation energy determined by electrochemical impedance spectroscopy.