Synthesis of Ilmenite-type ε-Mn₂O₃ and Its Properties

In contrast to the corundum-type A2X3 structure, which has only one crystallographic site available for trivalent cations (e.g., in hematite), closely related ABX3 ilmenite-type structure comprises two different octahedrally coordinated positions that are usually filled with differently charged ions Fe2+Ti4+O3 ilmenite). Here, we report a synthesis of first binary compound fabricated from simple transition-metal oxide (Mn2O3) at high-pressure high-temperature (HP-HT) conditions. We experimentally established that, normal conditions, Mn2+Mn4+O3 (ε-Mn2O3) is an n-type semiconductor indirect narrow band gap Eg = 0.55 eV. Comparative investigations electronic properties ε-Mn2O3 and previously discovered quadruple perovskite ζ-Mn2O3 phase were performed using X-ray absorption near edge spectroscopy. Magnetic susceptibility measurements reveal antiferromagnetic ordering below 210 K. The indicates HP-HT conditions can induce charge disproportionation oxides A2O3, potentially various mixed-valence polymorphs these oxides, example, ilmenite-type, LiNbO3-type, perovskite-type, other structures, could be stabilized