XRD Studies on the conversion from several manganese oxides to β-manganese dioxide during acid digestion in MnSO4H2SO4 system

The wet method to change crystal structure from several manganese oxides to β-manganese dioxide, iso-structural with rutile, was reported.Manganese oxides such as Mn₂O₃ and Mn₃O₄ gave the same XRD profiles as an electrolytic MnO₂ (EMD) on boiling in dilute H₂SO₄ solution at 90–100°C for several hours and finally gave the XRD pattern of β-MnO₂ for a prolonged reaction period. Interesting finding was that several MnO₂s such as δ-MnO₂, α-MnO₂, EMD and heat-treated EMD could be converted into β-MnO₂ by using the proton-assisted rearrangement reaction in a boiling dilute H₂SO₄ solution containing Mn²⁺ ion at 90–110°C for several hours to several weeks depending on starting materials. The complex situations on classifying artificial manganese dioxides especially EMDs in terms of crystal structure are discussed.