Solid‐Solid and Solid‐Vapor Reactions and a New Phase in the System Mn‐O

Abstract

The univariant equilibrium pressure‐temperature curve along which β‐MnO2, Mn2O3, and O2 are stable together has been determined up to a Po2 of 200 atmospheres with a trace of water as a catalyst. The analogous curve for the assemblage Mn2O3, Mn3O4, and O2 has also been determined. In both cases the experimental data differ considerably from the thermodynamic calculations. Interconversion studies of the γ, ρ, ɛ and ramsdellite phases indicate only that γ‐MnO, is probably not a poorly crystallized ramsdellite. A new phase probably containing mainly trivalent manganese has been obtained under a wide variety of conditions. The absence of any consistent X‐ray diffraction line shifts in either the MnO or Mn3O4 phases when they were prepared with different stoichiometries raises some question regarding the extent of stable solid solution in these two phases in the system Mn‐O.