Electrical conductivity and cation distribution in nickel manganite

A study has been made of the oxygen loss from nickel manganite at temperatures between 800 and 1220°C in atmospheres with oxygen partial pressures which varied from 0.12–100% oxygen using isothermal gravimetry. An atmosphere-temperature-composition diagram has been constructed which is used in conjunction with high temperature electrical conductance measurements to determine the concentration of conductance cations present in NiMn2O4. A comparison of results with those reported in the literature leads to a formula for the cation valence distribution in nickel manganite of Ni2+0.35Mn2+0.65 (Ni2+0.65Mn3+0.70Mn4+0.65) O2-4 at 900°C. An equation for the variation of the nickel inversion parameter with temperature has also been derived.