CONDUCTIVITY MEASUREMENTS ON PURE AND MIXED METAL DIOXIDES

A new low pressure method of power conductivity measurement is presented. Results are relatively reproducible. No significant differences have been found resulting from grain size. Activation energies have been calculated for β MnO2: 0.10 eV and for γ MnO2: 0.48 eV. Molar water content and electrochemical activity depend on the method of preparation. Ozone precipitated γ MnO2 shows an apparent relationship between conductance and acidity of the solution used in its preparation. Ozone precipitated PbO2 is electrochemically inactive but has a high conductivity. Mixed Mn/Pb metal dioxides show different structures. There is a minimum in conductance at the 1:1 molar mixture. A schematic model is given for the mechanism of semiconductivity in solids containing OH groups and having a [MeO6]x type structure. © 1979.