The physical properties of chromium oxide—aluminium oxide catalysts - II. Electrical properties

The electrical conductivity and thermo-electric potential of co-precipitated chromium oxide-alumina catalysts have been measured. The addition of alumina at first produces a rapid increase in the conductivity, but with higher concentrations of alumina this sub­sequently falls to values below that of chromium oxide alone. Catalysts reduced in hydrogen at 500°C are n -type semi-conductors if they contain more than about 35% of chromium oxide; those with lower chromium content, and all mixtures after heating in air, are p -type semi-conductors. Energies of activation for both types of conduction have been calculated.