Transport properties of molybdenum trioxide and its suboxides

The electrical conductivity σ AC and the thermoelectric power α for the MoO 3-MoO 3− n -MoO 2 system, namely MoO 3, Mo 13O 38, Mo 9O 26, Mo 8O 23, Mo 17O 47, Mo 4O 11 and MoO 2, are measured over a wide temperature range. The conductivity value at room temperature is found to increase with departure from stoichiometry. MoO 3 and its suboxides exhibit semiconducting behaviour while MoO 2 at low temperature exhibits semimetal-like character of 10 −2 Ω −1 cm −1 rather than a semiconducting one. Above room temperature MoO 2 gave a Δ E value of 0.85 eV, indicating that this metal-like conduction is not taking place. Some discontinuities are present in the log σ vs. 1/ T curves for all samples. These are confirmed by DTA. The thermoelectric power indicates that all oxides are n-types semiconductors up to 300°C. The value at room temperature decreases with departure from stoichiometry. The most pronounced change of both σ and α is at Mo 8O 23, i.e. at x=0.125.