Electrical properties of NbO and NbO2

The thermoelectric power and electrical conductivity were measured for NbO and NbO2 as functions of temperature at the limiting oxygen activities for the thermodynamic stability of each of the compounds. The electrical properties of NbO2 were essentially independent of oxygen pressure in the temperature range 50–1000°C, and the properties of NbO showed only a small dependence on oxygen activity. The thermoelectric power and electrical conductivity of NbO indicate that metallic bonding exists in this compound. This bonding is discussed on the basis of Kreb's model for the influence of homopolar bonds on the structure of inorganic compounds. The thermoelectric power and electrical conductivity of NbO2 indicate that this compound is an n-type intrinsic semiconductor. The nature of the predominant ionic defect in NbO2 and its dependence on oxygen activity are discussed.