Electrical Conductivity of Near-Stoichiometric α-Nb2O5

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Abstract
The electrical conductivity of α‐Nb2O5 monocrystalline and sintered specimens, measured under a constant ambient oxygen pressure and over the temperature range 300 to 900°C, exhibits an exponential temperature dependence with an activation energy of 1.65 ev. The isothermal conductivity, σ, of near‐stoichiometric α‐Nb2O5 is related to the ambient oxygen partial pressure, PO2, by the power law expression σ=const PO2—0.24±0.01. Both sets of observations may be rationalized on the basis that slightly‐reduced α‐Nb2O5 becomes a metal‐excess, n‐type semiconducting oxide containing oxygen vacancies capable of trapping electrons. A detailed analysis of the relation between conductivity and ambient oxygen pressure has indicated that the conductivity dependency may be ascribed to a mechanism whereby defect levels (due to oxygen ion vacancies with either one or two trapped electrons) are created and electrons are thermally excited from these levels into the conduction band.

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