Electrical Conductivity of Near-Stoichiometric α-Nb2O5

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.