Electrical resistance and defect structure of stable and metastable phases of the system Nb12O29ndash;Nb2O5between 800 and 1100thinsp;deg;C

摘要

The defect structure of oxides of the system Nb12O29ndash;Nb2O5have been studied by thermogravimetry and electrical resistance measurements. It has been clearly established that the stable oxides Nb2O5minus;x, Nb25O62minus;x, and Nb12O29minus;xare related to oxygen vacancies. On the other hand, the metastable phase of reduction of Nb2O5minus;xmay be related to interstitial trivalent cations and it is suggested that such a defect of structure may be a step before the formation of crystallographic shear planes. In that case, the electric conductivity has been found to resemble a hopping process.