Gravimetric and Electrical Conductivity Studies of Pure and Doped Niobium Pentoxide.
SYSTEMS RESEARCH LABS INC DAYTON OHIO
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Thermogravimetric and electrical conductivity measurements on alpha Nb2O5 were made over the temperature range 900-1300 degree C in COCO2 mixtures and in pure oxygen. Anomalous conductivity results at low PO2 suggest the presence of nonstoichiometric phases. The data at higher PO2 are analyzed on the basis of a defect model consisting of impurity control of the oxygen vacancy concentration at high PO2 with a transition to a predominance of electrons and fully ionized oxygen vacancies at lower PO2. The mobility, obtained by combining gravimetric and conductivity data, is shown to have negative temperature dependence with a value of 0.15 sq. cmV-sec at 1000C. A value of -175 kcalmole is obtained for the partial molar enthalpy of oxygen in Nb2O5-x over the range of x from 0.0025 to 0.01. Modified author abstract
- Solid State Physics