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Gravimetric and Electrical Conductivity Studies of Pure and Doped Niobium Pentoxide

J. M. Wimmer

出版	Defense Technical Information Center, 1973
URL	http://books.google.com.hk/books?id=S_JVNwAACAAJ&hl=&source=gbs_api

註釋

Thermogravimetric and electrical conductivity measurements on alpha Nb2O5 were made over the temperature range 900-1300 degree C in CO/CO2 mixtures and in pure oxygen. Anomalous conductivity results at low P(O)2 suggest the presence of nonstoichiometric phases. The data at higher P(O2) are analyzed on the basis of a defect model consisting of impurity control of the oxygen vacancy concentration at high P(O2) with a transition to a predominance of electrons and fully ionized oxygen vacancies at lower P(O2). The mobility, obtained by combining gravimetric and conductivity data, is shown to have negative temperature dependence with a value of 0.15 sq. cm/V-sec at 1000C. A value of -175 kcal/mole is obtained for the partial molar enthalpy of oxygen in Nb2O(5-x) over the range of x from 0.0025 to 0.01. (Modified author abstract).