Non-stoichiometric disorder in ?-Nb2O5 at elevated temperatures

Abstract

The electrical conductivity of polycrystallineα-Nb2O5 was determined for the oxygen partial pressure range of 100 to 10−20 atm and temperature range 700 to 1150 ° C. The data were found to be proportional to the −1/6th power of the oxygen partial pressure for the oxygen pressure range 10−20 to 10−9 atm, and proportional toPO 2 −1/4 for oxygen pressures greater than 10−9 atm. The region of linearity where electrical conductivity varies as the −1/4th power of $$P_{O_2 } $$ increased as the temperature was decreased. Thermogravimetric measurements were carried out in the temperature range 950 to 1250 ° C. The deviation from stoichiometry inα-Nb2O5 (x in Nb2O5−x ) as a function of partial pressure of oxygen showed two distinct regions, namely a region with an approximately −1/6th dependence on $$P_{O_2 } $$ and a region where the deviation was nearly independent of oxygen partial pressure. The electrical conductivity and thermogravimetric data are consistent with the presence of small amounts of acceptor impurities inα-Nb2O5.