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| - Electrical Properties of Niobium-Doped Titanium Dioxide. 2. Equilibration Kinetics
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| - The present work reports isothermal gas/solid equilibration kinetics for Nb-doped TiO2 (0.65 atom %) atelevated temperatures (1073−1298 K) within narrow ranges of oxygen activity spanning between 10-13 Paand 75 kPa. The equilibration kinetics were monitored using electrical conductivity measurements. The kineticdata were used to determine the chemical diffusion coefficient (Dchem). Dchem as a function of p(O2) exhibitsa complex dependence, which is considered in terms of defect disorder and the related concentrations ofelectronic charge carriers. The activation energy of Dchem in the p(O2) range 10 Pa < p(O2) < 75 kPa variesin the range 88.0−98.2 kJ/mol. It is important to note that the chemical diffusion coefficient in stronglyreduced conditions [p(O2) = 10-9 Pa] exhibits a negative temperature dependence of Dchem (−67.2 kJ/mol).This finding indicates that under these conditions transport in a chemical potential gradient is consistent withmetallic charge transport.
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