Electrical conductivity of Cr2O3 doped with TiO2

The electrical conductivity of Cr2O3 doped with TiO2 has been studied by th e four point technique as a function of the oxygen activity (O-2 + Ar, CO CO2 and H-2 + H2O) at 1000 degrees C and hydrogen activity (H-2 + H2O) at temperatures from 400 to 1000 degrees C, Ti-doped chromia is an n-conductor at reduced oxygen activities (ambient H-2 + H2O and CO + CO2 gas mixtures) and a p-conductor at near atmospheric oxygen activities. It is concluded t hat the Ti-dopant is compensated by the formation of chromium vacancies at near-atmospheric oxygen activities and by electrons at highly reduced oxyge n activities (near the Cr/Cr2O3 boundary). Chromia dissolves hydrogen as pr otons in ambient H-2 + H2O gas mixtures at reduced temperatures (<1000-800 degrees C), but the solubility of hydrogen is decreased by the presence of higher-valent Ti-dopant. (C) 1999 Elsevier Science B.V. All rights reserved .