TRANSPORT STUDY OF THE SOLID-ELECTROLYTE BACE0.9GD0.1O2.95 AT HIGH-TEMPERATURES

Doped barium cerate perovskites are of interest as electrolytes for so lid oxide fuel cells operating at 600-1000-degrees-C. Moreover, in thi s temperature range they display a transition from protonic to oxide i on conduction. In this study, the conductivity of BaCe0.9Gd0.1O2.95, p reviously reported only up to 800-degrees-C, was measured up to 1200-d egrees-C using the a.c. van der Pauw technique. Data obtained in a ran ge of atmospheres and plotted against log(P(O2)) displayed ionic, p-ty pe and n-type components, which could be resolved by curve fitting to standard conductivity equations. The activation energies of the three components, estimated separately, were 0.52 eV for sigma(i), 0.64 eV f or sigma(p), and 2.6 eV for sigma(n). These parameters were used to ca lculate the ionic transport number under high P(O2) and low P(O2) cond itions and to map out the compound's ionic domain. The ionic transport numbers obtained for low and high oxygen partial pressures have been compared to those measured previously using concentration cells.