Proton‐conducting solid‐electrolyte perovskite ceramics based on acceptor‐doped barium and strontium cerates have become the focus of extensive investigations as candidate materials for fuel cells that operate at moderate temperatures. To assess the suitability of a material for this application, it is necessary that bulk electrolyte conductivity be measured at the operating temperature. However, very little reliable published conductivity data exist above 600°C. Protonic conductivity in yttrium‐doped barium cerate has been observed to be less at high temperatures than would be expected, based on the activation energy and preexponential for hydrogen transport at temperatures <300°C. Conductivity data obtained from impedance spectroscopy on BaCe 0.9 Y 0.1 O 3–α over the extended temperature range of 100°–900°C are presented. An Arrhenius plot of the data shows two distinct linear regions, suggesting that two different rate‐limiting processes occur in series with a break‐over transition at ∼250°C. The decrease in conductivity is apparently not due to dehydration. An activation energy for protonic transport of 0.26 eV, about one‐half of the low‐temperature value, is proposed, based on curve fitting of the high‐temperature data.
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Coors et al. (2002) studied this question.