Stability of perovskite proton conductors

Stability of Gd and La-doped BaCeO 3 in water-containing atmospheres was examined from ∼ 97 to 400°C. All powders decomposed into Ba(OH) 2 and ceria when boiled in water (97°C). However, none decomposed in water vapor at ∼ I atm pressure at the same temperature and for the same time. Some of the powders decomposed in water vapor at 150 and 200°C when exposed for 7 and 14 days. These results demonstrate that: (1) BaCeO 3 -based materials are unstable in water-containing atmospheres at low temperatures (≥ 200°C). (2) The kinetics of decomposition are faster in water (liquid) than in water vapor. Mixed perovskites of type BaB' 0.5 B 0.5 O 3 where B' and B are respectively trivalent and pentavalent ions, however, were stable in boiling water. Their stability in water was attributed to their lower Madelung energies compared to ABO 3 perovskites with B ion of valence +4.