The stability of Gd‐doped and La‐doped BaCeO3 in water‐containing atmospheres was examined. Samples containing up to 20 mol % Gd and 30 mol % La were synthesized by calcining the requisite mixtures of precursors. Three types of tests were performed: (i) thermal treatment in an atmosphere containing water vapor false(pH2O=0.0964 normalatmfalse) between 150 and 400°C, (ii) boiling in water, and (iii) simultaneous exposure to boiling water and water vapor at essentially the same temperature. Samples were characterized by X‐ray diffraction. All powders boiled in water decomposed within a few hours, whereas none of the powders decomposed when exposed to ∼1 atm water vapor pressure at the same temperature. This difference was rationalized on the premise that the mechanisms of decomposition depend upon the form of water, liquid or vapor. In liquid water, the decomposition kinetics appear to be interface‐controlled. By contrast, in water vapor, the kinetics appear to be dictated by bulk diffusion of water into the lattice. © 1999 The Electrochemical Society. All rights reserved.

Perovskites such as BaZrO 3 , SrZrO 3 , BaCeO 3 , and SrCeO 3 when doped with a rare-earth oxide are known to be proton conductors at elevated temperatures (Ն600ЊC). [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] There is considerable interest in these perovskite proton conductors for high-temperature applications which include fuel cells, hydrogen sensors, steam electrolyzers for hydrogen production, hydrogen sulfide electrolyzers for desulfuration, HCl electrolyzers for Cl 2 recovery, hydrogenation or dehydrogenation of organic compounds, hydrogen extractors, hydrogen pumps, and hydrogen gas controllers.

No abstract