High-Temperature Proton Conductors Based on Strontium
and Barium Cerates: The Content, Interphase Exchange,
and Diffusion of Hydrogen

G. K. Vdovin and E. Kh. Kurumchin^z

Institute of High-Temperature Electrochemistry, Ural Division, Russian Academy of Sciences,
ul. S. Kovalevskoi 20, Yekaterinburg, 620219 Russia

Received June 11, 2003; in final form, September 22, 2003

Abstract—The hydrogen content and hydrogen exchange kinetics of doped cerates of strontium and barium
are studied in a reducing environment by the isotope balance and isotope exchange techniques. The measure-
ments are performed at 500840C and hydrogen pressures of 2.7–16 gPa. The interphase exchange of hydro-
gen is found to occur at high speed via dissociative mechanisms. The effective activation energy for the hydro-
gen heteroexchange is determined. The diffusion coefficient for hydrogen in BaCe_0.95Nd_0.05O_3- is computed.
The hydrogen content per formula unit appears to equal 0.48 0.05 in SrCe_0.95Y_0.05O_3- and 0.60 0.05 in
BaCe_0.95Nd_0.05O_3- at 550 and 720C, respectively, and a hydrogen pressure of 6.7 gPa. This is much greater
than in an oxidizing environment, where the hydrogen content in an oxide is approximately proportional to the
doping level of sublattice B. A possible explanation is connected with the presence of Ce³⁺ ions in the oxides
or the dissolution hydrogen in a neutral form.

Key words: barium cerate, strontium cerate, kinetics, isotope exchange, diffusion, hydrogen

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