Electrical and mechanical properties of proton conducting SrCe0.95Yb0.05O3-alpha

Yb3+-doped ceramic strontium cerate of exactly the composition SrCe0.95Yb0.05O3-alpha was prepared, having a relative density of 99.0 (+/-0.3%). Great care was taken to obtain homogeneous, carbonate free material. Analysis are made of the X-ray powder diffraction pattern of the as-prepared dense ceramic, resulting in the orthorhombic unit cell parameters a = 6.997(2) Angstrom, b = 12.296(3) Angstrom, c = 8.588(2) Angstrom, Z = 8 and d(x) = 5.806(2) g cm(-3). Bending strength values of the ceramic in non-proton and proton conducting state are found to be 177; and 194 MPa respectively The ceramic kept under proton conducting conditions for 500 h at 300 degrees C to 800 degrees C in a N-2 flow containing 155 mbar water Vapour and 245 mbar H-2, have shown to remain chemically and structurally stable. Impedance spectroscopy measurements of the bulk conductivity of the proton conducting ceramic revealed an activation energy of 53.2 kJ mol(-1) and a preexponential factor of 359.1 (Omega cm)(-1) K. In the non-proton conducting state the ceramic is mainly oxygen ion vacancy conducting, which indicates that charge compensation on substituting Yb+3 in SrCeO3 takes place by oxygen ion vacancies.