Powder X-ray diffraction analysis showed that the single-phase perovskite-type structure of Ba1-xLaxCe0.90-xY0.10+xO2.95, where x was between 0 and 0.40, could be maintained over a wide region of dopant levels via the simultaneous partial substitution of La3+ at the Ba2+ sites and of Y3+ at the Ce4+ sites of BaCeO3. The conduction properties of the oxides were investigated by using various electrochemical methods. At high O partial pressures, the oxides exhibited a mixed, ionic and p-type electronic, conductivity. At low O partial pressures, the conduction was almost protonic. Of these oxides, BaCe0.90Y0.10O2.95 exhibited the highest conductivity; with a value of 0.124S/cm in dry O and of 0.0565S/cm in wet H at 1000C. The proton and oxide ion conductivities under O or H atmospheres decreased monotonically with increasing substitution at Ba2+ and Ce4+ sites. The decrease in ionic conductivity appeared to be related to a decreased free volume of crystal lattice, as well as to an increased distortion of the lattice away from the ideal cubic perovskite structure.

Simultaneous Doping with La+ and Y3+ for Ba2+- and Ce4+-sites in BaCeO3, and Ionic Conduction. G.Ma, T.Shimura, H.Iwahara: Solid State Ionics, 1999, 120[1-4], 51-60