Simultaneous doping with La3+ and Y3+ for Ba2+- and Ce4+-sites in BaCeO3 and the ionic conduction

Abstract

Powder X-ray diffraction (XRD) analysis showed that the single phase perovskite-type structure of Ba1−xLaxCe0.90−xY0.10+xO3−α (0 <x< 0.40, α=0.05) could be maintained in a wide region of doping level by simultaneous partial substitution of La3+ for Ba2+-site and Y3+ for Ce4+-site in BaCeO3. The conduction properties of these oxides were investigated using various electrochemical methods in the same concentration of oxygen vacancy (α=0.05). At high oxygen partial pressure, these oxides exhibited a mixed oxide ionic and p-type electronic conduction while at low oxygen partial pressure their conduction was almost protonic. Among these oxides, BaCe0.90Y0.10O3−α exhibited the highest conductivities with a value of 1.24×10−1 S/cm in dry oxygen, and 5.65×10−2 S/cm in wet hydrogen at 1000°C. Both of the proton and oxide ion conductivities under oxygen and under hydrogen atmospheres decreased monotonically with the increasing substitution for Ba2+- and Ce4+-sites. The decreases in ion conductivities appear to relate to the decreased free volume (Vf) of crystal lattice as well as the increased distortion of lattice from ideal cubic perovskite structure.