Protonic and electronic conductivities of terbium doped strontium cerates

Abstract

Electronic and protonic conductivities of Tb doped SrCeO 3 were measured in a hydrogen containing and hydrogen-free atmosphere of the same oxygen partial pressure in 500–900 °C. In a H 2 containing atmosphere, the material exhibits mixed electronic and proton-conductivity and, for SrCe 0.95Tb 0.05O 3-δ, the proton transfer number increases with decreasing temperature, from about 0.4 at 900 °C to about 0.8 at 500 °C. The total conductivity for SrCe 0.95Tb 0.05O 3-δ decreases from about 3 × 10 − 3 S/cm in the reducing atmosphere to 4 × 10 − 5 S/cm in air at 900 °C with an activation energy respectively of 39 kJ/mol and 76 kJ/mol for protonic and n-type electronic conduction. Results of XRD analysis show a decrease in the lattice volume of the SrCe 1- x Tb x O 3-δ with increasing Tb concentration. SrCe 1- x Tb x O 3-δ exhibits negligible proton-conductivity with x smaller than 0.005. At 800 °C under a reducing atmosphere, SrCe 1-xTb xO 3-δ, with x > 0.005, are mixed electronic and proton conductors with a maximum proton-conductivity of about 3 × 10 − 3 S/cm at x = 0.025 and proton transfer number of about 0.7 for x in the range of 0.005–0.125.