High temperature properties of Ce1-xPrxO2-δ as an active layer material for SOFC cathodes

We prepared Ce1-xPrxO2-δ and investigated its high temperature properties as a material for the composite active layer of a solid oxide fuel cell (SOFC) cathode. We found that increasing the Pr concentration increases the total conductivity and oxygen vacancy concentration at high temperature, and this may lead to improvement of the cathodic reaction. When Ce1-xPrxO2-δ is heated, it expands significantly at a certain temperature (Tinf), and this expansion depends on the Ce1-xPrxO2-δ composition. The expansion is associated with an abrupt increase in the unit cell volume of the cubic structure. Abrupt increases in the total conductivity and oxygen vacancy concentration were also observed at Tinf. These results can be explained by oxygen vacancy and electron formation (n-type electronic conductivity increase) at Tinf and above Tinf. A sample with a Ce1-xPrxO2-δ composition where x = 1.0 has no such Tinf. A composition near x = 1.0 for Ce1-xPrxO2-δ is favorable for the active layer material of an SOFC cathode, because of the high conductivity and high concentration of oxygen vacancies.