Defects and transport in Gd-doped BaPrO3

The electrical conductivity of BaPr1-x GdxO3-delta has been characterized by means of the four-point van der Pauw technique at 200-1100 A degrees C as a function of pO(2) and pH(2)O. The contributions from ionic charge carriers were investigated by the EMF of concentration cells and the H+/D+ isotope effect on the total conductivity. BaPr1-x Gd (x) O3-delta is predominately a p-type electronic conductor under oxidizing conditions, while ionic conduction is barely measurable. Gd(III) substituted for Pr(IV) is charge compensated mainly by electron holes, with protons and oxygen vacancies contributing significantly but as minority defects only at low temperatures (wet conditions) and at high temperatures, respectively. The conductivity behaviour has been modelled under these assumptions to extract thermodynamic parameters for the defect reactions at play. The practical use of this material is limited by its poor chemical stability.