Defect and Structural Properties of Pr-Doped Strontium Cerate as a Mixed Conductor

Abstract

Proton conducting membranes that are designed for mixed ionic and electronic conductivity are often limited by their low electronic conductivity. Improving the electronic conductivity of these membranes would increase their hydrogen permeation flux. One of the most promising classes of materials for ceramic proton conductors, perovskites, have highly-tunable compositions that allow for the optimization of both ionic and electronic conductivity. Many of these perovskites that act as mixed conductors, such as SrCeO3, are primarily limited by their electronic conductivity, which becomes a bottleneck for overall hydrogen permeation. In this work Pr-doped SrCeO3 was studied over a wide range of oxygen partial pressures (pO2’s) and temperatures to determine its defect properties and conductivity. Under reducing conditions Pr-doped SrCeO3 was found to be chemically and structurally stable, with an optimal doping level of 10%. This composition also shows greater conductivity compared to previous reported Eu-doped SrCeO3. In the low pO2 region, Pr-doped SrCeO3 exhibited primarily n-type behavior as its conductivity dramatically increased in reducing atmosphere, suggesting that the electronic conductivity of SrCeO3 is significantly enhanced by Pr doping. Under high pO2 conditions, Pr-doped SrCeO3 showed a considerable improvement in conductivity in the presence of water, affirming its high protonic conductivity. This validates the use of Pr as a means of enhancing electronic conductivity in proton conducting perovskites.