Iron-doped perovskite La0.5Pr0.5BaCo2-xFexO5+δ as a potential cathode material for SOFC

A set of single-phase perovskite materials, La 0.5 Pr 0.5 BaCo 2- x Fe x O 5+ δ (LPBCF- x, 0 < x  ≤ 1.0) were prepared employing A/B site co-doping strategy with double lanthanide doping at A-site and partial replacement of Co with Fe at B-site. The corresponding thermal expansion behavior, thermochemical stability, electrical conductivity, and cathodic electrochemical impedance of these materials were systematically investigated. The experimental findings revealed that the doping of Fe into the B site of La 0.5 Pr 0.5 BaCo 2 O 5+ δ materials can effectively decrease the thermal expansion coefficient (TEC), with most significant reduction at x  ≤ 0.4. Excellent thermochemical stability of LPBCF- x materials with Ce 0.9 Gd 0.1 O 2- δ (GDC) was also verified through co-firing the powder mixtures at 1000 °C. Rather, doping of Fe generally results in the decrease of electrical conductivity and the increase of surface specific polarization resistance, LPBCF- x materials with low Fe content demonstrated comparable excellent overall conductivity with low activation energy and low surface specific polarization resistances in various conditions compared to the non-Fe-doped LPBCF-0.0. Especially, LPBCF-0.2 can provide the best overall performance combing the evaluation of thermo-mechanical, electrical and electrochemical properties. Further analysis of the electrochemical impedance spectra revealed that the electron charge transfer or the dissociation of absorbed oxygen, depending on the temperature, is the primary rate-determining step in the oxygen transport process through LPBCF- x materials.