Investigation of PO4 3- oxyanion-doping on the properties of CaFe0.4Ti0.6O3 d for potential application as symmetrical electrodes for SOFCs

Abstract

CaTi0.6-xFe0.4PxO3-d (0 x 0.075) perovskite series are investigated as potential symmetrical electrodes for SOFCs. Pure phase compounds with a cubic perovskite structure (s.g. Pm3m) are obtained for x 0.025, while higher doping level leads to the formation of Ca10(PO4)6(OH)2 as secondary phase. The P-doped compounds are structurally stable under reducing atmosphere unlike the undoped phase. Conductivity values of the P-doped samples are slightly higher than that of the undoped one, i.e. 0.11 and 0.07 Scm 1 for CaTi0.575Fe0.4P0.025O3-d and CaTi0.6Fe0.4O3-d, respectively, at 750 C in air. The performance of CaTi0.575Fe0.4P0.025O3-d acting simultaneously as both anode and cathode was also tested in a symmetrical solid oxide fuel cell with a 240 mm thick YSZ electrolyte. Hence, these results show that PO4 3 units can be introduced into CaTi0.6Fe0.4O3-d perovskite structure, having beneficial effects on the electrochemical performance and the phase stability.