Efficient stabilization of cubic perovskite SrCoO_3-δ by B-site low concentration scandium doping combined with sol-gel synthesis

SrCoO_3-δ is a material with multiple phase structures. The influence of Sc³⁺ doping in the B-site of SrCoO_3-δ on its lattice structure/phase stability, electrical conductivity, and cathode performance for intermediate-temperature solid oxide fuel cells (IT-SOFCs) was investigated by X-ray diffraction, four-probe dc conductivity and impedance spectroscopy measurements, respectively. The introduction of large-size Sc³⁺ (0.745 Å) cation together with the sol-gel synthesis technique, led to a substantial stabilization of the cubic phase of SrCoO_3-δ-even at a Sc³⁺ doping amount as low as 5 mol%. Such stabilization resulted in a sharp increase in the electrical conductivity of the material, which was found to be p-type in nature. A maximum electrical conductivity and favourable cubic phase stability of the material was reached at the Sc³⁺ doping concentration of 5-10 mol%. A further increase of Sc³⁺ doping, however, lowered the electrical conductivity due to the blocking effect of Sc³⁺ for the electron conduction. An area specific resistance (ASR) as low as 0.25 Ωcm² was reached at 600 °C for SrSc_0.1Co_0.9O_3-δ as a cathode material based on Sm_0.15Ce_0.85O_1.925 electrolyte.