Thermal expansion and electrochemical properties of Ni-doped GdBaCo2O5+δ double-perovskite type oxides

Layered GdBaCo2 −x NixO5 + δ (0 ≤ x ≤ 0.3) complex oxides were synthesized and investigated as cathodes for intermediate-temperature solid oxide fuel cell (IT-SOFCs). All compositions formed an orthorhombic double-perovskite structure after calcination at 1000 °C for 5 h. The thermal expansion coefficient (TEC) was effectively decreased due to the partial substitution of Ni for Co, but the cathodic polarization resistance slightly increased with the increasing Ni content. Among the tested oxides, the GdBaCo1.7Ni0.3O5 + δ composition showed a fairly reduced TEC (15.5 × 10−6 K−1) and reasonably low polarization resistances (e.g., 0.54 Ωcm2 at 600 °C), which was considered as a promising candidate for IT-SOFCs.