Effect of A-site doping with Gd³⁺ on Properties of Sr₂Fe_1.5Mo_0.5O_6-δ

Sr_2−xGd_xFe_1.5Mo_0.5O_6−δ (x=0, 0.1, 0.2, 0.3, 0.4) (SG_xFM) powders as anode of solid oxide fuel cell (SOFC) were synthesized by using a sol-gel method. Electrolyte supported SOFC single cell was assembled. XRD, XPS, SEM, TGA and electrochemical test were used to characterize the samples. The anode materials exhibited single phase double perovskite structure. With increasing concentration of Gd³⁺, the XRD diffraction peak shifted, which indicated that Gd³⁺ has well incorporated into Sr₂Fe_1.5Mo_0.5O_6−δ. SG_0.1FM had higher Fe²⁺/Fe³⁺ and Mo⁵⁺/Mo⁶⁺ ratios. According to TGA results, SG_0.1FM showed the highest oxygen loss, indicating that it has the highest concentration of oxygen vacancy. The electrode material presented a loose and porous microstructure, while the electrolyte was dense. The cell was tested at 550–800 ℃, with H₂ as fuel and static air as oxidant. At 800 ℃, the anode had a polarization impedance of 0.021 Ω·cm², while the maximum power density reached 264 mW·cm⁻². Therefore, Gd³⁺ ion doping can improve the performances of SFM.