A new family of barium-doped Sr₂Fe_1.5Mo _0.5O_6-δ perovskites for application in intermediate temperature solid oxide fuel cells

Sr_2-xBa_xFe_1.5Mo_0.5O _6-δ (x = 0, 0.2, 0.4, 0.6, 0.8, 1) perovskite materials have been prepared as potential cathodes for intermediate temperature solid oxide fuel cells (IT-SOFCs) via a sol-gel combustion method. X-ray diffraction (XRD) confirms that the expansion of the unit cell derived from the substitution of the large radius Ba atom, with the impurity phase structure only being detected when x = 0.8 and 1. Concurrently, thermal expansion coefficients (TECs) increase with increasing Ba doping. X-ray photoelectron spectrometry (XPS) measurements show that A-site doped Ba in the perovskite has an insignificant impact on the existence and ratio of Fe²⁺/Fe³⁺ and Mo ⁶⁺/Mo⁵⁺ species within the Sr_2-xBa _xFe_1.5Mo_0.5O_6-δ (x = 0.2, 0.4, 0.6) (SBFM) samples. Compared with Sr₂Fe_1.5Mo _0.5O_6-δ, the SBFM cathodes exhibited better electrochemical performance, which has been confirmed by the electrochemical impedance spectra (EIS). In particular, Sr_1.8Ba_0.2Fe _1.5Mo_0.5O_6-δ (SB_0.2FM) shows the lowest interface polarization (R_p). Furthermore the peak power densities of single cells based on the SB_0.2FM cathode are 0.87 and 1.30 W cm^-2 at 700 and 750 °C, respectively. All these results suggest that SBFM materials are promising cathodes for IT-SOFCs.