X-ray photoelectron (XPS) and Diffuse Reflectance Infra Fourier Transformation (DRIFT) study of Ba0.5Sr0.5CoxFe1−xO3−δ (BSCF: x=0–0.8) ceramics

The X-ray photoelectron spectra (XPS) of sintered BSCF ceramics (Ba0.5Sr0.5CoxFe1–xO3–δ,0≤x≤0.8) were measured at room temperature (RT). Peak areas of Fe2p1, Fe2p3, Fe3p and Co3p increased systematically with increasing cobalt concentration, while their binding energies (BEs) remained the same (723.3, 710.0, 55.0 and 60.9 eV, respectively). However, the BEs of lattice oxygen in O1s (528.1 eV) and Ba4d for the BaO bond (87.9V and 90.2 eV) increased with increasing cobalt concentration. The shoulder peak of Ba3d/Co2p increased from 778.0 to 778.7 eV, which implies that this peak can be attributed to another Ba XPS peak (described as Ba2nd in this study) due to the overlapping area between barium cations and oxygen anions. The overall peak areas of Ba4d increased up to x=0.4, and then decreased, which coincides with the behavior of the Diffuse Reflectance Infrared Fourier Transform (DRIFT) bands representing adsorbed CO32− (νCO32−) and structurally bonded CO32− (ν2, ν3) (800–1200 and 862/1433 cm−1, respectively).