X-ray photoelectron study on Ba0.5Sr0.5Co x Fe1−x O3−δ (BSCF: x = 0.2 and 0.8) ceramics annealed at different temperature and pO2

X-ray diffraction (XRD) and the X-ray photoelectron spectroscopy (XPS) were measured for the sintered BSCF ceramics (Ba0.5Sr0.5Co x Fe1−x O3−δ, x = 0.2 and 0.8: BSCF5528 and BSCF5582, respectively), which were annealed at different temperatures (700 and 950 °C) and gases (O2 and Ar). The unit cell of the annealed BSCF5528 at 950 °C under Ar expanded by 0.8%, while contracting by 0.45% under O2. The cubic and rhombohedral phases coexist in the BSCF5582 annealed at 700 °C under O2. The XPS peak areas of lattice oxygen (O2−) in O1s , ~528 eV, and the shoulder peak of Co2p /Ba3d in BSCF5582 (~778 eV) increased significantly after being annealed in O2. The areas of the peaks for BaCO3 (87.9/90.2 eV) in Ba4d preferentially were shown to decrease in Ar and increase in O2.