X-ray diffraction (XRD) and the X-ray photoelectron spectroscopy (XPS) were measured for the sintered BSCF ceramics (Ba(0.5)Sr(0.5)CoxFe(1-x)O(3-delta), x = 0.2 and 0.8: BSCF5528 and BSCF5582, respectively), which were annealed at different temperatures (700 and 950 degrees C) and gases (O-2 and Ar). The unit cell of the annealed BSCF5528 at 950 degrees C under Ar expanded by 0.8%, while contracting by 0.45% under O-2. The cubic and rhombohedral phases coexist in the BSCF5582 annealed at 700 degrees C under O-2. The XPS peak areas of lattice oxygen (O2-) in O-1s, similar to 528 eV, and the shoulder peak of Co-2p/Ba-3d in BSCF5582 (similar to 778 eV) increased significantly after being annealed in O-2. The areas of the peaks for BaCO3 (87.9/90.2 eV) in Ba-4d preferentially were shown to decrease in Ar and increase in O-2.