Effects of oxygen defects on structure and properties of Sm0.5Sr0.5CoO3-δ annealed in different atmospheres

Samples of Sm0.5Sr0.5CoO3–δ were annealed in different atmospheres (Ar, N2, and O2) and temperatures (400–1200 °C), and changes in their masses, structures, surface transport properties, optical properties, and oxygen nonstoichiometries were investigated using thermogravimetric (TG) analyses, X-ray diffraction (XRD) analyses, electrical conductivity measurements, re?ection spectra measurements, and X-ray photoelectron spectroscopy, respectively. The TG analyses, performed in air and an N2 atmosphere, allowed us to determine the changes in the masses of the samples. The results of the XRD analyses elucidated the changes in the structure of the samples under different conditions. The XPS spectra and simulation data indicated that the number of oxygen defects generated in the samples depended on the temperature and atmosphere. At high temperatures, the surface conductivities and full-spectrum reflectivities of the samples decreased with an increase in the number of oxygen vacancies. In an oxidative atmosphere, the samples exhibited outstanding visible and near-infrared light absorption. Furthermore, the samples were highly sensitive to a reducing atmosphere at various temperatures. On the basis of the fact that the properties of Sm0.5Sr0.5CoO3–δ vary with the environment, it has potential use in high-temperature applications such as weather sensors.