Valency of copper in 123 oxides

The valency of copper in freshly prepared as well asin situ high-temperature oxygen-treated 123 oxides was analysed by X-ray photoelectron spectroscopy. The results suggest the presence of Cu²⁺ and Cu³⁺ along with Cu⁺. This observation is supported by cyclic voltammograms of 123 oxides recorded in a formamide medium. The valence band of 1 23 oxides was probed using X-ray (MgK) and ultraviolet (He-I) sources. It was observed that the Cu-O hybridized orbital in YBa₂Cu₃O_7–x responsible for conduction decreases with time in an ultrahigh vacuum and increases with oxygen treatment temperature.