Determination of Depth Profile of CuO⁺ and Cu⁺ in Superconductors by a Wet-Chemical Method Using Flow-Coulometry

Abstract

Using a wet-chemical method based on flow-coulometry, an analytical method to measure unstable ions of copper, CuO⁺ and Cu⁺, in superconductors has been advanced. The distributions of these ions from the surface to inside of sample discs were determined by the developed method. The sample discs, which were prepared by the ceramic method, contained a lower CuO⁺/Cu_total ratio at the outermost surface, and gradually increased to a depth of 200 µm. On the contrary, the Cu⁺/Cu_total ratio in a YBa₂Cu₃O₆ sample was almost homogeneous. The positively electrolyzed La₂CuO_y disc as an electrode exhibited a much higher oxidation state than that without electrolysis. It was confirmed that the CuO⁺/Cu_total ratio on the surface and in the bulk of the electrolyzed La₂CuO_y had an influence on the superconducting characteristics.