ELECTROCHEMICAL BEHAVIOR OF YBa2Cu3O7

The corrosion behavior of the high-Tc-superconductor YBa2Cu3O7 in aqueous solutions was studied at room temperature by electrochemical dc and ac methods and surface analysis. The oxidic ceramics is found to be more stable in alkaline than in acid media. The surface stability decreases with the time of contact to the electrolyte and depends strongly on the polarization conditions. Segregation and decomposition effects are observed. Ageing effects are related to an increase of the ohmic resistance of the surface layers. A relatively positive reduction peak in cyclic voltammograms is correlated to the reduction of a formal Cu(III)-oxide species, which may be better explained in terms of a Cu(II)-peroxide species as [Cu2+ -O−]+. The high-Tc-superconductor YBa2Cu3O7 does not act as a special electrocatalyst for the anodic oxygen evolution reaction. The superconductivity of the samples is a bulk property and remains even after electrochemical surface treatment.