VOLUMETRIC MEASUREMENT OF LABILE IONS THROUGH CORROSION OF YBa2Cu3O7−x

Abstract

The stability of sintered YBa2Cu3O7−x {123} in various aqueous solutions was investigated. It was found that all aqueous solutions have detrimental effects on superconduction in {123}. Based on the evolution of O2 through the reaction of {123} with acid, the volumetric measurement technique has been established for determining the quantity of Cu3+ in {123} with excellent reproducibility. In nitric acid the sintered {123} is much more stable than Ag, Cu or Ni metals, which are sometimes used in processing {123}, for example as cladding in wire drawing. {123} tends to passivate in concentrated acid. Impurity-doped and multiphase specimens generally suffer enhanced corrosion in water due to the formation of micro-electrochemical cells. Material with the tetragonal crystal structure is more stable in water than that with the orthorhombic structure, indicating that the sensitivity of {123} to water can be attributed to the presence of Cu3+ which is the driving force for rapid oxidation and reduction reactions in water.