Evaluation of Oxygen Nonstoichiometry in High-Tc Superconductors

Abstract
A sensitive method has been developed for the determination of oxygen nonstoichiometry in YBa2Cu3O6.5+x superconductors to critically examine the orthorhombic phase containing low-T c or high-T c superconducting material. Oxygen is evolved on reacting a few mg of powdered sample with dilute nitric acid in helium atmosphere in a closed circuit in a specially designed glass sampler and analyzed by gas chromatographic techniques using a thermal conductivity detector. In the samples analyzed, the x value varies from 0.47 to 0 indicating the change from the high-T c to the low-T c orthorhombic phase. The accuracy of the measurement is better than 3%.