Development of the Titrimetric and Spectrophotometric Methods for Determination of the Oxygen Content in Superconducting Cuprates

This review article is concerned with the oxygen stoichiometry determination in YBa2Cu3Oy and REBa2Cu3Oy (RE = Er, Eu, Gd) superconductors. The nondestructive and destructive methods for the determination of the oxygen coefficient y (y = 6.5 + δ, δ is the non-stoichiometric oxygen coefficient) are described. The destructive methods as titrimetry and spectrophotometry are discussed in detail. The role of the reducing agent for Cu(III) ions from the superconductor sample is clarified. A number of new formulae for calculation δ- and y- coefficients of the oxygen are reviewed.

The advantages and disadvantages of the iodometric titrations and the spectrophotometric methods are given. Spectrophotometric methods without calibration of the analytical function and/or using small sample mass for analysis are preferable because: analysis with them is not expensive; the results are accurate; they can be applied to determine the oxygen stoichiometry of the superconducting thin film deposit into substrates. One of them has been developed and employed for the first time to determine the oxygen stoichiometry in Ca doped REBa2Cu3Oy high-Tc bulk materials.