Determination of non-stoichiometric oxygen in YBCO superconductors by coulometric titration

A coulometric titration method has been developed for the determination of non-stoichiometric oxygen in YBCO superconductors, The composition of the supporting electrolyte is 1 mol l(-1) HCl, 0.02 mol l(-1) CuSO4 and 0.17 mol l(-1) KBr. The powdered sample is introduced in the electrolytic cell containing a known excess of Cu(I), previously electrogenerated by galvanostatic reduction of Cu(II) ions, the sample is dissolved, and the non-reacted Cu(I) is back titrated with electrogenerated Br-2. The method was applied to an analysis of monophase YBa2Cu3O6.5+delta superconductor Spectrophotometry without calibration is used as a comparative method. The reproducibility of the results for the non-stoichiometric oxygen content obtained by the suggested method is much better than that of the comparative method. The new method is very suitable for series of analysis. (C) 1997 Elsevier Science B.V.