Determination of oxygen stoichiometry in YBCO superconductors by spectrophotometry

A spectrophotometric method is suggested for the determination of the oxygen stoichiometry in YBCO superconducting materials. Total copper is also determined together with the oxygen content. According to the method, the sample is dissolved in hydrochloric acid in the presence of KI, under inert atmosphere. The solution pH is increased to 4.9 ± 0.1 by adding acetate buffer. The Cu2+ ions are bound in a complex with EDTA. The iodine equivalent to the non-stoichiometric oxygen, and the total copper are determined from the absorptions of the solution measured at 430 and 730 nm, respectively. The oxygen coefficient y is calculated from the absorbance at 430 nm or from the relation of the absorbances at the two wavelengths. In the second case, the mass of the sample is not included in the calculation, which facilitates the applicability of the method to films and wafers. Model solutions are used to prove the absence of systematic errors. The YBa2Cu3Oy superconductor is analysed. The relative standard deviations of the oxygen coefficient and the total copper are 0.2% and 1.3%, respectively. The iodometric method based on two successive titrations is used as a comparative method.