SPECTROPHOTOMETRIC METHOD FOR THE DETERMINATION OF THE MOL RATIO BETWEEN THE NON-STOICHIOMETRIC OXYGEN AND COPPER IN SUPERCONDUCTIVE OXIDES

摘要

The method is used in superconductive oxides, in particularof volume specimen and film coatings containing yttrium(lanthanum), barium (strontium) and copper, as well as oxygenwhich is not bound in the form of oxides. In those cases when theoxide is monophase and the phase composition has been identified,the value of the oxygen stoichiometric coefficient is beingdetermined. By the method the mol ratio between thenon-stoichiometric oxygen and copper can be determined quickly andaccurately without any need for calibration and precisionmeasuring of the mass of the sample which is dissolved in amixture of hydrochloric acid and potassium iodide. The solution pHis increased to 4.9+0.1 after which two solutions are prepared, inone of which (solution 1) ethylenediaminotetraacetic acid isintroduced in order to block the copper (II) ions. The absorptionsof the solutions containing the K13 complex in quantity equivalentto the non-stoichiometric oxygen (solution 1) and of the sum ofthe non-stoichiometric oxygen and copper (solution 2) are measuredat 430 nm wavelength (for the analysis of volume specimens) or 355nm (for the analysis of film coatings). The differential measuringof the absorption of solution 2 in comparison with solution 1allow to find directly the mol ratio between thenon-stoichiometric oxygen and copper from the ratio between thetwo absorptions.