Confirmation of the pesence of trivalent copper and peroxidic oxygen in superconducting YBa2Cu3O7-x materials and approval of their dependence on annealing procedure

✍ Scribed by G. Tavčar; B. Ogorevc; V. Vudnik; S. Pejovnik

• Publisher: Elsevier Science
• Year: 1991
• Tongue: English
• Weight: 676 KB
• Volume: 175
• Category: Article
• ISSN: 0921-4534
• DOI: 10.1016/0921-4534(91)90273-2

✦ Synopsis

Ba-Cu-O system. With adequate heat treatment in oxygen or argon, the electrical properties were changed from superconducting to nonsuperconducting and vice versa to eliminate the influence of the processing parameters on the results of the analytical methods. The iodometric titration method was applied to determine the oxidizing power of the samples. Two independent specific methods were employed to assess the presence of trivalent copper: (i) a voltammetric method based on detection of Cu(III) species in a strong alkaline medium and (ii) a chemical method based on detection of free chlorine after Cu (III) oxidation of chloride anion. Both methods were checked on reference solutions containing copper (III) species. Two photometric methods were utilized for determination of peroxide in solution after an YBCO sample dissolution in hydrochloric medium. Trivalent copper was undoubtedly detected only when superconducting samples were assayed. On the other hand, peroxidic oxygen was determined in nonsuperconducting samples in a concentration of about 1% whereas in superconducting samples the value found was about 0. 1%. All the results obtained are correlated and discussed.