DETERMINATION OF THE OXYGEN-CONTENT IN SUPERCONDUCTING AND RELATED CUPRATES USING TEMPERATURE-PROGRAMMED REDUCTION

The oxygen content and reducibilities of four base metal oxides, six nonconducting cuprates, and three superconducting cuprates were investigated by temperature-programmed reduction (TPR) from 30 to 900°C. It was shown that the copper, bismuth, and thallium ions of these oxides were reduced to the zero valence state. Thus, TPR is a useful technique for determining the actual oxygen stoichiometry of cuprates. For multiphase Bi2CaSr2Cu2O8+x and Tl2CaBa2Cu2O8+x superconductors pretreated in air, x was found to be 2 ± 0.2 and 1 ± 0.2, respectively. Both values are significantly higher than previously reported. The reduction of superconducting and related cuprates required higher temperatures than CuO, but the reducibility of CuO decreased when it was calcined in air at 940°C. The Bi- and Y-based superconducting cuprates exhibited the lowest reducibility among the samples investigated. © 1991 Academic Press, Inc.