ON THE METAL AND OXYGEN-CONTENT DETERMINATION IN BI-2212 AND BI-2223 HTSCS

The oxygen content in Bi2Sr2Ca1Cu2O8+delta and Bi2Sr2Cu3O10+delta superconductor samples is determined using a iodometric titration technique and using a thermogravimetric reduction technique. The reliability of the iodometric oxygen determination was exemplified by the reproducibility of at least 0.01 in delta and the excellent agreement between results obtained separately from iodometry and thermal analysis on a series of samples. Compared to similar determinations in YBa2Cu3O7-delta superconductors, the determination of the metal content is an extra analytical requirement in the case of Bi and Pb containing ceramic materials. For the determination of the metal content, a reproducible and rapid method, based on differential pulse polarography, was optimized. Using EDTA-HCl as supporting electrolyte, we were able to determine the Pb, Bi and Cu content in a single experiment with a relative standard deviation (RSD) < 1%. Using the techniques mentioned above, we were able to investigate the relationship between T(c) and delta in a series of Bi-2212 and Bi-2223 HTSC's. There appears to be a maximum in the T(c)vs delta curves for both phases.