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

The oxygen content in Bi2Sr2Ca1Cu2O8+delta and Bi2Sr2Cu3O10+delta supe rconductor samples is determined using a iodometric titration techniqu e and using a thermogravimetric reduction technique. The reliability o f the iodometric oxygen determination was exemplified by the reproduci bility of at least 0.01 in delta and the excellent agreement between r esults obtained separately from iodometry and thermal analysis on a se ries of samples. Compared to similar determinations in YBa2Cu3O7-delta superconductors, the determination of the metal content is an extra a nalytical requirement in the case of Bi and Pb containing ceramic mate rials. 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 t he Pb, Bi and Cu content in a single experiment with a relative standa rd deviation (RSD) < 1%. Using the techniques mentioned above, we were able to investigate the relationship between T(c) and delta in a seri es of Bi-2212 and Bi-2223 HTSC's. There appears to be a maximum in the T(c)vs delta curves for both phases.