Preparation of single phase bismuth-based 2212 and 2223 superconducting oxides, and quantitative X-ray diffraction analysis of 2212 and 2223 phase mixtures

The preparation of single phase superconducting BiSrCaCu oxide powders with the nominal structural formulae Bi 2Sr 2Ca 2Cu 3O 10 and Bi 2Sr 2CaCu 20 8 from precursor oxide and carbonate mixture compositions with or without lead doping is described. In the absence of lead doping it is found that precursor compositions ranging from the stoichiometric ratio for the 2212 phase to the stoichiometric ratio for the 2223 phase yield only the ‘80K’ 2212 phase superconductor according to X-ray diffraction analysis. To synthesise the ‘110K’ 2223 phase it is necessary to dope with lead and to use the non-stoichiometric precursor composition, corresponding to Bi 1.84Pb 0.34Sr 1.91Ca 2.03Cu 3.060 y, established by Koyama et al. If the carbonate sources of the strontium and calcium oxides, plus copper oxide, are precalcined together before being combined with the bismuth and lead oxides (following the method of Arendt et al.) and the mixture is then calcined using a modification of the Koyama procedure, single phase 2223 material is produced. X-ray diffraction spectra from powder mixtures containing known proportions of the 2212 and 2223 phases are used to construct intensity ratio calibration curves for quantitative analysis of samples containing the two compounds.