QUANTITATIVE-ANALYSIS AND STUDIES OF THE TRANSFORMATION FROM BI2SR2CACU2O8+X TO BI2SR2CA2CU3O10+X USING RIETVELD ANALYSIS AND AC-SUSCEPTIBILITY

The transformation of the Bi2Sr2Ca1Cu2Oy (2212) phase into the Bi2Sr2Ca2Cu3Oy (2223) phase at a constant reaction temperature of 850-degrees-C in air for 73 days using as nominal initial composition Bi1.7Pb0.3Sr2Ca2Cu3Oy has been studied qualitatively and quantitatively by means of X-ray diffraction (Rietveld analysis) and AC-susceptibility. The quantitative analysis of the X-ray powder diffraction patterns revealed the coexistence of the (2212), (2223) and Ca2-zSrzCuO3 phases throughout the reaction. It is found that the percentage of the (2223) phase increases in accordance with the relation w = w0(1-exp(-kt)) and reaches an upper limit of 80 wt% of the sample. This, in fact, is in very good agreement with the results obtained from the AC-susceptibility studies on the same samples. Repeating the experiment at a higher temperature (i.e. 865-degrees-C) showed that the reaction kinetics improved, although the Bi2Sr2CuOy (2201 ) phase is added to the above phases. We have found that both Rietveld analysis and AC-susceptibility are excellent methods quite compatible in monitoring such phase transformations and therefore are useful for the preparation and characterization of these superconducting materials.