EFFECT OF FLUORINATION ON PREPARATION OF BI(PB)SCCO-2223 BY THE CITRATE PRECURSOR PROCESS

Citrate precursor technology was used to prepare fluorine substituted Bi(Pb)SCCO 2223 superconducting phase. Samples with the nominal compos ition of up to three F atoms per formula were synthesized. A number of experimental methods have been used to characterize the samples and t o trace the phase transformations during the preparation process: DTA/ TGA, XRD, EPMA (WDS and EDS), atomic absorption, potentiometry with fl uoride selective electrode, resistance and inductive measurements. Flu orine was shown to enhance considerably the formation of the 2223 phas e. Thermodynamic calculations of P-T-X equilibrium in the Bi-Pb-Sr-Ca- Cu-O-F-C-H-N system were made in a wide temperature range to determine the composition of the vapours coexisting with the solid phases at di fferent stages of the preparation process.