STRUCTURAL AND SUPERCONDUCTING PROPERTIES OF BI2-MPBMSR2CA2CU3O10-DELTA WITH 0-LESS-THAN-OR-EQUAL-TO-M-LESS-THAN-OR-EQUAL-TO-1

Substitution of Pb for Bi in polycrystalline ''Bi2-xPbxSr2Ca2Cu3O10-delta'' (2223 phase) has been achieved up to the solubility limit of x(Pb) = 0.35 +/- 0.03 by optimizing the annealing time and annealing temperature of each sample. Addition of Pb beyond its solubility limit results in changes of the liquidus compatibility relations. The microstructure of the samples and the chemical compositions of all phases present were studied by scanning electron microscopy (SEM), energy dispersive X-ray fluorescence (EDX) and electron probe microanalysis (EPMA). The lattice parameters of the 2223 phase determined by X-ray powder diffraction reveal also the incorporation of Pb for Bi. Single-crystal X-ray methods show a superstructure along [010] with an incommensurate modulation of q = 0.115b* for x(Pb) = 0.36. In spite of the drastic variations in the chemical composition of the 2223 phase, T-c remains constant over the whole observed range with T-c = 111.5 +/- 1.5 K.