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We report the results of resistivity, ac-susceptibility, and specific-heat measurements carried out on samples of Bi& Pb Sr~Ca2Cu30&0+"(O~x~0 .7) that were characterized by x-ray diffraction and high-resolution scanning tunneling microscopy. The zero resistance temperature, T, (R=O), shows a peak at x =0.3 and the susceptibility data indicate that although a high-T, 2:2:2:3 phase is present at 110 K, there is a second transition at 90 K that seems to indicate the existence of an additional low-T, 2:1:2:2phase. The specific-heat data unambiguously indicate a clear and distinct anomaly around T, for samples with x =0.3-0.4 and smearing of the anomaly for x )0.5. Based on the results obtained from these combinations of experiments, the role of lead substitution in Bi samples, particularly in the stabilization of the 2:2:2:3phase has been discussed.

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