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͑Received 29 March 1996͒c-axis-oriented superconducting Bi 2 Sr 2 Ca 2 Cu 3 O 10ϩ␦ ͑Bi-2223͒ tapes have been irradiated with 5.8-GeV Pb ions to produce columnar defects along the c axis. The magnetization M as a function of field and temperature were measured for both the unirradiated and irradiated samples at matching field B values of 1.28, 2.0, and 4 T. In striking contrast to the conventional log(B) dependence of the reversible M in the London regime, the field dependence of the reversible M for the irradiated samples exhibits some unusual characteristics. A large reduction in the value of M was observed at BрB ⌽ , while a maximum appears at BϾB ⌽ . We explain this field dependence in terms of the London model modified by the localization of the vortex lines in the columnar defects. Based on this study, we obtained the single vortex pinning energy for Bi-2223 by these columnar defects. ͓S0163-1829͑96͒50226-2͔ R79054 QIANG LI et al.

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We have synthesized new superconductors of nearly single phase with zero-resistance temperatures around 120 K employing a novel method for sintering. The samples included a nominal composition of (Tl0.64Pb0.2Bi0.16)Sr2Ca3Cu4Oz. This sample was prepared from the mixture of presynthesized (Tl0.64Pb0.2Bi0.16)Sr2CaCu2Oz (1212 phase), CaO, and CuO powders. The mixed powder was sintered at 920 °C in O2 gas and post-annealed at 400–600 °C in O2 gas. The powder x-ray diffraction revealed that the sample was isostructural with the Tl-based (Tl, Pb, Bi)Sr2Ca2Cu3Oz (1223 phase). The sample exhibited a sharp superconducting transition at Tonsetc=125 K and TR=0c=120 K and the superconducting diamagnetic signal at 10 K was about 20% of a full Meissner effect.