Electrical and magnetic properties of the superconducting oxides with nominal composition (Bi0.7 Pb0.3 )2Sr2Ca2 Cu3 Ox prepared from polymeric precursors have been investigated. Superconducting transition with zero-resistance temperature at T=108 K was achieved for a sample sintered at 840 °C under a low oxygen pressure. The critical current density at 77 K in a zero magnetic field is ∼400 A/cm2 , which is much higher than that of the Pb-free sample. Variations of the superconducting transition temperature, the critical current density, and magnetic properties with heat treatment time are discussed in connection with the structural properties.
We have fabricated superconductor-insulator-normal metal (SIN) tunnel junctions with c-axis oriented YBCO thin films as the superconducting electrodes, and studied the tunneling characteristics of the junctions by measuring the zero-bias junction resistance as a function of temperature and dI/dV as a function of the bias voltage. Measured junction resistance showed a characteristic tunneling properties with a strong semiconducting background which is ascribed to the imperfect tunnel barrier. dI/dV curves indicated gap structures at 27 mV and 4.5 mV, respectively, with a parabolic background.Phys. B 73, 32
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