Superconducting coupling nature at grain boundaries in BizSrzCaCuzO, glass-ceramics consisting mainly of the low-T, phase was first examined by measuring superconducting properties and temperature or ac field dependence of ac complex susceptibility. It was found from the ac loss peaks that superconducting coupling at grain boundaries was basically characterized by three types of weak links. The weak-link behaviors at grain boundaries depended strongly on cooling conditions after annealing and annealing time and temperature. Particularly, it was found that the weak links at grain boundaries were improved by prolonged annealing at 840°C. The furnace-cooled glass-ceramics obtained by annealing at 820" or 840°C for about 200 h exhibited a critical transport current density (77 K, zero magnetic field) of about 200 A/cmZ. [

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The Ag-coated superconducting Bi2 Sr2 CaCu2 Ox glass-ceramic fibers were successfully prepared. The glass fibers with a length of 50 cm, a width of 100–200 μm, and a thickness of about 20 μm were first drawn from glass plates with a thickness of 1 mm and then silver pastes were coated on the smooth surface of glass fibers. The Ag-coated glass fibers were converted into superconductors after annealing at temperatures of 820–860 °C. The main crystalline phase in the glass-ceramic fibers was the superconducting low Tc phase. The Ag-coated glass-ceramic fibers obtained by annealing at 840 °C for 5 h in air exhibited superconductivity with a Tc (zero)=70 K and a critical current density (60 K, zero magnetic field) of more than 40 A/cm2 .

We prepared many bulk glasses in compositions around BiSrCaCu2Ox using the conventional melt quenching method and examined superconducting properties of the glass ceramics obtained. It was found that the compositions in the Bi-Sr-Ca-Cu-O system had a great tendency to form a glass and Bi2O3 played an important role in the glass formation. The glass transition and crystallization temperatures for the glasses of BixSrCaCu2Ow (x=1.2-3) were in the range between 425•‹ and 370•Ž and in the range between 450•‹ and 430•Ž, respectively and both values tended to decrease with increasing Bi2O3 content. The ratio of SrO and CaO was also important for the glass formation and the coexistence of SrO and CaO was needed to form a glass. Many glasses became superconducting glass ceramics with the Tc values of around 75K by annealing at 820•Ž for 40h air.