SUPERCONDUCTING AND MECHANICAL-PROPERTIES OF YBCO AG COMPOSITES FABRICATED AT HIGH-PRESSURES UP TO 5.4 GPA

The YBCO/Ag superconducting composites were fabricated by compressing powders of YBCO and silver mixed at various volume proportions 0 to 100% under pressures of 2.0 and 5.4 GPa and subsequently sintering at 900-degrees-C for 10 h in a flowing oxygen atmosphere. The superconducting transition temperature, particularly T(c) (R = 0), was found to retain the value above 85 k up to 50 vol % Ag while the normal resistivity at 300 K to reduce below 10-mu-OMEGA-cm. The highest J(c) of 400 A cm-2 was attained for the sample containing 20 vol % Ag pressed at 5.4 GPa. The mechanical properties were also improved by the addition of silver: the compressive strength is increased by two to three times and the maximum strain, which is a measure of ductility, reached a value almost four times as large as that in the pure YBCO prepared under the ordinary pressure of 0.5 GPa. The persistence of the superconducting characteristics up to 70 vol % Ag is discussed in terms of the microstructure taken with the scanning electron microscope.