Superconducting Properties of Bi-Sr-Ca-Cu-O Ceramics Prepared by Utilization of Hot-Pressing

Abstract

The superconducting properties of the Bi-Sr-Ca-Cu-O ceramics has been studied in terms of the microstructure. The powders were uniaxially hot pressed at 5t/cm², 500°C for 5min. Then the compacts were heated and sintered again at 870°C in air for 10 and 100h, followed by furnace cooling. Resistivity of the specimens was measured by standered four-probe method. Zero resistivity was observed at 80.0K when the compact was heated at 870°C for 10h, while after heated for 100h the off-set was at high as 105.5K. The critical current density at 77K was very low as 168.4mA/cm². The specimens simply heated and sintered at 870°C for 10 and 100h after cold pressing at 5t/cm² (without hot pressing) showed very low off-set temperatures. It was found, however, that the prolonged heating at 870°C with or without hot pressing increased the formation of the high T_c phase in the Bi-Sr-Ca-Cu-O ceramics. The hot pressing prior to the heating at 870°C increased the bulk density and the grain sizes of the specimens. The improvement of the sintering behavior may assist the formation of superconducting contacts among the grains of the high T_c phase in the Bi-Sr-Ca-Cu-O ceramics.