Josephson junctions with bulk YBa/sub 2/Cu/sub 3/O/sub 7-x/, Bi/sub 2/Sr/sub 2/CaCu/sub 2/O/sub x/ and Tl/sub 2/Ca/sub 2/Ba/sub 2/Cu/sub 3/O/sub 10+x/

The characteristics of point contacts with combinations of Pb, YBa/sub 2/Cu/sub 3/O/sub 7-x/, Bi/sub 2/Sr/sub 2/CaCu/sub 2/O/sub x/, (YBCO), (BSCCO), and Tl/sub 2/Ca/sub 2/Ba/sub 2/Cu/sub 3/O/sub 10+x/ (TCBCO) have been measured in a shielded liquid helium dewar. Zero-voltage currents were found in all arrangements; diffraction patterns in the voltage-flux curves were observed with all materials. Electron pairs were confirmed as carriers in all investigated high-T/sub c/ materials. All junctions resembled weak-link bridge structures rather than tunnel junctions. Despite strong shunting, hysteresis was found in the I-V curves of some point contacts. A structure of unknown origin was found in the I-V curves of YBCO-BSCCO junctions. Both YBCO-YBCO and BSCCO-BSCCO junctions had much lower normal resistances and considerably higher critical currents than YBCO-BSCCO point contacts. The reason for this phenomenon is not yet understood.<
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