ALL-CERAMICS JOSEPHSON-JUNCTIONS OPERATIVE UP TO 90-K

Ba-Y-Cu-O/Ba-Y-Cu-O Josephson junctions are made by creasing fissures in the bulk Ba-Y-Cu-O ceramic superconductors. The critical current of the junction fissured at room temperature decreases exponentially with the increase in the operating temperature, similar to that of an S/N/S junction. However, with the junction fissured at cryogenic temperature, critical current persists all the way up to about 90 K (T//c of Ba-Y-Cu-O compound). The a. c. Josephson effect is observed for these junctions in all temperature range up till 90 K. The onset of the formation of the macroscopic quantum state just below 90 K is implied.