Experimental evidence for granular superconductivity in Y-Ba-Cu-O at 100 to 160 K

Abstract
We have observed anomalous voltage excursions as a function of temperature and magnetic field in samples of Y-Ba-Cu-O above 100 K. These transient voltages are attributed to flux jumps which are characteristic of granular superconductors. The field dependence of the effect strongly supports this interpretation. We conclude that there exists grains in the sample with superconducting transition temperatures at least as high as 160 K.