EFFECTS OF ELECTRON-IRRADIATION ON THE CRITICAL CURRENT-DENSITY OF Y1BA2CU3OX SUPERCONDUCTORS

Temperature and magnetic field dependence of the transport critical cu rrent density, J(c), of the polycrystalline YBa2Cu3Ox (YBCO) were deri ved from the I-V characteristic curves obtained below the critical tem perature, T(c). J(c) were remeasured after the sample being irradiated with 3 MeV-electron at a dose of 5 x 10(21) m-2. J(c) in zero field a s a function of temperature was found to decrease, but J(c) in magneti c fields of 0.01, 0.05 and 1.0 T was increased. The reduction of J(c) in zero field is attributed to weak links at the grain boundaries that had been degraded or produced by the irradiation, while the enhanceme nt of J(c) in magnetic field is discussed as due to the radiation-indu ced defects in the grains act as pinning centers for magnetic flux lin es. The difference in the profile of J(c)-T curves between low and hig h magnetic fields is discussed as due to the difference in the nature of magnetic flux penetration at those magnetic fields.