Electron Irradiation Effects on Y₁Ba₂Cu₃O_y Superconductors

Abstract

3 MeV electton irradiations are performed in the broad range of electton dose, up to 2.0 x 10¹⁸ e^- /cm² , to investigate the effect of irradiation-induced defects on the superconducting transition for oxygen-controlled specimens. The electron irradiations depress Tc at the rate of 0.5 ∿ 3.5 K/10¹⁸ e^- /cm² depending on the specimen treatments and the probe currents. A specimen with the lower contents of oxygens is more sensitive to the irradiation. The detailed analysis on the transition region reveals the complicated behaviors. The three typically different phenomena are found in the three kinds of specimens(y=6.6, 6.7 ∿ 6.8, 6.8 ∿ 6.9). In a specimen with y=6.8 ∿ 6.9, the two stage transition is observed, and only the transition at the lower temperature is shifted to the lower temperature region with increasing probe currents. The electron irradiations do not influence on this feature. In a specimen with y=6.7 ∿ 6.8, the single transition is observed. The single transition is shifted to the lower temperature region by the irradiation without changing the sharpness of the transition. Contrary to the above two cases, in a specimen with y=6.6, the two stage broad transition is found, and the transition at the lower temperature depends on the probe current. The irradiation affects both of the peaks. With the increase of the electron dose, the transition at the higher temperature is broadened, but the transition at the lower temperature is sharpened with the shift to the lower temperature region.