Effect of γ-irradiation on polycrystalline Tl₁Ba₂Ca₂Cu₃O_y superconductor

Specimens of polycrystalline Tl₁Ba₂Ca₂Cu₃O_y superconductor (Tl-1223) have been irradiated at room temperature by γ-rays. The variations of the normal state resistance, transition width and the critical current densities with γ-irradiation up to about 400 MR were studied. The normal state resistivity ρ(T) increases gradually up to a dose of 100 MR, whereas at higher doses, the effect of irradiation becomes rather negligible. The transition temperature T_c decreases slightly and the transition temperature width ΔT broadens at doses below 100 MR with almost no change at higher doses up to 400 MR. At relatively low temperatures and low γ-doses, the critical current densities J_c(T) increase with γ-irradiation, while the effect of γ-irradiation at temperatures very close to T_c is rather negligible. Obtained results confirmed the high sensitivity of (Tl-1223) superconductor to γ-irradiation at relatively low γ-doses. These results are discussed and explained in terms of the effect of γ-rays on the weak links and Josephson junctions between the grains.