Gamma irradiation effect on oxide high-temperature superconductor

Y-Ba-Cu-O and Bi-Sr-Ca-Cu-O superconducting thin films were sequentially irradiated with 60Co-γ rays at room temperature. The electrical resistivities of the films were measured as a function of temperature. As a result of 5.2 MGy irradiation, the resistivity of the Y-Ba-Cu-O thin film at 273 K increased to 4.2 times as large as unirradiated one. But the critical superconducting transition temperature (Tco) was not changed remarkably. The resistivity of normal conductive state in the 5.2 MGy irradiated sample took four figures down one place in 7 days after irradiation and the temperature characteristic of the thin film was not measured accurately. In the case of irradiation up to 6.2 MGy, a peak of the resistivity appeared at about 255 K. But the superconductivity of the thin film was not damaged completely. In the case of irradiation up to 7.2 MGy, the superconductivity of the film was damaged completely. The resistivity of the Bi-Sr-Ca-Cu-O thin film irradiated to 1.8 MGy increased to 11.6 times as large as unirradiated one at 273 K and Tco decreased from 72 K to 59 K. Upon further irradiation, the same phenomena as those of the Y-Ba-Cu-O thin film were observed in the Bi-Sr-Ca-Cu-O thin film. (author)