Enhancing the transport properties of polycrystalline MgB₂ superconductors

MgB₂ polycrystalline superconducting specimens were irradiated with 10 MR and 20 MR doses of γ-rays. An increase in the normal state resistance and a broadening of the resistive transition to the superconducting state were observed with increasing γ-irradiation dose within the temperature range of 28 -31 K. The change in the critical temperature, T _c was found to be insignificant after irradiation. The critical current density, J_c was found to be enhanced almost at all temperatures after irradiation. The enhancement of J_c was found to be linear with the irradiation dose at all temperatures. These results are explained by the effects of γ-rays and temperature on the migration of MgO impurities into the grains and the oxygen segregation in the grain boundaries.