Enhancement and degradation of T-c in Bi-HTSC due to Li3+ irradiations

Radiation damage in Bi2Sr2CaCu2O8+delta or Bi(2 2 1 2) by 55 MeV Li3+-beam has been studied from electrical resistivity and X-ray diffraction characte rizations. This irradiation increases electrical resistivity and broadens X -ray diffraction lines by generating defects in all samples. But supercondu cting critical temperature, T-c, is seen to increase for Bi(2 2 1 2) with e xcess oxygen and decrease for Bi(2 2 1 2) with O-content less than the opti mum, that gives maximum T-c. This increase of the superconducting critical temperature on Li-irradiation of O-rich Bi(2 2 1 2) as well as the decrease for low-O Bi(2 2 1 2) is due to O-displacement. This is in agreement with our earlier He-irradiation results. (C) 1999 Elsevier Science B.V. All righ ts reserved.