STRUCTURE AND SUPERCONDUCTIVITY STUDIES ON FE AND CO DOPED BI-2212

Systematic studies of the Bi-2212 superconducting phase, substituting at the Cu-site by Fe and Co, have been carried out on an off-stoichiometric composition Bi2.1Sr1.93Ca0.97(Cu2-xMx)O8+y (M=Fe, Co; 0 less-than-or-equal-to x less-than-or-equal-to 0.12 for Fe and 0 less-than-or-equal-to x less-than-or-equal-to 0.1 for Co). For the x=0 phase, T(c,zero) values in the range 74-76 K have been obtained consistently. X-ray diffraction studies show that the solid solubility exists up to x=0.12 for M=Fe and x=0.1 for M=Co. A monotonic decrease in T(c) with increasing dopant concentration is observed from resistivity as well as AC susceptibility measurements, and the results are discussed.