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 ≤ x ≤ 0.12 for Fe and 0 ≤ x ≤ 0.1 for Co). For the x = 0 phase, Tc,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 Tc with increasing dopant concentration is observed from resistivity as well as AC susceptibility measurements, and the results are discussed. © 1993.