Substitution of transition metals for Cu in Bi2(SrCa)n+2Cun+1Oy whisker crystals: Fe and Pd

We have measured the resistive superconducting transition temperature of single-crystal whiskers of Bi₂(SrCa)_n+2(Cu_{1- x}M_x)_n+1O_y in which M represents the transition metals Fe and Pd that have been partially substituted for Cu. Combining these measurements with our earlier results for Co, Ni, and Zn substitutes, we derive a general relationship for the rate at which T_C is depressed by substitution of transition metals: dT_C/dx~-780 K for all these elements and both the 2212 (n=1) and 2223 (n=2) phases. Further, the normalized residual resistance is also a universal function of x. This is contrary to what others find for YBa₂Cu₃O_7-δ (YBCO), in which Zn and Ni substitutions act quite differently on dT_C/dx. The explanation of this effect in YBCO apparently does not involve the general behavior of the Cu-O planes. The magnitude of dT_C/dx is about half that predicted by the Abrikosov-Gorkov relation, as seen in other Cu-O superconductors.