SUPERCONDUCTIVITY IN NI SUBSTITUTED BI2CA1SR2CU2-XNIXOY

The effect of partial substitution of Ni in place of Cu in Bi2Ca1Sr2NixCu2-xOy has been systematically investigated for 0≤x≤0.2. The XRD of the samples confirms them to be of single phase. The superconducting critical temperature Tc monotonically decreases with Ni concentration; the rate of Tc decrease is around 2.5 K/% of the nominal substitution. All the samples have been subjected to XPS studies. The results show that Ni is incorporated in the lattice in the divalent state with Ni-O bonds substituting for the Cu-O bonds while keeping Bi-O, Sr-O and Ca-O bonds intact. Change in the Ni content does not seem to affect the valence state of Cu. The question of Tc decrease with Ni substitution is examined. © 1990.