Influence of transition metals substitution on the superconductor Bi₄Ca₃Sr₃Cu₄O_y

Abstract

The results of our investigation on the specimens Bi₄Ca₃Sr₃Cu_4−x T_xO_y (T=Fe, Co, Ni,x≤0.5) synthesized in air are presented. Fe and Co substituents result in the formation of Bi₂Sr₂CuO_y-type of phase, with considerable depression of T_c of the main phase. However, Ni is completely soluble with Cu in this concentration range without significant depression of superconducting transition temperature (T_c). This difference in the solubility behaviour of Fe and Co on the one hand and Ni on the other is explained taking into account ionic charge and coordination number mismatches.