Effects of compositional variations on the properties of superconducting (Bi,Pb)2Sr2Ca2Cu3Oδ

The results of a systematic study on compositional variations within the Bi2-xPbxSr2Ca2Cu3O δ superconducting system are reported. It is found that a secondary phase (or phases), likely composed of Pb-Sr-Ca-Cu-O, forms when x exceeds 0.35, indicating that this is an upper limit on the amount of Pb which replaces Bi. Varying the Sr:Ca or Bi:Ca ratio has dramatic effects on the resistive and magnetic properties. It is suggested that there is a very limited range of solution among the alkaline-earth elements. Bi occupying Ca sites is probably deleterious for both Tc and the structural stability of the 2223 phase. Preliminary results on textured ceramic samples have yielded J c (77 K) as high as 580 A/cm2.