Chemistry and valence of Sb-substitution for Bi in high Tc Bi1−xSbxSrCaCu2Oy and Bi2−xSbxSr2CaCu2Oy superconductors

Abstract The effect of Sb-substitution for Bi has been studied in the high T c superconducting materials Bi 1− x Sb x SrCaCu 2 O y ( T c ∼ 70 K) and Bi 2− x Sb x Sr 2 CaCu 2 O y ( T c ∼ 100 K). For materials synthesized in an oxidizing atmosphere the solubility o f Sb is quite low and its substitution for Bi leads to a complex chemistry which results in the depression of T c with increasing Sb concentration. Mossbauer effect measurements at 121 Sb sites indicate that the valence state is near Sb(V) in both compound systems.