Chemistry and superconducting behavior of Sb-substituted Bi/Pb-based oxides

Abstract The effect of Sb-substitution for Bi has been studied in the high T c Bi-based oxide superconducting compounds Pb 0.3 Bi 1.8−x Sb x Sr 1.9 Ca 2 Cu 3 O y (0 x ≤ 0.3). The solubility of Sb is quite low and its substitution for Bi leads to a complex chemistry with the formation of a new phase whose fractional concentration increases with increasing Sb content. The superconducting T c is depressed by the addition of Sb for materials prepared in an oxidizing atmosphere, but is not affected if preparation is in a mildly oxidizing atmosphere. No T c above 110K is found for any Sb-doped Pb/Bi 2223 compounds. A 121 Sb Mossbauer effect study of the microchemistry shows that Sb is in a valence state near 5+ for all compositions.