SUPERCONDUCTIVITY IN A AG-DOPED BI-PB-SR-CA-CU-O SYSTEM

For the Bi-Pb-Sr-Ca-Cu-O (BPSCCO) system, a consistent set of data for Tc, x-ray diffraction, and scanning electron microscopy shows that Ag additions strongly react with BPSCCO to destabilize the 110 K superconducting phase, resulting in a strong depression in Tc and lattice parameters when samples are treated in air or pure oxygen. This is in contrast to the behavior for the Y-Ba-Cu-O and Bi-Sr-Ca-Cu-O systems, which do not show such degradation. However, Ag additions show no effects on Tc and lattice parameters when samples are treated under low oxygen pressure. The formation of a low-melting eutectic liquid with Ag2O-PbO-CuO solid solution affects the composition of the superconducting phase and degrades superconductivity, while the eutectic may be suppressed by reducing the oxygen partial pressure.