Effect of MgO and Ag2O Mix-Additions on the Formation and Superconducting Properties of Bi-2223 Phase

Abstract

The bulk samples with the composition Bi1.8Pb0.4Sr1.9Ca2.1Cu3.5Oy + x wt% MgO + (5-x) wt% Ag2O (x = 0, 1, 2, 3, 4 and 5) were prepared by sintering at 840°C for 240 h after partial­melting at 870°C for 1 h. The sample with individual Ag2O addition shows the lowest melting temperature and the lowest proportion of the Bi-2223 phase, whereas the sample with individual MgO addition shows the highest melting temperature. The highest proportion of the Bi-2223 phase appears in the sample with 1wt% MgO and 4 wt%Ag2O mix-additions. With increasing MgO content, the width of hysteresis loop ΔM of the bulk samples at 77 K increases (0≦x≦2), and then decreases (2≦x≦5). The largest ΔM appears in the sample with 2 wt% MgO and 3 wt% Ag2O mix-additions.