Effect of MgO and Ag_2O Mix-additions on the Formation and Superconducting Properties of Bi-2223 Phase

摘要

The bulk samples with the composition Bi_(1.8)Pb_(0.4)Sr_(1.9)Ca_(2.1)Cu_(3.5)O_y + x wt% MgO + (5-x) wt% Ag_2O (x = 0, 1, 2, 3, 4 and 5) were prepared by sintering at 840°C for 240 h after partial-melting at 870°C for 1 h. The sample with individual Ag_2O 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 lwt% MgO and 4 wt%Ag_2O mix-additions. With increasing MgO content, the width of hysteresis loop AM of the bulk samples at 77 K increases (0<=x<=2), and then decreases (2<=x<=5). The largest AM appears in the sample with 2 wt% MgO and 3 wt% Ag_2O mix-additions.