Bulk Bi2Sr2CaCu2Ox With MgO Particles Embedded By Partial Melting Process

To extend the practical applications of hight Tc bulk materials such as Bi-2212, the factors which influence the value of the critical current density are studied . The creation in different ways of pinning centres is one feasible solution of the problem. Recently, studying of bulk Bi-2212 embedded with MgO particles by partial melting process is intensified. Addition of nanosize MgO increases the critical current when the maximum heat treatment temperature is 910ºC. The use of this sintering temperature leads, however, to a larger non-superconducting phase in the sample. If lower sintering temperature is used, such as 892ºC, a second main phase of 2201 type appears. It was also shown that addition of 20 mol% nanosize MgO to the Bi-2212 enhances the sample magnetization, while addition of 20 mol% microsize MgO does not change it. On the other hand, the magnetization becomes worse with 11 mol% nanosize MgO. On the contrary, the introduction of 5 wt% MgO particles of 0.5-1.0 µm in size significantly reduces the second -phase inclusions, and insinificantly changes the grain alignment at Tmax=885ºC. It is a controversial point whether nanosize particles themselves play the role of pinning centres, or the pinning centres must be the interface between MgO particles and superconductor matrix. The aim of this study is to introduce randomly distributed in size micro- and nano-MgO particles with different concentrations by partial-melting process usually employed for preperation of pure Bi-2212 samples.