Magnetic properties and critical current density of bulk MgB2 polycrystalline with Bi-2212 addition
Abstract:Bulk samples of MgB2 were prepared with 0, 3, 5, and 10 wt% Bi2Sr2CaCu2O8 (Bi-2212) particles, added using a simple solid-state reaction route in order to investigate the effect of inclusions of a material with higher Tc than the superconducting matrix. The density, diamagnetic signal, and critical current density, Jc, of the samples change significantly with the doping level. It is found that Jc is significantly enhanced by the Bi-2212 addition. Microstructural analysis indicates that a small amount of Bi-2212 is decomposed into Cu2O and other impurity phases while a significant amount of unreacted Bi-2212 particles remains in MgB2 matrix, and these act as effective pinning centres for vortices. The enhanced pinning force is mainly attributable to these highly dispersed inclusions inserted in the MgB2 grains. Despite the effectiveness of the high-Tc inclusions in increasing superconducting critical currents in our experiment, our results seem to demonstrate the superiority of attractive centres over repulsive ones. A pinning mechanism is proposed to account for the contribution of this type of pinning centre in MgB2 superconductors.
Document Type: Research Article
Publication date: August 1, 2005