Critical current density of MgB2 superconductor with (Bi,Pb)-2223 addition

Abstract

Polycrystalline MgB2 pellets with and without addition of superconducting Bi1.8Pb0.26Sr2Ca2Cu3O10+x powder has been synthesized by solid reaction. The effect of (Bi,Pb)-2223 addition on structural and critical current density of MgB2 superconductor has been investigated. XRD data reveals no substitution for Mg or B. The superconducting transition temperature (Tc0) of MgB2 (∼37.97K) remains almost invariant with 2223 addition. Temperature dependence of the normal state electrical resistivity of 2223 added MgB2 is well explained by modified Rowell’s model and it suggests that 2223 addition in MgB2 marginally influences the percentage connectivity and intragrain residual resistivity. Critical current density (Jc) has been estimated at 4, 10, 20 and 30K from M–H curves using Bean’s model. MgB2 sample with 1wt.% of 2223 addition gives the best performance and display nearly two times enhancement in Jc compared to that of pure MgB2 in the field range between 0 and ±6T. Our analysis confirms that the observed magnetic field dependence of Jc of the present system is explained well in terms of the collective pinning model. Using the best fitted parameters (Jc (0) and H0) of collective pinning model, an excellent scaling is established between the reduced critical current density, Jn (=Jc/Jc (0)) and the reduced field hn (=H/H0) at different temperatures for both pure and 2223 added MgB2 polycrystalline pellets. It is also confirmed that δTc type pinning dominates in pure MgB2 and for 2223 added MgB2 major contribution originates from δl type pinning at lower temperatures.