ENHANCEMENT OF SUPERCONDUCTING PROPERTIES OF MgB 2 SUPERCONDUCTOR BY DOPING OF NANO-ALUMINA AND NANO-CARBON

The importance of MgB2 lies in its simple crystal structure, relatively high TC (39K), low cost, large coherence length and transparency of grain boundaries to current flow. Systematic preparation of a series of bulk MgB2 samples of Mg1-x Alx (B1-y Cy)2, x=2% ; y = 0%,1%,2%, 3%, 4%,6%, 10%, were carried out on nano alumina MgB2 co-doped with nano carbon. Bulk MgB2 samples have prepared by standard solid-state reaction method, followed by ball milling. As the concentration of nano carbon doped MgB2 increases their resistivity increases accordingly, results the lowering of transition temperature, Tc. Here, we report that co-doping play an important role in decreasing the lattice parameters. A systematical comparison of nano alumina and nano carbon doped MgB2 with structure; superconducting transition, resistivity and dc-susceptibility are discussed. Keeping this in mind we investigated the effect of simultaneous doping of nano Al and nano C in different ratio on JC around 20K.. We found more than one order of increase in JC at 20K in 4.8 T field for particular ratio of Al and C. Keyword - MgB2, nano-Alumina, nano-carbon, co-doped, superconductivity, critical current.