Cooperative doping effects of Ti and C on critical current density and irreversibility field of MgB2

Abstract

Carbon and titanium concurrently doped Mg B2 alloys with a composition of Mg1-x Tix B2-y Cy have been prepared by an in situ solid state reaction method. The combination effects of carbon and Ti doping on structure, microstructure, irreversibility field (Hirr), and critical current density (Jc) of Mg B2 have been investigated. It is found that doping Ti in Mg B2 does not reduce the solubility of carbon in Mg B2, but, on the contrary, it eliminates the porosity present in the carbon-doped Mg B2, resulting in an improved intergrain connectivity. As a result, Jc and Hirr of Mg B2 have been significantly improved, sharply contrasted to the situation of C-only-doped or Ti-only-doped Mg B2 bulks. Our results clearly reveal that carbon and Ti codoping are largely cooperative in improving the performance of Mg B2 in the high magnetic fields (>3 T) and at high temperature (∼20 K). © 2006 American Institute of Physics.