Cooperative doping effects of Ti and nano-SiC on transport critical current density and grain connectivity of in situ MgB2 tapes

Abstract

By now, nano-SiC powder (20–30nm) is still the most effective additive for improving upper critical field and critical current density of MgB2-based superconducting materials. However, some decomposed carbon aggregates at grain boundaries and results in serious weak-links of MgB2 grains, and these weak-links limit the further improvement of critical current density, Jc of MgB2, especially at lower fields. Ti doping is reported to increase the compactness of MgB2, and modify its intergranular coupling by forming ultrathin TiB2 layer at grain boundaries. In this work, we studied the cooperative doping effects of Ti and nano-SiC on transport Jc and grain connectivity of MgB2 and the possibility to improve transport Jc of SiC doped MgB2 by introducing Ti additive. The results suggest the Ti addition can obviously improve Jc of MgB2 at lower fields and also enhance the Jc of SiC doped MgB2 by improving their grain connectivity which shows serious intergranular weak-links.