Benzoic acid doping to enhance electromagnetic properties of MgB2 superconductors

The effect of benzoic acid doping on lattice parameters, microstructure, critical temperature (T-c), critical current density (J(c)) and flux pinning force of MgB2 has been studied. In this work we used benzoic acid as an example of aromatic acids as an additive to MgB2. For different sintering process, actual carbon (C) substitution for boron (B) was estimated to be from 3.5 at% to 5.0 at% of B while T-c dropped about 2-4 K. The advantages of aromatic acid doping include homogeneous mixing of precursor powders, avoidance of expansive nano-additives, production of highly reactive C and significant enhancement in J(c) of MgB2, compared to undoped samples. High level C substitution of B can induce the MgB2 crystals grow into bar shape microstructure. The J(c) value of 1.5 x 10(4) Acm(-2) at 5 K and 8 T for preheated 10 wt% C7H6O2 doped MgB2 sample is higher than that of the undoped MgB2 by a factor of 13. As there are numerous aromatic acids readily available this finding has significant ramifications not only for the fabrication of MgB2 but also for many C based compounds and composites.