Strongly enhanced critical current density in MgB2/Fe tapes by stearic acid and stearate doping

摘要

Fe-sheathed MgB2 tapes with cheap stearic acid, Mg stearate and Zn stearate doping were prepared through the in situ powder-in-tube method. It is found that J(c), H-irr and H-c2 were significantly enhanced by doping. Compared to the pure tapes, J(c) for all the doped samples was improved by more than an order of magnitude in a high-field regime. At 4.2 K, the transport J(c) reached 2.02 x 10(4) A cm(-2) at 10 T for the Zn stearate doped tapes and 3.72 x 10(3) A cm(-2) at 14 T for the stearic acid doped samples, respectively. Moreover, at 20 K, H-irr for the Zn stearate doped tape achieved 10 T, which is comparable to that of the commercial NbTi at 4.2 K. The improvement of J(c)-H properties in doped samples can be attributed to the increase of H-c2 resulting from the incorporation of C atoms into the MgB2 crystal lattice as well as a high density of flux-pinning centres.