Significant enhancement of critical current density in MgB2 with HgO doping under high pressure

A series of HgO-doped MgB2 samples have been prepared under high pressure. Even 27 and 43 wt% impurities have been observed in the Mg1.05-x(HgO)(x)B-2 samples with x = 0.05 and 0.075, the critical current density, J(c), have been significantly improved under both low and high magnetic fields. XRD and scanning electron microscope (SEM) analyses revealed that HgO reacted with Mg to form MgHg alloy. The formation of MgHg alloy contributed not only to the refinement of MgB2 grain size and improvement of grain connection, but also to homogeneous distribution of a large amount of impurities in the MgB2 matrix. As a consequence, grain-boundary pinning was strengthened and new point pinning was generated. Effective improvement of flux pinning together with the very high impurity tolerance in HgO-doped MgB2 samples might provide another potential route to prepare high-performance MgB2 bulks and wires on an industrial scale. (C) 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim