Improved critical current densities in MgB2 tapes with ZrB2 doping
  MgB2/Fe tapes with 2.5-15 at.% ZrB2 additions were prepared through the in situ powder-in-tube method. Compared to the pure tape, a significant improvement in the in-field critical current density Jc was observed, most notably for 10 at.% doping, while the critical temperature decreased slightly. At 4.2 K, the transport Jc for the 10 at.% doped sample increased by more than an order of magnitude than the undoped one in magnetic fields above 9 T. Nanoscale segregates or defects caused by the ZrB2 additions which act as effective flux pinning centers are proposed to be the main reason for the improved Jc field performance. 
Xianping Zhang, Zhaoshun Gao, Dongliang Wang, Zhengguang Yu, Yanwei   Ma, S. Awaji, K. Watanabe