Improved critical current densities in MgB₂ tapes with ZrB ₂ doping

MgB₂/Fe tapes with 2.5-15 at. % ZrB₂ additions were prepared through the in situ powder-in-tube method. The phases, microstructures, critical current density, and flux pinning were characterized by means of x-ray diffraction, scanning electron microscope, and magnetic and transport property measurements. Compared to the pure tape, a significant improvement in the in-field J_C was observed for all the ZrB₂ doped samples, while the critical temperature decreased slightly. The highest J_C value was achieved for the 10 at. % doped sample. At 4.2 K, the transport J _C 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 reasons for the improved J_C field performance.