Doping effects of ZrC and ZrB_2 in the powder-in-tube processed MgB_2 tapes

We have investigated the effects of ZrC and ZrB2 doping on the superconducting properties of the powder-in-tube processed MgB2/Fe tapes. Sam- ples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM/EDX), transport and magnetic measurements. We confirmed the fol- lowing quite different roles of ZrC and ZrB2 in MgB2. ZrC doping was found to decrease the transport critical current density (Jc) at 4.2 K, while the critical temperature (Tc) kept constant. In contrast, the Jc values in magnetic fields were enhanced greatly by the ZrB2 addition, which resulted in a decrease in Tc by only 0.5 K. The reason for different effects of two dopants is also discussed.

We have investigated the effects of ZrC and ZrB2 doping on the superconducting properties of the powder-in-tube processed MgB2/Fe tapes. Sampies were characterized by X-ray diffraction （XRD）, scanning electron microscopy （SEM/EDX）, transport and magnetic measurements. We confirmed the following quite different roles of ZrC and ZrB2 in MgB2. ZrC doping was found to decrease the transport critical current density （Jc） at 4.2 K, while the critical temperature （To） kept constant. In contrast, the Jc values in magnetic fields were enhanced greatly by the ZrB2 addition, which resulted in a decrease in Tc by only 0.5 K. The reason for different effects of two dopants is also discussed.