The effects of various impurity additions have been investigated for MgB2 tapes fabricated by the in-situ process of the powder-in-tube method. As impurities, we tried SiO2, SiC and ZrB2. These powders were added to powder mixtures of Mg and B and MgH2 and B. The powder mixtures were then stuffed into Fe tubes and cold worked into tapes using a combination of grove rolling and flat rolling. Heat treatment was performed at the relatively lower temperature of 600 °C for 1 h with argon flowing and in an Ar gas atmosphere in a closed chamber after evacuating up to 10−5 Torr. From the XRD observation of each tape, Mg2Si was formed for tapes to which SiO2 and SiC were added. ZrB2 did not react with Mg and B. We obtained JC enhancements for all of the additives in the Mg + B in-situ processed tapes. Much higher JC values were obtained using the MgH2+B powder. A high JC value of 1.6 x 104 A/cm2 at 4.2 K and 10 T was obtained for the MgH2+B powder mixture to which 10 at%SiC was added. JC values in the high magnetic fields were increased, while the JC values in the low magnetic fields were decreased by the addition of SiC. The irreversibility field of MgB2 tape was enhanced from 17 T to 23 T by the addition of SiC. However, at low fields of ∼4T, the JC enhancement resulting from the addition of SiC seemed to be very small. The highest JC value, 2.1 x 104 A/cm2 at 10 T, was achieved with the 5at% SiC-doped tape heated in an atmosphere with very small oxygen impurity.
