High critical current density in Ti-doped MgB2/Ta/Cu tape by powder-in-tube process

Ti-doped MgB2/Cu tapes with Ta as a buffer layer were prepared through the in situ powder in tube method by using Mg, Ti, and B powders. The phase compositions, microstructure features, and superconducting properties were investigated by x-ray diffraction, scanning electron microscope, and superconducting quantum interference device magnetometer. It is found that TiB2 phase was formed in Ti-doped MgB2 tape. Magnetization measurement results show that the critical transition temperature of MgB2/Ta/Cu tape with Ti doping is around 38 K. The irreversibility field H-irr and critical current density J(c) can be greatly enhanced by Ti doping. H-irr of the Mg0.9Ti0.1B2 tape is as high as 7.4 T at 10 K. The high critical current density J(c) of 1.5x10(6) A/cm(2) (10 K, self field) and 9.3x10(5) A/cm(2) (20 K, self field) are obtained in the Mg0.9Ti0.1B2 tape. In addition, a suitable amount of Ti doping can lead to a high density and fine grain size of MgB2, which may be the reason for high J(c) in Ti-doped MgB2 tapes. (C) 2002 American Institute of Physics.