Fabrication and magnetoresistivit of ex-situ processed MgB2/Fe monofilament tapes without any intermediate annealing

We have fabricated MgB2/Fe monofilament wires and tapes by a powder-in tube (PIT) technique, using an ex-situ process without any intermediate annealing. MgB2/Fe monofilament tapes were annealed at 650-1,050A degrees C for 60 min and 950A degrees C for 30-240 min. We have investigated the effect of annealing temperatures and times on the formation of MgB2 phase, activation energy, temperature dependence of irreversibility field H (irr)(T) and upper critical field H (c2)(T), transition temperature (T (c)), lattice parameters (a and c), full width at half maximum, crystallinity, resistivity, residual resistivity ratio, active cross-sectional area fraction and critical current densities. We observed that the activation energies of the MgB2/Fe monofilament samples increased with increasing annealing temperature up to 950A degrees C and with increasing annealing time up to 60 min while it decreased with increasing magnetic field. For the MgB2/Fe monofilament tape, the slope of the H (c2)-T and H (irr)-T curves decreased with increasing annealing temperature from 850 to 950A degrees C as well as with increasing annealing time from 30 to 60 min. The transport and microstructure investigations show that T (c), J (c) and microstructure properties are remarkably enhanced with increasing annealing temperature. The highest value of critical current density is obtained for the sample annealed at 950A degrees C for 60 min. The J (c) and T (c) (offset) values of the sample annealed at 950A degrees C for 60 min were found to be 260.43 A/cm(2) at 20 and 38.1 K, respectively.