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 650–1,050°C for 60 min and 950°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 950°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 950°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 950°C for 60 min. The J c and T c offset values of the sample annealed at 950°C for 60 min were found to be 260.43 A/cm2 at 20 and 38.1 K, respectively.
KeywordsCritical Current Density Increase Annealing Temperature Physical Property Measurement System Increase Annealing Time Room Temperature Resistivity
This work is financially supported by the National Boron Research Institute (BOREN) (Project no: 2006-22-Ç21-15) and partly by the Scientific and Technological Research Council of Turkey (TUBITAK) (Project no: 108M201), and partly by the Turkish State Planning Organization (DPT) (Project no: 2004K120200).
- 6.M.J. Qin, X.L. Wang, S. Soltanian, Li AH, H.K. Liu, S.X. Dou, Phys. Rev. B 64, 060505(R) (2001)Google Scholar
- 20.S.M. Hwang, J.H. Choi, C.M. Lee, E.C. Park, J.H. Lim, J. Joo, W.N. Kang, C.-J. Kim, IEEE Trans. Appl. Supercond 19, 3 (2009)Google Scholar
- 30.B.D. Cullity, Element of X-ray Diffraction (Addition-Wesley, Reading, MA, 1978)Google Scholar