The effects of annealing temperature on the in-field Jc and surface pinning in silicone oil doped MgB2 bulks and wires

The effects of sintering temperature on the lattice parameters, full width at half maximum (FWHM), strain, critical temperature (Tc), critical current density (Jc), irreversibility field (Hirr), upper critical field (Hc2), and resistivity (ρ) of 10 wt % silicone oil doped MgB2 bulk and wire samples are investigated in state of the art by this article. The a-lattice parameter of the silicone oil doped samples which were sintered at different temperatures was drastically reduced from 3.0864 Å to 3.0745 Å, compared to the un-doped samples, which indicates the substitution of the carbon (C) into the boron sites. It was found that sintered samples at the low temperature of 600 oC shows more enhancement in lattice distortion, more C-substitution, lower Tc, larger lattice strain, higher impurity scattering, and much more enhancement in both Jc and Hc2, compared to those sintered samples at high temperatures. The flux pinning mechanism has been analyzed based on the extended normalized pinning force density fp = Fp/Fp,max scaled with b = B/Bmax. Results show that surface pinning is the dominant pinning mechanism for the doped sample sintered at the low temperature of 600 oC, while point pinning is dominant for the un-doped sample. The MgB2 wire was also fabricated by using of this cheap doping and found that both Jc and n-factor increased which proves this silicone oil doping can be a good candidate for industrial application.