The effects of annealing temperature on the in-field J c and surface pinning in silicone oil doped MgB 2 bulks and wires

The effects of sintering temperature on the lattice parameters, full width at half maximum (FWHM), strain, critical temperature (T-c), critical current density (J(c)), irreversibility field (H-irr), upper critical field (H-c2), and resistivity (rho) 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 angstrom to 3.0745 angstrom, 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 degrees C shows more lattice distortion by more C-substitution and higher strain, lower T-c, higher impurity scattering, and enhancement of both magnetic J(c) and H-c2, compared to those sintered samples at high temperatures. The flux pinning mechanism has been analyzed based on the extended normalized pinning force density f(p) = F-p/F-p,F-max scaled with b = B/B-max. Results show that surface pinning is the dominant pinning mechanism for the doped sample sintered at the low temperature of 600 degrees C, while point pinning is dominant for the un-doped sample. The powder in tube (PIT) MgB2 wire was also fabricated by using of this liquid doping and found that both transport J(c) and n-factor increased which proves this cheap and abundant silicone oil doping can be a good candidate for industrial application. (C) 2012 Elsevier Ltd. All rights reserved.