Pinning behaviour of carbon black reinforced MgB2 superconductor fabricated by field assisted sintering technique.

In this study, the pinning behaviour of carbon black reinforced MgB 2 bulk superconductors produced by in-situ field assisted sintering technique (FAST), also called spark plasma sintering (SPS) technique, was investigated. It is well known that the superconducting parameters of MgB 2 are enhanced by chemical doping. Carbon-containing additives replace boron in the MgB 2 crystal structure, creating pinning centres and increasing both the upper critical field and the critical current density. For this purpose, a series of polycrystalline samples with chemical composition MgB 2-x C x (x = 0, 0.1, 0.2, 0.3 and 0.4) were prepared. The density of the samples was determined by the Archimedes principle and it was found that the relative density decreased with increasing carbon content. It is well known that carbon-containing additives suppress the transition or critical temperature (T c) of the MgB 2 superconductor. In this study, the critical temperatures of superconductors decreased with carbon black reinforcement. The critical current densities (J c) of the samples were determined from the width of the hysteresis curves by using the Bean critical model, and it was determined that the critical current densities deteriorated with this reinforcement. This degradation in critical current densities was accompanied by a reduction in the irreversibility field (H irr) and pinning force (F p). It was concluded that the carbon black used as a reinforcement element did not act as a pinning centre. • Carbon black reinforced MgB 2 superconductor can be sintered with SPS at lower temperature and in a shorter time. • Carbon black reinforced MgB 2 superconductors were produced for the first time with the in-situ spark plasma technique. • It has been observed that the materials produced with SPS exhibit a highly porous structure. • The grain boundary density decreased, which led to the deterioration of critical parameters of MgB 2 such as T c , J c , F p , H irr etc. [ABSTRACT FROM AUTHOR]