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

In this study, the pinning behaviour of carbon black reinforced MgB2 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 MgB2 are enhanced by chemical doping. Carboncontaining additives replace boron in the MgB2 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 MgB2-xCx (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 (Tc) of the MgB2 superconductor. In this study, the critical temperatures of superconductors decreased with carbon black reinforcement. The critical current densities (Jc) 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 (Hirr) and pinning force (Fp). It was concluded that the carbon black used as a reinforcement element did not act as a pinning centre.