Effect of Sintering Temperature on the Superconducting Properties of MgB₂ Superconductor Co-Added with a High Concentration of Si and C

Publisher： Trans Tech Publications

E-ISSN： 1662-8985|2015|1107|589-594

ISSN： 1022-6680

Source： Advanced Materials Research, Vol.2015, Iss.1107, 2015-07, pp. : 589-594

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Abstract

In this study, as much as 10 and 15 wt.% nanosized silicon and carbon (Si+C) were reacted with (Mg+2B) at 650°C and 850°C, respectively, for 1 hour. The phase formation, surface morphology and superconducting properties of these samples were evaluated. The relative peak intensity as calculated from the XRD patterns indicates the formation of large Mg₂Si volume fraction at low sintering temperature. MgB₄ phase was detected in the samples sintered at high temperature as a result of Mg deficiency. The C substitution level as estimated from the lattice parameters, was shown to increase in the samples reacted with a higher amount of (Si+C) at high temperature. Scanning electron micrograph showed that (Si+C) co-addition had refined the grain size and improved the grain coupling of MgB₂. The superconducting transition temperature was found to decrease with increasing addition level. The superconducting transition width was also broadened because of a large volume fraction of secondary phases. The improved field dependent critical current density at both 5 K and 20 K is accounted to enhanced scattering by C substitution and grain boundary pinning.