Abstract. In this paper we report the effect of carbon doping on the structural and superconducting properties of MgB₂ using citric and oxalic acids as carbon sources. The bulk polycrystalline samples have been synthesized via a standard solid state reaction route with composition MgB₂+x wt% of citric and oxalic acids (x = 0, 5 and 10). The x-ray diffraction results reveal the formation of dominantly MgB₂ with only a small amount of impurity phase MgO and substitution of C at the B site of MgB₂ for both dopants. Improvements in the upper critical field (H_C2), irreversibility field (H_irr) and high field (>2.5 T) critical current density (J_C) have been observed on C doping in the samples. The correlations between superconducting properties and structural characteristics of the samples are described and discussed in this paper.

Print publication: Issue 12 (December 2009)
Received 2 July 2009, in final form 3 September 2009
Published 23 October 2009