Structure and superconductivity of Mg(B1-xCx)(2) compounds

In this paper, we report on the structural properties and superconductivity of Mg(B1-xCx)(2) compounds. Powder X-ray diffraction results indicate that the samples crystallize in a hexagonal AlB2-type structure. Due to the che mical activity of Mg powders, a small amount of MgO impurity phase is detec ted by X-ray diffraction. The lattice parameters decrease slightly with the increasing carbon content. Magnetization measurements indicate that the no n-stoichiometry of MgB2 has no influence on the superconducting transition temperature and the transition temperature width. The addition of carbon re sults in a decrease of T-c and an increase of the superconducting transitio n width, implying the loss of superconductivity.