Intralayer carbon substitution in the MgB2 superconductor - art. no. 134513

We report that the ternary MgB2-xCx compounds adopt an isostructural AlB2-t ype hexagonal structure in a relatively small range of nominal carbon conce ntration, x<0.1. The lattice parameter a decreases almost linearly with inc reasing carbon content x, while the c parameter remains unchanged, indicati ng that carbon is exclusively substituted in the boron honeycomb layer with out affecting the interlayer interactions. The superconducting transition t emperature T-c decreases quasilinearly as a function of the carbon concentr ation. with a slope steeper than that for the isoelectronic Mg1-xAlxB2.