It was recalled that ultra-fine carbide powders exhibited an appreciable electrical conductivity after annealing at between 1500 and 1800C. The cause of this phenomenon was considered with regard to delocalized paramagnetic centres. Structural evolution of nanomaterials during annealing was monitored by means of 29Si and 13C magic-angle spinning nuclear magnetic resonance. An analysis of the electron paramagnetic resonance spectrum revealed the coexistence of 2 paramagnetic centres (DI, DII) which were localized in crystal sites of the polytypes. Delocalized DIII paramagnetic species were partially created by the thermal conversion of DII defects, with energies that did not exceed 0.013eV. The spin susceptibility, as deduced from electron paramagnetic resonance measurements, was marked by delocalized paramagnetic species above 150K and by strongly correlated (DIII) unpaired spins at around 30K.

Investigation of the Paramagnetic Centres and Electronic Properties of Silicon Carbide Nanomaterials. S.Charpentier, A.Kassiba, J.Emery, M.Cauchetier: Journal of Physics - Condensed Matter, 1999, 11[25], 4887-97