MAGNETIC AND TRANSPORT PROPERTIES OF NANOCRYSTALLINE TITANIUM CARBIDE IN CARBON MATRIX

Samples of titanium carbide (TiCx) in a carbon matrix have been prepared by the nonhydrolytic sol-gel process. The nanocomposite powder samples containing one the TiCx of average size ca. 30 nm encapsulated in carbon cages of 3 wt.% and other the TiCx in carbon matrix (ca. 10 wt.%) have been obtained. The temperature dependence of the EPR spectra of titanium carbide has shown coexistence of two different paramagnetic centers, one arising from conducting electrons and the other from trivalent titanium ion complexes. Comparison with a, similar titanium nitride (TiNx) is made, where no EPR spectra of trivalent titanium ions exist. The titanium nitride has shown only the EPR spectra arising from magnetic localized centers and not from trivalent titanium ion complexes. The magnetic ordering and superconducting states are observed in titanium carbide in the low temperature region, while in titanium nitride only the later state is recorded. The titanium nitride is a good conducting material while the titanium carbide shows an extraordinary behaviour, especially in the higher temperature region where a sharp jump in conductivity is recorded about 250 K. It is suggested that the disorder-order processes are more intense in the nonstoichiometric titanium carbide.