Structure des Carbures de Niobium

The preparation of thin films of two niobium carbides, NbC and Nb2C, for electron diffraction studies has been accomplished by heating in vacuo double evaporated films (carbon+Nb). NbC is formed by a carburization process in high vacuum, whilst thin films of Nb2C are produced by decomposition of NbC in air at reduced pressure (10-2∼10-3 Torr) by the reaction 2 NbC+O2 → Nb2C+CO2. The crystal structure of NbC is based on the f.c.c. lattice of Nb atoms and the carbon atoms occupy interstitial positions in a statistical manner. Nb2C, however, shows a hexagonal superlattice structure of the same type as that of ε-phase of Fe2N.