10 - Interstitial Nitrides: Structure and Composition

Abstract

This chapter provides a review of the structural characteristics, structure, and composition of the interstitial nitrides. The interstitial nitrides, titanium nitride in particular, are major industrial materials. Interstitial nitrides are crystalline compounds of a host metal and nitrogen where the nitrogen atom occupies specific interstitial sites in the metal structure, which is generally close packed. This places a lower limit on the size of the metal atom for the nitrogen atom to fit in the available sites of the metal structure. Interstitial nitrides are similar to interstitial carbides in structure and composition and the two groups of materials closely resemble each other. The nitrides however are not as refractory as carbides. The interstitial nitrides are susceptible to the presence of even minute amounts of impurities, particularly oxygen, which tend to distort the structure. Like the carbides, the interstitial nitrides allow nonmetal vacancies (i.e., nitrogen) in the lattice, but unlike the carbides they also tolerate metal-atom vacancies.