Structural investigations on epsilon-phase-type nitrides M3N1+x with M = Mn, Fe, Ni

We examined the ordering of N in hexagonal interstitial 'epsilon-type' nitr ides M3N1+x with M = Mn, Fe, Ni as a function of temperature by neutron pow der diffraction. Depending on the atomic number of the metal strongly diffe rent behaviour was observed: Mn3N1.17 shows an order-disorder transition at 550 K. Ni-3 N keeps its RT ordering up to its decomposition temperature ab out 600 K. epsilon-Fe3N, epsilon-Fe3N1.10 and epsilon-Fe3N1.22 show an inte rmediate behaviour, i.e. partial disorder with increasing temperature. Thes e observations are interpreted in terms of distances between interstitial N atoms and coordination numbers of M. (C) 2000 Elsevier Science B.V. AII ri ghts reserved.