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Synthesis and high-resolution study distinguishing between very similar interstitial iron nitride structures

2015; Taylor & Francis; Volume: 35; Issue: 1 Linguagem: Inglês

10.1080/08957959.2014.996561

1477-2299

George Serghiou, Gang Ji, N. Odling, H. J. Reichmann, D. J. Frost, Jonathan P. Wright,

Diamond and Carbon-based Materials Research

Angle-dispersive X-ray diffraction and microfluorescence together with precession electron diffraction (PED) and scanning electron microscopy measurements on iron nitride prepared at 15 GPa and 1800 K from iron and sodium azide starting materials reveal synthesis of both hexagonal P6322 and trigonal P312 Fe3N1+x modifications (a = 4.745 (1) Å, c = 4.403 (1) Å, Z = 2). Nitrogen access to vacant interstitial sites, repulsions between nitrogen ions and metal nitride thermal stability are the factors relating iron nitride-phase relations to those of other early (Hf, Zr, Ti)-N and late (Ni-N) transition metal nitrides subjected to similar pressure and temperature conditions. Here, Fe3N1+x can accommodate pressure and x variability by situating nitrogen in a broader range of interstitial crystallographic sites in the intimately related hexagonal and trigonal crystal structures.