The lattice parameters of ε-iron nitrides:: lattice strains due to a varying degree of nitrogen ordering

The effect of the cooling procedure on the lattice parameters of hexagonal F-iron nitride powders, after equilibration at elevated temperature, was studied: epsilon-Fe3N1 (+) (x), with x = 0.00, 0.10, 0.22 and 0.33, was annealed at 573 K and, subsequently, either quenched or slowly cooled. X-ray diffraction measurements showed for x = 0.00 and 0.10 significantly higher axial ratios c/a after quenching than after slow cooling. For x = 0.22 and 0.33 this effect was virtually absent. By means of neutron diffraction analysis applied to slowly cooled and quenched Fe3N1.00 it was shown that quenching, as compared to slow cooling, is associated with a higher (retained) disorder of the superstructure of nitrogen and a slightly smaller magnetic moment of iron. Both for slowly cooled and quenched samples new relations between the lattice parameters and the nitrogen content are given. (C) 2003 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.