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

Abstract The effect of the cooling procedure on the lattice parameters of hexagonal e-iron nitride powders, after equilibration at elevated temperature, was studied: e-Fe 3 N 1 + 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 Fe 3 N 1.00 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.