Neutron-diffraction study of zinc-nickel ferrite powders prepared by combustion synthesis

The NixZn1-xFe2O4 ferrites were prepared with different powder sizes of Fe, NiO, ZnO and Fe2O3 by self-propagating high-temperature synthesis at the O-2 partial pressures of 2.6 and 5.0 MPa. The analysis of neutron-diffraction patterns revealed that the final stoichiometries of the ferrites were Ni0.40Zn0.60Fe2O4 and Ni0.38Zn0.62Fe2O4, respectively. The lattice parameter of the Ni0.40Zn0.60Fe2O4 phase formed at 2.6 MPa of oxygen pressure was a = 0.84097 nm, whereas the lattice parameter of the Ni0.38Zn0.62Fe2O4 phase formed at 5.0 MPa of oxygen pressure was a = 0.84123 nm. The lattice parameter of the ferrite significantly depended on the initial ratio of ZnO/NiO powder sizes, which supports the assumption that the reaction mechanism involves the comparative reduction reactions of ZnO and NiO with Fe on the powder surface.