Nickel zinc ferrites prepared by the citrate precursor method

Ni1-xZnxFe2O4 (X = 0.2, 0.4, 0.5, 0.6 and 0.7) were prepared by a combustion method. The precursors for the solids were different gels obtained from metal nitrates and citric acid by a sol-process. The gels thus obtained were heated at 200degreesC and they exhibited self-propagating combustion behavior. The residues were heated for 2h at 1000degreesC. XRD analysis of the intermediates and final solids revealed that, after combustion, the gel is directly transformed into single-phased, nano-sized Ni,Zn ferrite particles. The sintering processes increased the crystallinity of the solids and the domain sizes. Lattice parameters also increase with the increment of x. The insertion of small amounts of different R(111) cations (R = Ruthenium, Yttrium and rare-earth cations) into a nickel zinc ferrite (Ni0.5Zn0.5Fe2O4) has been also investigated. XRD studies have been carried out in order to determine if the R(111) cations enter the spinel structure. Samples with several Ni0.5Zn0.5Fe2-yR(y)O(4) compositions were prepared by the auto-combustion method. In all cases, XRD measurements show distortions in the spinel cell and, in some cases, the formation of various rare earth iron oxides. (C) 2002 Elsevier Science B.V. All rights reserved.