Optimization of synthesis of nickel-zinc-ferrite from oxalates and oxalato hydrazinate precursors

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Abstract

Ferrites, Ni x Zn1−x Fe2O4 are being synthesised by five different methods, namely (a) autocatalytic decomposition and air sintering of mixed-metal oxalato hydrazinate prepared by a solution method, (b) decomposition of oxalato hydrazinate precursors prepared by the under hydrazine method and sintering in air, (c) decomposition of mixed metal oxalates prepared by coprecipitation method in air and sintering in air, and (d) decomposing the oxalates in a controlled atmosphere (N2 + H2O + air) and sintering in (i) air and (ii) an N2 atmosphere. The decomposition of the precursors and formation of ferrite was studied by differential thermal analysis (DTA), total weight loss studies, infrared, chemical analysis, and X-ray diffraction (XRD). The saturation magnetization values of all the decomposed products and at various stages of sintering were measured. TheX-T curves were plotted to find out the Curie temperature of the sintered ferrites and the shape of these curves was compared. The saturation magnetization was plotted against the concentration of solid solution of nickel ferrite with zinc addition. If γ-Fe2O3 is taken as one of the constituents in synthesis of ferrite, the spinelization is easy, it is obsesrved in our studies that γ-Fe2O3 type phase is formedin situ in methods (a), (b) and (d). Among all five methods, method (b) is the easiest.