Development of low frequency ferrite core materials using magnetite, a beach sand mineral

Abstract

Low frequency ferrite core materials of iron deficient Ni-Zn ferrites and iron excess Mn-Zn ferrites have been developed using cheap beach sand mineral magnetite (Fe3O4) as the basic ingredient as well as with the addition of low melting CuO, V2O5, Eu2O3 and In2O3 from the following compositions: (i) Ni0.65Zn0.35Fe1.96O4+x[CuO, V2O5, Eu2O3, In2O3] (ii) Mn0.451Zn0.484Fe2.065O4+x[CuO, V2O5, Eu2O3, In2O3] A series of polycrystalline samples of mixed ferrites were prepared by standard ceramic method for systematic investigation of their physical, magnetic and electrical properties. Single phase cubic spinel structure of the prepared core materials has been confirmed by X-ray diffraction analysis. Physical properties such as; sintered density, lattice constant and microstructural properties of the materials have been measured. The magnetic and electrical properties of the core materials have been investigated by studying saturation magnetization, Curie temperature, initial magnetic permeability, normalized loss factor, dc resistivity and eddy current loss. The addition of divalent V2O5 (melting point 700°C) and CuO (melting point (1026°C-1235°C) in the composition of iron deficient Ni-Zn ferrite enhances the chemical reactivity of the resulting mixture, facilitates the attainment of high degree of uniformity in the sintered body, increases the anion vacancy concentration and prohibit discontinuous grain growth which in turn enhances the density of the core materials. The lattice constant values of the ferrite system remain almost unaffected with the addition of V2O5 and CuO. The saturation magnetization, Curie temperature and initial magnetic permeability are enhanced appreciably with the addition of these two oxides. The minimum value of normalized loss factor, maximum value of dc resistivity and minimum value of eddy current loss are achieved for core samples containing 0.4 mol% and 1 mol% of V2O5 content respectively. For CuO addition, the minimum value of normalized loss factor, maximum value of dc resistivity and minimum value of eddy current loss are achieved for core samples containing 2 mol% of CuO content. The addition of trivalent In2O3 (melting point 680°C) and Eu2O3 (melting point 623°C) in the composition of iron deficient Ni-Zn ferrite enhances the chemical reactivity of the resulting mixture, forms liquid phase on the grain surface of the ferrite and facilitates the attainment of high degree of uniformity in the sintered body which eventually promotes densification. The lattice constant values of the ferrite system increase almost linearly with the addition of these two oxides. The saturation magnetization, Curie temperature and initial magnetic permeability of the ferrite system decrease with the addition of In2O3. Whereas, all these parameters of the ferrite system increase markably with the addition of Eu2O3. However, the minimum value of normalized loss factor, the maximum value of dc resistivity and minimum value of eddy current loss of the ferrite system are achieved for core samples containing 3.5 mol% of In2O3 and 2 mol% of Eu2O3 respectively. The addition of CuO and V2O5 in the composition of iron excess Mn-Zn ferrite enhances the density, however the lattice constant values of the ferrite system remain almost unaffected. The saturation magnetization of the ferrite system increases appreciably, whereas the Curie temperature decreases a little with the addition of CuO. The saturation magnetization and Curie temperature of the ferrite system increases markably with the addition of V2O5. However, the initial magnetic permeability of the ferrite system increases appreciably with the addition of CuO and V2O5. The minimum value of normalized loss factor, maximum value of dc resistivity and minimum value of eddy current loss are achieved for core samples containing 4 mol% of CuO. For V2O5 addition, the minimum value of normalized loss factor, maximum value of dc resistivity and minimum value of eddy current loss can be attained for core samples containing 0.6 mol% and 1 mol% of V2O5 content respectively. The addition of Eu2O3 and In2O3 in the composition of iron excess Mn-Zn ferrite enhances the density as well as the lattice constant values of the ferrite system. The saturation magnetization and initial magnetic permeability of the ferrite system increases markably with the addition of these two oxides. There is no noticeable influence of Eu2O3 on the Curie temperature of the ferrite system. Whereas, the Curie temperature values of the ferrite system decrease with the increasing addition of In2O3.The minimum value of normalized loss factor, maximum value of dc resistivity and minimum value of eddy current loss can be achieved for core samples containing 2 mol% and 4 mol% of Eu2O3 content respectively. However the minimum value of normalized loss factor, maximum value of dc resistivitiy and minimum value of eddy current loss can be achieved for core sample containing 3.5 mol% of In2O3 addition. The possible applications of developed ferrite core materials are also discussed.