On the Formation and Constitution of Nickel-Ferrite

Abstract

The authors have studied on the formation, constiution, magnetic properties, and microstructures of Ni-ferrite, and also prepared the single crystals of Ni-ferrite. The intimate mixtures of NiO and Fe₂O₃ powder of various molar ratio were used as raw materials. The samples were heated at various temperature and were investigated by X-ray and magnetic analyses. The main results obtained were as follows. 1) Ni-ferrite is formed from oxides mixture at above 675℃. 2) NiFe₂O₄ dissolves excess NiO and Fe₂O₃ at above 1250° and 1200℃ respectively. At 1300°, the single spinel phase is obtained in the range of Fe₂O₃ content of from 52% to 86.5% in weight. 3) Ni-ferrite which dissolves excess Fe₂O₃ precipitate free Fe₂O₃ by annealing at 700℃ for 3 hours. 4) Ni-ferrite is a ferromagnetic compound and the intensity of magnetization shows a sharp maximum at the 1-2 sample at above 1200℃. The magnetism of the samples containing excess Fe₂O₃ are weakend remarkably by annealing at above 500℃, and this phenomena seems to be connected with precipitation of excess Fe₂O₃. 5) The growth steps are recognized on the crystals which developes on the sintered surface of Ni-ferrite. 6) The lattice constant of Ni-ferrite is about 8.22~8.23Å, and Curie point is about 588℃. 7) Ni-ferrite single crystal forms regular octahedron.