Preparation of Co-containing γ-Fe₂O₃ by Solid State Reaction

Abstract

Co-containing γ-Fe₂O₃ is not prepared by solid state reaction of γ-Fe₂O₃ and CoO at high temperature but is prepared by wet method, because γ-Fe₂O₃ transforms into α-Fe₂O₃ above 400-500°C. However, γ-Fe₂O₃ is stabilized by the addition of potassium. To be reported here is a finding that the solid state reaction of acicular γ-Fe₂O₃ and Co(NO₃)₂⋅6H₂O can be accomplished by the addition of K₂CO₃. When a mixture of γ-Fe₂O₃:Co(NO₃)₂⋅6H₂O:K₂CO₃=5:1:0.2(molar ratio)was heated at 500-600°C, the coercivity of the product was above 1000 Oe. In addition, the magnetic property was also improved in the squareness ratio compared with the original γ-Fe₂O₃. The particle morphology of the obtained Co-containing γ-Fe₂O₃ was maintained acicular even after the heat treatment.