Abstract
Highly coercive magnetic powder was obtained by growing cobalt ferrite on the surface of γ-Fe 2O 3 particles in highly alkaline suspensions containing cobalt and ferrous ions in a Co/Fe molar ratio = 1 2 . The mechanism of the growth and the structure of cobalt ferrite on γ-Fe 2O 3 were studied by X-ray diffraction and electron diffraction techniques. Results show that crystals of cobalt ferrite CoFe 2O 4 with a spinel type crystal structure of lattice constant 8.415 Å grew epitaxially on γ-Fe 2O 3. The acicular direction of the epitaxially grown Co-γ-Fe 2O 3 as well as γ-Fe 2O 3 was in the [ 1 01] direction. It was found that from the lattice constant value and the half width of X-ray diffraction peaks, the lattice constant epitaxially grown Co γ-Fe 2O 3 may be attributed to two kinds of crystals, viz., seed γ-Fe 2O 3 ( a = 8.35 ∼ 8.37 A ̊ ) which was partly reduced to Fe 3O 4, and surface layer CoFe 2O 4 ( a = 8.415 A ̊ ). The crystal growth in the interface between the seed crystals and the growth layer was affected by the crystal structure of the seed crystals. The lattice constant of CoFe 2O 4 which was located in the vicinity of the interface was almost equal to that of the seed crystals.
Published Version
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