Phase Transition Temperature of γ-Fe_2O_3 Ultrafine Particle(Cross-disciplinary Physics and Related Areas of Science and Technology)

概要

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The iron oxide ultrafine particles prepared by the gas evaporation method, in which commercial α-Fe_2O_3 powder is evaporated, are composed of α-Fe_2O_3 particles covered with a γ-Fe_2O_3 mantle layer. To study the phase transition temperature of the γ-Fe_2O_3 mantle layer, the particles were heated and observed in a transmission electron microscope. The present specimen of γ-Fe_2O_3 transformed completely to α-Fe_2O_3 at above 700℃, and this phase transition was irreversible. The phase transition temperature was 1.4 times higher than the bulk value. The growth mechanism of the present specimen of α-Fe_2O_3 particles covered with the γ-Fe_2O_3 mantle layer has been discussed in terms of the difference in the cooling rates between the inside and the surface of the particle at around the evaporation source.
社団法人日本物理学会の論文
2004-07-15