Preparation of a γ-Alumina Film Doped with Fine γ-Iron(III) Oxide Particles

A poly(vinyl alcohol)−alumina hydrate composite film prepared by using a sol−gel process was transparent in the visible region. The composite film was insoluble in water after being heated at about 100 °C but exhibited hydrophilicity. These characteristics are suitable for the deposition of Fe 2 O 3 · n H 2 O in the film by a counter diffusion method. By heating at 600 °C in air, this deposited film was transformed to a γ-Fe 2 O 3 -doped γ-Al 2 O 3 film. No absorption peaks were observed in the visible region at a wavelength of >550 nm. The crystallite size could be controlled in the range 3−8 nm by changing the counter diffusion time. Due to the orientation of the alumina hydrate matrix, the γ-Fe 2 O 3 -doped film was more easily magnetized in the direction parallel to the film plane than to the perpendicular.