Fe3O4 was prepared on the TiO2-coated natural mica substrate. The natural mica has an average particle size of 22 ㎛. The substrate was coated on TiO2 thin films using hydrothermal synthesis at pH 1.5-2.5 at 75℃. The Fe precursor solution was prepared by mixing FeSO4 (for Fe2+ ion) and FeCl3 (for Fe3+ ions) with different molar ratios such as 1/2, 1/1, 2/1, 3/0, and Fe3O4 only. X-ray diffraction analysis shows that the crystal structure depends on the FeCl3-to-FeSO4 molar ratio. Fe3O4 crystal phase could be obtained at higher FeSO4 contents.
