Formation of α-Fe2O3 particles in aqueous medium and their properties

• Published in: Materials letters 1997-10, Vol.32 (5-6), p.301-305
• Main Authors: MUSIC, S, CZAKO-NAGY, I, SALAJ-OBELIC, I, LJUBESIC, N
• Format: Article
• Language: English
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Exact sciences and technology; Fine-particle systems; Magnetic properties and materials; Physics; Small particles and nanoscale materials; Studies of specific magnetic materials
• ISSN: 0167-577X; 1873-4979
• DOI: 10.1016/S0167-577X(97)00051-7

The formation of alpha-Fe2O3 particles by forced hydrolysis of partially neutralised FeCl3 solutions with tetramethylammonium hydroxide (TMAH) was investigated. The effect of full neutralisation of FeCl3 solution with TMAH on the phase composition of the precipitate was also monitored. At low pH values the hydrolytical product was beta-FeOOH which transformed to alpha-Fe2O3. The shape of the FT-IR spectrum of alpha-Fe2O3 depended on the size and morphology of the particles. The presence of polycrystalline particles, consisting of much smaller oriented alpha-Fe2O3 crystallites, was considered. The surface magnetism and magnetic coupling between these crystallites was supposed to be responsible for the inner broadening of the Mossbauer spectroscopic lines. In alkaline medium (pH about 11), a mixture of alpha-FeOOH and alpha-Fe2O3 was obtained. Alpha-FeOOH and alpha-Fe2O3 obtained at high pH showed pronounced intraparticle porosity. 21 refs.