Characterization of Spinel-Structured Iron Oxide Nanoparticles Synthesized by Heating of α-FeOOH Platelets in Tetra-Ethylene Glycol

Abstract

Fe₃O₄ particles were synthesized from platelet α-FeOOH particles by a liquid-phase reduction process using tetra-ethylene glycol as reduction agent, for their application in hyperthermia or thermoablation therapies that employ hysteresis-loss heating. Fe₃O₄ particles 60–100 nm in size were finally obtained by heating. The saturation magnetization of the obtained particles increased with the heating time to reach a maximum value of approximately 80 Am²/kg. In contrast, the coercive force of the particles was nearly constant at approximately 12–13 kA/m and was independent of the heating time. Lattice image observation of the synthesized Fe₃O₄ particles revealed to obtain single crystals. On the basis of experimental results, it was concluded that the single-crystal Fe₃O₄ particles were formed by recrystallization through the dissolution and precipitation of iron ions from α-Fe₂O₃ formed by the dehydration of α-FeOOH. The recrystallization of the Fe₃O₄ particles was promoted with increasing α-FeOOH particle content in tetra-ethylene glycol up to about 0.022 g/mL.