Aluminium Substituted Magnetite by Wet Method

Abstract
Aluminium substituted magnetite particles with Al³⁺ content in the range from 0.7 to 4.0wt% were synthesized by the hydrothermal oxidation reaction. It was found that the mixing procedure was critical to prepare single-phase ferrite particles : it was required that Al ions were neutralized before the precipitation of Fe ions. As the aluminium content increases, the magnetization of the obtained particles decreased in the range from 86 to 60emu/g. The lattice constant also decreased from 0.840 to 0.836nm. XPS analysis indicated that aluminium in the obtained particles was both in hydroxide and oxide states, and that the molar fraction of them was approximately 20% and 80%, respectively. The lattice constant was in good agreement with the calculated value using the Vegard's law in Fe₃O₄- γ-Fe₂O₃-FeAl₂O₄ solid solution and taking into account of the existence of aluininium hydroxide.