Effects of Lithium and Oxygen Losses on Magnetic and Crystallographic Properties of Spinel Lithium Ferrite

The effects of sintering temperature and cooling rate on the magnetic and crystallographic properties of lithium ferrite were studied. The magnetic moments and lattice parameters increased with increasing sintering temperature; these increases result from correlated oxygen and lithium oxide losses. Either annealing at lower temperatures or slow cooling under O₂ causes reoxidation of the Fe²⁺ formed at higher temperatures with attendant decreases in moment and lattice parameter and gradual precipitation of α-Fe₂O₃ as a second phase. The products formed on rapid cooling are equivalent to solid solutions of spinel lithium ferrite with Fe₃O₄, and those formed on slow cooling, to solid solutions of lithium ferrite and γ-Fe₂O₃ with precipitation of α-Fe₂O₃. Lithium losses and α-Fe₂O₃ precipitate amounts are calculated. The magnetic moment of stoichiometric lithium ferrite at 25°C is 3736±20 G; the lattice parameter at 28°C is 8.3296±0.0005 Å.