Formation of nanosize Li-ferrites from acetylacetonato complexes and their crystal structure, microstructure and order–disorder phase transition.

Nanosize Li-ferrites were synthesised by the thermal decomposition of an appropriate mixture of complex compounds with acetylacetone - (2,4 pentadione) ligands ([M(AA)_x]; M=Li and Fe) at 500 °C. The obtained sample is composed of three phases determined by the standard Rietveld procedure: Li_0.5Fe_2.5O₄ (S.G. P4₃32), Li_1.16Fe₃O₄ (S.G. Fd 3̄ m) and LiFeO₂ (S.G. Fm 3̄ m). Cation distribution in nanosize ordered spinel Li_0.5Fe_2.5O₄ deviates from that of the bulk counterpart. Microstructure parameters (crystallite size of ∼23 nm and strain of 3.2526(9)×10³) were determined by the Rietveld refinement of the TCH-pV parameters. SEM microphotographs show a particle size of ∼50–60 nm. An order–disorder phase transition in ordered spinel Li_0.5Fe_2.5O₄was studied by DSC measurements and in situ XRPD technique.The temperature of phase transition was found to be 762 °C (DSC) and (±) 7455°C.(XRPD) [ABSTRACT FROM AUTHOR]