Effect of the Red / Ox ratio on the structure and magnetic behavior of Li0.5Fe2.5O4 nanocrystals synthesized by solution combustion approach

In this research, nanocrystalline lithium ferrite (Li0.5Fe2.5O4) was synthesized using the solution combustion approach with using glycine as fuel and a chelating agent at various Red / Ox ratios (“glycine to nitrate” ratio G / N = 0.4, 0.6, 0.8, 1.0). According to the data of energy-dispersive X-ray spectroscopy (EDX) and atomic absorption spectroscopy (AAS), the prepared samples correspond in their composition to stoichiometric ferrite Li0.5Fe2.5O4 within the error of the determination methods used. The results of powder X-ray diffractometry (PXRD) confirmed the formation of α-Li0.5Fe2.5O4 at G / N ratio of 0.8 and 1.0 and the presence of β-Li0.5Fe2.5O4 modification in case of deficiency (G / N = 0.4) and stoichiometry (G / N = 0.6) of the chelating agent. It is shown that a change in the Red / Ox composition of reacting solutions affects not only the phase composition of the synthesized lithium ferrite samples, but also the crystallite size, which lies in the range from 22 to 35 nm. Based on the scanning electron microscopy (SEM) data, it was found that Li0.5Fe2.5O4 powders had a developed porous microstructure consisting of micron agglomerates. According to the vibration magnetometry data of nanocrystalline lithium ferrite powders, it follows that all synthesized compositions have a pronounced ferrimagnetic behavior, despite the presence of β-modification in some of them. It is shown that by varying the Red / Ox environment and, as a consequence, the phase composition and crystallite size, it is possible to obtain Li0.5Fe2.5O4 nanocrystals with magnetic parameters in the following ranges: saturation magnetization (Ms) = 51.6 – 61.9 emu / g, residual magnetization (Mr) = 14.3 –17.8 emu / g, coercive force (Hc) =109 –135 Oe.