EFFECT OF LITHIUM ON THERMAL STABILITY OF NANO-SIZED NON-STOICHIOMETERIC MAGNESIUM ALUMINATE SPINEL

The use of LiF as a sintering additive for fabrication of transparent polycrystalline magnesium aluminate spinel has been widely discussed in the literature. In the present talk the thermal stability of Li-doped non-stoichiometric nano-sized magnesium aluminate spinel, synthesized using a combustion synthesis method was studied using XRD, FTIR, SEM and high temperature differential scanning calorimetry (DSC). It was found that the Li content within the magnesium aluminate spinel is a function of the crystallite size and stoichiometry. Moreover, the limited homogeneity range between LiAl₅O₈ and MgO·nAl₂O₃ spinel (n is the ratio between Al₂O₃ and MgO) found to increase with the reduction in crystallite size. Structural analysis using FTIR spectroscopy indicated that as-synthesized materials were heavily disordered. The effect of the Li on the surface and interfacial enthalpy and coarsening path will be discussed.