Thermal Evolution of Magnesium Aluminate Spinel Nanoparticles Prepared By Coprecipitation Technique

MgAl2O4 spinel nanoparticles were prepared by coprecipitation method and followed by thermal heating at temperatures 550°C, 700°C, 850°C and 1000°C for 4 hours, in air. The samples were structurally characterized by TGA-TGT, XRD, FTIR and SEM with EDS. The effects of heat treatment on the structural properties of MgAl2O4 nanoparticles were investigated. The double hydroxide of magnesium and aluminium powders transformed from the amorphous phase, via intermediate cubic oxide (γ-Al2O4, a rock salt type structure) disordered phase, into face-centred cubic MgAl2O4 spinel nanoparticles. In a low calcination temperature range 700-850°C for 4h, MgAl2O4 face-centred cubic disordered spinel nanoparticles with grain size ~ 6 nm is obtained. At 1000°C (4h), disorder-order phase transformation results in a sudden increase in the lattice increased constant. Single phase MgAl2O4 cubic ordered-spinel nanoparticles (grain size ~ 12 nm) with a good chemical homogeneity, narrow particle size distribution are obtained. It is also shown that heat treatment enhances the crystallinity and transmission of the spinel; and also controls dislocation density and amount of stress at the surface and hence yields the strength of the material. Results of FTIR and SEM support XRD studies. The realization of temperature dependent structural properties makes the applicability of the MgAl2O4 nanocrystalline powders more versatile.