Investigation of lattice constant, sintering and properties of nano Mg–Al spinels

Mg–Al spinel powders with a molar ratios (Al2O3/MgO) of 1.0, 1.1, 1.2, 1.3 and 1.4 were prepared by co-melting method from the corresponding magnesium and aluminum nitrate to investigate the lattice parameter, and properties of the obtained powders. XRD, TGA, TEM, and IR were used to investigate the prepared powders. Another series of stoichiometric Mg–Al spinel (molar ratio 1.0) with addition 0.5, 1.0 and 2.0 wt.% of Fe2O3 as a sintering aid were prepared by the same method. Effect of sintering temperature up to 1650 °C on the densification and properties of the sintered bodies were studied. sults revealed that, well crystalline Mg–Al spinel were obtained after calcination at 1000 °C. Their crystallinity decrease with the higher alumina content than the amount required to form stoichiometric spinel due to the decrease of lattice parameter and grain sizes. The obtained crystal size was between 12 and 59 nm and particle size around 10–60 nm. Infrared spectroscopy showed bands corresponding to the existence of AlO6 groups building up the magnesium aluminate spinel, which was the only crystallite present at 1000 °C. The presence of 0.5, 1.0 and 2 wt.% of Fe2O3 as sintering aids for stoichoimetric spinel lead to the increase of sinterability after firing up to 1650 °C. The higher density was for the samples contain 2 wt.% Fe2O3 which reached about >98 TD and the prepared ceramics have improved mechanical properties.