The structure and infrared spectra of nanostructured MgO-Al2O3 solid solution powders prepared by the chemical method

Alumina ceramics has been used widely as an industrial material because of its high heat resistance and excellent wear resistance. Nanosize metal oxide used as raw materials would decrease the sintering temperature of ceramics and enable their physical and chemical properties to be developed fully. This paper studies the synthesis of nanostructured alumina-magnesia powders. The whole compositional range for the binary Al2O3-MgO system is studied. The powder samples are characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), differential thermal analysis (DTA) and infrared spectroscopy (IRS). The results show that the nanostructured alumina-magnesia powders form solid solutions in a wide range of composition. In the alumina-rich side, the gamma-Al2O3 phase is found and the maximum amount of magnesia that can be incorporated is 30%. In the magnesia-rich side, the MgO phase is present and the range of solid solutions is from 0 to 20 wt% Al2O3 It is also found that the lattice parameter a(0) of gamma-Al2O3 increases with increase in the amount of magnesia, but the lattice parameter of the MgO phase decreases with increase in the amount of alumina. The grain size increases linearly with the amount of magnesia added and is smaller than 3.6 nm for alumina solid solution. It changes in a parabolic manner with the amount of alumina and is smaller than 15 nm for magnesia solid solution. The specific surface is about 140 m(2) g(-1) for the powders. The heat decomposition temperature of the precursor determined by DTA is not changed with increase in the amount of magnesia in the gamma-Al2O3 solid solution range. The heat decomposition temperature increases with increase in the amount of alumina in the MgO solid solution range. In the range of mixed phase, it is greater than those in the range of two solid solutions. The results for IRS of the nanostructured alumina-magnesia powders are discussed. (C) 1999 Published by Elsevier Science S.A. All rights reserved.