Chemical synthesis of magnesium aluminate spinel powders: A comparative study of the sol–gel and self-combustion routes

Magnesium Aluminate Spinel powders have been synthesized using sol–gel and self-combustion routes. The sol–gel powder was obtained using Mg(NO₃)₂ and aluminum tri-secbutoxide as the cation sources dissolved in isopropanol to obtain a gel that was calcined from 400 to 1100 °C to elucidate its thermal evolution. Besides, the self-combustion route was selected as a simple and time-saving method. In the later, a so-called Deep Eutectic Solvent (DES) was prepared using Mg(NO₃)₂, Al(NO₃)₃, and urea as the fuel. The DES was introduced in a furnace pre-heated at 400 °C and up to 1100 °C to evaluate the evolution of the spinel phase. Self-combustion powders are closer to stoichiometry and crystallize at a lower temperature (600 °C) than those obtained by the sol–gel route. These changes were attributed to the exothermic nature of the self-combustion reaction. Upon firing at 1100 °C, both methods lead to submicron particles consisting of nanocrystalline grains of less than 40 nm.