Synthesis and characterization of nano MgAl2O4 spinel by the co-precipitated method

Magnesium aluminate (MgAl2O4) spinel powders were prepared by co-precipitation of stoichiometric amounts of magnesium and aluminum chlorides at 80 °C. Some sintering aids such as ZnO and MnO2 were added in the form of chlorides during the precipitation to study their effect on densification. The co-precipitated materials were a mixture of Mg–Al double hydroxide with the presence of few amounts of gibbsite and brucite. After heat-treatment of the precipitated powders up to 1000 °C, a crystalline spinel powder was obtained. The presence of 0.5, 1, 2 and 3 wt.% of ZnO or MnO2 as sintering aids increased sinterability after firing up to 1550 °C. The highest density was obtained for the samples containing 2 wt.% ZnO or 3 wt.% MnO2 which reached about >94 and 96% theoretical density (TD), respectively. The mechanical properties increased by adding ZnO or MnO2, an exception being the sample containing 0.5 wt.% of ZnO for which relatively smaller value were obtained.