SYNTHESES OF SUBMICRON MAGNESIUM-OXIDE

Submicron MgO powders have been synthesized from thermal decomposition of magnesium chelates or acetate at around 200 degrees C in liquid alcohol or supercritical alcohol-CO2 mixtures. Because of a similar coordination of the magnesium atom in both types of precursors, a common amorphous alkoxy-hydroxy derivative is first obtained. When the reaction occurs in a supercritical medium with carbon dioxide as cosolvent, the microstructure of the solid is quite different and a CO2 group is incorporated into the alkoxy bond. In all cases, the intermediate compound crystallizes into cubic magnesium oxide under thermal treatment between 400 and 600 degrees C; the elementary particle size in the powders obtained is less than 100 nm.