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 al cohol or supercritical alcohol-CO2 mixtures. Because of a similar coor dination of the magnesium atom in both types of precursors, a common a morphous alkoxy-hydroxy derivative is first obtained. When the reactio n occurs in a supercritical medium with carbon dioxide as cosolvent, t he microstructure of the solid is quite different and a CO2 group is i ncorporated into the alkoxy bond. In all cases, the intermediate compo und crystallizes into cubic magnesium oxide under thermal treatment be tween 400 and 600 degrees C; the elementary particle size in the powde rs obtained is less than 100 nm.