Thermal and particle size effects in magnesium oxide

X-ray line widths, surface areas and heats of solution of MgO samples prepared by vacuum dehydration of Mg(OH)2 at different temperatures in the range 350–1 200°C have been studied. While the surface energy of particles shows a steady decrease with the temperature of preparation, the heats of solution shows an abrupt decrease over a narrow temperature range. The results have been interpreted in terms of pseudocrystallization of the highly disordered oxide followed by sintering; the pseudocrystallization of colloidal oxides appear to be similar to glass transitions.