Low temperature synthesis of spinel (MgAl2O4)

Spinel (MgAl2O4) is prepared by a combined gelation-precipitation process from a mixed solution of sulphates of aluminium and magnesium. X-ray diffraction of gel samples calcined at different temperatures shows that a spinel-like phase starts forming at 600 degrees C and complete conversion is obtained at 1000 degrees C in 1 h. The average particle size of the calcined powder is 0.2 mu-m. Pressed pellets have good sinterability even at low temperatures (1100 degrees C to 1450 degrees C). At 1450 degrees C, 95% of the theoretical density is achieved within 3 h. Scanning electron micrographs reveal faceted grains and fine grain size.