The effects of the size of the alkoxy group on the thermal decomposition behavior of magnesium alkoxides (magnesium methoxide and ethoxide) and the crystallization behavior of MgO was investigated using thermogravimetry, Fourier-transformed infrared spectroscopy, X-ray powder diffraction, and transmission electron microscopy. As the size of the alkyl group increased, the decomposition temperature decreased and resultant MgO crystallization of the alkoxide precursor was enhanced. In an inert N-2 atmosphere, the decomposition temperature of magnesium ethoxide was about 260degreesC, which was lower than that of magnesium methoxide by approximately 70degreesC. The degree of the crystallization of MgO particles from the ethoxide was also significantly higher than that of the methoxide. This result is explained in terms of the O-R bonding strength of the alkoxide. With use of the Kissinger method, the activation energy for the thermal decomposition of magnesium alkoxide was found to be dependent on the size of the alkyl group. The activation energies were 161 23 and 130 +/- 24 kJ/mol for the magnesium methoxide and the magnesium ethoxide, respectively. (C) 2003 Elsevier Science (USA). All rights reserved.