Deformation mechanism of fine-grained magnesium aluminate spinel prepared using an alkoxide precursor

Polycrystalline MgAl2O4 spinel with high purity and stoichiometric composit ion was prepared using alkoxide precursors. The average grain size of the p olycrystal was fine (1.7 mu m). The deformation mechanism of the polycrysta l was investigated in air at temperatures of 1300 degrees-1400 degrees C. A t 1300 degrees C, oxygen lattice diffusion controlled the deformation, desp ite the fine grain size; however, increases in the temperature and applied stress caused cavities to nucleate and grow. Spinel possessed better creep resistance than alumina of comparative grain size. The effective diffusion coefficient,vas determined as follows: D-eff(m(2)/s) = 1.9 x 10(-1) exp(- (421+/-26 kJ/mol)/(RT)).