Fundamental studies in the millimeter-wave and microwave sintering of alumina compacts

The microwave sintering of fine- and ultra-fine-grained alumina compacts at both 35 and 2.45 GHz have not indicated the presence of a significant non-thermal `microwave effect'. These are consistent with the estimates of the nonthermal microwave interaction with grain lattice vacancies using the Rybakov and Semenov (RS) model since the resulting microwave stress was calculated to be smaller than the surface energy stress which was the usual driving force for sintering. The RS model predicts that microwave stress effect should be affected, and enhanced, if the defect structure at the grain boundary is modified.