Abstract
T. T. Meek proposed a model for a microwave ceramic sintering mechanism in his seminal paper. Meek's summary of the model states: "-the initial electric field intensity and power density between the ceramic grains will be greater than in the grains themselves, and thus heating will concentrate exactly where we want it to. Once dense regions begin to form, however, the microwave field will begin to decouple from these regions and couple more strongly to the regions of low density and low dielectric constant. Accordingly, the electromagnetic field will sweep through the composite coupling more strongly to the less sintered regions resulting in a driving force toward a uniformly sintered material, with a uniform dielectric constant."
To test the model, the authors prepared pairs of Al2O3 and Si3N4 samples whose densities were different. Each pair was heated in a uniform electromagnetic field. The temperature of the higher density samples increased faster than the temperature of the lower density samples in every case. This result indicates that Meek's model is incorrect. Meek assumed that the loss tangent of the lower density composite phase is approximately equal to that of the higher density phase. This assumption appears to be the source of the error.