ABSTRACT. During microwave sintering, the electric field distribution within a ceramic body on a macroscopic scale is determined by a combination of the operating frequency, the sample and applicator shape, the manner in which the electromagnetic waves illuminate the sample, and the sample permittivity and permeability. Within the sample, the spatial variation of the electric field occurs on length scales comparable to the wavelength or skin depth of the electromagnetic waves within the ceramic. However, this is only true if one is considering the variation of fields over volumes much larger than the characteristic feature sizes of the microstructure (i.e., grain sizes, rough surfaces of grains, and inter particle contact zones). Within the microstructure itself the electric field exhibits violent variation in magnitude and direction. Furthermore, the electric field in certain areas of a realistic microstructure can be orders of magnitude stronger than the spatially averaged electric field, and it can exhibit preferred directions despite being illuminated by a randomly polarized electric field. In this paper calculations of electric field distributions within ensembles of ceramic particles, joined by spherical necks, will be presented. The relation between the predicted electric field enhancements and current theories of microwave sintering will be discussed.

---