Dielectric Properties of Ceramics at Microwave Frequencies

The dielectric properties of alumina and silicon nitride have been determined using modified rectangular microwave waveguide techniques from 220 to 900 deg C over 8-12 GHz and modified coax techniques from 25 deg to 500 deg C over 2-18 GHz. The coax techniques were used to determine the temperature and frequency dependence of the dielectric properties of silicon nitride and of phosphate bonded alumina reinforced with silicon carbide whiskers. The coax techniques provide broadband dielectric property data that can be applied to the understanding and enhancement of the coupling behavior of ceramics, especially in the initial heat-up period of microwave processing.