Microwave transmission performance of mullite refractory ceramics over wide temperature range at 915 MHz and 2450 MHz

Abstract

Refractory materials are extensively applied in microwave heating instruments. Knowledge of the microwave transmission performance of refractory materials is key to improving the heating efficiency of microwave instruments. In this study, the microwave transmission performance of mullite refractory ceramics was systematically investigated with respect to various key factors, including temperature, microwave frequency, material thickness, incident angle, and polarization modes. The results indicated that the microwave transmission performance of mullite ceramics at 915 MHz is generally superior to that at 2450 MHz. As the temperature increases, the microwave transmission performance at both frequencies degrades, and the corresponding high transmissivity (power transmission coefficient > 0.7) zone also decreases. The microwave transmission performance between both polarization modes is significantly different, which is optimal at 0° (vertical incidence) and Brewster's angle, respectively. Moreover, the preferred thickness of mullite ceramics at different frequencies and temperatures was determined. This research provides references for the selection of incident angles and the optimization of material thickness during microwave heating.