Microwave cavity perturbation technique for high-temperature dielectric measurements

The present work is motivated by the use of microwaves for the catalytic conversion of carbon dioxide to carbon monoxide. Chemical reactions like this are running at catalyst temperatures of more than 800 °C. The appropriate design of the microwave assisted reactor requires the exact knowledge of the dielectric properties of the catalyst and catalyst support materials up to those high temperatures. For this purpose a measurements system based on the cavity perturbation method was built. The system is using a rectangular TE₁₀₄ cavity with a resonance frequency at 2.45 GHz and a quality factor Q ≈ 12000. A novel synthetic calibration method based on numerical full-wave modeling has been developed as an alternative to traditional calibration methods. The results of high temperature dielectric measurements for polyether ether ketone (PEEK), MACOR glass ceramics and zirconia are presented.