Dynamic measurement of temperature dependence of complex permittivities at microwave frequency

A method is presented for measuring relatively easily the temperature dependence, particularly at high temperature, of the complex permittivity at microwave frequencies. In this method, a sample is inserted into a cavity resonator and is heated with a micowave source. The change of input admittance of the cavity is measured while heated, and the temperature dependence of complex permittivity of the sample is calculated by a perturbation method. Since the microwave power for heating and the microwave signal for measurement is performed, configurations of the measurement apparatus is simmple and the temperature dependence over a broad range can be measured in a short period of time. A TE103 rectangular cavity at 2.45 GHz has been used for a mullite (3A12O3 · 2SiO2) protective tube. The results indicate that the method is effective for temperature range from room temperature to about 1000°C.