MW-DETA

Microwave Dielectric and Thermal Measurements (MW-DETA) as a function of temperature

MW-DETA is an innovative device and methodology engineered to measure the temperature-dependent variations of dielectric properties of materials at microwave frequencies with the simultaneous application of microwave irradiation.

The MW-DETA is designed in an 105dx85h mm dual-mode cylindrical cavity reactor, featuring two non-interfering, distinct swept-frequency microwave sources. The TE111 mode near 2.45 GHz is used to heat an approximate 15x10mm sample with high-power microwaves, while the TM010 mode around 2.1 GHz measures dielectric properties as a function of temperature.

Dielectric properties of materials as a function of temperature are calculated by an improved cavity perturbation method from the changes in resonant frequency and quality factor in the microwave cavity during heating. Accuracy of complex permittivity results has been evaluated with an error lower than 5% with respect to a rigorous analysis of the cavity.

The functionality of the microwave dielectric measurement system has been demonstrated by heating and measuring hundreds of samples of materials to more than 1000ºC.

The correlation of the complex permittivity with the heating rate, temperature, absorbed power and other processing parameters can help to better understand the interactions that take place during microwave heating of materials at high temperatures compared to conventional heating.

The cavity also incorporates access holes for introducing the material sample within a quartz tube, sample inspection via a video camera and enabling temperature measurements using an infrared pyrometer.

The specific methodology employed to determine dielectric properties is reported in the publication [Catalá-Civera 2015].