Dielectric powder characterization by radio frequency measurements technique for hydrogen sensor applications: Application to iron oxide

This work presents a characterization technique developed to study the gas sensitivity of dielectric powder in Radio Frequency (RF) domain for hydrogen sensing application at room temperature. The method is based on the measurement of S parameters of sample holder loaded with dielectric powder. The sample holder used is designed and adapted to fit in a gas test bench for materials characterization under gas environment. The non-ideal cylindrical sample holder is modeled to extract dielectric permittivity of the filled powder in the frequency range of 25 MHz to 350 MHz. Then, the measurement technique with the designed setup is applied to iron (II, III) oxide dielectric powder to extract dielectric permittivity variation under hydrogen atmosphere. The results show a significant dielectric constant variation in presence of hydrogen. In addition, the presented model has advantages of a high accuracy in wide permittivity range validity from 1 to 25. This technique allows characterizing dielectric material for sensing application and to be used for other gas sensing application.