G. Roussy et al., Microwave broadband permittivity measurement with a multimode helical resonator for studying catalysts, MEAS SCI T, 12(4), 2001, pp. 542-547
The authors present a resonant permittivity measurement method which works
over a large microwave frequency domain, with a very small volume sample of
dielectric material. The cell is a helical resonator having many modes of
resonance. The shifts of resonance frequency and Q-factors are better inter
preted with a bilinear function which depends on the complex permittivity o
f the material than by applying the classical perturbation formula. Results
concerning two different catalysts which are used in the coupling oxidatio
n methane reaction are given as a function of the temperature and the frequ
ency to illustrate the correlation of both data sets and the differences in
catalytic mechanisms.