A microwave technique for measuring the complex dielectric permittivity of liquids by using a cylindrical cavity oscillating in the TM010 mode is described. The liquid is placed in a cylindrical teflon cell and the dielectric constant and loss of the liquid are evaluated by measuring accurately the changes in the resonant frequency and Q of the cavity for the composite sample and for the teflon alone. This technique has been used to measure the dielectric constant and loss at 2.4 GHz of some pure liquids and solutions in benzene of ortho and meta isomers of difluoro-, dichloro-, dibromo-, and diiodo-benzene. The measured values for the pure liquids are in good agreement with the literature values. The dielectric relaxation times and dipole moments of the dihalobenzenes in benzene solution evaluated by assuming a simple Debye type dispersion show good agreement with the earlier calculated values derived from Cole–Cole plots based on measurements at several microwave frequencies. This technique, by virtue of the use of a teflon cell and of gold plated end caps, allows the determination of the dielectric properties of corrosive liquids at microwave frequencies and another advantage is that very small liquid samples are required.
Numerical Characterization of Vanadium Dioxide Thin Films Applied to Thermal Building Insulation: Determination of Dielectric Constant Using PSO Algorithm
