High frequency dielectric reference materials BCR projekt 43. Final report of phase 1

The Group of High Frequency Specialists from Belgium, France, Germany, The Netherlands and the UK, was awarded contracts in 1975 to carry out a programme of measurements on the high frequency dielectric properties of materials. The object of this first phase of a projected three phase programme was to establish the reliability of existing methods of measurement and to examine the possibilities of specifying and producing some standard reference materials, both liquid and solid, which could be used for calibrating and checking the performance of industrial measurement equipment. The liquids chosen for the first phase were cyclohexane, cis and trans decalin, chlorobenzene and 0.1, 1, and 10% solutions of chlorobenzene in cyclohexane. Each group had a limited frequency range over which it could make meaningful measurements but there was sufficient overlap to ensure that all random and systematic errors could be quantitatively assayed. The real (epsilon') and imaginary (epsilon'') components of the complex permittivity for all the liquids were measured over the frequency range 10 - 3,000 GHz and for the two most lossy liquids (chlorobenzene and 10% chlorobenzene in cyclohexane) this range was extended downwards to one GHz. The programme established for the first time the possible experimental imprecisions to be expected in high frequency dielecric measurements and showed that the chosen liquids could be useful standard reference materials if sufficiently pure specimens could be obtained commercially at a reasonable price. The programme did however reveal an unexpected snag in that the liquids, especially cyclohexane, were found to be rather more liable to contamination than expected. Since cyclohexane is a very low-loss liquid, only a small amount of a lossy contaminant need be absorbed to make the observed loss increase dramatically. This report contains all the measured results in both tabular and graphical form and in addition full technical details are given of the measurement procedures