International Comparison of Dielectric Measurements

Three materials, i.e.,fused silica, glass, and alumina, were selected for comparison based on known or expected homogeneity, isotropy, and stability. Measurements were made by the three Government laboratories (U. K., U. S. A., and Canada), both in the radio-frequency range, using capacitor-type holders either with or without an air gap, and at microwave frequencies, using either cavity-resonance methods or transmission-line impedance methods. The range among the laboratories on the real part of the permittivity is 0.4, 0.8, and 0.2 per cent for the three materials, respectively. The agreement on loss tangent is of the order of 0.0001 in many cases, but larger discrepancies exist. An introductory statistical analysis for systematic differences between laboratories is given.