The measurement of the principal dielectric constants of sapphire by a mechanical action method

A new mechanical action method for the determination of the principal dielectric constants of synthetic sapphire is described. It is based on measurements of the couple experienced by a sphere of the material suspended in a uniform electric field. The values were found to be [perpendicular] = 7·9 ± 0·5 and [parallel] = 6·5 ± 0·4 when measured at a frequency of 50 Hz, and these values compare favourably with those obtained by other methods. The method may be applied to anisotropic crystals in general, and it is suggested that with slight modification it may be used for the corresponding electrical conductivity determinations.