ASTM D2520 is useful for specification acceptance, service evaluation, manufacturing control, and research and development of ceramics, glasses, and organic dielectric materials. Complex permittivity (dielectric constant and dissipation factor) is an important value used in designing transmission lines, resonators, antennas. Dielectric constant is the measure of the amount of potential energy stored due to polarization, and dissipation factor is the measure of energy lost during reversal of polarization.
Complex permittivity is a measure of the electric polarizability of a dielectric. A material with high permittivity polarizes more in response to an applied electric field than a material with low permittivity, thereby storing more energy in the material.
There are three test methods for ASTM D2520:
Test Method A is for specimens precisely formed to the inside dimension of a waveguide.
Test Method B is for specimens of specified geometry that occupy a very small portion of the space inside a resonant cavity.
Test Method C uses a resonant cavity with fewer restrictions on specimen size, geometry, and placement than Test Methods A and B.
For ASTM D2520, the width of the specimen must be less than that of the transmission line. The front and back faces of the sample must be parallel and perpendicular to the axis of the transmission line. The corners of the specimen should be slightly rounded.
ASTM D2520 is used to determine complex permittivity (dielectric constant and dissipation factor) of Solid Electrical Insulating Materials at Microwave Frequencies and Temperatures up to 1650 °C.