The electrical behavior of ceramic-to-metal seals

Radio-frequency energy generated in a vacuum tube is-partially dissipated as heat on passing through its output window. The electrical losses arise because of dielectric loss in the ceramic window itself and losses in the seal between the ceramic and the metal member of the tube. The most common method of effecting a ceramic-to-metal seal is by metallizing the ceramic, followed by brazing it to the metal member. For this complex joint, electrical losses can be primarily separated into those due to conduction and to those due to dielectric polarization of the non-metallic phases present in the seal. Secondary sources of loss may arise due to electrostructive, magneto strictive and semi-conductive effects.