EFFECT OF X-IRRADIATION AND FRICTION ON THE PROPERTIES OF INSULATORS

The study of ceramics is tackled from the space-charge physics point of view. The role of the polarization and relaxation mechanisms is demonstrated for friction coefficient and wear, as well as for breakdown voltage, therefore these characteristics depend on the permittivity. This approach is based on experiments performed with pure or X-irradiated single crystal alumina (sapphire) or polycrystalline alumina. A new method (mirror method) is presented in which the possibility of creating trapped electrical charges in a given material is measured using the electron beam of a scanning electron microscope X-ray irradiation changes permittivity, Young modulus and charging properties. These changes can modify both the irradiated and the unirradiated areas. Friction, and consequently machining, create defects everywhere in the material i.e. inside as well as outside the contact or wear tracks.