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 result is based on experiments performed with pure or X-irradiated single crystal alumina (sapphire) or polycrystalline alumina. A method called the 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. This method is based on the fact that X-ray irradiation changes permittivity, Young modulus, and charging properties. Therefore, when a dielectric material is under irradiation, the trap and the bond energies will be modified and consequently changes in electrical and mechanical properties of the material are expected. It is shown that these changes can modify both irradiated and nonirradiated areas. >