Insulators properties related to both tribology and space charge physics

Space charge physics based on the analysis of polarization and relaxation of dielectric materials is shown to give a consistent description of various phenomena observed in ceramics subjected to stresses of various kins (electrical, mechanical, thermal etc.) Pure sapphire was the model material tested. Defects introduced in ceramic (by irradiation, diffusion, mechanical stresses, etc.) locally change the polarizability, and modify the capacity of the charge and thus the properties of the material. These changes in properties affect the whole ceramic, not only the bulk areas with defects. Sites of trapping are created by friction everywhere in the material (i.e., inside and outside the contact track). Therefore, the behavior can be modified by a machining process. The mechanical relaxation of the energy stored in a charged lattice is eventually converted into shock waves producing flashover, fracture, or wear located in the trapping areas