Characterization of the conduction mechanisms in polycrystalline alumina

This work shows that the recovery parameter R_s, used to investigate charge stability in polycrystalline alumina ceramics, can be connected with conduction mechanisms. This is achieved through a phenomenological model describing the SEE yield decay during electron irradiation. The insight provided by the new framework is utilized to identify the conduction mechanism involved in polycrystalline alumina containing only 150 ppm of various impurities. The enhancement of the parameter R_s with the temperature leads to an activation energy E_a of about 0.14 eV for grain diameters varying over the range 1.7-4.5 ¿m. This activation energy is attributed to hopping mechanism via localized states associated to impurities that have segregated at grain boundaries during the sintering process.