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Thermal diffusion of protons, deuterons and tritons forming OH−, OD− and OT− radicals respectively was monitored by infrared absorption measurements in MgO, Al2O3, LiNbO3 and TiO2 single crystals. The electric charge and/or ionic radius is shown to be more important than mass in affecting the diffusion behaviour in these oxides. The influence of selected impurities and crystal orientation on the diffusion parameters was also investigated. Thermal diffusion of protons occupying substitutional anion vacancies (hydride ions) or [H−]+ centres was studied in thermochemically reduced MgO crystals. Simulations using an ab initio Hartree–Fock cluster approach indicate that the mobile defect is more compatible with the H− ion than with the proton. Application of even a moderate electric field is very effective in enhancing the H+ ↔ D+ exchange in crystals containing hydroxyl ions. In addition, deuterons can be effectively incorporated in crystals with undetectable hydrogen concentrations by applying moderate electric fields at elevated temperatures. The incorporation of deuterons occurs without proton replacement, which indicates the possibility of D+(H+) doping. Under electron irradiation, otherwise stable hydrogenic species become mobile at temperatures as low as 85 K. Ionizing radiation breaks the O–H bond with exceedingly large cross-sections (108 barns at room temperature), which is a strong function of the irradiating temperature. The displacement cross-section of protons is twice that of deuterons. Radiation induced displacement of protons from hydride ions at room temperature is also discussed. Out-diffusion of hydrogen isotopes can be induced in TiO2 crystals near room temperature by breaking the hydroxyl bond by electron irradiation and subsequently sweeping out hydrogenic species along the c-axis by application of an electric field.

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When a ceramic oxide with an applied electric field is subjected to extended irradiation with energetic particles at elevated temperatures, the electrical conductivity has been reported to increase, a phenomenon termed radiation-induced electrical degradation ͑RIED͒. In the present study ␣-Al 2 O 3 crystals were subjected to 1800 V/cm while irradiated with 1.8 MeV electrons at 773 K. Above a critical dose the conductivity increased. During the conductivity enhancement, the applied field was reversed, resulting in a decrease in the conductivity. This result demonstrates that RIED was caused by carriers injected from the electrodes, in concert with electrons and holes created during ionizing irradiation. A model for RIED is proposed: the injected carriers are trapped mainly at impurities near the electrodes, leading to formation of dislocations. These dislocations serve as traps for electrons and holes generated during ionizing radiation. A network of interconnecting dislocations is associated with the enhanced conductivity.