Influence of OH- ion point-defect complexes on the electron irradiation damage response of MgO crystals

摘要

Microstructural evolution and radiation damage kinetics have been studied in a wide variety of MgO single crystals by in-situ observations under electron irradiation in a high-voltage electron microscope. Electron irradiation induces interstitial dislocation loops, no defect clusters and bubbles in MgO crystals, depending on the source and the history of the crystals. We have found evidence that the presence of structural vacancies in MgO may suppress the nucleation and growth of dislocation loops during electron irradiation, thereby enhancing the radiation resistance of this ceramic. The vacancies that appear to promote radiation tolerance in MgO are related to the incorporation of OH- ions in the crystal lattice. In fact, these vacancies are actually point-defect complexes, consisting of one or two OH- ions residing on O lattice sites, together with a vacancy on a Mg site. These configurations yield either a fully charge-compensated point defect complex ((OHVMg)-V-." HO.)(X) or a singly charged point-defect complex ((OHVMg)-V-.")'. [References: 12]