Study of Vacancy Clusters and Antisite Defects in Titanium Beryllide Be12Ti Using Positron Annihilation Spectroscopy

Abstract

Beryllium (Be) intermetallic compounds (beryllides) are promising materials for neutron multiplication in fusion reactors. In particular, titanium beryllide (Be12Ti) exhibits low swelling and good corrosion resistance compared to other beryllides. Herein, the defects in neutron‐irradiated Be12Ti are investigated using positron annihilation spectroscopy, and the results are analyzed based on positron annihilation calculations. Calculation results indicate that the positron lifetime in a perfect Be12Ti crystal is 134.2 ps, while that of a Be monovacancy is found to be within the 177.3–195.0 ps range, depending on the configuration of the monovacancy. On the other hand, the positron lifetime of the Ti monovacancy is 222.7 ps. In addition, the lifetimes of the Be and Ti vacancy clusters increase with an increase in the number of vacancies. Finally, the positron lifetimes of the antisite defects in different configurations are found to be within the 137.9–141.7 ps range. In contrast to the calculated results, the positron lifetime of unirradiated Be12Ti is 141.1 ps. Furthermore, in the neutron‐irradiated Be12Ti, no vacancies are detected and only Be dislocation loop formation occur based on the calculation results. Although the irradiation dose of Be12Ti is low, its irradiation resistance is satisfactory.