Effects of grain size and deuteration conditions on the microstructure of erbium deuteride films

Abstract

Erbium is widely considered as a promising tritium storage material due to its high capacity and stability. In this work, the influences of the grain size of original erbium and the deuteration conditions on the microstructure of erbium deuteride film were studied by SEM, FIB-TEM and XRD. The results indicate that the erbium films with small grains transformed into large grains after deuteration, whereas those with large grains changed to smaller grains. The lattice expansion after the loading of deuterium was measured, which confirmed that the films possess small grains present a weaker expansion (7.7%) than those with large grains (10.8%). All of the as-prepared erbium deuteride films exhibited a strong (111) preferred orientation and the film with smaller change of grain size during deuteration presents much stronger preferential growth. It is demonstrated that the deuteration temperature and pressure have a significant effect on the grain size of erbium deuteride films, which the higher deuteration temperature and pressure would induce a bigger change of grain size. In final, the underlying cause of the effect of grain size and deuteration conditions is discussed based on the thermodynamic and kinetics. The higher reaction rate under high deuteration temperature and pressure would prefer to increase the internal stress and the transformation of grain size.