3He bubble evolution in ErT2: A survey of experimental results

For the past several years we have been carrying out a long term experimental study of 3He in ErT2 (erbium di-tritide). This study has attempted to answer questions regarding the evolution of helium bubbles in ErT2-xHex. ErT2 samples have been studied periodically over four years using Transmission Electron Microscopy (TEM), X-ray Diffraction (XRD), and Nano-Indentation (NI). In ErT2-xHex, helium bubbles are plate-like and grow along {1 1 1} planes. The bubbles grow in three distinct phases. First, they nucleate and grow as “Griffith-cracks” until an age of ∼0.15 He:M. Second, around 0.15 He:M the diameter stops increasing and instead the bubbles grow in thickness by punching dislocation dipoles. Third, the bubbles grow in size until ∼0.3 He:M at which point the bubbles begin to link.