Dynamics of hydrogen, oxygen, and dislocations in yttrium by acoustic spectroscopy

The nature of the numerous thermally activated processes occurring in yttrium has been investigated by acoustic spectroscopy in polycrystalline samples. The measurements have been carried out between 1.1 and 600 K in the kHz range, varying the concentration of interstitial hydrogen and oxygen in annealed and deformed samples. Four processes have been observed, besides the main dissipation peak around room temperature due to the formation or dissolution of H pairs and that at liquid He temperature attributed to H tunneling. The processes below 300 K have been interpreted in terms of the motion of interstitial hydrogen trapped by oxygen or dragged by dislocations, while the large relaxation detected around 450 K has been attributed to the hopping of oxygen in a solid solution.