Nanostructural evolution and behavior of H and Li in ion-implanted γ-LiAlO2

In-situ He+ ion irradiation is performed under a helium ion microscope to study nanostructural evolution in polycrystalline γ-LiAlO2 pellets. Various locations within a grain, across grain boundaries and at a cavity are selected. The results exhibit He bubble formation, grain-boundary cracking, nanoparticle agglomeration, increasing surface brightness with dose, and material loss from the surface. Similar brightening effects at grain boundaries are also observed under a scanning electron microscope. Li diffusion and loss from polycrystalline γ-LiAlO2 is faster than its monocrystalline counterpart during H2+ ion implantation at elevated temperatures. There is also more significant H diffusion and release from polycrystalline pellets during thermal annealing of 300 K implanted samples. Grain boundaries and cavities could provide a faster pathway for H and Li diffusion. H release is slightly faster from the 573 K implanted monocrystalline γ-LiAlO2 during annealing at 773 K. Metal hydrides could be formed preferentially along the grain boundaries to immobilize hydrogen.