Microstructural evolution and precipitation in γ-LiAlO2 during ion irradiation

Abstract

Polycrystalline γ-LiAlO2 pellets were sequentially irradiated with 120 keV He+ and 80 keV D2+ ions to the fluences of 1 × 1017 and 2 × 1017 (He+ + D+)/cm2 at 573 K. Additional irradiation was performed to a fluence of 2 × 1017 (He+ + D+)/cm2 at 773 K. The irradiated pellets were characterized using scanning transmission electron microscopy, time-of-flight secondary ion mass spectrometry, and grazing incidence x-ray diffraction. Lattice damage, amorphization, and fractures are observed with no evidence for the formation of secondary-phase precipitates in the pellets irradiated up to an ion fluence of 2 × 1017 (He+ + D+)/cm2 at 573 K. In contrast, faceted precipitates with sizes larger than 100 nm formed in a pellet irradiated to 2 × 1017 (He+ + D+)/cm2 at 773 K. Analyses of the diffraction and composition data suggest that the precipitates have a spinel-type structure, likely a non-stoichiometric LiAl5O8 with Li depletion. This could be an intermediate phase with Li atoms at the octahedral and possibly tetrahedral sites as well. It is speculated that as the dose increases, Li loss will continue and the precipitates will approach a composition of alumina primarily in phases of α-Al2O3 and amorphized Al2O3.

Surface Microstructure Changes Induced by Ion Beam Irradiation

“…Experimentally has been determined that if the solute atoms are smaller than the solvent atoms, the solute atoms will migrate toward sinks (surfaces, grain boundaries, dislocations, etc. ), and larger atoms decrease their concentration near these sinks [7].…”

Molecular dynamics simulations of displacement cascades in LiAlO2 and LiAl5O8 ceramics

“…Gamma lithium aluminate (γ-LiAlO 2 ) is used in the production of tritium for the strategic stockpile and is being considered for fusion reactor blanket applications. It has excellent thermomechanical durability and low volumetric swelling when exposed to neutron irradiation 1 . It is used in tritium-producing burnable absorber rods (TPBARs) 2 in the form of high density pellets enriched in 6 Li.…”