PNNL

Abstract

Lithium (Li) penta-aluminate (LiAl5O8) is investigated as a potential tritium (T) breeding material, with a focus on microstructural response to ion irradiation and deuterium (D) diffusion behavior. Under high-fluence ion irradiation (2E17 (He++D+)/cm2) at 773 K, LiAl5O8 exhibits significant disorder on the Li sublattice, as revealed by atomic-resolution scanning transmission electron microscopy, while the Al and O sublattices remain stable, demonstrating strong resistance to structural amorphization. Irradiation induces the formation of platelet-shaped antiphase boundaries (APBs), which may serve as effective D trapping sites. Atom probe tomography suggests the presence of 6LiD clusters in the mass spectra, though definite conclusions regarding APB composition are hindered by signal overlap and limited data statistics. Time-of-flight secondary ion mass spectrometry reveals that D retention approaches to saturation at 3E17 (He++D+)/cm2. Isothermal and isochronal annealing studies determine an average diffusivity of 1.6E-13 at 773 K and an effective activation energy of 0.8 ± 0.1 eV for D migration. Compared to ?-LiAlO2, LiAl5O8 demonstrates superior irradiation resistance, minimal Li loss, and enhanced D retention, underscoring its potential as a durable breeder material for T production. These findings provide key insights into the microstructural evolution, defect dynamics, and D retention mechanisms in LiAl5O8 under reactor-relevant conditions.