Solid-state lithium compounds, such as γ-LiAlO2, are proposed materials to use as tritium breeders in fusion reactors. The purpose of this study was to investigate the chemical behavior and the structural incorporation of lithium in lithium aluminate samples formed via the internal gelation sol-gel process. Internal gelation is a versatile synthesis method wherein hydrous metal oxide gels are formed through the heating of colloidal precursors. This process can produce large quantities of high-quality metal oxide microspheres and enables the tuning of structural properties. Lithium does not form a gel with this process, but aluminum forms a strong gel that can be used as a carrier for lithium. FTIR, Raman spectroscopy, P-XRD and NMR were used to analyze the samples throughout the gelation process to gain insights about lithium incorporation. The results indicate that lithium does not significantly influence the gelation system until after the gels have been washed and dried, wherein lithium coordination with oxygen is apparent and lithium appears to influence the coordination of aluminum. Upon calcination, the initially amorphous samples appear to undergo a transition through a partially crystalline layered double hydroxide structure before full calcination yields γ-LiAlO2 and LiAl5O8. The lack of alumina phases indicates a homogenous distribution of lithium. However, the presence of the lithium deficient pentaphase lithium aluminate indicates lithium deficiency in the fully-calcined sample. Future studies will focus on applying the insights about the lithium incorporation gained by our studies to the synthesis of stoichiometric lithium aluminate precursors for breeder blanket applications.

Investigating structural incorporation of Li into sol-gel fabricated lithium for breeder blanket materials in fusion reactors

ACS Spring 2022

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