Phase formation of γ-LiAlO2 via transformation of a layered double hydroxide (LDH) by internal gelation

Interest in controlled deuterium-tritium fusion as a clean-energy technology has grown in recent years. Solid tritium breeder materials, such as γ-LiAlO ₂, need to release tritium to allow the fusion reaction to occur and control over the microstructure can help tune tritium release. Internal gelation is a synthesis technique that allows control over the sample`s microstructure. In this process, droplets of an aqueous precursor are heated to form a gel, which is washed, dried, and calcined to produce oxide spheres. Past attempts applying internal gelation to fabricate γ-LiAlO ₂ revealed that lithium was lost during wash processes, leading to a lithium deficient final product. To overcome lithium deficiency, the chemistry and reaction pathway must be unraveled. Therefore, this work strove to elucidate the mechanisms of lithium aluminate formation and lithium deficiency. Complementary characterization techniques revealed that lithium aluminate produced via internal gelation formed an aluminum-lithium layered double hydroxide (LDH) structure as an intermediate species. This LDH has a stoichiometry of Li(Al(OH) ₃) ₂NO ₃·xH ₂O and the 1:2 ratio of Li to Al is thought to limit the overall lithium content of the final lithium aluminate product due to loss of unbound lithium during washing. This work also indicates that infusing amorphous aluminum hydroxide samples with lithium after gelation appears to incorporate lithium beyond this LDH stoichiometric limit and is one potential pathway towards the desired γ-LiAlO ₂ final product. The results of this work highlight the influence that the LDH intermediate species has upon the formation and stoichiometry of the final, calcined product.