Microstructural Characterization of Dehydrogenated Products of the LiBH₄-YH₃ Composite

Abstract The dehydrogenated microstructure of the lithium borohydride-yttrium hydride (LiBH₄-YH₃) composite obtained at 350°C under 0.3 MPa of hydrogen and static vacuum was investigated by transmission electron microscopy combined with a focused ion beam technique. The dehydrogenation reaction between LiBH₄ and YH₃ into LiH and YB₄ takes place under 0.3 MPa of hydrogen, which produces YB₄ nano-crystallites that are uniformly distributed in the LiH matrix. This microstructural feature seems to be beneficial for rehydrogenation of the dehydrogenation products. On the other hand, the dehydrogenation process is incomplete under static vacuum, leading to the unreacted microstructure, where YH₃ and YH₂ crystallites are embedded in LiBH₄ matrix. High resolution imaging confirmed the presence of crystalline B resulting from the self-decomposition of LiBH₄. However, Li₂B₁₂H₁₂, which is assumed to be present in the LiBH₄ matrix, was not clearly observed.