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YAl crystallizes in the orthorhombic Cmcm space group. The structure is three-dimensional. Y is bonded in a 7-coordinate geometry to seven equivalent Al atoms. There are a spread of Y–Al bond distances ranging from 3.09–3.24 Å. Al is bonded in a 9-coordinate geometry to seven equivalent Y and two equivalent Al atoms. Both Al–Al bond lengths are 2.76 Å.
YAl is Tetraauricupride structured and crystallizes in the cubic Pm-3m space group. The structure is three-dimensional. Y is bonded in a body-centered cubic geometry to eight equivalent Al atoms. All Y–Al bond lengths are 3.12 Å. Al is bonded in a body-centered cubic geometry to eight equivalent Y atoms.
Yttrium hydride is a promising material for a high-temperature neutron moderator in advanced micro and space reactors due to its high hydrogen density and relative thermal stability compared to other metal hydrides. However, yttrium hydride desorbs hydrogen rapidly at temperatures above 800°C, which is below the operational temperature range of some reactor designs. A hydrogen barrier coating of oxide on the hydride surface may inhibit hydrogen loss at 800°C and beyond, but the high-temperature compatibility between yttrium hydride and many oxides is currently unknown. The high-temperature compatibility of Al 2 O 3 , MgO, and Y 2 O 3 with YH 1.92 was examined by subjecting mixed oxide–hydride pellets to a 1200°C heat treatment then using a combination of diffractometry, microscopy, and spectroscopy to determine changes in the pellet composition as a result. Yttrium scavenged oxygen from both Al 2 O 3 and MgO to form Y 2 O 3 , resulting in significant loss of YH 1.92 . Yttrium reacted with reduced aluminum to form YAl 2 and several other compounds. Reduced magnesium volatilized above 1091°C and vacated the pellet. Only Y 2 O 3 did not appreciably react with YH 1.92 . Of the three oxides tested, only Y 2 O 3 was compatible with YH 1.92 at 1200°C based on the experimental criteria.