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 Al2O3, MgO, and Y2O3 with YH1.92 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 Al2O3 and MgO to form Y2O3, resulting in significant loss of YH1.92. Yttrium reacted with reduced aluminum to form YAl2 and several other compounds. Reduced magnesium volatilized above 1091°C and vacated the pellet. Only Y2O3 did not appreciably react with YH1.92. Of the three oxides tested, only Y2O3 was compatible with YH1.92 at 1200°C based on the experimental criteria.