Hydrogenation of palladium rich compounds of aluminium, gallium and indium

Palladium rich intermetallic compounds of aluminium, gallium and indium have been studied before and after hydrogenation by powder X-ray diffraction and during hydrogenation by in situ thermal analysis (DSC) at hydrogen gas pressures up to 39 MPa and temperatures up to 700 K. Very weak DSC signals and small unit cell increases of below 1% for AlPd₂, AlPd₃, GaPd₂, Ga₅Pd₁₃, In₃Pd₅, and InPd₂ suggest negligible hydrogen uptake. In contrast, for both tetragonal modifications of InPd₃ (ZrAl₃ and TiAl₃ type), heating to 523 K at 2 MPa hydrogen pressure leads to a rearrangement of the intermetallic structure to a cubic AuCu₃ type with an increase in unit cell volume per formula unit by 3.6-3.9%. Gravimetric analysis suggests a composition InPd₃H_≈0.8 for the hydrogenation product. Very similar behaviour is found for the deuteration of InPd₃.