Solvent-free Ca(AlD 4 ) 2 and CaAlD 5 were synthesized directly by mechanochemical milling of CaD 2 and AlD 3 in the molar ratios of 1:2 and 1:1, respectively, under deuterium gas pressure of 0.3MPa. The products were characterized by high-resolution synchrotron radiation powder X-ray diffraction (SR-PXD), powder neutron diffraction (PND), Raman spectroscopy, and thermogravimetry (TG) analysis. The crystal structure of Ca(AlD 4 ) 2 was determined and refined with the SR-PXD and PND data. It takes an orthorhombic Ca(BF 4 ) 2 -type structure with a=13.4491(27)Å, b=9.5334(19)Å, and c=9.0203(20)Å in the space group Pbca (No. 61) and Z=8. The Raman spectrum shows bending and stretching modes of the AlD 4 tetrahedron at 480–650cm −1 and 1290–1340cm −1 , respectively. TG analysis showed that Ca(AlD 4 ) 2 releases 4.8wt.% of deuterium gas at the onset-temperature of 427K. The crystal structure of CaAlD 5 was determined and refined from the PND data and was found to be a monoclinic α-SrAlF 5 -type structure with a=9.8000(19)Å, b=6.9081(13)Å, c=12.4503(23)Å, and β=137.936(4)° in the space group P2 1 /c (No. 14) and Z=8. The Raman spectrum of CaAlD 5 shows bending and stretching modes of the AlD 6 octahedron at 725 and 1060–1170cm −1 , respectively. From TG analysis, CaAlD 5 releases 7.1wt.% of deuterium gas at the onset-temperature of 554K.