Solvent-free Ca(AlD4)2 and CaAlD5 were synthesized directly by mechanochemical milling of CaD2 and AlD3 in the molar ratios of 1:2 and 1:1, respectively, under deuterium gas pressure of 0.3 MPa. 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(AlD4)2 was determined and refined with the SR-PXD and PND data. It takes an orthorhombic Ca(BF4)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 AlD4 tetrahedron at 480-650 cm-1 and 1290-1340 cm-1, respectively. TG analysis showed that Ca(AlD4)2 releases 4.8 wt.% of deuterium gas at the onset-temperature of 427 K. The crystal structure of CaAlD5 was determined and refined from the PND data and was found to be a monoclinic α-SrAlF5-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 P21/c (No. 14) and Z = 8. The Raman spectrum of CaAlD5 shows bending and stretching modes of the AlD6 octahedron at 725 and 1060-1170 cm-1, respectively. From TG analysis, CaAlD5 releases 7.1 wt.% of deuterium gas at the onset-temperature of 554 K.
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