Yttrium dihydride

Lattice constants (a and c), calculated distances dx (between the hexagonal planes) and dy (nearest neighbor distances) and molar volume for yttrium, yttrium dihydride and yttrium trihydride reported for bulk (Kooij et al., 2000) and thin films (Huiberts et al., 1996b). The values corresponding to thin films are bolded... 

In a later paper Chouinard and Gustafson (1971) reported angular correlations of positron annihilation in erbium, gadolinium, holmium and ytterbium hydrides. The correlations were again claimed to be consistent with the predictions of the protonic model. Recent studies on yttrium dihydride (Sabin et al., 1972 Rozen-feld and Debowska, 1975) were interpreted on the basis of the proton model, but it was pointed out that the model fails for higher hydrogen concentrations, i.e. YH2-YH3 (Rozenfeld and Debowska, 1975). 

All of these complexes decompose cleanly at low temperature to produce acetonitrile, carbon dioxide, and initially, the metal hydroxide (equation 45). The decomposition temperatures are 144,176, and 198 °C for Ba, Cu, and Y, respectively. In the case of copper and yttrium, the final product is the metal oxide produced by the dehydration of the hydroxide, while barium hydroxide recombines with carbon dioxide to yield the carbonate. Barium carbonate formation can be avoided, however, by use of a different ligand that avoids carbon dioxide formation. Benzoin a-oxime (Hbo) (13) has been found to be a quite suitable diprotic ligand for this purpose. The barium salt is easily prepared by reaction of the oxime with the metal dihydride (equation 46), and it decomposes cleanly to barium oxide by loss of benzaldehyde and benzonitrile at 250 °C (equation 47). 

Fig. 93. Yttrium concentration (y) dependence of the (i) lattice parameters (a,c) and (ii) molar volume of Lai j,Yj,H c (Vtn) for th as-deposited, dihydride and trihydride states. The open symbols are the literature values (Gschneidner and Calderwood, 1982 Mueller et al., 1968). The vertical lines represent the phase boundaries fa-the various structural phases (solid lines) and mixed phase region (dotted lines) (van Gogh et al., 2001).

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