Synthetic Study of Some Rare-Earth-Metal Monohalide Hydrides MXHxand Their Alkali-Metal Intercalates

Abstract

The quantitative syntheses of MXHxphases (M = Sc, La, Gd, Er, Lu; X = Cl (and Br for Gd, Er); x = 0.6-0.7) together with their intercalates AzMXHx(A = Li, some Na, K; M = Sc, Y, Gd (but not Er, Lu)) have been accomplished by stoichiometric reactions of MX3, MH2(or H2), M, and AX in sealed Ta or Nb containers at 750–900 °C, All MXHxphases have the ZrCl-or ZrBr-type (3R) heavy-atom structures. The phases ScCIHx, nonstoichiometric for 0.3 < x 0.75, and LaCIH are indistinguishable from the previously reported monochlorides. The X-ray structure of ScCIH has been refined. The lithium intercalates, LizMClHx, for M = Sc, Y, and Gd are also nonstoichiometric in hydrogen, and all intercalates have the ZrBr heavy-atom structure. The Li0.2YCl and Li0.5GdCl phases previously reported from X-ray studies are obtained only in the presence of hydrogen. High values of x result in explusion of much of the lithium from the yttrium and gadolinium chloride derivatives. Hydrogen pressure, phase, and volume relationships are also considered. © 1986, American Chemical Society. All rights reserved.