Observation of Novel Phases During Deuteration of Lithium Nitride from in situ Neutron Diffraction

We report details of in situ neutron diffraction measurements during the deuteration of Li3N. A number of novel observations are described: The presence of cubic quasi-imide phases with composition-dependent lattice parameters, the identification of a Li4ND phase and the suppression of LiD formation in the initial stages of deuteration. On the basis of these observations, we propose that the quasi-imide phase is formed from the reaction of Li4NH and Li2NH, having a composition Li2+xND. Charge balance is accomplished in this compound by the inclusion of both H+ and H-; the former species being present in the form of (NH)2- . At low deuterium content, the quasi-imide is present as at least two phases, with the lattice parameters decreasing with deuterium up-take. A minimum in lattice parameter is observed at [D]/[Li3N]~0.7, after which a single phase is observed, with the lattice parameter monotonically increasing with deuterium content. Two mechanisms for the observed variation in lattice parameter are discussed; (i) a vacancy mediated mechanism, (ii) the formation of intergrowth compounds.

WEIDNER RONNEFELD Eveline;  BULL D. J.;  SHABALIN I;  KEENS S.;  TELLING M.T.F.;  ROSS Keith; 

2007-08-20

ELSEVIER SCIENCE BV

JRC37190

https://publications.jrc.ec.europa.eu/repository/handle/JRC37190,   

10.1016/j.cplett.2007.07.010,