Phase evolution of Li2ND, LiD and LiND2 in hydriding/dehydriding of Li3N

Neutron and synchrotron studies have been performed on in situ hydriding of Li3N. Commercial Li3N is composed of a phase (similar to 70 wt.%) and beta phase (similar to 30 wt.%). We have performed experiments to convert beta -> alpha, and studied in situ deuteration using neutron diffraction experiments. We found concurrent phase evolution of Li2ND, LiD, and LiND2. Mass percentages of the phases evolved as a function of time and temperature have been quantified using General Structure Analysis System (GSAS) refinement of the neutron diffraction data. The problem of formation of the stable LiD is discussed in light of decreasing of the amount of LiD phase when the temperature is increased from 200 to 320 degrees C during dehydriding, and in addition the concentration of Li2ND phase increased at this temperature. Lattice parameters, volume changes, phase evolutions in wt.% as a function of temperature and time are presented. (C) 2007 Elsevier B.V. All rights reserved.