Structural Studies of Deuteration and Dedeuteration of Li3N by Use of In Situ Neutron Diffraction

Abstract

In situ neutron diffraction studies were carried out on the deuterium absorption and desorption of pure α-lithium nitride. When the sample was exposed to deuterium gas (D2) at 150 °C, no absorption was observed for 12 h. Incomplete reaction between the nitride and D2 at 200 °C with 4 wt % hydrogen uptake (based on 8% D2 equivalent calculated from diffraction measurements) followed by a total of 7.2 wt % hydrogen uptake at 250 °C was observed. A change in the unit cell volume of lithium imide during absorption and desorption at 250 °C indicates a possible stoichiometry change during this process. At the end of the experiment, when the sample was cooled to room temperature, two cubic phases in the sample with slightly different lattice parameters were identified. We propose that these measurements indicate that the mechanism for absorption and desorption of deuterium by this system is dictated by defect formation in the cubic lithium imide lattice.