alpha-Li3N (stable at room temperature and pressure) has an unusual crystal structure that consists of two types of layers: one layer has the composition Li2N− contains 6-coordinate N centers and the other layer consists only of lithium cations.[3]
Two other forms are known:
beta-Li3N, formed from the alpha phase at 0.42 GPa has the sodium arsenide (Na3As) structure;
gamma-Li3N (same structure as lithium bismuthide Li3Bi) forms from the beta form at 35 to 45 GPa.[4]
Lithium nitride shows ionic conductivity for Li+, with a value of c. 2×10−4 Ω−1cm−1, and an (intracrystal) activation energy of c. 0.26 eV (c. 24 kJ/mol). Hydrogendoping increases conductivity, whilst doping with metal ions (Al, Cu, Mg) reduces it.[5][6] The activation energy for lithium transfer across lithium nitride crystals (intercrystalline) has been determined to be higher, at c. 68.5 kJ/mol.[7] The alpha form is a semiconductor with band gap of c. 2.1 eV.[4]
Under hydrogen at around 200°C, Li3N will react to form lithium amide.[10]
Li3N + 2 H2 → 2LiH + 2LiNH2
At higher temperatures it will react further to form ammonia and lithium hydride.
LiNH2 + H2 → LiH + NH3
Lithium imide can also be formed under certain conditions. Some research has explored this as a possible industrial process to produce ammonia since lithium hydride can be thermally decomposed back to lithium metal.
Lithium nitride has been investigated as a storage medium for hydrogen gas, as the reaction is reversible at 270 °C. Up to 11.5% by weight absorption of hydrogen has been achieved.[11]
^E. Döneges "Lithium Nitride" in Handbook of Preparative Inorganic Chemistry, 2nd Ed. Edited by G. Brauer, Academic Press, 1963, New York. Vol. 1. p. 984.
^Barker M. G.; Blake A. J.; Edwards P. P.; Gregory D. H.; Hamor T. A.; Siddons D. J.; Smith S. E. (1999). "Novel layered lithium nitridonickelates; effect of Li vacancy concentration on N co-ordination geometry and Ni oxidation state". Chemical Communications (13): 1187–1188. doi:10.1039/a902962a.
^ abWalker, G, ed. (2008). Solid-State Hydrogen Storage: Materials and Chemistry. §16.2.1 Lithium nitride and hydrogen:a historical perspective.
^Lapp, Torben; Skaarup, Steen; Hooper, Alan (October 1983). "Ionic conductivity of pure and doped Li3N". Solid State Ionics. 11 (2): 97–103. doi:10.1016/0167-2738(83)90045-0.
^Boukamp, B. A.; Huggins, R. A. (January 1978). "Fast ionic conductivity in lithium nitride". Materials Research Bulletin. 13 (1): 23–32. doi:10.1016/0025-5408(78)90023-5.
^Yun Hang Hu, Yan Huo (12 September 2011). "Fast and Exothermic Reaction of CO2 and Li3N into C–N-Containing Solid Materials". The Journal of Physical Chemistry A. 115 (42). The Journal of Physical Chemistry A 115 (42), 11678-11681: 11678–11681. Bibcode:2011JPCA..11511678H. doi:10.1021/jp205499e. PMID21910502.
