alpha-Li3N (stable at room temperature and pressure) has an unusual crystal structure that consists of two types of layers: one layer has the compositionLi2N− contains6-coordinate N centers and the other layer consists only of lithium cations.[3]
Two other forms are known:
beta-Li3N, formed from thealpha phase at 0.42GPa has thesodium arsenide (Na3As) structure;
gamma-Li3N (same structure as lithium bismuthideLi3Bi) forms from thebeta form at 35 to 45 GPa.[4]
Lithium nitride showsionic conductivity forLi+, 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 increasesconductivity, 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] Thealpha form is asemiconductor withband gap of c. 2.1 eV.[4]
Under hydrogen at around 200°C, Li3N will react to formlithium amide.[10]
Li3N + 2 H2 → 2LiH + LiNH2
At higher temperatures it will react further to form ammonia andlithium 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 astorage medium forhydrogen 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" inHandbook 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.
