Structures of lithium nitride (α-Li3N) and ternary nitridometalates Li3-x-yMxN (M = Ni, Cu) have been refined from time-of-flight powder neutron diffraction data using the Rietveld method. The parent binary nitride was synthesized by reaction of lithium metal with nitrogen using liquid sodium as a solvent. The ternary nitrides were prepared by reaction of Li3N with the respective transition metals under nitrogen. Refined data confirm the hexagonal structure previously reported by single-crystal X-ray diffraction for lithium nitride (P6/mmm, a = 3.6576(1) Å, c = 3.8735(1) Å, Z = 1) and show that the α-Li3N phase contains close to 3% Li vacancies at room temperature. The substituted nitridometalates, Li1.36Ni0.79N and Li2.21Cu0.40N, both form structures analogous to α-Li3N (P6/mmm, a = 3.7697(1) Å, c = 3.5270(1) A and a = 3.6791(1) Å, c = 3.7725(1) Å, respectively) in which the transition metal is disordered with Li between [Li2-yN] planes and Li vacancies are disordered within these planes. The nickel and copper nitrides contain 43% (y = 0.85) and 16% (y = 0.32) Li vacancies, respectively, within the [Li2N] planes and consequently contain transition metals predominantly in the +2 oxidation state.
All Science Journal Classification (ASJC) codes
- Chemical Engineering(all)
- Materials Chemistry