Ternary lithium nitridocuprates, Li_3-x-yCu_xN: Crystal growth, bulk synthesis, structure and magnetic properties

Systematic studies within the ternary Li-Cu-N system have examined the effects of varying starting materials, transition metal stoichiometry, reaction temperature/duration and cooling rate on crystal growth and bulk phase formation of ternary nitridocuprates. Resulting lithium transition metal compounds, Li_3-x-y□_yCu_xN (□=Li vacancy), have been characterised by single crystal and powder XRD. The maximum copper substituent level (x≈0.45) and vacancy level, y, appear insensitive to reaction temperature. Both vacancies and copper are disordered with Li when reaction mixtures are quenched (α-Li₃N-type: P6/mmm, α≈3.7 Å, c≈3.8 Å, Z=1), whereas evidence of copper and/or vacancy ordering exists on slow cooling. Morphology of crystallites has been evaluated by SEM and magnetic properties have been investigated using SQUID magnetometry. Magnetic data show compounds exhibit temperature dependent paramagnetism in contrast to the parent nitride, Li₃N.