Synthesis and structure of the ternary and quaternary strontium nitride halides, Sr2N(X, X′) (X, X′=Cl, Br, I)

A number of new, layered nitride mixed halides have been synthesised in the quaternary phase systems Sr–N–Cl–Br and Sr–N–Br–I. The variation in structure with composition has been investigated by powder X-ray and powder neutron diffraction techniques and the structure of strontium nitride iodide, Sr2NI, has been determined for the first time (rhombohedral space group R-3m  , a=4.0103(1)Å, c=23.1138(2)Å, Z=3Z=3). A continuous solid solution exists between Sr2NCl and Sr2NBr with intermediate compounds adopting the same anti-α-NaFeO2 structure (rhombohedral space group R-3m) as the ternary end members. A similar smooth and linear relationship between structure and composition is seen from Sr2NBr to Sr2NI and hence cubic close packing of metal–nitrogen layers is adopted regardless of halide, X (X′). While nitride and halide anions occupy distinct crystallographic sites, there is no ordering of the halides in the quaternary materials irrespective of stoichiometry or temperature (between 3 and 673 K).

New ternary and quaternary nitride halides, Sr2N(Cl, Br) and Sr2N(Br, I) have been synthesised. The CCP layered structures of the insulating nitride halides persist irrespective of the halide, X, or the temperatures investigated.Figure optionsDownload as PowerPoint slide