An Unusual Metallic Nitride: Sr2NiN2

• Published in: Journal of solid state chemistry Vol. 154; no. 2; pp. 542 - 550
• Main Authors: Kowach, Glen R., Brese, N.E., Bolle, U.M., Warren, C.J., DiSalvo, F.J.
• Format: Journal Article
• Language: English
• Published: San Diego, CA Elsevier Inc 01-11-2000; Elsevier
• Subjects: Chemistry; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Conductivity phenomena in semiconductors and insulators; Electronic transport in condensed matter; Elements and non-metal compounds (oxides, hydroxides, hydrides, sulfides, carbides, ...); Exact sciences and technology; flux crystal growth; Hydrides, borides, nitrides, etc., and metalloidal compounds; Inorganic chemistry and origins of life; Inorganic compounds; liquid sodium; Low-field transport and mobility; piezoresistance; Magnetic properties and materials; Magnetically ordered materials: other intrinsic properties; nitride; Physics; Preparations and properties; Saturation moments and magnetic susceptibilities; Structure of solids and liquids; crystallography; Structure of specific crystalline solids; superstructure; twinning; flux crystal growth; twinning; liquid sodium; nitride; superstructure; Band structure; Electrical conductivity; Flux growth; Experimental study; X ray diffraction; Inorganic compound; Magnetic susceptibility; Nickel nitride; Electronic structure; Transition metal compounds; Chemical preparation; Superstructure; Paramagnetic materials; Crystal growth from solutions; Growth from solution; Strontium nitride; Crystalline structure
• ISSN: 0022-4596; 1095-726X
• DOI: 10.1006/jssc.2000.8877

The synthesis of single crystals of Sr2NiN2 has been accomplished in a liquid sodium flux from strontium or strontium nitride, nickel, and sodium azide. The decomposition of sodium azide provides additional nitrogen for the synthesis. The structure of Sr2NiN2 is derived from the Na2HgO2 structure type. However, Sr2NiN2 forms with a twinned superstructure. Single crystal X-ray diffraction was used to determine the structure of the tetragonal subcell: I4/mmm, a=3.8874(3) Å, c=13.992(2) Å, Z=2, R(F)=5.2%, and Rw(F)=5.0% with the Ni and N positions split into two sites, each half occupied. The superstructure can be modeled as a 2×1×1 ordering of the subcell in Pnma. The physical properties are unusual since Sr2NiN2 displays metallic conductivity and Pauli paramagnetism even though it is comprised of isolated NiN2 units. In addition, Sr2NiN2 possesses a Ni2+ formal charge, whereas the oxidation states for nickel nitrides are typically Ni+ and Ni0.