IngentaConnect An Unusual Metallic Nitride: Sr2NiN2

Authors: Kowach G.R.; Brese N.E.; Bolle U.M.; Warren C.J.; DiSalvo F.J.

Source: Journal of Solid State Chemistry, Volume 154, Number 2, November 2000 , pp. 542-550(9)

Abstract:

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 R_w(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. Copyright 2000 Academic Press.

Keywords: liquid sodium; flux crystal growth; nitride; twinning; superstructure.

Language: English

Document Type: Research article

Affiliations: Baker Laboratory, Cornell University, Ithaca, New York, 14853:

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