Lithium Intercalated Beta-Zirconium Nitride Chloride

Class: Intercalation Solid, Synthetic

Related Structures: Lithium intercalated hafnium nitrogen chloride, SmSI

Notable Properties: Superconductivity, Electrochromism

Crystal structure of LiZrNCl. Zr, yellow), N blue), Cl green).
Crystal structure of ZrNCl, a wide bandgap semiconductor. Zr, (yellow), N (blue), Cl (green).

 

Description:

Zirconium nitrogen chloride is a layered structure with a double layer of ZrNCl. The chloride anions order similarly to the cadmium iodide structure type though the geometry at the Zr centers is now seven coordinate. Nitride centers occupy pseudo-tetrahedral site. As synthesized (from ZrH2 and NH4Cl heated to 650 °C), ZrNCl is a 3 eV bandgap semiconductor. However, the solid can be reduced post-synthetically via reductive intercalation of lithium.

Crystal structure of LiZrNCl. Li white), Zr, yellow), N blue), Cl green).
Crystal structure of LixZrNCl, a superconductor at 13 K. Li (white), Zr, (yellow), N (blue), Cl (green).

By reduction with n-butyllithium in THF the nonstoichiometric phase LixZrNCl(THF)y can be synthesized to yield a rare case of what is formally trivalent zirconium. Upon reduction the material goes from electronically insulating to metallic at room temperature and transitions to a superconductor at about 13 K (link). Hafnium forms an isostructural phase that is superconducting below 25.5 K (link). These materials represented the first case of superconductivity in a metal nitride and displays a particularly dramatic change in electronic properties for an intercalation reaction.

Formula: LixZrNCl(THF)2x 0 < x < 0.13 (structure reported without THF upto x = 0.43)

Space Group: R-3m

Lattice Parameters: a = 3.59; c = 27.839

Similar phases: LixZrNBr(THF)2x  and LixHfNCl(THF)2x

Reaction Notes: Reductive intercalation (assumed reversible)

Further Reading:

A new layer-structured nitride superconductor. Lithium-intercalated β-zirconium nitride chloride, LixZrNCl
Superconductivity at 25.5 K in electron-doped layered hafnium nitride
Superconductivity of Alkali Metal Intercalated alpha-Zirconium Nitride Chloride, AxZrNCl (A = Li, Na, K)
Preparation and Superconductivity of New Stage and Polytypic Phases in Potassium-Intercalated Zirconium Nitride Chloride (KxZrNCl)
Superconducting intercalation compounds of metal nitride halides

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