Tungsten nitride (W2N, WN, WN2) is an inorganic compound, a nitride of tungsten. It is a hard, solid, brown-colored ceramic material that is electrically conductive and decomposes in water. It is used in microelectronics as a contact material, for conductive layers, and barrier layers between silicon and other metals, e.g. tungsten or copper. It is less commonly used than titanium nitride or tungsten films. Tungsten nitride forms together with tungsten dioxide, tungsten trioxide, and tungsten pentoxide when an incandescent light bulb breaks while the filament is heated. Tungsten silicide is another material with similar use.
High-pressure tungsten nitrides In addition to the tungsten nitrides used industrially, two novel ultra-incompressible tungsten nitrides, W2N3 and W3N5, were synthesized in 2024 through the direct reaction of tungsten with molecular nitrogen at 35 and 56 GPa respectively, in laser-heated diamond anvil cells. Their crystal structures were solved using synchrotron single-crystal X-ray diffraction: W2N3 contains only discrete N3− nitride anions, while W3N5 also features N24− pernitride dimers. Both compounds are built from WN7 polyhedra and have experimentally determined bulk moduli of 380 and 406 GPa respectively, qualifying them as ultra-incompressible. Density functional theory calculations found Vickers hardness values of 30 and 34 GPa for W2N3 and W3N5, and predicted superconducting transition temperatures at ambient pressure of 11.6 K and 9.4 K; transport measurements on W2N3 at 50 GPa showed a resistance drop consistent with superconductivity at 11.2 K, close to the calculated value. Both nitrides were found to be recoverable to ambient conditions and stable in air.
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