- Source: Hafnium nitrides
The hafnium nitrides are the various salts produced from combining hafnium and nitrogen. The two most important such are hafnium(III) nitride, HfN; and hafnium(IV) nitride, Hf3N4. None can be prepared from hafnium oxide, but must instead be prepared from the elemental metal or a different hafnium nitride salt; attempted nitridation of the oxide gives an oxynitride instead.
HfN is refractory and generally produced as a thin film coating, although zone annealing gives the bulk material. HfN adopts the rock-salt crystal structure. The surplus hafnium electron delocalizes, so that HfN is a metal, conducting at room temperature and superconducting below 8.8 K (−443.83 °F). Its bright gold color is a cheaper alternative to gilding.
The dark red semiconductor Hf3N4 does not form at room temperature, but requires high pressure, high temperature synthesis in a diamond anvil cell. At 18 GPa (180,000 atm) and 2,800 K (4,580 °F), it adopts the cubic crystal structure and repeats according to space group I{{{1}}}3d. At lower pressures, the cubic structure is believed metastable, decaying to the orthorhombic structure of zirconium(IV) nitride. That structure forms outright at 19 GPa and 2,000 K (3,140 °F), and another metastable tetragonal structure forms at 12 GPa and 1,500 K (2,240 °F). Computational studies suggest that it may catalyze polymerization of nitrogen at very high temperatures, through a catenary anion in HfN10.
In systems with limited nitrogen, hafnium also forms Hf3N2, as well as a solid solution hafnium alloy.
References
Kata Kunci Pencarian:
- Boron
- Hafnium nitrides
- Hafnium
- Hafnium(IV) oxide
- Hafnium carbonitride
- Hafnium carbide
- Cubic crystal system
- Group 4 element
- Hafnium compounds
- Zirconium
- Nitrogen
