Hafnium nitrides

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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. [1]

HfN is refractory and generally produced as a thin film coating, [2] although zone annealing gives the bulk material. [3] HfN adopts the rock-salt crystal structure. [2] 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. [4]

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. [2] At lower pressures, the cubic structure is believed metastable, decaying to the orthorhombic structure of zirconium(IV) nitride. [4] [5] 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. [5]

In systems with limited nitrogen, hafnium also forms Hf3N2, as well as a solid solution hafnium alloy. [6]

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Boron nitride is a thermally and chemically resistant refractory compound of boron and nitrogen with the chemical formula BN. It exists in various crystalline forms that are isoelectronic to a similarly structured carbon lattice. The hexagonal form corresponding to graphite is the most stable and soft among BN polymorphs, and is therefore used as a lubricant and an additive to cosmetic products. The cubic variety analogous to diamond is called c-BN; it is softer than diamond, but its thermal and chemical stability is superior. The rare wurtzite BN modification is similar to lonsdaleite but slightly softer than the cubic form.

<span class="mw-page-title-main">Hafnium</span> Chemical element, symbol Hf and atomic number 72

Hafnium is a chemical element; it has symbol Hf and atomic number 72. A lustrous, silvery gray, tetravalent transition metal, hafnium chemically resembles zirconium and is found in many zirconium minerals. Its existence was predicted by Dmitri Mendeleev in 1869, though it was not identified until 1922, by Dirk Coster and George de Hevesy, making it one of the last two stable elements to be discovered. Hafnium is named after Hafnia, the Latin name for Copenhagen, where it was discovered.

Metallic hydrogen is a phase of hydrogen in which it behaves like an electrical conductor. This phase was predicted in 1935 on theoretical grounds by Eugene Wigner and Hillard Bell Huntington.

<span class="mw-page-title-main">Group 4 element</span> Group of chemical elements

Group 4 is the second group of transition metals in the periodic table. It contains the four elements titanium (Ti), zirconium (Zr), hafnium (Hf), and rutherfordium (Rf). The group is also called the titanium group or titanium family after its lightest member.

<span class="mw-page-title-main">Aluminium nitride</span> Chemical compound

Aluminium nitride (AlN) is a solid nitride of aluminium. It has a high thermal conductivity of up to 321 W/(m·K) and is an electrical insulator. Its wurtzite phase (w-AlN) has a band gap of ~6 eV at room temperature and has a potential application in optoelectronics operating at deep ultraviolet frequencies.

<span class="mw-page-title-main">Superhard material</span> Material with Vickers hardness exceeding 40 gigapascals

A superhard material is a material with a hardness value exceeding 40 gigapascals (GPa) when measured by the Vickers hardness test. They are virtually incompressible solids with high electron density and high bond covalency. As a result of their unique properties, these materials are of great interest in many industrial areas including, but not limited to, abrasives, polishing and cutting tools, disc brakes, and wear-resistant and protective coatings.

In chemistry, a nitride is an inorganic compound of nitrogen. The "nitride" anion, N3- ion, is very elusive but compounds of nitride are numerous, although rarely naturally occurring. Some nitrides have a found applications, such as wear-resistant coatings (e.g., titanium nitride, TiN), hard ceramic materials (e.g., silicon nitride, Si3N4), and semiconductors (e.g., gallium nitride, GaN). The development of GaN-based light emitting diodes was recognized by the 2014 Nobel Prize in Physics. Metal nitrido complexes are also common.

In the semiconductor industry, the term high-κ dielectric refers to a material with a high dielectric constant, as compared to silicon dioxide. High-κ dielectrics are used in semiconductor manufacturing processes where they are usually used to replace a silicon dioxide gate dielectric or another dielectric layer of a device. The implementation of high-κ gate dielectrics is one of several strategies developed to allow further miniaturization of microelectronic components, colloquially referred to as extending Moore's Law.

<span class="mw-page-title-main">Zirconium hydride</span> Alloy of zirconium and hydrogen

Zirconium hydride describes an alloy made by combining zirconium and hydrogen. Hydrogen acts as a hardening agent, preventing dislocations in the zirconium atom crystal lattice from sliding past one another. Varying the amount of hydrogen and the form of its presence in the zirconium hydride controls qualities such as the hardness, ductility, and tensile strength of the resulting zirconium hydride. Zirconium hydride with increased hydrogen content can be made harder and stronger than zirconium, but such zirconium hydride is also less ductile than zirconium.

<span class="mw-page-title-main">Hafnium carbide</span> Chemical compound

Hafnium carbide (HfC) is a chemical compound of hafnium and carbon. Previously the material was estimated to have a melting point of about 3,900 °C. More recent tests have been able to conclusively prove that the substance has an even higher melting point of 3,958 °C exceeding those of tantalum carbide and tantalum hafnium carbide which were both previously estimated to be higher. However, it has a low oxidation resistance, with the oxidation starting at temperatures as low as 430 °C. Experimental testing in 2018 confirmed the higher melting point yielding a result of 3,982 (±30°C) with a small possibility that the melting point may even exceed 4,000°C.

<span class="mw-page-title-main">Hafnium(IV) oxide</span> Chemical compound

Hafnium(IV) oxide is the inorganic compound with the formula HfO
2. Also known as hafnium dioxide or hafnia, this colourless solid is one of the most common and stable compounds of hafnium. It is an electrical insulator with a band gap of 5.3~5.7 eV. Hafnium dioxide is an intermediate in some processes that give hafnium metal.

<span class="mw-page-title-main">Vanadium nitride</span> Chemical compound

Vanadium nitride, VN, is a chemical compound of vanadium and nitrogen.

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Solid nitrogen is a number of solid forms of the element nitrogen, first observed in 1884. Solid nitrogen is mainly the subject of academic research, but low-temperature, low-pressure solid nitrogen is a substantial component of bodies in the outer Solar System and high-temperature, high-pressure solid nitrogen is a powerful explosive, with higher energy density than any other non-nuclear material.

In chemistry, a hydridonitride is a chemical compound that contains hydride and nitride ions in a single phase. These inorganic compounds are distinct from inorganic amides and imides as the hydrogen does not share a bond with nitrogen, and contain a larger proportion of metals.

Lanthanum hafnate or lanthanum hafnium oxide is a mixed oxide of lanthanum and hafnium.

Hafnium carbonitride (HfCN) is an ultra-high temperature ceramic (UHTC) mixed anion compound composed of hafnium (Hf), carbon (C) and nitrogen (N).

Samarium compounds are compounds formed by the lanthanide metal samarium (Sm). In these compounds, samarium generally exhibits the +3 oxidation state, such as SmCl3, Sm(NO3)3 and Sm(C2O4)3. Compounds with samarium in the +2 oxidation state are also known, for example SmI2.

Hafnium compounds are compounds containing the element hafnium (Hf). Due to the lanthanide contraction, the ionic radius of hafnium(IV) (0.78 ångström) is almost the same as that of zirconium(IV) (0.79 angstroms). Consequently, compounds of hafnium(IV) and zirconium(IV) have very similar chemical and physical properties. Hafnium and zirconium tend to occur together in nature and the similarity of their ionic radii makes their chemical separation rather difficult. Hafnium tends to form inorganic compounds in the oxidation state of +4. Halogens react with it to form hafnium tetrahalides. At higher temperatures, hafnium reacts with oxygen, nitrogen, carbon, boron, sulfur, and silicon. Some compounds of hafnium in lower oxidation states are known.

Polynitrides are solid chemical compounds with a large amount of nitrogen, beyond what would be expected from valencies. Some with N2 ions are termed pernitrides. Azides are not considered polynitrides, although pentazolates are.

References

  1. ↑ Bazhanov, D. I.; Knizhnik, A. A.; Safonov, A. A.; Bagatur’yants, A. A.; Stoker, M. W.; Korkin, A. A. (2005-02-15). "Structure and electronic properties of zirconium and hafnium nitrides and oxynitrides". Journal of Applied Physics. 97 (4). doi:10.1063/1.1851000. ISSN   0021-8979.
  2. 1 2 3 Zerr, Andreas; Miehe, Gerhard; Riedel, Ralf (2003-03-01). "Synthesis of cubic zirconium and hafnium nitride having Th3P4 structure". Nature Materials. 2 (3): 185–189. doi:10.1038/nmat836. ISSN   1476-1122.
  3. ↑ Christensen, A. Nørlund; Kress, W.; Miura, M.; Lehner, N. (1983-07-15). "Phonon anomalies in transition-metal nitrides: HfN". Physical Review B. 28 (2): 977–981. doi:10.1103/PhysRevB.28.977. ISSN   0163-1829.
  4. 1 2 Kroll, Peter (2003-03-25). "Hafnium Nitride with Thorium Phosphide Structure: Physical Properties and an Assessment of the Hf-N, Zr-N, and Ti-N Phase Diagrams at High Pressures and Temperatures". Physical Review Letters. 90 (12). doi:10.1103/PhysRevLett.90.125501. ISSN   0031-9007.
  5. 1 2 Zhang, Jin; Oganov, Artem R.; Li, Xinfeng; Niu, Haiyang (2017-01-18). "Pressure-stabilized hafnium nitrides and their properties". Physical Review B. 95 (2). doi: 10.1103/PhysRevB.95.020103 . ISSN   2469-9950.
  6. ↑ Ushakov, Sergey V.; Navrotsky, Alexandra; Hong, Qi-Jun; van de Walle, Axel (26 Aug 2019) [6 Aug 2019]. "Carbides and nitrides of zirconium and hafnium". Materials. 2019 (12). Basel: MDPI. doi: 10.3390/ma12172728 .
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