Hafnium(IV) oxide

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Hafnium(IV) oxide
Hafnium(IV) oxide structure
Hafnium(IV) oxide
Names
IUPAC name
Hafnium(IV) oxide
Other names
Hafnium dioxide
Hafnia
Identifiers
3D model (
JSmol
)
ChemSpider
ECHA InfoCard
 100.031.818 Edit this at Wikidata
EC Number
  • 235-013-2
UNII
  • InChI=1S/Hf.2O checkY
    Key: CJNBYAVZURUTKZ-UHFFFAOYSA-N checkY
  • InChI=1/Hf.2O/rHfO2/c2-1-3
    Key: CJNBYAVZURUTKZ-MSHMTBKAAI
  • O=[Hf]=O
Properties
HfO2
Molar mass 210.49 g/mol
Appearance off-white powder
Density 9.68 g/cm3, solid
Melting point 2,758 °C (4,996 °F; 3,031 K)
Boiling point 5,400 °C (9,750 °F; 5,670 K)
insoluble
−23.0·10−6 cm3/mol
Hazards
Flash point Non-flammable
Related compounds
Other cations
Zirconium(IV) oxide
Related compounds
 Hafnium nitride
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Hafnium(IV) oxide is the

eV.[1]
Hafnium dioxide is an intermediate in some processes that give hafnium metal.

Hafnium(IV) oxide is quite inert. It reacts with strong acids such as concentrated sulfuric acid and with strong bases. It dissolves slowly in hydrofluoric acid to give fluorohafnate anions. At elevated temperatures, it reacts with chlorine in the presence of graphite or carbon tetrachloride to give hafnium tetrachloride.

Structure

Hafnia typically adopts the same structure as zirconia (ZrO2). Unlike TiO2, which features six-coordinate Ti in all phases, zirconia and hafnia consist of seven-coordinate metal centres. A variety of other crystalline phases have been experimentally observed, including cubic fluorite (Fm3m), tetragonal (P42/nmc), monoclinic (P21/c) and orthorhombic (Pbca and Pnma).[2] It is also known that hafnia may adopt two other orthorhombic metastable phases (space group Pca21 and Pmn21) over a wide range of pressures and temperatures,[3] presumably being the sources of the ferroelectricity observed in thin films of hafnia.[4]

Thin films of hafnium oxides deposited by

hafnium silicates), which have a higher crystallization temperature than hafnium oxide.[5]

Applications

Hafnia is used in

dielectric constant: the dielectric constant of HfO2 is 4–6 times higher than that of SiO2.[8]
The dielectric constant and other properties depend on the deposition method, composition and microstructure of the material.

Hafnium oxide (as well as doped and oxygen-deficient hafnium oxide) attracts additional interest as a possible candidate for resistive-switching memories

FeFET memory) and memory chips.[10][11][12][13]

Because of its very high melting point, hafnia is also used as a refractory material in the insulation of such devices as thermocouples, where it can operate at temperatures up to 2500 °C.[14]

Multilayered films of hafnium dioxide, silica, and other materials have been developed for use in passive cooling of buildings. The films reflect sunlight and radiate heat at wavelengths that pass through Earth's atmosphere, and can have temperatures several degrees cooler than surrounding materials under the same conditions.[15]

References

  1. doi:10.1103/PhysRevB.78.085114
    .
  2. doi:10.1063/1.4757907
    .
  3. S2CID 53347579
    .
  4. doi:10.1063/1.3634052
    .
  5. doi:10.1016/j.mser.2010.12.001
    .
  6. S2CID 7806254
    .
  7. Intel (11 November 2007). "Intel's Fundamental Advance in Transistor Design Extends Moore's Law, Computing Performance"
    .
  8. doi:10.1063/1.1361065.{{cite journal}}: CS1 maint: multiple names: authors list (link
    ), Table 1
  9. doi:10.1063/1.3567915
    .
  10. Imec (7 June 2017). "Imec demonstrates breakthrough in CMOS-compatible Ferroelectric Memory"
    .
  11. ^ The Ferroelectric Memory Company (8 June 2017). "World's first FeFET-based 3D NAND demonstration".
  12. ISBN 978-1-4577-0505-2
    .
  13. ^ Nivole Ahner (August 2018). Mit HFO2 voll CMOS-kompatibel (in German). Elektronik Industrie.
  14. ^ Very High Temperature Exotic Thermocouple Probes product data, Omega Engineering, Inc., retrieved 2008-12-03
  15. ^ "Aaswath Raman | Innovators Under 35 | MIT Technology Review". August 2015. Retrieved 2015-09-02.
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