|Jmol-3D images||Image 1|
|Molar mass||210.49 g/mol|
|Density||9.68 g/cm3, solid|
|Solubility in water||insoluble|
|EU Index||Not listed|
|Other cations||Titanium(IV) oxide
|Related compounds||Hafnium nitride|
| (what is: / ?)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Hafnium(IV) oxide is the inorganic compound with the formula HfO2. Also known as 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 approximately 6 eV. 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.
Hafnia is used in optical coatings, and as a high-k dielectric in DRAM capacitors. Hafnium-based oxides are currently leading candidates to replace silicon oxide as a gate insulator in field effect transistors. The advantage for transistors is its high dielectric constant: The dielectric constant of HfO2 is 25, whereas the dielectric constant of SiO2 is only 3.9.
- Review article by Wilk et al. in the Journal of Applied Physics, Table 1
- Very High Temperature Exotic Thermocouple Probes product data, Omega Engineering, Inc., retrieved 2008-12-03
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