|Molar mass||82.94 g/mol|
|Appearance||Deep Blue Powder|
|Density||4.571 g/cm3 (monoclinic)
4.653 g/cm3 (tetragonal)
|Crystal structure||Distorted rutile (<70 °C, monoclinic)
Rutile (>70 °C, tetragonal)
|EU Index||Not listed|
|Other anions||Vanadium disulfide
|Other cations||Niobium(IV) oxide
|Related vanadium oxides||Vanadium(II) oxide
| (what is: / ?)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Vanadium(IV) oxide is the inorganic compound with the formula VO2. It is a dark blue solid. Vanadium(IV) oxide is amphoteric, dissolving in non-oxidising acids to give the vanadyl ion, [VO]2+ and in alkali to give the [V4O9]2− ion, or at high pH [VO4]4−.
Synthesis and structure
- V2O5 + V2O3 → 4 VO2
At room temperature VO2 has a distorted rutile structure with shorter distances between pairs of V atoms indicating metal-metal bonding. Above 68 °C the structure changes to an undistorted rutile structure and the metal-metal bonds are broken causing an increase in electrical conductivity and magnetic susceptibility as the bonding electrons are "released". The origin of this metal to insulator transition remains controversial and is of interest in condensed matter physics.
Tungsten-doped vanadium dioxide (W:VO2) with 1.9% tungsten content has been investigated for use as a "spectrally-selective" window coating to block infrared transmission and reduce the loss of building interior heat through windows. This material behaves like a semiconductor at temperatures below 29 °C, allowing more transmission, and like a conductor at higher temperatures, providing much greater reflectivity. Varying the amount of tungsten allows regulating the phase transition temperature. However, the coating has a slight yellow-green color.
Vanadium dioxide can act as extremely fast optical shutters, optical modulators, infrared modulators for missile guidance systems, cameras, data storage, and other applications.. The thermochromic phase transition between the transparent semiconductive and reflective conductive phase, occurring at 68 °C, can happen in times as short as 100 femtoseconds.
- Greenwood, Norman N.; Earnshaw, Alan (1984). Chemistry of the Elements. Oxford: Pergamon Press. pp. 1144–45. ISBN 0-08-022057-6.
- Handbook of Preparative Inorganic Chemistry, 2nd Ed. Edited by G. Brauer, Academic Press, 1963, NY. Vol. 1. p. 1267.
- "Sol-Gel Vanadium oxide". Solgel.com. Retrieved 2012-09-12.
- "Intelligent Window Coatings that Allow Light In but Keep Heat Out - News Item". Azom.com. Retrieved 2012-09-12.
- "Eye on Technology". oe magazine. 2009-11-03. Retrieved 2012-09-12.
- "Timing nature’s fastest optical shutter". Physorg.com. Retrieved 2012-09-12.