Scandium fluoride

Scandium fluoride
IUPAC name

Scandium(III) fluoride
Other names

Scandium trifluoride
Identifiers
CAS number 13709-47-2 N
PubChem 83678
RTECS number VQ8930000
Properties
Molecular formula ScF3
Molar mass 101.95112 g/mol
Appearance bright white powder
Density 2.53 g/cm3
Melting point

1552 °C[1]
Boiling point

1607 °C[1]
Structure
Crystal structure Rhombohedral, R32
Space group hR12, No. 155
Hazards
NFPA 704
0
2
0
Related compounds
Related compounds Scandium(III) chloride
Scandium(III) nitrate
 N (verify) (what is: Y/N?)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Scandium(III) fluoride, ScF3, is an ionic compound. It is slightly soluble in water but dissolves in the presence of excess fluoride to form ScF63−.[1] ScF3 can be produced by reacting scandium and fluorine.[2] It is also formed during the extraction from the ore thortveitite by the reaction of Sc2O3 with ammonium bifluoride at high temperature:[3]

Sc2O3 + NH4HF2 → 2ScF3 + 6NH4F + 3H2O

The resulting mixture contains a number of metal fluorides and this is reduced by reaction with calcium metal at high temperature.[3] Further purification steps are required to produce usable metallic scandium.[3]

Cubic Scandium trifluoride has an unusual Negative thermal expansion property, meaning it shrinks as it gets hotter. This is explained by the quartic oscillation of the fluoride ions. The energy stored in the bending strain of the fluoride ion is proportional to the fourth power of the displacement angle, unlike most other materials where it is proportional to the square of the displacement. A fluorine atom is bound to two scandium atoms, and as temperature increases the fluorine oscillates more perpendicularly to its bonds. This draws the scandium atoms together throughout the material and it contracts.[4] ScF3 exhibits this property from 10K to 1100K above which it shows the normal positive thermal expansion.[5]

References

  1. ^ a b c Egon Wiberg, Arnold Frederick Holleman (2001) Inorganic Chemistry, Elsevier ISBN 0123526515
  2. ^ S.A.Cotton, Scandium, Yttrium and the Lanthanides:Inorganic and Coordination Chemistry, Encyclopedia of Inorganic Chemistry, 1994, John Wiley & Sons, ISBN 0471936200
  3. ^ a b c Pradyot Patnaik, 2003, Handbook of Inorganic Chemicals, McGraw-Hill Professional, ISBN 0070494398
  4. ^ Woo, Marcus (7 November 2011). "An incredible shrinking material: Engineers reveal how scandium trifluoride contracts with heat". Physorg. http://www.physorg.com/news/2011-11-incredible-material-reveal-scandium-trifluoride.html. Retrieved 8 November 2011. 
  5. ^ Greve, Benjamin K.; Kenneth L. Martin, Peter L. Lee, Peter J. Chupas, Karena W. Chapman, Angus P. Wilkinson (19 October 2010). "Pronounced negative thermal expansion from a simple structure: cubic ScF(3).". Journal of the American Chemical Society 132 (44): 15496–15498. doi:10.1021/ja106711v. PMID 20958035. http://pubs.acs.org/doi/abs/10.1021/ja106711v.