Strontium fluoride, SrF2, also called strontium difluoride and strontium(II) fluoride, is a fluoride of strontium. It is a brittle white crystalline solid. In nature, it appears as the very rare mineral strontiofluorite.[2][3]

Preparation

Strontium fluoride is prepared by the action of hydrofluoric acid on strontium carbonate.[4]

Structure

The solid adopts the fluorite structure. In the vapour phase the SrF2 molecule is non-linear with an F−Sr−F angle of approximately 120°.[5] This is an exception to VSEPR theory which would predict a linear structure. Ab initio calculations have been cited to propose that contributions from d orbitals in the shell below the valence shell are responsible.[6] Another proposal is that polarization of the electron core of the strontium atom creates an approximately tetrahedral distribution of charge that interacts with the Sr−F bonds.[7]

Properties

It is almost insoluble in water (its Ksp value is approximately 2.0x10−10 at 25 degrees Celsius).

It irritates eyes and skin, and is harmful when inhaled or ingested.
Similar to CaF2 and BaF2, SrF2 displays superionic conductivity at elevated temperatures.[8]

Strontium fluoride is transparent to light in the wavelengths from vacuum ultraviolet (150 nm) to infrared (11 μm). Its optical properties are intermediate to calcium fluoride and barium fluoride.[9]

Uses

Strontium fluoride is used as an optical material for a small range of special applications, for example, as an optical coating on lenses and also as a thermoluminescent dosimeter crystal.

Another use is as a carrier of strontium-90 radioisotope in radioisotope thermoelectric generators.

References

  1. ^ John Rumble (June 18, 2018). CRC Handbook of Chemistry and Physics (99 ed.). CRC Press. pp. 5–189. ISBN 978-1138561632.
  2. ^ "Strontiofluorite".
  3. ^ "List of Minerals". 21 March 2011.
  4. ^ W. Kwasnik (1963). "Strontium Fluoride". In G. Brauer (ed.). Handbook of Preparative Inorganic Chemistry, 2nd Ed. Vol. 1. NY, NY: Academic Press. p. 234.
  5. ^ Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8.
  6. ^ Ab initio model potential study of the equilibrium geometry of alkaline earth dihalides: MX2 (M = Mg, Ca, Sr, Ba; X=F, Cl, Br, I)Seijo L.,Barandiarán Z J. Chem. Phys. 94, 3762 (1991) doi:10.1063/1.459748
  7. ^ Core Distortions and Geometries of the Difluorides and Dihydrides of Ca, Sr, and Ba Bytheway I, Gillespie RJ, Tang TH, Bader RF Inorganic Chemistry, Vol.34, No.9, 2407-2414, 1995 doi:10.1021/ic00113a023
  8. ^ "Newmet Koch - Strontium". Archived from the original on 2005-12-14.
  9. ^ Mediatopia Ltd. "Strontium Fluoride SrF2". Crystran.com. Retrieved 2025-02-08.
Allikas: https://en.wikipedia.org/wiki/Strontium_fluoride
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