Strontium fluoride
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.[1][2]
Preparation
Strontium fluoride is prepared by the action of hydrofluoric acid on strontium carbonate.[3]
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°.[4] 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.[5] 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.[6]
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.[7]
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.[8]
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
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- ↑ 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) Script error: No such module "CS1 identifiers".
- ↑ 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 Script error: No such module "CS1 identifiers".
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