Calcium fluoride

Calcium fluoride

Identifiers
CAS Number	7789-75-5  Y
3D model (JSmol)	Interactive image Interactive image
ChEBI	CHEBI:35437  Y
ChemSpider	23019  Y
ECHA InfoCard	100.029.262
EC Number	232-188-7
PubChem CID	24617
RTECS number	EW1760000
UNII	O3B55K4YKI  Y
CompTox Dashboard (EPA)	DTXSID4050487
InChI InChI=1S/Ca.2FH/h;2*1H/q+2;;/p-2 Y Key: WUKWITHWXAAZEY-UHFFFAOYSA-L Y InChI=1/Ca.2FH/h;2*1H/q+2;;/p-2 Key: WUKWITHWXAAZEY-NUQVWONBAZ
SMILES [Ca+2].[F-].[F-] F[Ca]F
Properties
Chemical formula	CaF2
Molar mass	78.075 g·mol−1
Appearance	White crystalline solid (single crystals are transparent)
Density	3.18 g/cm3
Melting point	1,418 °C (2,584 °F; 1,691 K)
Boiling point	2,533 °C (4,591 °F; 2,806 K)
Solubility in water	0.015 g/L (18 °C) 0.016 g/L (20 °C)
Solubility product (Ksp)	3.9 × 10−11 [1]
Solubility	insoluble in acetone slightly soluble in acid
Magnetic susceptibility (χ)	−28.0·10−6 cm3/mol
Refractive index (nD)	1.4338
Structure
Crystal structure	cubic crystal system, cF12 [2]
Space group	Fm3m, #225
Lattice constant	a = 5.451 Å, b = 5.451 Å, c = 5.451 Å α = 90°, β = 90°, γ = 90°
Coordination geometry	Ca, 8, cubic F, 4, tetrahedral
Hazards
Occupational safety and health (OHS/OSH):
Main hazards	Reacts with concentrated sulfuric acid to produce hydrofluoric acid
NFPA 704 (fire diamond)	0 0 0
Flash point	Non-flammable
Lethal dose or concentration (LD, LC):
LDLo (lowest published)	>5000 mg/kg (oral, guinea pig) 4250 mg/kg (oral, rat) [3]
Safety data sheet (SDS)	ICSC 1323
Related compounds
Other anions	Calcium chloride Calcium bromide Calcium iodide
Other cations	Beryllium fluoride Magnesium fluoride Strontium fluoride Barium fluoride
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Y  verify  (what is  YN ?) Infobox references

Calcium fluoride is the inorganic compound of the elements calcium and fluorine with the formula CaF₂. It is a white solid that is practically insoluble in water. It occurs as the mineral fluorite (also called fluorspar), which is often deeply coloured owing to impurities.

Chemical structure

Main article: Fluorite structure

The compound crystallizes in a cubic motif called the fluorite structure.

Unit cell of CaF₂, known as fluorite structure, from two equivalent perspectives. The second origin is often used when visualising point defects centred on the cation.

Ca²⁺ centres are eight-coordinate, being centred in a cube of eight F⁻ centres. Each F⁻ centre is coordinated to four Ca²⁺ centres in the shape of a tetrahedron. ^[5] Although perfectly packed crystalline samples are colorless, the mineral is often deeply colored due to the presence of F-centers. The same crystal structure is found in numerous ionic compounds with formula AB₂, such as CeO₂, cubic ZrO₂, UO₂, ThO₂, and PuO₂. In the corresponding anti-structure, called the antifluorite structure, anions and cations are swapped, such as Be₂C.

Gas phase

The gas phase is noteworthy for failing the predictions of VSEPR theory; the CaF₂ molecule is not linear like MgF₂, but bent with a bond angle of approximately 145°; the strontium and barium dihalides also have a bent geometry. ^[6] It has been proposed that this is due to the fluoride ligands interacting with the electron core ^{[7] [8]} or the d-subshell ^[9] of the calcium atom.

Preparation

Main article: Fluorite

Naturally occurring mineral fluorite(CaF₂)is the principal source of hydrogen fluoride, a commodity chemical used to produce a wide range of materials. Calcium fluoride in the fluorite state is of significant commercial importance as a fluoride source. ^[10] Hydrogen fluoride is liberated from the mineral by the action of concentrated sulfuric acid: ^{[11] [12]}

CaF₂ + H₂SO₄ → CaSO₄(solid) + 2 HF

High purity CaF₂ is produced from the HF in the above reaction by treating calcium carbonate with hydrofluoric acid: ^[13]

CaCO₃ + 2 HF → CaF₂ + CO₂ + H₂O

Waste Product

Separately, calcium fluoride can be generated as a waste product via ion exchange of PFAS rich water using a durable layered double hydroxide(LDH) membrane of copper and aluminum heated to 500C. ^{[14] [15]}

Commercial Uses of Calcium Fluoride

Optical Applications

Lenses and Windows: Calcium fluoride is transparent over a broad range from ultraviolet (UV) to infrared (IR) frequencies. Its low refractive index reduces the need for anti-reflection coatings. Its insolubility in water is convenient as well.^{[ citation needed ]} It also allows much smaller wavelengths to pass through.^{[ citation needed ]} Calcium fluoride is used to manufacture optical components such as windows and lenses used in:

• thermal imaging systems
• spectroscopy
• telescopes
• excimer lasers (used for photolithography in the form of a fused lens).

Metallurgical Applications

• Flux in Metal Production: Acts as a flux in the production of aluminum and steel, helping to remove impurities and improve metal quality.
• Cement and Concrete: Enhances properties in cement production, reducing melting points and improving energy efficiency.

Chemical Industry

• Source of Hydrogen Fluoride: Serves as a precursor for producing hydrogen fluoride, which is essential in various chemical processes:

1. Feedstock for the creation of fluorochemical refrigerants ^[16]

• Pesticides and Fungicides: Used in formulations to stabilize products and protect crops.
• Certain well-categorized molecular calcium fluorides can serve as reagents for nucleophilic fluoride addition to organic compounds. ^{[17] [18]} Well-characterized molecular calcium fluorides are clusters are formed by treating CaF₂ with large, multidentate ligands. ^[19]

Glass and Ceramics

• Specialty Glass Manufacturing: Contributes to the production of glasses with improved thermal and chemical resistance.
• Ceramics: Enhances the mechanical properties of ceramic materials.

Dental and Health Products

• Fluoride Supplements: Incorporated into dental products to strengthen tooth enamel and prevent decay.

Medical Applications

• Doped calcium fluoride, like natural fluorite, exhibits thermoluminescence and is used in thermoluminescent dosimeters. It forms when fluorine combines with calcium.^{[ citation needed ]}durability.

Other Applications

• Paints and Coatings: Functions as an opacifying agent in paints, improving brightness and durability.
• Sealants and Adhesives: Used as an inert filler in sealants, enhancing performance.

Safety

CaF₂ is classified as "not dangerous", although reacting it with sulfuric acid produces hydrofluoric acid, which is highly corrosive and toxic. With regards to inhalation, the NIOSH-recommended concentration of fluorine-containing dusts is 2.5 mg/m³ in air. ^[13]

See also

• List of laser types
• Photolithography
• Skeletal fluorosis

References

1. Pradyot Patnaik. Handbook of Inorganic Chemicals. McGraw-Hill, 2002, ISBN   0-07-049439-8.
2. X-ray Diffraction Investigations of CaF₂ at High Pressure, L. Gerward, J. S. Olsen, S. Steenstrup, M. Malinowski, S. Åsbrink and A. Waskowska, Journal of Applied Crystallography (1992), 25, 578–581, doi:10.1107/S0021889892004096.
3. "Fluorides (as F)". Immediately Dangerous to Life or Health Concentrations. National Institute for Occupational Safety and Health.
4. Burr, P. A.; Cooper, M. W. D. (2017-09-15). "Importance of elastic finite-size effects: Neutral defects in ionic compounds". Physical Review B. 96 (9) 094107. arXiv: 1709.02037 . Bibcode:2017PhRvB..96i4107B. doi:10.1103/PhysRevB.96.094107. S2CID   119056949.
5. G. L. Miessler and D. A. Tarr "Inorganic Chemistry" 3rd Ed, Pearson/Prentice Hall publisher, ISBN   0-13-035471-6.
6. Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. doi:10.1016/C2009-0-30414-6. ISBN   978-0-08-037941-8.
7. Gillespie, R. J.; Robinson, E. A. (2005). "Models of molecular geometry". Chem. Soc. Rev. 34 (5): 396–407. doi:10.1039/b405359c. PMID   15852152.
8. Bytheway, I.; Gillespie, R. J.; Tang, T. H.; Bader, R.F (1995). "Core Distortions and Geometries of the Difluorides and Dihydrides of Ca, Sr, and Ba". Inorg. Chem. 34 (9): 2407–2414. doi:10.1021/ic00113a023.
9. Seijo, Luis; Barandiarán, Zoila; Huzinaga, Sigeru (1991). "Ab initio model potential study of the equilibrium geometry of alkaline earth dihalides: MX₂ (M=Mg, Ca, Sr, Ba; X=F, Cl, Br, I)" (PDF). J. Chem. Phys. 94 (5): 3762. Bibcode:1991JChPh..94.3762S. doi:10.1063/1.459748. hdl: 10486/7315 .
10. Aigueperse, Jean; Mollard, Paul; Devilliers, Didier; Chemla, Marius; Faron, Robert; Romano, René; Cuer, Jean Pierre (2000). "Fluorine Compounds, Inorganic". Ullmann's Encyclopedia of Industrial Chemistry. doi:10.1002/14356007.a11_307. ISBN   3-527-30673-0.
11. Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. ISBN   0-12-352651-5.
12. Harsanyi, Antal; Sandford, Graham (2015). "Organofluorine chemistry: applications, sources and sustainability". Green Chemistry. 17 (4): 2081–2086. doi:10.1039/C4GC02166E. ISSN   1463-9262.
13. Aigueperse, Jean; Mollard, Paul; Devilliers, Didier; Chemla, Marius; Faron, Robert; Romano, René; Cuer, Jean Pierre (2000). "Fluorine Compounds, Inorganic". Ullmann's Encyclopedia of Industrial Chemistry . Weinheim: Wiley-VCH. doi:10.1002/14356007.a11_307. ISBN   3527306730.
14. Perkins, Tom (2026-01-23). "New filtration technology could be gamechanger in removal of Pfas 'forever chemicals'". The Guardian. ISSN   0261-3077 . Retrieved 2026-01-24.
15. Kim, Keon-Han; Chung, Youngkun; Kenyon, Philip; Tran, Thi Nhung; Rees, Nicholas H.; Choi, Seung-Ju; Huang, Xiaopeng; Choi, Jong Hui; Scotland, Phelecia; Kim, Sion; Ateia, Mohamed; Lee, Do-Kyoung; Tour, James M.; Alvarez, Pedro J. J.; Wong, Michael S. (2026). "Regenerable Water Remediation Platform for Ultrafast Capture and Mineralization of Per- and Polyfluoroalkyl Substances". Advanced Materials. 38 (1) e09842. doi:10.1002/adma.202509842. ISSN   1521-4095.
16. "A Safer, More Sustainable Process for Industrial Fluorine Feedstocks". AG CHEMI GROUP Blog. 2024-12-04. Retrieved 2026-01-24.
17. Apolinar, Omar; Struijs, Job J. C.; Sarkar, Debotra; Gouverneur, Véronique; Aldridge, Simon (2024-11-09). "Nucleophilic Fluoride Anion Delivery from Triazacyclononane-Supported Molecular Ca–F Complexes". Angewandte Chemie International Edition. 64 (2) e202414790. doi: 10.1002/anie.202414790 . ISSN   1433-7851. PMC   11720380 . PMID   39305186.
18. Struijs, Job J. C.; Ellwanger, Mathias A.; Crumpton, Agamemnon E.; Gouverneur, Véronique; Aldridge, Simon (September 2024). "Enabling nucleophilic reactivity in molecular calcium fluoride complexes". Nature Chemistry. 16 (9): 1473–1480. Bibcode:2024NatCh..16.1473S. doi:10.1038/s41557-024-01524-x. ISSN   1755-4330. PMC   11375610 . PMID   38744913.
19. Pevec, Andrej; Demsar, Alojz; Gramlich, Volker; Petricek, Sasa; Roesky, Herbert W. (1997). "Reactions of molecular CaF2 with [(C5Me5)TiF3] and [(C5Me4Et)TiF3]: symbiosis between ionic solids and organometallic compounds" . Journal of the Chemical Society, Dalton Transactions (13): 2215–2216. doi:10.1039/a702807e.

External links

• NIST webbook thermochemistry data
• Charles Townes on the history of lasers
• National Pollutant Inventory - Fluoride and compounds fact sheet
• Crystran Material Data Archived 2012-11-10 at the Wayback Machine
• MSDS Archived 2011-11-21 at the Wayback Machine (University of Oxford)