Lithium fluoride (single-crystal LiF) LiF
LiF · CAS 7789-24-4 · cubic, Fm3m (#221), NaCl structure
Lithium fluoride is the cubic NaCl-structure crystal LiF.
Evidence level
2 of 5
Lab-measured
- 0Predicted only. No one has made it, or no measurement exists.
- 1Calculated. Only calculated or predicted values from sources.
- 2Lab-measured. Measured properties with their conditions stated.
- 3Space-relevant tests. Measured in conditions relevant to space, such as vacuum or atomic oxygen.
- 4Ground-qualified. Qualified for an application on the ground.
- 5Flown or field-proven. Flight or field results exist.
Range
0.12 to 6 µm
Refraction
1.392
Heat
848 °C
Stiffness
64.97 GPa
Recipe, share of the weight
- Li not statedLithium
- F not statedFluorine
Best for
Optics that must transmit into the vacuum ultraviolet, down to 121 nm (Crystran)
Weakest at
Brittleness: the crystal cleaves easily on (100), and it reacts with strong mineral acids (Crystran; SDS)
Risk at a glance
- People Low. Harmful if swallowed or inhaled; irritating
- If it fails Moderate. Cleavage on (100)
- Corrosion Moderate. Lithium fluoride reacts with strong mineral acids and strong oxidising materials, and gives off hydrogen fluoride gas in contact with a mineral acid.
Quick facts: LiF
| Property | Value | Basis |
|---|---|---|
| Density | 2.64 g/cm³ | 1 sourced value |
| Young's modulus | 65 GPa | 1 sourced value |
| Thermal conductivity | 11.3 W/(m·K) | 1 sourced value |
| Thermal expansion (CTE) | 37 ppm/K | 1 sourced value |
| Melting point | 848 °C | 1 sourced value |
| Specific heat | 1,562 J/(kg·K) | 1 sourced value |
What is the density of Lithium fluoride (LiF)?
Lithium fluoride (LiF) has a density of 2.64 g/cm³. The source and test conditions are listed in the properties table on this page.
What is the thermal conductivity of Lithium fluoride (LiF)?
Lithium fluoride (LiF) has a thermal conductivity of 11.3 W/(m·K). The source and test conditions are listed in the properties table on this page.
What is the coefficient of thermal expansion of Lithium fluoride (LiF)?
Lithium fluoride (LiF) has a coefficient of thermal expansion of 37 ppm/K. The source and test conditions are listed in the properties table on this page.
What is the melting point of Lithium fluoride (LiF)?
Lithium fluoride (LiF) has a melting point of 848 °C. The source and test conditions are listed in the properties table on this page.
What is the Young's modulus of Lithium fluoride (LiF)?
Lithium fluoride (LiF) has a Young's modulus of 65 GPa. The source and test conditions are listed in the properties table on this page.
What is Lithium fluoride (LiF) used for?
Uses recorded in the sources include Special UV optics and vacuum-ultraviolet windows; X-ray monochromator plates; Thermoluminescent dosimeters (LiF:Mg,Ti).
Why it exists
Lithium fluoride is a cubic crystal that Crystran supplies for the deepest ultraviolet optics. Its data sheet gives a refractive index of 1.392 at 0.6 µm, a transmission range of 0.12 to 6 µm, a density of 2.639 g/cc and a melting point of 848 °C. Its use is driven by ultraviolet transmission, X-ray monochromators and thermoluminescent dosimetry, rather than by mechanical strength: the crystal cleaves easily and its apparent elastic limit is 11.2 MPa.
Where it's used
Vacuum-ultraviolet optics
Crystran says lithium fluoride has the most extreme UV transmission of all its materials, and transmits into the vacuum ultraviolet at the 121 nm hydrogen Lyman-alpha line and beyond.
X-ray monochromators
Crystran says its lattice spacing makes lithium fluoride the most useful analysis crystal for X-ray monochromator plates.
Thermoluminescent dosimetry
A 2021 open-access paper on LiF:Mg,Ti detectors says that prediction of their thermoluminescence efficiency is particularly important in space dosimetry.
Lithium-metal battery interphase
A 2020 PNAS study looks at LiF-enriched interphases on lithium anodes, which are formed either artificially or from fluorinated electrolytes, and finds that LiF's mechanical integrity is easily compromised.
Recipe
LiF
Lithium fluoride is LiF, one lithium ion and one fluoride ion per formula unit, with a sodium-chloride-type structure. It is prepared from lithium hydroxide or lithium carbonate with hydrogen fluoride (Wikipedia). Crystran grows the optical crystal by the vacuum Stockbarger technique in ingots about 100 mm in diameter. Hydrogen fluoride, the fluorine source, is made from fluorspar, which USGS names as the feedstock for virtually all fluorine-bearing chemicals.
| Ingredient | Share of the weight | What it does |
|---|---|---|
| Lithium Li | not stated | The mobile ion. Lithium ions are the species that carry charge in a lithium-metal interphase and in the lithium salts that the material supplies. |
| Fluorine F | not stated | The anion. Fluoride ions give the crystal its wide transmission in the ultraviolet and make it reactive with strong acids. |
Weight shares are as printed in the sources.
What it can do
Range
0.12 to 6 µm
Crystran's data table gives a transmission range of 0.12 to 6 µm, and says the material reaches the 121 nm Lyman-alpha line.
Refraction
1.392
Refractive index 1.392 at 0.6 µm and 1.3266 at 5 µm, per the Crystran data table and its refractive index table.
Heat
848 °C
Melting point 848 °C on the data sheet (842 °C on the safety sheet). Thermal conductivity 11.3 W/(m·K) at 314 K.
Stiffness
64.97 GPa
Young's modulus 64.97 GPa, shear modulus 55.14 GPa and bulk modulus 62.03 GPa, from the Crystran data table.
How it compares
This profile does not compare numbers with the other fluorides in this collection, because their sheets were not read in this run. Crystran describes lithium fluoride as having the most extreme UV transmission of all its materials, and its own sheet shows that it is soft and easily cleaved: its apparent elastic limit is 11.2 MPa and it cleaves on (100). The sources read give no side-by-side ground or space test.
The same measurements for each material, so you can compare them. Each row names the key condition under the value; the full conditions and methods are in the numbered notes under Technical details. Other materials are shown beside it; each was measured under its own conditions, so open its page before comparing closely. Compare every grade in the family.
| Measurement | LiF | Al2O3 | Cr:Al2O3 | CaF2 | ZnSe | ZnS | CsI | CdSe | Be3Al2Si6O18 / SiO2 / CuAl6(PO4)4(OH)8 / KAlSi3O8 / (Mg,Fe)2SiO4 |
|---|---|---|---|---|---|---|---|---|---|
| Thermal behavior and safety | |||||||||
| Melting point | 848 °C5 | 2040 to 2054 °C | 2040 °C | 1360 °C | 1525 °C | 1827 °C | 621 °C | 1537 °C | no data |
| Thermal conductivity | 11.3 W/(m·K)7 | 42 W/(m·K) | 0.35 W/(cm·K) | 9.71 W/(m·K) | 18 W m-1 K-1 | 27.2 W/(m·K) | 1.1 W/(m·K) | 6.9 W/(m × K) | no data |
| Specific heat capacity | 1562 J/(kg·K)9 | 0.75 J/(g·K) | 761 J/(kg·K) | 854 J/(kg·K) | 0.339 J/(g K) | 515 J/(kg·K) | 201 J/(kg·K) | 258 J/(kg × K) | no data |
| Physical and electrical | |||||||||
| Density | 2.639 g/cc4 | 3.97 g/cm³ | 3.98 g/cm³ | 3.18 g/cc | 5.27 g/cm³ | 4.09 g/cm³ | 4.51 g/cc | 5.81 g/cm³ | 2.63 to 2.97 g/cm³ |
| Temperature behavior | |||||||||
| Refractive index change with temperature (dn/dT) | -16 ppm/K16 | no data | no data | -10.6 ppm/K | no data | no data | -99.3 ppm/K | no data | no data |
| Other measurements | |||||||||
| Refractive index at 0.6 µm | 1.392 -1 | 1.768 - | 1.759 - | 1.399 - | 2.403 - | 2.201 - | 1.739 - | 2.431 - | 1.567 to 1.61 - |
| Refractive index at 5 µm | 1.327 -2 | 1.768 - | 1.759 - | 1.399 - | 2.403 - | 2.201 - | 1.739 - | 2.431 - | 1.567 to 1.61 - |
| Transmission range | 0.12 to 6 µm3 | no data | no data | 0.13 to 10 µm | 0.6 to 21 µm | no data | 0.25 to 55 µm | 0.75 to 25.5 µm | no data |
| Boiling point | 1676 °C6 | 2977 °C | no data | 2500 °C | no data | no data | no data | no data | no data |
| Coefficient of thermal expansion | 37 ppm/K8 | 7.7 ppm/K | 4.78 ppm/K | 18.85 ppm/K | 7.1 x10-6/K | 6.5 ppm/K | 48.3 ppm/K | 2.45 x10-6/K | no data |
| Young's modulus | 64.97 GPa10 | 470 GPa | no data | 75.8 GPa | 67.2 GPa | 74.5 GPa | 5.3 GPa | no data | no data |
| Shear modulusValue printed in the PDF data sheet | 55.14 GPa11 | 148.1 GPa | no data | 33.77 GPa | no data | no data | 6.24 GPa | no data | no data |
| Bulk modulus | 62.03 GPa12 | 240 GPa | no data | 82.71 GPa | 40 GPa | no data | 12.67 GPa | no data | no data |
| Poisson ratio | 0.326 -13 | 0.18 to 0.29 - | no data | 0.26 - | 0.28 - | 0.28 - | 0.214 - | no data | no data |
| Apparent elastic limit | 11.2 MPa14 | 300 MPa | no data | 36.54 MPa | no data | 26.9 MPa | 5.6 MPa | no data | no data |
| Reststrahlen peak | 25 µm15 | no data | no data | 35 µm | no data | no data | 145.8 µm | no data | no data |
| Solubility in water at 20 °C | 0.27 g/100 g water17 | 9.8×10^-5 g/100 g water | no data | 0.0017 g/100 g water | 0.001 g/100 g water | 6.5×10^-5 g/100 g water | 44 g/100 g water | no data | no data |
Why choose it, and why not
Good for
- Vacuum-ultraviolet optics that must transmit to 121 nm (Crystran).
- X-ray monochromator plates, where its lattice spacing suits analysis (Crystran).
- Thermoluminescent dosimetry with LiF:Mg,Ti detectors, where space dosimetry relies on predicting their response (2021 paper).
Watch out for
- Cleavage. The crystal cleaves easily on (100), and polishing at steep radii can cause rip-out (Crystran).
- Acids. Strong mineral acids and strong oxidising materials react with it and give off hydrogen fluoride (safety sheet).
- Solubility. It dissolves to 0.27 g per 100 g of water at 20 C, and the safety sheet lists it as hazardous to drinking water.
- No space test. No flight, radiation-ageing or outgassing result for lithium fluoride was found in the sources read.
Lithium fluoride is Crystran's choice for the deepest ultraviolet optics, with a 0.12 to 6 µm transmission range and a reach to 121 nm. Its brittleness and acid sensitivity are the trade-off. The thermoluminescent and battery uses rest on papers rather than flight data, and this profile does not establish its behaviour in orbit.
Technical details
For scientists and researchers. Everything above comes from the record below: every number with its method, its conditions and its source.
Notes
The method, full conditions and any caveat for the numbered rows above.
| # | Measurement | Method | Conditions | Caveat |
|---|---|---|---|---|
| 1 | Refractive index at 0.6 µm | Value printed on the Crystran materials data sheet (footnote 1, Laporte et al., J. Opt. Soc. Am. 73, 1062); the same sheet prints a reflection loss of 5.2 percent at 0.6 µm | wavelength 0.6 µm | — |
| 2 | Refractive index at 5 µm | Value printed in the refractive index table of the Crystran data sheet | wavelength 5 µm | — |
| 3 | Transmission range | Range printed on the Crystran data sheet; the Crystran product page gives the same range | thickness not stated on the page | The data sheet shows a VUV transmission curve for a 1 mm to 48 mm sample range; the range is taken from the data table, not the curve. |
| 4 | Density | Value printed on a manufacturer materials data sheet | temperature not stated on the page | — |
| 5 | Melting point | Value printed on the Crystran data sheet (footnote 6, Douglas and Dever, J. Am. Chem. Soc. 1954) | form single crystal | The Crystran safety data sheet prints 842 C for the same material; the data sheet value is used. |
| 6 | Boiling point | Value printed in section 9.1 of the Crystran safety data sheet | pressure 760 mmHg | — |
| 7 | Thermal conductivity | Value printed on the Crystran data sheet (footnote 2, Combes et al. 1951) | temperature 314 K | — |
| 8 | Coefficient of thermal expansion | Printed as 37 x 10-6 K-1 on the data sheet, which is the same as ppm/K; no conversion of the number | unit in source x 10-6 K-1temperature 283 K | — |
| 9 | Specific heat capacity | Value printed on a manufacturer materials data sheet | temperature not stated on the page | — |
| 10 | Young's modulus | Value printed on the Crystran data sheet (footnote 2, Combes et al. 1951) | temperature not stated on the page | — |
| 11 | Shear modulus | — | temperature not stated on the page | The Crystran product web page prints 54.14 GPa for the same material; the PDF value is used. |
| 12 | Bulk modulus | Value printed on a manufacturer materials data sheet | temperature not stated on the page | — |
| 13 | Poisson ratio | Printed on the data sheet as calculated by the supplier | temperature not stated on the page | — |
| 14 | Apparent elastic limit | Value printed on the data sheet as 11.2 MPa (1620 psi); not a canonical property name | temperature not stated on the page | — |
| 15 | Reststrahlen peak | Value printed on the data sheet; not a canonical property name | temperature not stated on the page | — |
| 16 | Refractive index change with temperature (dn/dT) | Printed as -16 x 10-6 at 1.15 µm on the data sheet, which is the same as ppm/K; not a canonical property name | unit in source x 10-6 K-1wavelength 1.15 µm | — |
| 17 | Solubility in water at 20 °C | Value printed on the data sheet; the safety sheet prints the same figure as 270 mg/100 ml at 20 C; not a canonical property name | temperature 20 °C | — |
Corrosion and compatibility
What happens when it meets other materials and environments.
| Environment | Concern | What happens |
|---|---|---|
| Strong mineral acids and strong oxidising materials | moderate | Lithium fluoride reacts with strong mineral acids and strong oxidising materials, and gives off hydrogen fluoride gas in contact with a mineral acid.1 |
| Water at 20 °C | low | Lithium fluoride is slightly soluble in water.2 |
| # | Environment | Details | Test conditions |
|---|---|---|---|
| 1 | Strong mineral acids and strong oxidising materials | The Crystran safety sheet lists strong mineral acids and strong oxidising materials as incompatible, says it avoids acids, particularly hot concentrated sulphuric acid, and gives hydrogen fluoride as the decomposition product. No rate or concentration is printed, so the rating is qualitative. | basis qualitative reactivity statement; no rate or concentration printedagent strong mineral acids and strong oxidising materials |
| 2 | Water at 20 °C | The data sheet gives a solubility of 0.27 g per 100 g of water at 20 C, and the safety sheet says slightly soluble, 270 mg per 100 ml at 20 C. The safety sheet also lists the material as hazardous to drinking water. No dissolution or corrosion test is printed. | temperature 20 °Cnote solubility figure, not a corrosion rate |
Risks and side effects
Hazards to people, what happens when a cell overheats, and how the material is handled and stored.
For people
The Crystran safety sheet (revision 2026) classes lithium fluoride as a Class 6.1 poison with H302, H315, H319 and H332, and gives an oral LD50 above 143 mg/kg in rats.
- Dust
- The sheet gives an occupational limit of 2.5 mg/m3 as fluoride, as an 8 hour average, and says to avoid making dust.
- Swallowed
- If swallowed, the material causes nausea, vomiting, stomach pains and diarrhoea, according to the sheet.
- Scope
- Only the Crystran safety sheet was read. PubChem could not be opened, and other suppliers' classifications are not checked here.
If it fails
The failure results come from supplier data sheets and one interphase study. No flight failure record was read.
- Cleavage
- The data sheet says the crystal cleaves easily on (100), and that polishing, particularly at steep radii, often causes surface rip-out.
- Interphase
- The 2020 PNAS study finds that LiF in a lithium-metal interphase is easily broken during plating, so the electrolyte's repair of the interface matters more.
Handling and storage
- Protective equipment
- PVA gloves, a laboratory coat and safety goggles where chipping or dust may occur, with mechanical and local exhaust ventilation.
- Incompatible materials
- Strong mineral acids and strong oxidising materials. Hydrogen fluoride gas forms in contact with a mineral acid.
- Not covered
- The sheets give no storage temperature or humidity limit.
Test details
The original wording and numbers from the sources, for readers who want them.
Failure risks
| Failure | Trigger and consequence |
|---|---|
| Cleavage on (100)moderate severity | Impact, mechanical stress, or polishing at steep radiiThe data sheet says lithium fluoride cleaves easily and must be worked with extreme care, and that polishing, particularly at steep radii, often causes surface rip-out. The apparent elastic limit is 11.2 MPa. |
| Loss of mechanical integrity in a LiF-rich interphase on lithium metalmoderate severity | Plating of lithium metal against a LiF-enriched interphaseThe PNAS study finds that the mechanical integrity of LiF is easily compromised during plating, so LiF alone cannot protect the lithium. It finds that in situ repair of the interface by the electrolyte is the more critical determinant of electrode performance. |
Side effects on surrounding parts
| Affects | Effect |
|---|---|
| Operators and nearby equipment | In contact with a mineral acid the material gives off hydrogen fluoride gas, according to the safety sheet. |
Handling and storage
- Wear PVA gloves, a laboratory coat and safety goggles where chipping or dust may occur. Provide general mechanical and local exhaust ventilation, and wash hands immediately after handling.
- Avoid generating dust. Take up and containerise broken pieces for disposal, and do not let product enter drains.
- Keep away from heat, foodstuffs, acids and strong bases, and protect the crystal from physical damage.
Mitigations
- Keep the crystal away from strong mineral acids and strong oxidising materials, which react with it.
Supply and geography
How common the raw materials are and where they come from.
Lithium (feedstock, 2025 world mine production)
- Top producers (2025)
- Australia 31.7%, China 21.4%, Chile 19.3%, Zimbabwe 9.7%, Argentina 7.9%
- Critical mineral lists
- US: listed, EU: listed
- Recycling
- USGS: construction of lithium battery recycling plants continued throughout 2025.
- Substitutes
- USGS: substitution for lithium compounds is possible in batteries, ceramics, greases and manufactured glass.
Fluorspar (fluorine feedstock, 2025 world mine production)
- Top producers (2025)
- China 60%, Mexico 15%, Mongolia 15%, South Africa 4.1%
- Critical mineral lists
- US: listed, EU: listed
- Recycling
- USGS: synthetic fluorspar may be produced from waste neutralization in uranium enrichment, petroleum alkylation and stainless-steel pickling, but undesirable impurities constrain its use.
- Substitutes
- USGS: fluosilicic acid has been used as an alternative to fluorspar in producing aluminum fluoride and hydrogen fluoride.
Documents
Datasheets, safety data sheets, papers and standards you can open.
Full record
The complete spore, as stored. Free to reuse under CC-BY-4.0. Images keep the licence shown with each one.
Show the full YAML
spore: profile
id: lithium-fluoride
spore_version: 0.2
family: optical-crystals
name: Lithium fluoride (single-crystal LiF)
abbreviation: LiF
role: VUV and X-ray optical crystal, with dosimetry and battery-interphase uses
category: glasses-optics
type: optical-crystals
summary: |
Lithium fluoride is the cubic NaCl-structure crystal LiF. Crystran grows it by the vacuum Stockbarger method in ingots about 100 mm in diameter and says it has the most extreme UV transmission of all its materials, reaching the hydrogen Lyman-alpha line at 121 nm. Its data sheet gives a refractive index of 1.392 at 0.6 µm, a transmission range of 0.12 to 6 µm, a density of 2.639 g/cc and a melting point of 848 °C, and it says the crystal cleaves easily. Lithium fluoride is also used in thermoluminescent dosimeters, and a 2020 PNAS study finds that its role in lithium-metal battery interphases is limited by its mechanical integrity. The sources read give no space or radiation-ageing test for lithium fluoride.
best_for: Optics that must transmit into the vacuum ultraviolet, down to 121 nm (Crystran)
weakest_at: 'Brittleness: the crystal cleaves easily on (100), and it reacts with strong mineral acids (Crystran; SDS)'
identity:
formula: LiF
cas: 7789-24-4
crystal_system: cubic
space_group: Fm3m (#221), NaCl structure
source: crystran-lif-datasheet
where: Class/Structure row (Cubic FCC, Fm3m (#221), NaCl structure, (100) cleavage); CAS 7789-24-4 and EC 232-152-0 from crystran-lif-msds section 3.1; molecular weight 25.94 on the Crystran data sheet
tags:
environments: []
stresses: []
applications:
- optics-and-cameras
- batteries
- habitats-and-suits
properties:
- benchmark: refractive_index
label: Refractive index at 0.6 µm
value: 1.392
unit: '-'
scope: material
conditions:
wavelength: 0.6 µm
method: Value printed on the Crystran materials data sheet (footnote 1, Laporte et al., J. Opt. Soc. Am. 73, 1062); the same sheet prints a reflection loss of 5.2 percent at 0.6 µm
status: ground
source: crystran-lif-datasheet
where: Data table, Refractive Index row (1.392 at 0.6µm)
- benchmark: refractive_index
label: Refractive index at 5 µm
value: 1.3266
unit: '-'
scope: material
conditions:
wavelength: 5 µm
method: Value printed in the refractive index table of the Crystran data sheet
status: ground
source: crystran-lif-datasheet
where: Refractive Index table, row 5.000 µm
- benchmark: transmission_range
label: Transmission range
value: 0.12
value_high: 6
bound: range
unit: µm
scope: material
conditions:
thickness: not stated on the page
method: Range printed on the Crystran data sheet; the Crystran product page gives the same range
status: ground
note: The data sheet shows a VUV transmission curve for a 1 mm to 48 mm sample range; the range is taken from the data table, not the curve.
source: crystran-lif-datasheet
where: Data table, Transmission Range row
- benchmark: density
label: Density
value: 2.639
unit: g/cc
scope: material
conditions:
temperature: not stated on the page
method: Value printed on a manufacturer materials data sheet
status: ground
source: crystran-lif-datasheet
where: Data table, Density row
- benchmark: melting_point
label: Melting point
value: 848
unit: °C
scope: material
conditions:
form: single crystal
method: Value printed on the Crystran data sheet (footnote 6, Douglas and Dever, J. Am. Chem. Soc. 1954)
status: ground
note: The Crystran safety data sheet prints 842 C for the same material; the data sheet value is used.
source: crystran-lif-datasheet
where: Data table, Melting Point row
- benchmark: boiling_point
label: Boiling point
value: 1676
unit: °C
scope: material
conditions:
pressure: 760 mmHg
method: Value printed in section 9.1 of the Crystran safety data sheet
status: ground
source: crystran-lif-msds
where: Section 9.1, BOILING POINT (760mm Hg) row
- benchmark: thermal_conductivity
label: Thermal conductivity
value: 11.3
unit: W/(m·K)
scope: material
conditions:
temperature: 314 K
method: Value printed on the Crystran data sheet (footnote 2, Combes et al. 1951)
status: ground
source: crystran-lif-datasheet
where: Data table, Thermal Conductivity row
- benchmark: cte
label: Coefficient of thermal expansion
value: 37
unit: ppm/K
scope: material
conditions:
unit_in_source: x 10-6 K-1
temperature: 283 K
method: Printed as 37 x 10-6 K-1 on the data sheet, which is the same as ppm/K; no conversion of the number
status: ground
source: crystran-lif-datasheet
where: Data table, Thermal Expansion row
- benchmark: specific_heat
label: Specific heat capacity
value: 1562
unit: J/(kg·K)
scope: material
conditions:
temperature: not stated on the page
method: Value printed on a manufacturer materials data sheet
status: ground
source: crystran-lif-datasheet
where: Data table, Specific Heat Capacity row
- benchmark: elastic_modulus
label: Young's modulus
value: 64.97
unit: GPa
scope: material
conditions:
temperature: not stated on the page
method: Value printed on the Crystran data sheet (footnote 2, Combes et al. 1951)
status: ground
source: crystran-lif-datasheet
where: Data table, Youngs Modulus (E) row
- benchmark: shear_modulus
label: Shear modulus
value: 55.14
unit: GPa
scope: material
conditions:
temperature: not stated on the page
method: Value printed in the PDF data sheet
status: ground
note: The Crystran product web page prints 54.14 GPa for the same material; the PDF value is used.
source: crystran-lif-datasheet
where: Data table, Shear Modulus (G) row
- benchmark: bulk_modulus
label: Bulk modulus
value: 62.03
unit: GPa
scope: material
conditions:
temperature: not stated on the page
method: Value printed on a manufacturer materials data sheet
status: ground
source: crystran-lif-datasheet
where: Data table, Bulk Modulus (K) row
- benchmark: poissons_ratio
label: Poisson ratio
value: 0.326
unit: '-'
scope: material
conditions:
temperature: not stated on the page
method: Printed on the data sheet as calculated by the supplier
status: ground
source: crystran-lif-datasheet
where: Data table, Poisson Ratio row
- benchmark: apparent_elastic_limit
label: Apparent elastic limit
value: 11.2
unit: MPa
scope: material
conditions:
temperature: not stated on the page
method: Value printed on the data sheet as 11.2 MPa (1620 psi); not a canonical property name
status: ground
source: crystran-lif-datasheet
where: Data table, Apparent Elastic Limit row
- benchmark: reststrahlen_peak
label: Reststrahlen peak
value: 25
unit: µm
scope: material
conditions:
temperature: not stated on the page
method: Value printed on the data sheet; not a canonical property name
status: ground
source: crystran-lif-datasheet
where: Data table, Reststrahlen Peak row
- benchmark: refractive_index_temperature_coefficient
label: Refractive index change with temperature (dn/dT)
value: -16
unit: ppm/K
scope: material
conditions:
unit_in_source: x 10-6 K-1
wavelength: 1.15 µm
method: Printed as -16 x 10-6 at 1.15 µm on the data sheet, which is the same as ppm/K; not a canonical property name
status: ground
source: crystran-lif-datasheet
where: Data table, dn/dT row
- benchmark: water_solubility
label: Solubility in water at 20 °C
value: 0.27
unit: g/100 g water
scope: material
conditions:
temperature: 20 °C
method: Value printed on the data sheet; the safety sheet prints the same figure as 270 mg/100 ml at 20 C; not a canonical property name
status: ground
source: crystran-lif-datasheet
where: Data table, Solubility row
corrosion:
- environment: Strong mineral acids and strong oxidising materials
headline: Lithium fluoride reacts with strong mineral acids and strong oxidising materials, and gives off hydrogen fluoride gas in contact with a mineral acid.
effect: The Crystran safety sheet lists strong mineral acids and strong oxidising materials as incompatible, says it avoids acids, particularly hot concentrated sulphuric acid, and gives hydrogen fluoride as the decomposition product. No rate or concentration is printed, so the rating is qualitative.
rating: moderate
conditions:
basis: qualitative reactivity statement; no rate or concentration printed
agent: strong mineral acids and strong oxidising materials
source: crystran-lif-msds
where: Sections 7.2, 10.1, 10.4, 10.5 and 10.6
- environment: Water at 20 °C
headline: Lithium fluoride is slightly soluble in water.
effect: The data sheet gives a solubility of 0.27 g per 100 g of water at 20 C, and the safety sheet says slightly soluble, 270 mg per 100 ml at 20 C. The safety sheet also lists the material as hazardous to drinking water. No dissolution or corrosion test is printed.
rating: low
conditions:
temperature: 20 °C
note: solubility figure, not a corrosion rate
source: crystran-lif-datasheet
where: Data table, Solubility row; crystran-lif-msds sections 9.1 and 12.1
risks:
hazards:
- text: The Crystran safety sheet (revision 2026) classes lithium fluoride as a Class 6.1 poison, with signal word Warning and the statements H302 (harmful if swallowed), H315 (causes skin irritation), H319 (causes serious eye irritation) and H332 (harmful if inhaled).
ghs:
- H302
- H315
- H319
- H332
source: crystran-lif-msds
where: Sections 2.1 and 2.2
- text: The same sheet gives an oral LD50 above 143 mg/kg in rats and 119 mg/kg in mice, and says that if swallowed the material causes nausea, vomiting, stomach pains and diarrhoea.
ghs: []
source: crystran-lif-msds
where: Sections 2.1 and 11.1
- text: The sheet gives an occupational exposure limit of 2.5 mg/m3 as fluoride, as an 8 hour time-weighted average, and advises avoiding dust.
ghs: []
source: crystran-lif-msds
where: Sections 6.1 and 8.1
- text: For transport the sheet gives UN 3288, Toxic solid, inorganic, N.O.S. (Lithium Fluoride), class 6.1, packing group III, and marine pollutant.
ghs: []
source: crystran-lif-msds
where: Section 14
failure_risks:
- mode: Cleavage on (100)
trigger: Impact, mechanical stress, or polishing at steep radii
consequence: The data sheet says lithium fluoride cleaves easily and must be worked with extreme care, and that polishing, particularly at steep radii, often causes surface rip-out. The apparent elastic limit is 11.2 MPa.
severity: moderate
source: crystran-lif-datasheet
where: Introduction text; Apparent Elastic Limit row; Class/Structure row
- mode: Loss of mechanical integrity in a LiF-rich interphase on lithium metal
trigger: Plating of lithium metal against a LiF-enriched interphase
consequence: The PNAS study finds that the mechanical integrity of LiF is easily compromised during plating, so LiF alone cannot protect the lithium. It finds that in situ repair of the interface by the electrolyte is the more critical determinant of electrode performance.
severity: moderate
source: he-pnas-2020
where: Abstract
side_effects:
- text: In contact with a mineral acid the material gives off hydrogen fluoride gas, according to the safety sheet.
affects: Operators and nearby equipment
source: crystran-lif-msds
where: Section 10.6
handling:
- text: Wear PVA gloves, a laboratory coat and safety goggles where chipping or dust may occur. Provide general mechanical and local exhaust ventilation, and wash hands immediately after handling.
source: crystran-lif-msds
where: Section 8.2
- text: Avoid generating dust. Take up and containerise broken pieces for disposal, and do not let product enter drains.
source: crystran-lif-msds
where: Sections 6.1, 6.2, 6.3 and 7.1
- text: Keep away from heat, foodstuffs, acids and strong bases, and protect the crystal from physical damage.
source: crystran-lif-msds
where: Sections 7.1 and 7.2
mitigations:
- text: Keep the crystal away from strong mineral acids and strong oxidising materials, which react with it.
source: crystran-lif-msds
where: Sections 10.1 and 10.5
uses:
- application: optics-and-cameras
device: Special UV optics and vacuum-ultraviolet windows
example: Crystran says lithium fluoride is the material with the most extreme UV transmission of all, and that it transmits well into the vacuum ultraviolet at the hydrogen Lyman-alpha line (121 nm) and beyond.
source: crystran-lif-datasheet
where: Materials data text, applications paragraph
- application: optics-and-cameras
device: X-ray monochromator plates
example: Crystran says lithium fluoride is used for X-ray monochromator plates, where its lattice spacing makes it the most useful analysis crystal.
source: crystran-lif-datasheet
where: Materials data text, applications paragraph
- application: habitats-and-suits
device: Thermoluminescent dosimeters (LiF:Mg,Ti)
example: A 2021 paper on LiF:Mg,Ti detectors states that a fraction of the thermoluminescence signal comes from the supralinear dose range, and that prediction of TL efficiency is particularly important in space dosimetry.
source: tl-pmc7840113
where: Abstract
- application: batteries
device: Lithium-metal anode solid electrolyte interphase
example: A 2020 PNAS study examines LiF-enriched interphases on lithium anodes, made artificially or from fluorinated electrolytes, and finds that LiF's mechanical integrity is easily compromised during plating.
source: he-pnas-2020
where: Abstract
supply:
- subject: Lithium (feedstock, 2025 world mine production)
producers:
- country: Australia
share_percent: 31.7
year: 2025
- country: China
share_percent: 21.4
year: 2025
- country: Chile
share_percent: 19.3
year: 2025
- country: Zimbabwe
share_percent: 9.7
year: 2025
- country: Argentina
share_percent: 7.9
year: 2025
critical_lists:
- list: USGS 2025 List of Critical Minerals (lithium, used in rechargeable batteries)
listed: true
- list: EU critical raw materials list (Regulation (EU) 2024/1252, fifth list)
listed: true
recycling: 'USGS: construction of lithium battery recycling plants continued throughout 2025.'
substitutes:
- 'USGS: substitution for lithium compounds is possible in batteries, ceramics, greases and manufactured glass.'
source: usgs-mcs2026-lithium
where: World Mine Production and Reserves table, 2025 column (shares calculated by Space Mushroom as country value divided by the 290,000 t world total); Recycling; Substitutes
- subject: Fluorspar (fluorine feedstock, 2025 world mine production)
producers:
- country: China
share_percent: 60
year: 2025
- country: Mexico
share_percent: 15
year: 2025
- country: Mongolia
share_percent: 15
year: 2025
- country: South Africa
share_percent: 4.1
year: 2025
critical_lists:
- list: USGS 2025 List of Critical Minerals (fluorspar)
listed: true
- list: EU critical raw materials list (fluorspar)
listed: true
recycling: 'USGS: synthetic fluorspar may be produced from waste neutralization in uranium enrichment, petroleum alkylation and stainless-steel pickling, but undesirable impurities constrain its use.'
substitutes:
- 'USGS: fluosilicic acid has been used as an alternative to fluorspar in producing aluminum fluoride and hydrogen fluoride.'
source: usgs-mcs2026-fluorspar
where: World Mine Production and Reserves table, 2025 column (China 6,000, Mexico 1,500, Mongolia 1,500, South Africa 410 of a world total of 10,000 thousand tons; shares calculated by Space Mushroom); Recycling; Substitutes
documents:
- title: 'Crystran: Lithium Fluoride (LiF) materials data sheet (PDF, data table and refractive index table)'
type: datasheet
url: https://www.crystran.com/wp-content/uploads/2025/09/lithium-fluoride-lif-data-sheet.pdf
year: 2026
- title: 'Crystran: Safety Data Sheet, Lithium Fluoride Optical Crystal (revision 2026, issued 6 July 2026)'
type: sds
url: https://www.crystran.com/wp-content/uploads/2025/09/lithium-fluoride-lif-msds.pdf
year: 2026
- title: 'USGS Mineral Commodity Summaries 2026: Lithium'
type: report
url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-lithium.pdf
year: 2026
- title: 'USGS Mineral Commodity Summaries 2026: Fluorspar'
type: report
url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-fluorspar.pdf
year: 2026
- title: Microdosimetric understanding of dose response and relative efficiency of thermoluminescence detectors (Radiat Prot Dosimetry 2021, open access)
type: paper
url: https://pmc.ncbi.nlm.nih.gov/articles/PMC7840113/
year: 2021
- title: 'He et al.: The intrinsic behavior of lithium fluoride in solid electrolyte interphases on lithium (PNAS 2020)'
type: paper
url: https://doi.org/10.1073/pnas.1911017116
year: 2020
gaps:
- No space, radiation-ageing, UV-ageing, outgassing (TML/CVCM) or atomic-oxygen result for lithium fluoride was found in a source we could open.
- The molten-salt reactor role of LiF is not sourced in this file. The ORNL/OSTI record, the RSC and DOAJ article pages and the IPEN repository could not be opened in this run, so no LiF-BeF2 mixture figures are entered.
- PubChem could not be read (bot check). Hazard data rest on one supplier safety data sheet (Crystran), and other suppliers' classifications are not checked.
- 'Melting point differs: 848 C on the data sheet and 842 C on the safety sheet. The data sheet value is used.'
- Dielectric constant is printed as 0.1 on the data sheet. That looks wrong for a fluoride, so it is not entered.
- Knoop hardness is printed as 102 with a 600 g indenter, without a scale unit, so it is not entered.
- Absorption coefficient 5.9 x 10-3 cm-1 at 4.3 µm and 300 K is printed on the data sheet but not entered; it can be added once the value is checked against the cited page.
- 'Five benchmark names are kept as snake_case and may not be canonical: apparent_elastic_limit, reststrahlen_peak, refractive_index_temperature_coefficient, water_solubility and transmission_range.'
- 'Wikipedia gives a lower water solubility and describes the crystals as hygroscopic. Neither is entered: Wikipedia is not used for values, and no supplier sheet read here confirms either point.'
- The transmission curves are not read as numbers; the range is from the data table only.
- Lithium and fluorspar supply shares are Space Mushroom calculations from the USGS 2025 production tables, not printed shares.
- No media (photograph or drawing with a licence) was checked for this profile.
license: CC-BY-4.0
updated: '2026-10-26'
review:
status: draft
method: assistant
checked_values: 17
unreachable: 5
caveats: 4
note: 'Written by an AI assistant on 2026-10-26 from the Crystran data sheet and safety sheet (both read as PDF text), USGS Mineral Commodity Summaries 2026 for lithium and fluorspar, a 2021 open-access paper on TL detectors and a 2020 PNAS paper, read in the same run. Caveats: PubChem, OSTI, RSC, DOAJ and IPEN could not be opened; the molten-salt reactor use is not sourced; the Crystran dielectric constant is not entered.'
sources:
crystran-lif-datasheet:
title: 'Crystran: Lithium Fluoride (LiF) materials data sheet (data table, refractive index table, VUV transmission curve)'
id: lithium-fluoride-lif-data-sheet.pdf (undated; pages 66 and 67)
url: https://www.crystran.com/wp-content/uploads/2025/09/lithium-fluoride-lif-data-sheet.pdf
year: 2026
kind: datasheet
license: supplier document, linked not reproduced
crystran-lif-msds:
title: 'Crystran: Safety Data Sheet, Lithium Fluoride Optical Crystal (REACH format, revision 2026)'
id: Revision 2026, issued 6 July 2026; CAS 7789-24-4; EC 232-152-0
url: https://www.crystran.com/wp-content/uploads/2025/09/lithium-fluoride-lif-msds.pdf
year: 2026
kind: datasheet
license: supplier document, linked not reproduced
usgs-mcs2026-lithium:
title: Mineral Commodity Summaries 2026, Lithium (USGS)
id: USGS MCS 2026, February 2026
url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-lithium.pdf
year: 2026
kind: report
license: public domain (USGS)
usgs-mcs2026-fluorspar:
title: Mineral Commodity Summaries 2026, Fluorspar (USGS, Vanessa Londono)
id: USGS MCS 2026, February 2026
url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-fluorspar.pdf
year: 2026
kind: report
license: public domain (USGS)
usgs-crit2025:
title: About the 2025 List of Critical Minerals (USGS, final list of 60 minerals)
id: Final 2025 List of Critical Minerals, November 2025
url: https://www.usgs.gov/programs/mineral-resources-program/science/about-2025-list-critical-minerals
year: 2025
kind: web
license: public domain (USGS)
ec-crm:
title: Critical raw materials (European Commission, list of 34 critical raw materials under Regulation (EU) 2024/1252)
id: Regulation (EU) 2024/1252
url: https://single-market-economy.ec.europa.eu/sectors/raw-materials/areas-specific-interest/critical-raw-materials_en
year: 2024
kind: web
license: European Commission web page
tl-pmc7840113:
title: Microdosimetric understanding of dose response and relative efficiency of thermoluminescence detectors
id: doi:10.1093/rpd/ncaa211 (Radiat Prot Dosimetry 192(2), 165-177, 2021; PMC7840113)
url: https://pmc.ncbi.nlm.nih.gov/articles/PMC7840113/
year: 2021
kind: paper
license: open access (Oxford University Press, PMC copy)
he-pnas-2020:
title: The intrinsic behavior of lithium fluoride in solid electrolyte interphases on lithium
id: doi:10.1073/PNAS.1911017116 (PNAS 2020; He, Guo, Hobold, Gao, Gallant)
url: https://doi.org/10.1073/pnas.1911017116
year: 2020
kind: paper
license: MIT DSpace open access record; publisher terms apply
wikipedia-lif:
title: Lithium fluoride (Wikipedia article)
id: en.wikipedia.org, accessed 2026-10-26; used for preparation route only
url: https://en.wikipedia.org/wiki/Lithium_fluoride
year: 2026
kind: web
license: CC BY-SA 4.0
story:
recipe:
line: Lithium fluoride is LiF, one lithium ion and one fluoride ion per formula unit, with a sodium-chloride-type structure. It is prepared from lithium hydroxide or lithium carbonate with hydrogen fluoride (Wikipedia). Crystran grows the optical crystal by the vacuum Stockbarger technique in ingots about 100 mm in diameter. Hydrogen fluoride, the fluorine source, is made from fluorspar, which USGS names as the feedstock for virtually all fluorine-bearing chemicals.
parts:
- name: Lithium
symbol: Li
role: The mobile ion. Lithium ions are the species that carry charge in a lithium-metal interphase and in the lithium salts that the material supplies.
- name: Fluorine
symbol: F
role: The anion. Fluoride ions give the crystal its wide transmission in the ultraviolet and make it reactive with strong acids.
risk_groups:
- title: For people
level: 1
verdict: Harmful if swallowed or inhaled; irritating
lead: The Crystran safety sheet (revision 2026) classes lithium fluoride as a Class 6.1 poison with H302, H315, H319 and H332, and gives an oral LD50 above 143 mg/kg in rats.
points:
- label: Dust
line: The sheet gives an occupational limit of 2.5 mg/m3 as fluoride, as an 8 hour average, and says to avoid making dust.
- label: Swallowed
line: If swallowed, the material causes nausea, vomiting, stomach pains and diarrhoea, according to the sheet.
- label: Scope
line: Only the Crystran safety sheet was read. PubChem could not be opened, and other suppliers' classifications are not checked here.
- title: If it fails
lead: The failure results come from supplier data sheets and one interphase study. No flight failure record was read.
points:
- label: Cleavage
line: The data sheet says the crystal cleaves easily on (100), and that polishing, particularly at steep radii, often causes surface rip-out.
- label: Interphase
line: The 2020 PNAS study finds that LiF in a lithium-metal interphase is easily broken during plating, so the electrolyte's repair of the interface matters more.
- title: Handling and storage
gap: The sheets give no storage temperature or humidity limit.
points:
- label: Protective equipment
line: PVA gloves, a laboratory coat and safety goggles where chipping or dust may occur, with mechanical and local exhaust ventilation.
- label: Incompatible materials
line: Strong mineral acids and strong oxidising materials. Hydrogen fluoride gas forms in contact with a mineral acid.
why: 'Lithium fluoride is a cubic crystal that Crystran supplies for the deepest ultraviolet optics. Its data sheet gives a refractive index of 1.392 at 0.6 µm, a transmission range of 0.12 to 6 µm, a density of 2.639 g/cc and a melting point of 848 °C. Its use is driven by ultraviolet transmission, X-ray monochromators and thermoluminescent dosimetry, rather than by mechanical strength: the crystal cleaves easily and its apparent elastic limit is 11.2 MPa.'
uses:
- where: Vacuum-ultraviolet optics
line: Crystran says lithium fluoride has the most extreme UV transmission of all its materials, and transmits into the vacuum ultraviolet at the 121 nm hydrogen Lyman-alpha line and beyond.
- where: X-ray monochromators
line: Crystran says its lattice spacing makes lithium fluoride the most useful analysis crystal for X-ray monochromator plates.
- where: Thermoluminescent dosimetry
line: A 2021 open-access paper on LiF:Mg,Ti detectors says that prediction of their thermoluminescence efficiency is particularly important in space dosimetry.
- where: Lithium-metal battery interphase
line: A 2020 PNAS study looks at LiF-enriched interphases on lithium anodes, which are formed either artificially or from fluorinated electrolytes, and finds that LiF's mechanical integrity is easily compromised.
can_do:
- label: Range
value: 0.12 to 6 µm
line: Crystran's data table gives a transmission range of 0.12 to 6 µm, and says the material reaches the 121 nm Lyman-alpha line.
- label: Refraction
value: '1.392'
line: Refractive index 1.392 at 0.6 µm and 1.3266 at 5 µm, per the Crystran data table and its refractive index table.
- label: Heat
value: 848 °C
line: Melting point 848 °C on the data sheet (842 °C on the safety sheet). Thermal conductivity 11.3 W/(m·K) at 314 K.
- label: Stiffness
value: 64.97 GPa
line: Young's modulus 64.97 GPa, shear modulus 55.14 GPa and bulk modulus 62.03 GPa, from the Crystran data table.
compare: 'This profile does not compare numbers with the other fluorides in this collection, because their sheets were not read in this run. Crystran describes lithium fluoride as having the most extreme UV transmission of all its materials, and its own sheet shows that it is soft and easily cleaved: its apparent elastic limit is 11.2 MPa and it cleaves on (100). The sources read give no side-by-side ground or space test.'
compare_rows:
- label: Heat conduction
benchmark: thermal_conductivity
- label: Thermal expansion
benchmark: cte
- label: Stiffness
benchmark: elastic_modulus
handling:
- Wear PVA gloves and goggles where chipping or dust may occur, and avoid making dust when cutting, grinding or cleaning.
- Keep the crystal away from strong mineral acids and strong oxidising materials, which give off hydrogen fluoride gas on reaction.
- Do not let product enter drains, and take up broken pieces into containers for disposal.
good_for:
- Vacuum-ultraviolet optics that must transmit to 121 nm (Crystran).
- X-ray monochromator plates, where its lattice spacing suits analysis (Crystran).
- Thermoluminescent dosimetry with LiF:Mg,Ti detectors, where space dosimetry relies on predicting their response (2021 paper).
watch_out:
- Cleavage. The crystal cleaves easily on (100), and polishing at steep radii can cause rip-out (Crystran).
- Acids. Strong mineral acids and strong oxidising materials react with it and give off hydrogen fluoride (safety sheet).
- Solubility. It dissolves to 0.27 g per 100 g of water at 20 C, and the safety sheet lists it as hazardous to drinking water.
- No space test. No flight, radiation-ageing or outgassing result for lithium fluoride was found in the sources read.
verdict: Lithium fluoride is Crystran's choice for the deepest ultraviolet optics, with a 0.12 to 6 µm transmission range and a reach to 121 nm. Its brittleness and acid sensitivity are the trade-off. The thermoluminescent and battery uses rest on papers rather than flight data, and this profile does not establish its behaviour in orbit.
References
Every number above carries a reference number. Click one to see the source and where in it the value comes from.
| # | Source | Type | Year | Used for |
|---|---|---|---|---|
| Crystran: Lithium Fluoride (LiF) materials data sheet (data table, refractive index table, VUV transmission curve) | datasheet | 2026 | 21 values | |
| Crystran: Safety Data Sheet, Lithium Fluoride Optical Crystal (REACH format, revision 2026) | datasheet | 2026 | 11 values | |
| Mineral Commodity Summaries 2026, Lithium (USGS) | report | 2026 | 1 value | |
| Mineral Commodity Summaries 2026, Fluorspar (USGS, Vanessa Londono) | report | 2026 | 1 value | |
| About the 2025 List of Critical Minerals (USGS, final list of 60 minerals) | web | 2025 | 0 values | |
| Critical raw materials (European Commission, list of 34 critical raw materials under Regulation (EU) 2024/1252) | web | 2024 | 0 values | |
| Microdosimetric understanding of dose response and relative efficiency of thermoluminescence detectors | paper | 2021 | 1 value | |
| The intrinsic behavior of lithium fluoride in solid electrolyte interphases on lithium | paper | 2020 | 2 values | |
| Lithium fluoride (Wikipedia article) | web | 2026 | 0 values |