Lithium fluoride

Material
LiF

Lithium fluoride is commonly used for optical components in wide spectrum band from the vacuum ultraviolet to the infrared, since it is transparent over the entire range of wavelengths (from 0.104µm to 7.0µm). The refractive index of LiF is the lowest of all common infrared materials but it possesses the highest UV transmission of any material. Furthermore, it transmits in the vacuum ultraviolet range at the hydrogen Lyman-alpha line (121nm). Optical parts of infrared devices work without protective coatings.

If heated to 400 °C, LiF gets corroded by water, but in dry environment, it can be used up to 600 °C. However, Lithium Fluoride is sensitive to thermal shock and irradiation produces color centers. It is slightly plastic, that's why it can be bent into radius plates. LiF can be cleaved. Due to its wide band gap, Lithium Fluoride also has a very high electrical resistance. It is soluble in HDF and other acids but can be cleaned with alcohol.

Lithium Fluoride is used for production of windows, prisms, lenses and other optical items in the range from the vacuum ultraviolet to the infrared or as active laser element, passive Q-switch. LiF crystals with reflecting surface of (100) are used as standards or monochromators in X-ray field.

We use for our optics high quality LiF crystals growth on the Czochralsky and Bridgman Methods and supply high transparency and low loss optical windows, prisms, lenses, and other optical components. LiF is sold in two qualities (monodomain and polydomain) and in two grades - IR- and UV-grade.

Properties
Optical properties
Transmission range in µm (minimum 10%)
0,12‐8,7
Transmission range in µm (minimum 50%)
0,12‐7,4
Refractive index @633nm
1,39126
Reflection losses in % at 1 surface
2,65 @633nm
Reflection losses in % at 2 surfaces
5,2 @600nm
dN/dT in 1/K
-16 · 10-6 @1,15µm
Physical properties
Density in g/cm3
2,639
Melting point in °C
848
Spezific heat capacity in J/(kg · K)
1562
Thermal conductivity in W/(m · K)
11,3
Thermal expension in 1/K
37 · 10-6
Dielectric constants
9
Solubility in water in g/100g
0,27 @18°C
Mohs hardness
4
Knoop hardness in kg/mm²
102
Material type
single crystalline, synthetic
Crystal type
cubic, face-centered, NaCl structure
Crystal structure
Fm3m
Lattice constant in Å
a = 4,02
Elastic coefficient in GPa
C11 = 112

C12 = 45,6

C42 = 63,2

Young's Modulus (E) in Gpa
64,79
Shear Modulus (G) in GPa
33,7
Bulk Modulus (K) in GPa
62,03
Rupture Modulus in MPa
10,9
Apparent elastic limit in MPa
11,2
Poisson ratio
0,22
Spectral properties
Optical properties
Transmission range @10% min. 0,12 - 8,7
Transmission range @50% min. 0,12 - 7,4
Brechungsindex @ 633nm 1,39126
Reflection losses in % at 1 surface 2,65 @ 633nm
Reflection losses in % at 2 surfaces 5,2 @ 600nm
dn/dT in 1/K -16 · 10-6 @ 1,15µm
Physical properties
Density in g/cm³ 2,639
Melting point in °C 848
Spezific heat capacity in J/(kg · K) 1562
Thermal conductivity in W/(m · K) 11,3
Thermal expension in 1/K 37 · 10-6
Dielectric constants 9
Solubility in water in g/100g 0,27 @ 18°C
Mohs hardness 4
Knoop hardness in kg/mm² 102
Material type single crystalline, synthetic
Crystal type kubisch flächenzentriert, NaCl-Struktur
Crystal structure cF12
Lattice constant in Å a = 4,02
Elastic coefficient in GPa C11 = 112
C12 = 45,6
C44 = 63,2
Young's Modulus (E) in Gpa 64,79
Shear Modulus (G) in GPa 55,14
Bulk Modulus (K) in GPa 62,03
Rupture Modulus in MPa 10,9
Apparent elastic limit in MPa 11,2
Poisson ratio 0,22
Spectral properties