Calcium fluoride

Material
CaF2

 

Calcium fluoride is commonly used for optical components in wide spectrum band from ultraviolet to infrared wavelengths, since it is transparent in these regions (about 0.15µm to 9µm) and exhibits extremely weak birefringence.

 

The material combines splendid mechanical, technical and operation characteristics with transparency in a wide range of spectra, high optical homogeneity, high radiation resistance. All optical characteristics of these crystals are highly stable.

 

Calcium Fluoride material is chemically fairly inert so that polished surfaces are stable and is long-lasting under normal conditions. Its low refractive index allows it to be used also without anti-reflection coating. These crystals have been used in high power laser optics because CaF2 possesses low absorption. Due to its composition, it has a much longer useful lifetime than most materials when used in fluorine environment.

 

Calcium Fluoride is used to produce optical windows, prisms, lenses and other optical items in the range from the ultraviolet to the infrared. Optical items of CaF2 are used without protective coverings. The crystals with reflecting surface of <111> may be used as standards or monochromators in X-ray field.

 

We use for our optics high quality Calcium fluoride crystals growth on the Czochralsky and Bridgman Methods and supply high transparency and low loss CaF2 optical windows, prisms, lenses, achromatic lenses, and other optical components. Calcium Fluoride is sold in two qualities (monodomain and polydomain) and in two grades - IR-grade and UV-grade where UV-grade crystals are more expensive.

Properties
Optical properties
Transmission range in µm (minimum 10%)
0,12‐11,8
Transmission range in µm (minimum 50%)
0,13‐10,5
Refractive index @633nm
1,432888

(1,39908 @5µm)

Reflection losses in % at 1 surface
2,89 @4µm
Reflection losses in % at 2 surfaces
5,4 @5µm
dN/dT in 1/K
-10,6 · 10-6
Physical properties
Density in g/cm3
3,18
Melting point in °C
1418
Spezific heat capacity in J/(kg · K)
854
Thermal conductivity in W/(m · K)
9,71
Thermal expension in 1/K
18,9 · 10-6
Dielectric constants
6,76
Solubility in water in g/100g
0,16 · 10-4 @25°C
Mohs hardness
4
Knoop hardness in kg/mm²
163
Material type
single crystalline, synthetic
Crystal type
cubic, face-centered
Crystal structure
cF12
Lattice constant in Å
a = 5,46
Elastic coefficient in GPa
C11 = 165

C12 = 47

C44 = 33,9

Young's Modulus (E) in Gpa
75,8
Shear Modulus (G) in GPa
33,7
Bulk Modulus (K) in GPa
82,71
Rupture Modulus in MPa
40
Apparent elastic limit in MPa
36,5
Poisson ratio
0,29
Spectral properties
Optical properties
Transmission range @10% min. 0,12 - 11,8
Transmission range @50% min. 0,13 - 10,5
Brechungsindex @ 633nm 1,432888
(1,39908 @5µm)
Reflection losses in % at 1 surface 2,89 @ 4µm
Reflection losses in % at 2 surfaces 5,4 @ 5µm
dn/dT in 1/K -10,6 · 10-6
Physical properties
Density in g/cm³ 3,18
Melting point in °C 1418
Spezific heat capacity in J/(kg · K) 854
Thermal conductivity in W/(m · K) 9,71
Thermal expension in 1/K 18,9 · 10-6
Dielectric constants 6,76
Solubility in water in g/100g 0,16 · 10-4 @ 25°C
Mohs hardness 4
Knoop hardness in kg/mm² 163
Material type single crystalline, synthetic
Crystal type kubisch flächenzentriert
Crystal structure cF12
Lattice constant in Å a = 5,46
Elastic coefficient in GPa C11 = 165
C12 = 47
C44 = 33,9
Young's Modulus (E) in Gpa 75,8
Shear Modulus (G) in GPa 33,7
Bulk Modulus (K) in GPa 82,71
Rupture Modulus in MPa 40
Apparent elastic limit in MPa 36,5
Poisson ratio 0,29
Spectral properties