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Potassium chloride

Material
KCl

Kaliumchlorid (KCl) has high transmission in the wavelength range between 0.3 µm and 20 µm. The material has a low refractive index and a high optical damage threshold. Potassium chloride is hygroscopic and highly soluble in water, so it must be stored in a dry environment or protected against moisture by means of a protective coating. Thermally, the use of KCl is limited to 400 °C.

Optics made of KCl are used in IR spectroscopy and as protective windows for CO2 lasers.2 lasers.

Properties
Optical and spectral properties
Transmission range in µm (minimum 10%)
0,18‐25,1
Transmission range in µm (minimum 50%)
0,18‐25,0
Refractive index @633nm
1,488

(1,456 @10µm)

Reflection losses in % at 1 surface
3,45 @10µm
Reflection losses, % for two surfaces
6,7 @10,6µm
dN/dT in 1/K
-33,2 · 10-6
Physical properties
Density in g/cm3
19,989
Melting point in °C
776
Specific heat capacity in J/(kg · K)
693
Thermal conductivity in W/(m · K)
6,53
Thermal expansion in 1/K
36 · 10-6
Dielectric constant
4,64
Solubility in water in g/100g
34,7 @25°C
Mohs hardness
2
Knoop hardness in kg/mm²
9,3 (<100>)
Material type
single crystalline, synthetic
Crystal type
cubic, face-centered
Crystal structure
Fm3m
Lattice constant in Å
a = 6,29
Elastic coefficient in GPa
C11 = 40,5

C12 = 6,9

C44 = 6,27

Young's Modulus (E) in Gpa
29,63
Shear Modulus (G) in GPa
6,24
Bulk Modulus (K) in GPa
17,36
Rupture Modulus in MPa
4,4
Apparent elastic limit in MPa
4,4
Poisson's ratio
0,29
Spectral properties
sample thickness: 2 mm
Optical Properties
Transmission range in µm @10% min. 0.18 - 25.1
Transmission range in µm @50% min. 0.18 - 25.0
Refractive index @ 633nm 1.488099
(1.45644 @10µm)
Reflection losses in % at 1 surface 3.45 @ 10µm
Reflection losses in % at 2 surfaces 6.7 @ 10.6µm
dn/dT in 1/K -33.2 · 10-6
Physical Properties
Density in g/cm³ 1.989
Melting point in °C 776
Specific heat capacity in J/(kg · K) 6936
Thermal Conductivity in W/(m · K) 6.53
Thermal Expansion in 1/K 36 · 10-6
Dielectric constant 4.64
Solubility in water in g/100g 34.7 @ 20°C
Mohs hardness 2
Knoop hardness in kg/mm² 18,2 (<100>)
Material type Single crystal, synthetic
Crystal type cubic face-centered
Crystal structure Fm3m
Lattice constant in Å a = 6.29
Elastic coeficients in GPa C11 = 40.5
C12 = 6.9
C44 = 6.27
Young's Modulus (E) in GPa 29.63
Shear Modulus (G) in GPa 6.24
Bulk Modulus (K) in GPa 17.36
Rupture Modulus in MPa 4.4
Apparent elastic limit in MPa 4.4
Poisson ratio 0.29
Spectral Properties
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