Potassium chloride

Material
KCl

 

Potassium chloride is commonly used for optical components in wide spectrum band from the ultraviolet to the infrared, since it is transparent over the entire range of wavelengths about 0.3µm to 20µm. Its transmission extends beyond that of Sodium Chloride. Potassium Chloride has a low refractive index (1.454 at 10.6µm); its damage threshold is high. That's why optical windows from Potassium Chloride are particularly useful for spatter barrier windows in CO2  lasers.

 

Potassium Chloride can be used up to 400°C. The material is hygroscopic and highly soluble in water, that's why it must be kept in a dry environment or protected against moisture degradation of polished surfaces.

 

Potassium Chloride is commonly used for optical windows, lenses, prisms and other optical items in the range from the ultraviolet to the infrared. It is one of the most useful materials for IR spectroscopic components and optical items for Fourier transform infrared (FTIR) spectroscopy. Due to its low cost, it is mainly used for CO2 laser protection windows.

Properties
Optical 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 in % at 2 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
Spezific heat capacity in J/(kg · K)
693
Thermal conductivity in W/(m · K)
6,53
Thermal expension in 1/K
36 · 10-6
Dielectric constants
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 ratio
0,29
Spectral properties
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