Potassium Bromide

Potassium Bromide is commonly used for optical components in expanded spectrum band from the near ultraviolet to long wave infrared regions, since it is transparent over an extremely wide range of wavelengths (about 0.25 µm to 26 µm).

Potassium Bromide has a refractive index about 1.55 at 1.0 µm and no significant optical absorption lines in its high transmission region. It can be used at temperatures up to 300 °C. The material cleaves readily, its irradiation produces color centers. Potassium Bromide 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. The material can be polished to a high standard under humidity controlled conditions.

Potassium Bromide is 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 beamsplitter for CO2 -lasers.
Optical Properties
Transmission range in µm @10% min. 0.2 - 25
Transmission range in µm @50% min. 0.23 - 25
Refractive index @ 633nm 1.55655
(1.537 @10µm)
Reflection losses in % at 1 surface 4.34 @ 10µm
Reflection losses in % at 2 surfaces 8.3 @ 10.6µm
dn/dT in 1/K -40.83 · 10-6
Physical Properties
Density in g/cm³ 2.7533
Melting point in °C 730
Specific heat capacity in J/(kg · K) 435
Thermal Conductivity in W/(m · K) 4.8
Thermal Expansion in 1/K 43 · 10-6
Dielectric constant 4.9
Solubility in water in g/100g 67.8 @ 25°C
Mohs hardness 1.5
Knoop hardness in kg/mm² 7 (<100>)
Material type Single crystal, synthetic
Crystal type cubic face-centered
Crystal structure Fm3m
Lattice constant in Å a = 6.598
Elastic coeficients in GPa C11 = 34.5
C12 = 5.4
C44 = 5.08
Young's Modulus (E) in GPa 26.8
Shear Modulus (G) in GPa 5.08
Bulk Modulus (K) in GPa 15.03
Rupture Modulus in MPa 3.3
Apparent elastic limit in MPa 3.3
Poisson ratio 0.3
Spectral Properties