Potassium Bromide (KBr)

Potassium Bromide is one of the most useful materials for general purpose spectroscopic windows and applications where sensitivity to moisture is unimportant. KBr is the most commonly used beamsplitter material for IR spectrophotometers. Potassium Bromide is used for windows and prisms when transmission through the 0.25 µm - 26 µm range is desired. Potassium Bromide is water soluble and must be protected against moisture degradation of polished surfaces. The material cleaves readily, and can be used at temperatures up to 300 °C. Irradiation of Potassium Bromide produces color centers. Potassium Bromide is produced in large ingots by the Kyropoulos growth method. It cleaves easily. With care it can be polished to a high standard under humidity controlled conditions. Maximum available size: 140 mm Dia x 30 mm Thk

Base Properties

PARAMETER

VALUE

OPTICAL  
Transmission Range 0.23 to 25 microns
Refractive Index 1.52404 at 11 microns
Reflection Loss 8.3% at 11 microns (2 surfaces)
Absorption Coefficient 1.6 x 10-4 cm-1 at 3.8µm
Restrahlen Peak 77.6 microns
dN/dT -40.83 x 10-6/°C
dN/dµ = 0 4.2 microns
PHYSICAL  
Density 2.753 g/cm3
Melting Point 730°C
Thermal Conductivity 4.816Wm-1K-1 at 319K
Thermal Expansion 43 x 10-6/K at 300K
Hardness Knoop 7 in <100> with 200g indenter
Specific Heat Capacity 435 J kg-1K-1
Dielectric Constant 4.9 at 1MHz
Young’s Modulus (E) 26.8 GPa
Shear Modulus (G) 5.08 GPa
Bulk Modulus (K) 15.03 GPa
Elastic Coefficients C11 = 34.5 C12 = 5.4 C44 = 5.08
Apparent Elastic Limit 1.1 MPa (160psi)
Poisson Ratio 0.203
CHEMICAL  
Solubility 53.48g/100g water at 273K
Molecular Weight 119.01
Class/Structure Cubic FCC, NaCl, Fm3m, (100) cleavage

Refractive Index

Wavelength, µm

0.39

0.44

0.49

0.59

0.80

1.50

8.50

12.0

17.0

18.1

20.5

22.0

23.9

25.2

Refractive Index

1.59

1.58

1.57

1.56

1.55

1.54

1.53

1.52

1.51

1.50

1.49

1.48

1.47

1.46

 

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