Potassium bromide ( KBr )

Crystal  properties

Crystal Type

cubic, NaCl  type structure 

Transmission Range

0.23 ... 25 µm 

Refractive Index

1.52695 @ 9.724 µm 

Reflective Loss

8.4 % @ 10.0 µm 

Reststrahlen

77.6 µm 

^Density.

2.7533 g/cm³ 

Melting Point

730 °C 

Molecular Weight

119.002 

Thermal Conductivity

4.816 W/(m K) @ 46 °C 

Specific Heat

435 J/(kg K) @ 0 °C 

Thermal Expansion^.

43 × 10^–6 / K 

Hardness (Knoop)

5.9 <110>
7.0 <100>
Indenter load 200 g
 

Young’s Modulus

26.8 GPa 

Shear Modulus

5.08 GPa 

Bulk Modulus

15.03 GPa 

Rupture Modulus

0.33 MPa 

Elastic Coefficient 

C₁₁ = 34.5
 C₁₂ = 5.4  
C₄₄ = 5.08 GPa

Dielectric Constant

5.65 @ 25 °C, f = 100 Hz ... 10 GHz 

Solubility in Water

53.4 g / 100 g @ 0 °C 

Crystal Structure

Single crystal,  synthetic 

Cleavage Planes

(100) 

Standard Diameter

180 mm 

Application

IR spectroscopy
FTIR beamsplitters
CO₂ laser optics
protective windows

Remarks

coatings available 

List of Optical Crystals

Materials

Refractive Index

Transmission
Range (mm)

Density
(g/cm³)

Thermal Expansion 
Coefficient (10^-6/K) 

BK7 glass

1.5164 (588 nm)

0.330 – 2.1

2.51

7.5 

SF11 glass

1.78472 (588 nm)

0.370 – 2.5

4.74

6.8 

F2 glass

1.62004 (588 nm)

0.420 – 2.0

3.61

8.2 

Fused Silica

1.4858 (308 nm)

0.185 – 2.5

2.20

0.55 

CaF₂

1.399  (5.0 mm)

 0.170 – 7.8

3.18

 18.85 

BaF₂

 1.460 (3.0 um)

 0.15 – 12.0

4.88

 18.4 

Sapphire

1.755 (1.0mm)

0.180 – 4.5

3.98

8.4 

Silicon

3.4179 (10mm)

 1.200 – 7.0

2.33

 4.15 

Ge

4.003 (10 mm)

 1.900 – 16

5.33

 6.1 

ZnSe

2.40  (10 mm)

0.630 – 18

5.27

7.8 

ZnS

2.2 (10mm)

0.380 –14

4.09

6.5 

LiF

1.39 (500 nm)

 0.150 – 5.2

2.64

37 

KBr

1.526 (10 mm)

 0.280 – 22

2.75

43 

 MgF₂

n_o =  1.3836
n_e = 1.3957
(405 nm)

0.130 – 7.0

7.37

a: 13.7
b: 8.48 

YVO₄

n_o = 1.9500
n_e = 2.1554
(1.3 mm)

0.400 – 5.0

4.22

a: 4.46
b: 11.37 

Calcite

n_o =  1.6557
n_e = 1.4852
(633 nm)

0.210 – 2.3

2.75

a: 24.39
b: 5.68 

Quartz

n_o =  1.5427
n_e = 1.5518
(633 nm)

0.200 – 2.3

2.65

7.07 

?-BBO

n_o =  1.6749
n_e = 1.5555
(532 nm)

0.190 – 3.5

3.85

a: 4.0
c: 36 

LiNbO₃

 n_o =  2.2863
n_e = 2.2027
(633 nm)

0.370 – 4.5

4.64

a: 16.7
c: 2.0