Chemical formula

BaF₂

CaF₂

MgF₂

LiF

Crystal structure

Cubic

Cubic

Tetragonal

Cubic

Lattice constant (Å )

6.196

5.462

a = 4.64
c = 3.06

4.026

Melting point ( ^oC )

1354

1418

1255

870

Density  ( g / cm³ )

4.88

3.18

3.18

2.60

Hardness

3

4

6

4

Thermal expansion coef.
( ^oC^-1x 10^-6 )

18.1

18.85

13.7

37.0

Refractive index

h_o 1.47443

h_o 1.43382

h_o 1.37740
h_e 1.38945

h_o 1.39212

Transmission waveband (microns)

0.15 - 13.00

0.11 - 12.00

0.11 - 7.5

0.11 - 7.0

Transmission efficient

> 93% @  5 m
> 75% @ 0.2 m

> 94% @ 5 m
> 85% @ 0.2 m

> 93% @5 m
> 85% @ 0.2 m

> 85% @ 5 m
> 65% @ 0.2 m

Chromatic dispersion (h_f-h_c)

0.00578

0.00455

0.00355

0.00395

Temperature coeff. ( dh / dt x 10^-6 )

-15.2 ~ 6.2@ 0.8 m

-10. 6 @ 0.8 m

2.3 ~1.7 @ 0.4 m

-12.7 @ 0.6 m

Crystal growth method

Bridgeman

Bridgeman

Bridgeman

Bridgeman

Cleavage plane

<111>

<111>

<100> or <110>

<100>

Max. Crystal size ( mm)

f 2" x 80

f 8" x 150

f 4" x 100

f 4" x 80

Application

IR and UV window , prism, substrate

IR window and Lens, prism

VUV window and mirror, lens

UV window and prism, without deliquescence