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LiF
crystals shows excellent transmittance in the VUV region. It is used for
windows, prisms, and lenses in the visible and infrared in 0.104 μm -
7 μm. LiF crystalis sensitive to thermal shock and would be attacked
by atmospheric moisture at 400°C. In addition irradiation produces color
centers. Modest precautions should be taken against moisture and high
energy radiation damage. Besides LiF is softens at 600°C and is slightly
plastic that can be bent into radius plates. The material can be cleaved
along (100) and less commonly (110). Although the optical characteristics
are good the structure is not perfect and cleavage is difficult. For good
structure LiF is less commonly grown by the Kyropoulos method (air-grown)
specifically for monochromator plates. High quality LiF is usually grown
by modified Bridgman technique. Maximum available size in diameters is
115mm. LiF is slightly plastic and can be bent into radius plates.
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Material and
Specifications:
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Transmission
Range (µm)
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0.12
~ 6
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Refractive
Index at 0.6 µm
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1.39181
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Reflection
Loss at 0.6 µm
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5.2%
(2 surfaces)
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Absorption
Coefficient at 2.7µm (cm-1)
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0.74×10-3
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Density
(g/cm3)
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2.639
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Melting
Point (°C)
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870
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Thermal
Conductivity at 314K (Wm-1K-1)
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4.01
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Thermal
Expansion at 283K (K-1)
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37×10-6
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Knoop
Hardness
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102
with 600g indenter
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Specific
Heat Capacity (J Kgm-1K-1)
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1562
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Elastic
Coefficient
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C11=112;
C12=46; C44= 63.5
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Apparent
Elastic Limit
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11.2
Mpa (1620 psi)
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Poisson
Ratio
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0.326
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Solubility
in 100g water at 20°C
(g)
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0.27
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Cleavage
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(100)
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