Lithium Fluoride (LiF)
Lithium fluoride is the material with the most extreme UV transmission of all and is used for special UV optics. Lithium fluoride transmits well into the VUV region at the hydrogen Lyman-alpha line (121nm) and beyond. Lithium fluoride is also used for X-ray monochromator plates where its lattice spacing makes it the most useful analysis crystal.
 
Product Data -----------------------------------------------------
 
Transmission Range : 0.12 to 6 μm
Refractive Index : 1.392 at 0.6 μm (1)
Reflection Loss : 5.2% at 0.6 μm (2 Surfaces)
Absorption Coefficient : 5.9 x 10-3 cm-1 at 4.3 μm @ 300K (5)
Reststrahlen Peak : 25 μm
dn/dT : -16 x 10-6 at 1.15 μm
dn/dμ = 0 : 1.3 μm
Density : 2.639 g/cc
Melting Point : 870 °C
Thermal Conductivity : 4.01 W m-1 K-1 at 314 K (2)
Thermal Expansion : 37 x 10-6 K-1 at 283 K (2)
Hardness : Knoop 102 with 600g indenter (2)
Specific Heat Capacity : 1562 J Kg-1 K-1
Dielectric Constant : 0.1
Youngs Modulus (E) : 64.97 GPa (2)
Shear Modulus (G) : 55.14 GPa (2)
Bulk Modulus (K) : 62.03 GPa (2)
Elastic Coefficients : C11=112; C12=46; C44=63.5 (3)
Apparent Elastic Limit : 11.2 MPa (1620 psi) (4)
Poisson Ratio : 0.326 (calculated)
Solubility : 0.27g / 100g water at 20 °C
Molecular Weight : 25.94
Class/Structure : Cubic FCC, NaCl, Fm3m, (100) cleavage
 
Refractive Index and Optical Transmittance curve----
Refractive Index(No = Ordinary Ray):
µm    No µm    No µm    No
0.106    1.9130 0.108    1.8330 0.110    1.7770
0.121    1.6240 0.130    1.5690 0.140    1.5300
0.150    1.5030 0.160    1.4840 0.170    1.4690
0.180    1.4850 0.190    1.4455 0.200    1.4391
0.220    1.4291 0.250    1.4189 0.260    1.4164
0.270    1.4141 0.280    1.4121 0.290    1.4103
0.300    1.4087 0.310    1.4073 0.320    1.4060
0.330    1.4048 0.340    1.4037 0.350    1.4028
0.360    1.4019 0.400    1.3989 0.500    1.3943
0.600    1.3918 0.700    1.3902 0.800    1.3890
0.900    1.3880 1.000    1.3871 1.500    1.3832
2.000    1.3788 2.500    1.37327 3.000    1.3666
3.500    1.3587 4.000    1.3494 4.500    1.3388
5.000    1.3266 5.100    1.3240 5.200    1.3213
5.300    1.3186 5.400    1.3158 5.500    1.3129
5.600    1.3099 5.700    1.3069 5.800    1.3038
5.900    1.3007 6.000    1.2975
Optical Transmittance Curve of LiF (Reference Data):
lithium-fluoride-lif Transmittance
 
Special properties of LiF-----------------------------------

Its birefringence should be taken into consideration before selection of this material in an optical design..

It is resistant to thermal and mechanical shock..

It is twice as hard as CaF2 but only half as hard as Ge.

It is significantly more expensive than CaF2 and BaF2,but usually not more expensive than LiF.

MgF2 is diamond turnable.

Typeical application:Thermal imaging, Astronomical, Excimer laser applications..

Products manufactured:Lenses, Aspheric lenses, Windows, Wedges, Prisms.

Surface finish:Typical specifications for surface quality in the infrared are a 40-20 scratch dig in the 0.75 to μm spectral region and 60-40 or 80-50 scratch-dig for the 3-7μm area depending upon system performance requirements. LiF is diamond turnable.

Surface figure:In the infrared, typical surface figure ranges from 1/2 wave to 4 waves @0.6328μm depending upon system performance requirements.

AR coating options:LiF can be AR coated for use in the infrared, but generally without much improvement in transmission due to its low index of refraction and already high transmission
Product Notes:------------ --------------------------------------

Lithium Fluoride is grown by vacuum Stockbarger technique in ingots approximately 100mm diameter. Lithium Fluoride cleaves easily and must be worked with extreme care. Polishing, particularly steep radii, often causes surface "rip-out".

REFERENCES:
(1) Laporte et. al. J.Opt. Soc. Am. V73, No 8, p1062
(2) Combes et. al. J.Opt. Soc. Am. V41, p215. 1951
(3) Huntingdon, Phys Review. V72, p321, 1947
(4) Ballard et. al. J.Opt. Soc. Am. V42, p684. 1952
(5) H.H.Li, Absorption Coefficients, Int.J.Therm, V1, No. I, 1980

Data provided is extracted from our technical handbook of materials. While every attempt has been made to verify the source of the information, ultiQuest Technology accept no responsibility for accuracy of data

 Contact
If you have any questions or comments, please contact us by filling-in the mail form.

 
Copyright 1999-2011 Ultiquest Technology Ltd. | Privacy Policy | Terms of Use | Web Mail Site Credits