Barium Fluoride (BaF2)
Barium Fluoride is used in spectroscopic components. Barium Fluoride is often suitable for applications in the passive IR band (8 to 14 ¦Ìm) and is often used as a viewport window for thermography. For an equivalent thickness the transmission extends approximately 1 micron further into the IR than Calcium Fluoride. The highest quality Barium Fluoride also has application as the fastest known scintillator material and is used in High Energy Physics Experiments.
 
Product Data -----------------------------------------------------
 
Transmission Range : 0.15 to 12 ¦Ìm
Refractive Index : 1.45 at 5 ¦Ìm (1)
Reflection Loss : 6.5% at 5 ¦Ìm (2 surfaces)
Absorption Coefficient : 3.2 x 10-4 cm-1 @ 6 ¦Ìm
Reststrahlen Peak : 47 ¦Ìm
dn/dT : -15.2 x 10-6/¡ãC (2)
dn/d¦Ì = 0 : 1.95 ¦Ìm
Density : 4.89 g/cc
Melting Point : 1386¡ãC
Thermal Conductivity : 11.72 W m-1 K-1 @ 286 K
Thermal Expansion : 18.1 x 10-6/¡ãC @ 273 K
Hardness : Knoop 82 with 500g indenter (4)
Specific Heat Capacity : 410 J Kg-1 K-1 (3)
Dielectric Constant : 7.33 at 1 MHz
Youngs Modulus (E) : 53.07 GPa (3)
Shear Modulus (G) : 25.4 GPa (3)
Bulk Modulus (K) : 56.4 GPa
Elastic Coefficients : C11 = 89.2 C12 = 40.0 C44 = 25.4 (2)
Apparent Elastic Limit : 26.9 MPa (300psi) (4)
Poisson Ratio : 0.343
Solubility : 0.17g/100g water at 23¡ãC
Molecular Weight : 175.36
Class/Structure : Cubic CaF2, Fm3m, (111) cleavage
 
Refractive Index and Optical Transmittance curve----
Refractive Index(No = Ordinary Ray):
µm    No µm    No µm    No
0.1408    1.8150 0.1452    1.7820 0.1477    1.7670
0.1500    1.6780 0.2000    1.557 0.2652    1.5122
0.2803    1.5066 0.2893    1.5039 0.2967    1.5019
0.3021    1.5004 0.3130    1.4978 0.3254    1.4952
0.3403    1.4925 0.3466    1.4915 0.3610    1.4894
0.3663    1.4887 0.4046    1.4844 0.5461    1.4759
0.5893    1.4744 0.6438    1.4730 0.6563    1.4727
0.7065    1.4718 0.8521    1.4699 0.8944    1.4694
1.0140    1.4685 1.1287    1.4678 1.3673    1.4667
1.5295    1.4661 1.6810    1.4656 1.7012    1.4655
1.9701    1.4647 2.3254    1.4636 2.6738    1.4623
3.2434    1.4602 3.4220    1.4594 5.1380    1.4501
5.5490    1.44732 6.2380    1.4422 6.6331    1.4390
7.0442    1.4353 7.2680    1.4331 9.7240    1.4051
10.346    1.3936
Optical Transmittance Curve of BaF2 (Reference Data):
Barium Fluoride(BaF2) Transmittance
 
Special properties of BaF2-----------------------------------

BaF2 is generally used in the VIS,NIR and / or MW spectral regions.

The hardness of BaF2 is about half that of CaF2.

BaF2 is also more susceptible to thermal shock than CaF2.

BaF2 is somewhat more expensive than CaF2.

Not as readily available in large sizes as CaF2.

BaF2 is diamond turnable.

Typeical application: Thermal imaging,astronomy,laser.

Products manufactured: Lenses, Aspheric lenses, Windows, Optical Beamsplitters, Optical Filters, Wedges, Prisms.

Surface finish: Polishes of 20-10 scratch-dig are mostly specified for use in UV and visible applications. Typical specifications for surface quality in the infrared are a 40-20 scratch dig in the 0.75 to 3μm spectral region and 60-40 scratch-dig for the 3-7μm area. BaF2 is diamond turnable.

Surface figure: Surface figure of a 1/10 wave to 1/2 wave @0.6328 μm are specified mostly on lenses for ultraviolet and visible use. In the infrared, typical required surface figure ranges from 1/2 wave to 2 waves @0.6328 μm depending on the system performance requirements.

AR coating options: Typical available coatings for BaF2 include BBAR for 0.8 to 2.5 μm, 3 to 5μm or the 1 to 5μm spectral regions.
Product Notes:------------ --------------------------------------

Barium Fluoride is grown by vacuum Stockbarger technique. Unlike CaF2, BaF2 is not found in the native state and all material must be synthesised chemically making BaF2 relatively expensive to produce. Barium Fluoride cleaves easily and is highly susceptible to thermal shock. It polishes well and can be etched (5). The highest purity Barium Fluoride VUV material can be qualified as fast scintillator grade. (6)

REFERENCES:
(1) Handbook Optical Constants, ed Palik, V3, ISBN 0-12-544423-0
(2) I.H.Malitson; J.Opt.Soc.Am. Vol52, p1377, 1962
(3) D.Girlich; Elastic Constants of BaF2; Phys.Rev. Vol135, p1826, 1964
(4) S.Ballard et al; J.Opt.Soc.Am. Vol42, p684, 1952
(5) US patent. Chemical polish. 4,040,896 1977
(6) M.Laval et al; Nu. Insts.Meth, V206 p169, 1983

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

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