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 μm) 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. Windows intended primarily for IR use and noted as having IR polish may have restricted transmission in the VUV being made from lower purity BaF2 crystal.
The highest quality Barium Fluoride also has application as the fastest known scintillator material and is used in High Energy Physics Experiments.
|Transmission Range :||0.15 to 12 μm (Note: IR grade may have restricted performance in UV)|
|Refractive Index :||1.45 at 5 μm (1)|
|Reflection Loss :||6.5% at 5 μm (2 surfaces)|
|Absorption Coefficient :||3.2 x 10-4 cm-1 @ 6 μm|
|Reststrahlen Peak :||47 μm|
|dn/dT :||-15.2 x 10-6/°C (2)|
|dn/dμ = 0 :||1.95 μm|
|Density :||4.89 g/cc|
|Melting Point :||1386°C|
|Thermal Conductivity :||11.72 W m-1 K-1 @ 286 K|
|Thermal Expansion :||18.1 x 10-6/°C @ 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 (3900psi) (4)|
|Poisson Ratio :||0.343|
|Solubility :||0.17g/100g water at 23°C|
|Molecular Weight :||175.36|
|Class/Structure :||Cubic Fm3m (#225) Fluorite structure. Cleaves on (111)|
Not all crystal is manufactured from the highest grade of chemical; for IR grade optics a lower specification of raw material is adequate and reduces cost, however the transmission in the UV may be restricted.
To download this data or our MSDS safety data sheet as a pdf, please click on the links at the top of the page. To expand the transmission graphs, please click on the image.
Not all crystal is manufactured from the highest grade of chemical; for IR grade optics lower specification is adequate and reduces cost, however the transmission in the UV and VUV is restricted.
The highest purity Barium Fluoride VUV material can be qualified as fast scintillator grade. (6)
(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
Wikipedia.org - Has an entry with further information on Barium Fluoride.