Barium Fluoride is commonly used for optical components in expanded spectrum band from ultraviolet to infrared regions, since it is transparent over an extremely wide range of wavelengths (from 0.15-0.20 µm to 11-11.5 µm). Barium Fluoride (BaF2) transmittance at 200 nm is relatively low (~60%), but at 500 nm Barium Fluoride (BaF2) goes up to 96%-97% and stays at that level until 9 µm, then it starts falling off (85% for 10 µm and 42% for 12 µm).
BaF2 is hard but is very sensitive to thermal shock. In dry environment, BaF2 can be used up to 800 °C, but its resistance to water is less than that of Calcium Fluoride. That’s why it is corroded by water when it is heated to 500 °C. Nevertheless, BaF2 is the most resistant of all optical fluorides to high-energy radiation.
BaF2 is used for optical windows, lenses, prisms and other optical items in the range from the ultraviolet to the infrared. For an equivalent thickness the transmission extends approximately 1 micron further into the IR than Calcium Fluoride. In addition, BaF2 has application as the fastest known scintillator material and is used for production of fast-acting and radiation resistant scintillation detectors for positron-emission tomography, nuclear calorimetry, gamma-spectroscopy and for identification of charged particles, neutrons and Cherenkov counters.
We use for our Barium Fluoride (BaF2) optics high quality crystals grown by Czochralsky and Bridgman Methods and supply high transparent and low-loss BaF2 optical windows, prisms, lenses, achromatic lenses and other optical components. BaF2 is sold in two qualities (monodomain and polydomain) and in three grades – IR-, UV- and scintillator-grade.
|Transmission range in µm @10% min.||0.14 - 15|
|Transmission range in µm @50% min.||0.14 - 14|
|Refractive index @ 633nm||1.47326 (1.45@5µm)|
|Reflexion loss in % at 1 surface||3.4 @ 4µm|
|Reflexion loss in % at 2 surfaces||6.5 @ 5µm|
|dn/dT in 1/K||-15.2 · 10-6|
|Density in g/cm³||4.89|
|Melting Point in °C||1368|
|Specific heat capacity in J/(kg · K)||410|
|Thermal Conductivity in W/(m · K)||10.9|
|Thermal Expansion in 1/K||18.4 · 10-6|
|Solubility in water in g/100g||0.16 @ 25°C|
|Knoop hardness in kg/mm²||82|
|Material type||Single crystal, synthetic|
|Crystal Type||Cubic, CaF2 strukture|
|Lattice Constant in Å||a = 6.2|
|Elastic Coefficients in GPa||C11 = 91 C12 = 41.2 C44 = 25.3|
|Youngs's Modulus (E) in GPa||53.07|
|Shear Modulus (G) in GPa||25.4|
|Bulk Modulus (K) in GPa||57.8|
|Rupture Modulus in MPa||26.9|
|Apparent elastic limit in MPa||26,9|