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Specifications:
| Materials | IR Grade Barium fluoride Crystals | Diameter Range | ~ 200mm |
| Aperture | >90% | Dimension Tolerance | +0.0/-0.1mm |
| Thickness Tolerance | +/-0.2mm | Surface Quality | 60/40 S/D |
| Parallelism | 1 arc minute | Chamfer | 0.3-0.5mmx45degree |
| Coating | Optional protective coating |
Physical and Optical Properties:
| Transmission Range | 0.15 to 12 μm | Refractive Index | 1.45 at 5 μm (1) |
| Reflection Loss | 6.5% at 5 μm (2 surfaces) | Absorption Coefficient | 3.2 x 10-4cm-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 (300psi) (4) | Poisson Ratio | 0.343 |
| Solubility | 0.17g/100g water at 23°C | Molecular Weight | 175.36 |
| Class/Structure | Cubic CaF2, Fm3m, (111) , cleavage |
Barium Fluoride Windows, with their extensive transmission range from the deep UV to LWIR spectrum (0.2-11.0μm), is prevalent for Infrared applications requiring additional transmission in the Ultraviolet region. Barium Fluoride windows are excellent when being used for IR spectroscopes and as viewport windows for thermal imaging inspection in electric power facilities and petroleum industries. A low refractive index of 1.48 implies that BaF2 windows have high transmission rates without anti-reflection coating.
BaF2 has similar properties to CaF2, the main difference is that barium fluoride is more resistant to high-energy radiation, and with an equivalent thickness, the transmission range of BaF2 stretches about 1 micron further into the LWIR spectrum. However, exposure to moisture will increase its sensitivity to temperature and reduce its transmission rate to UV lights. The transmission of BaF2 substrate begins to drop at 500 °C under the attacks of water, but when kept dry, it endures temperatures up to 800 °C.
Shanghai North Optics offers BaF2 Windows with protective coatings and assembled windows with metal holders. It is worth noting that BaF2 is a toxic material, so please wear gloves during the handling process. You might also contact us to obtain detailed instructions.
Curves:
Transmission curve of the BaF2 windows of different thickness
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