Calcium Fluoride is superior to UV Fused Silica in deep UV applications. It has a transmission greater than 75% between 0.15-9µm and transmits efficiently up to about 8µm transmitting over 90%. Calcium Fluoride has a hardness of HK158, which is approximately twice as hard as BaF₂. Calcium Fluoride is not readily degraded under normal atmospheric conditions until 600°C when it starts to soften. In dry conditions Calcium Fluoride has a maximum operating temperature of 800°C. Calcium fluoride can be vulnerable to thermal shock at high temperatures. When calcium fluoride powder is compressed in moulds the resulting material is called Irtran-3.
Material | Calcium Fluoride |
AR Coating Range | 0.15-9um |
Diameter Tolerance | +0.0/-0.1 mm |
Thickness Tolerance | ±0.1 mm |
Surface Quality | 60-40 Scratch-Dig |
Surface Flatness (Plano Side) | λ/2 at 633nm |
Surface Irregularity (Peak to Valley) | λ/4 at 633nm |
Angle tolerance | 3 arcmin (5 seconds according to customer requirements) |
Chemical Formula | CaF2 |
Crystal Class | Cubic, cleaves [111] plane |
Lattice Constant, Å | 5.46 |
Density, g/cm3 (20 °C) | 3.18 |
Molecular Weight | 78.08 |
Reflection Loss | 5.4% at 5 μm |
Absorption Coefficient | 7.8 x 10-4 cm-1 @ 2.7 μm |
Dielectric Constant for 105 Hz | 6.76 |
Melting Temperature, K | 1630 |
Thermal Conductivity, W/(m K) at 273 K | 10 |
Thermal Expansion, 1/K at 300 K | 18.9 x 10-6 |
Specific Heat, cal/(g K) at 273 K | 0.204 |
Debye Temperature, K | 510 |
Young's Modulus, GPa | 75.79 |
Rupture Modulus, GPa | 0.0365 |
Shear Modulus, GPa | 33.76 |
Bulk Modulus, GPa | 83.03 |
Poisson's Ratio | 0.28 |
Knoop Hardness, kg/mm2 | 178 [100], 160 [110] |