Magnesium Fluoride is used for optical elements in the infrared where extreme ruggerness and durability is required. The single MgF2 crystal exhibits slight birefringence through its useful transmission range and birefringence in the infrared could be useful.
Magnesium Fluoride is similar to Calcium Fluoride in its resistance to water. The MgF2 windows is sensitive to thermal shock, but does not cleave. Irradiation does not lead to color centers. MgF2 transmits well into the DUV / VUV region at the hydrogen Lyman-alpha line (121nm) and beyond. MgF2 windows and lenses are also used for most UV optics and is excellent for eximer laser application
transmission of 6mm thick MgF2 sample | |||||
nm | T | nm | T | nm | T |
115 | 24.0 | 145 | 78.0 | 185 | 90.0 |
117.5 | 38.5 | 147.5 | 79.5 | 190 | 91.0 |
120 | 50.0 | 150 | 80.0 | 195 | 91.0 |
122.5 | 58.5 | 152.5 | 82.0 | 200 | 92.0 |
125 | 64.0 | 155 | 83.0 | 202 | 92.0 |
127.5 | 68.0 | 157.5 | 84.0 | 204 | 93.0 |
130 | 69.0 | 160 | 85.0 | 205 | 93.0 |
132.5 | 71.0 | 162.5 | 86.0 | 206 | 93.0 |
135 | 72.0 | 165 | 86.0 | 208 | 93.0 |
137.5 | 74.0 | 170 | 87.0 | 210 | 93.0 |
140 | 75.0 | 175 | 88.0 | 215 | 93.0 |
142.5 | 76.0 | 180 | 89.0 | 220 | 93.0 |
MgF2 Magnesium fluoride data | |
Chemical Formula | MgF2 |
Crystal Class | tetragonal |
Lattice Constant, Å | a=4.64; c=3.06 |
Molecular Weight | 62.31 |
Density, g/cm3 at 291 K | 3.18 |
Reflection Loss, % for two surfaces in the visible | 4.8 |
Dielectric Constant for 95 x 103-42×106 Hz | 5.45 |
Melting Temperature, K | 1528 |
Thermal Conductivity, W/(m K) at 300 K | 14-15 |
Thermal Expansion, 1/K at 310 K parallel perpendicular |
14×10-6 8.9×10-6 |
Specific Heat, cal/(g K) at 298 K at 1700 K |
0.24 0.362 |
Bandgap, eV | 10.8 |
Solubility in water | None |
Knoop Hardness, kg/mm2 | 415 |
Young’s Modulus, GPa | 138.5 |
Shear Modulus, GPa | 54.66 |
Bulk Modulus, GPa | 101.32 |
Apparent Elastic Limit, MPa | 49.64 |
Poisson Ratio | 0.276 |
MgF2 Refractive Index | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
No = Ordinary Ray Ne = Extraordinary Ray
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