MgF2

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

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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

µm    No Ne µm    No Ne µm    No Ne
0.1137    1.7805   0.1149    1.7420   0.1179    1.6800  
0.1198    1.6510   0.121    1.628 1.632 0.130    1.566 1.568
0.140    1.5095 1.523 0.150    1.480 1.494 0.160    1.461 1.475
0.170    1.448 1.462 0.180    1.439 1.453 0.190    1.431 1.444
0.200    1.423 1.437 0.220    1.413 1.426 0.248    1.403 1.416
0.257    1.401 1.414 0.266    1.399 1.412 0.280    1.396 1.409
0.300    1.393 1.405 0.330    1.389 1.402 0.337    1.389 1.401
0.350    1.387 1.400 0.355    1.386 1.399 0.400    1.384 1.396
0.546    1.379 1.390 0.700    1.376 1.388 1.087    1.373 1.385
1.512    1.370 1.382 2.000    1.368 1.379 2.5    1.364 1.375
3.030    1.360 1.370 3.571    1.354 1.364 4.000    1.349 1.359
4.546    1.341 1.350 5.000    1.334 1.343 5.556    1.324 1.332
6.060    1.314 1.321