Strontium Fluoride SrF2
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Transmission Range
0.15 to 11 μm
Refractive Index
1.439 at 0.55 μm (1)
Reflection Loss
6.3% at 0.55 μm (2 surfaces)
Absorption Coefficient
<1 x 10-3 cm-1 @ 5 μm
Reststrahlen Peak
46 μm
dn/dT
-12 x 10-6 K-1
dn/dμ = 0
n/a
Density
4.24 g/cc
Melting Point
1450°C
Thermal Conductivity
8.3 W m-1 K-1 @ 293 K (2)
Thermal Expansion
18.4 x 10-6/°C @ 293 K
Hardness
Knoop 154 (100) & 140 (110)
Specific Heat Capacity
543 J Kg-1 K-1
Dielectric Constant
7.69 at 2 MHz
Youngs Modulus (E)
89.1 GPa
Shear Modulus (G)
34.6 GPa
Bulk Modulus (K)
24.65 GPa
Elastic Coefficients
C11 = 124 C12 = 45 C44 = 31.7
Apparent Elastic Limit
36.5 MPa (5300psi)
Poisson Ratio
0.25
Solubility
0.012g/100g water at 27°C
Molecular Weight
125.62
Class/Structure
Cubic Fm3m (#225) Cleaves on (111)
| µm | No |
|---|---|
| 0.15 | 1.594 |
| 0.20 | 1.504 |
| 0.31 | 1.45725 |
| 0.41 | 1.44556 |
| 0.51 | 1.44029 |
| 0.61 | 1.43740 |
| 0.71 | 1.43560 |
| 0.81 | 1.43435 |
| µm | No |
|---|---|
| 0.91 | 1.43343 |
| 1.01 | 1.43269 |
| 1.51 | 1.43003 |
| 2.01 | 1.42761 |
| 3.01 | 1.42159 |
| 4.01 | 1.41337 |
| 5.01 | 1.40269 |
| 6.01 | 1.38934 |
| µm | No |
|---|---|
| 7.01 | 1.37308 |
| 8.01 | 1.35362 |
| 8.1 | 1.3517 |
| 8.6 | 1.3405 |
| 9.1 | 1.3283 |
| 9.6 | 1.3151 |
| 10.6 | 1.2854 |
| 11.1 | 1.2686 |
Strontium fluoride is produced by the vacuum Stockbarger growth technique.
REFERENCES:
(1) Handbook of Optical Constants, ed Palik, V3, ISBN 0-12-544423-0
(2) For Thermal Conductivity (Tc) a figure of 1.42 W/(mK) is in wide circuation but is plainly incorrect based on observation of UKRI STFC (2019) plus logically the Tc should be intermediate between BaF2 and CaF2. OSTI.GOV gives (p44) 0.016 cal cm-1 s C-1 for 25°C which converts to 6.7 W m-1 K-1. OSA PUBLISHING confirms (p95) our existing Tc for CaF2 as 9.71W m-1K-1 and offers for SrF2 as 8.3 W m-1 K-1