氟化镁晶体 Magnesium fluoride (MgF2) crystal
氟化镁晶体（MgF2）属于四方晶系，熔点为1255℃，硬度高，机械性能好，化学性能稳定，不易潮解和腐蚀。在真空紫外110nm到红外的7.5μm光谱范围内，氟化镁晶体具有非常优异的透过率和低的折射率，使得该晶体的折射率损失很低。光学性能方面其主要特点是在真空紫外波段具有较高的透过率（170nm透过率仍在80%以上），该晶体被广泛用于光纤通信、军工领域及各种光学元件，如窗口、镜面、透镜、棱镜、偏光镜、楔形和衬底。此外，氟化镁晶体是唯一既有宽光谱透射范围又有双折射性能的晶体。
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Properties |
Value |
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Transmission Range : |
0.12 to 7 μm (1) |
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Refractive Index : |
No 1.413 at 0.22 μm (4) |
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Reflection Loss : |
5.7% at 0.22 μm (2 surfaces) |
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Absorption Coefficient : |
40 x 10-3 cm-1 at 2.7 μm |
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Reststrahlen Peak : |
20 μm (1) |
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dn/dT : |
2.3 (para) 1.7 (perp) at 0.4 μm (1) |
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dn/dμ = 0 : |
1.4 μm |
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Density : |
3.18g/cc |
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Melting Point : |
1255°C |
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Thermal Conductivity : |
21 (para) 33.6 (perp) W m-1 K-1 at 300K (3) |
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Thermal Expansion : |
13.7 (para) 8.9 (perp) x 10-6 /K (1) |
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Hardness : |
Knoop 415 |
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Specific Heat Capacity : |
1003 J Kg m-1 K-1 |
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Dielectric Constant : |
4.87 (para) 5.45 (perp) at 1MHz (1) |
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Youngs Modulus (E) : |
138 GPa (2) |
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Shear Modulus (G) : |
54.66GPa (2) |
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Bulk Modulus (K) : |
101.32 GPa (2) |
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Elastic Coefficients : |
C11=140 C12=89 C44=57 C13=63 C66=96 (2) |
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Apparent Elastic Limit : |
49.6 MPa (7200 psi) |
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Poisson Ratio : |
0.276 (2) |
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Solubility : |
0.0002g/100g water |
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Molecular Weight : |
62.32 |
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Class/Structure : |
Tetragonal, can cleave on c-axis |