Lithium Fluoride (LiF) Optical Material
Lithium fluoride is a non-glass, inorganic optical material. It has the highest heat capacity and a fairly low density among non-glass optical ceramics. The graph bars on the material properties cards below compare lithium fluoride to other non-glass optical ceramics (top) and the entire database (bottom). A full bar means this is the highest value in the relevant set. A half-full bar means it's 50% of the highest, and so on.
Mechanical Properties
Elastic (Young's, Tensile) Modulus
120 GPa 17 x 106 psi
Poisson's Ratio
0.27
Shear Modulus
52 GPa 7.5 x 106 psi
Thermal Properties
Melting Onset (Solidus)
870 °C 1600 °F
Specific Heat Capacity
1560 J/kg-K 0.37 BTU/lb-°F
Thermal Conductivity
12 W/m-K 6.9 BTU/h-ft-°F
Thermal Expansion
32 µm/m-K
Electrical Properties
Dielectric Constant (Relative Permittivity) At 1 MHz
9.0
Electrical Dissipation At 1 MHz
0.00020
Otherwise Unclassified Properties
Density
2.6 g/cm3 160 lb/ft3
Light Transmission Range
0.12 to 6.5 µm
Refractive Index
1.4
Common Calculations
Stiffness to Weight: Axial
24 points
Stiffness to Weight: Bending
62 points
Thermal Diffusivity
2.9 mm2/s
Followup Questions
Further Reading
Handbook of Optical Materials, Marvin J. Weber, 2003
Handbook of Optical Constants of Solids, Edward D. Palik (editor), 1998
Ceramics and Composites: Processing Methods, Narottam P. Bansal and Aldo R. Boccaccini (editors), 2012