Thallium Bromoiodide (KRS-5) Optical Material
Thallium bromoiodide is a non-glass, inorganic optical material. It has the highest density among non-glass optical ceramics. In addition, it has the lowest melting temperature and the lowest heat capacity. The graph bars on the material properties cards below compare thallium bromoiodide 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
31 GPa 4.5 x 106 psi
Poisson's Ratio
0.37
Shear Modulus
12 GPa 1.7 x 106 psi
Thermal Properties
Melting Onset (Solidus)
420 °C 780 °F
Specific Heat Capacity
150 J/kg-K 0.036 BTU/lb-°F
Thermal Conductivity
0.55 W/m-K 0.32 BTU/h-ft-°F
Thermal Expansion
6.0 µm/m-K
Otherwise Unclassified Properties
Density
7.4 g/cm3 460 lb/ft3
Light Transmission Range
0.6 to 40 µm
Refractive Index
2.4
Common Calculations
Stiffness to Weight: Axial
2.3 points
Stiffness to Weight: Bending
14 points
Thermal Diffusivity
0.5 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