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Potassium Chloride (KCl) Optical Material

Potassium chloride is a non-glass, inorganic optical material. It has the lowest density among the non-glass optical ceramics in the database. The graph bars on the material properties cards below compare potassium chloride 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

28 GPa 4.0 x 106 psi

Poisson's Ratio


Shear Modulus

8.5 GPa 1.2 x 106 psi

Thermal Properties

Melting Onset (Solidus)

780 °C 1440 °F

Specific Heat Capacity

690 J/kg-K 0.16 BTU/lb-°F

Thermal Conductivity

6.5 W/m-K 3.8 BTU/h-ft-°F

Thermal Expansion

36 µm/m-K

Electrical Properties

Dielectric Constant (Relative Permittivity) At 1 MHz


Electrical Dissipation At 1 MHz


Otherwise Unclassified Properties


2.0 g/cm3 120 lb/ft3

Light Transmission Range

0.21 to 20 µm

Refractive Index


Common Calculations

Stiffness to Weight: Axial

7.7 points

Stiffness to Weight: Bending

51 points

Thermal Diffusivity

4.7 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