Ge Material
Germanium (Ge) is the preferred lens and window material for high performance infrared imaging systems in the 8–12 μm wavelength band. Its high refractive index makes Ge ideal for low power imaging systems because of minimum surface curvature. Chromatic aberration is small, often eliminating the need for correction.

Crystallographic properties
Syngony Cubic
Crystal Form Poly or Single Crystal
Lattice Constant 5.66
Cleavability <111>, non-perfect
Molecular Weight 72.6
Physical properties
Density, at 20 °C 5.33
Hardness, Mohs 6.3
Dielectric Constant for 9.37 × 109 Hz at 300 K 16.6
Melting 937
Thermal Conductivity, W/m·K at at 293 K 59
Thermal Expansion, 1/K at 298 K 6.1 × 10-6
Specific Heat Capacity, J/(kgK) at 273-373 K 0.074
Bandgap, eV 0.67
Knoop Hardness, kg/mm2 800
Youngs Modulus, Gpa 102.66
Shear Modulus, GPa 67.04
Bulk Modulus, GPa 77.86
Debye Temperature, K 370
Poissons Ratio 0.278
Elastic Coefficient C11=129, C12=48.3, C44=67.1
Apparent Elastic Limit 89.6 MPa (13000psi)
Chemical properties
Solubility in water None
Solubility in acids Soluble
Molecular Weight 72.59

Ms. Lin

Mr. Wen