Sapphire [Al2O3] Window Specifications

Index of Refraction N0: 1.768 (c-axis)
Ne: 1.760 (c-axis)
Birefringence (N0 - Ne) 0.008
Density 3.97 gm/cm³
Compressive Strength 300,000 psi
Young Modulus 50-55 x 106 psi
Flexural Strength ~100,000 psi
Tensile Strength ~60,000 psi (at ~25°C)
Poisson's Ratio 0.28-0.33
Hardness 9 mohs
1800 Knoop parallel to c-axis
2200 Knoop perpendicular to c-axis
Coefficient of Friction Against Steel 0.15
Porosity 0%
Dielectric Strength 480,000 v/cm
Dielectric Constant (parallel to c-axis) average 11.5
Dielectric Constant (perpendicular to c-axis) average 9.3
Volume Resistivity >1014 Ω-cm3
Melting Point 2,050°C
Coeffecient of Expansion (parallel to c-axis) 5.3 x 10-6
Coeffecient of Expansion (perpendicular to c-axis) 4.5 x 10-6
Conductivity 0.086 cal/gm
Heat Capacity 77.8 joules/deg. Mole