Synthetic Sapphire
Synthetic sapphire is an oxide-based engineering ceramic. It has the highest tensile strength among oxide-based engineering ceramics. In addition, it has a very high thermal conductivity and a moderately high density.
The graph bars on the material properties cards below compare synthetic sapphire to other oxide-based engineering 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
Compressive (Crushing) Strength
2700 MPa 390 x 103 psi
Elastic (Young's, Tensile) Modulus
450 GPa 65 x 106 psi
Flexural Strength
1090 MPa 160 x 103 psi
Fracture Toughness
1.9 MPa-m1/2 1.7 x 103 psi-in1/2
Knoop Hardness
1860
Poisson's Ratio
0.28
Shear Modulus
150 GPa 22 x 106 psi
Tensile Strength: Ultimate (UTS)
2470 MPa 360 x 103 psi
Thermal Properties
Maximum Temperature: Mechanical
2000 °C 3630 °F
Melting Onset (Solidus)
2050 °C 3720 °F
Specific Heat Capacity
760 J/kg-K 0.18 BTU/lb-°F
Thermal Conductivity
30 W/m-K 17 BTU/h-ft-°F
Thermal Expansion
5.3 µm/m-K
Electrical Properties
Dielectric Constant (Relative Permittivity) At 1 MHz
10
Dielectric Strength (Breakdown Potential)
9.9 kV/mm 0.39 V/mil
Electrical Resistivity Order of Magnitude
17 10x Ω-m
Otherwise Unclassified Properties
Density
4.0 g/cm3 250 lb/ft3
Light Transmission Range
0.17 to 5.5 µm
Refractive Index
1.8
Common Calculations
Stiffness to Weight: Axial
63 points
Stiffness to Weight: Bending
64 points
Strength to Weight: Axial
170 points
Strength to Weight: Bending
100 points
Thermal Diffusivity
9.9 mm2/s
Thermal Shock Resistance
74 points
Followup Questions
Further Reading
Ceramics and Composites: Processing Methods, Narottam P. Bansal and Aldo R. Boccaccini (editors), 2012
Springer Handbook of Condensed Matter and Materials Data, W. Martienssen and H. Warlimont (editors), 2005
CRC Materials Science and Engineering Handbook, 4th ed., James F. Shackelford et al. (editors), 2015