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65-80% Al2O3 Mullite (IEC 60672 Type C-620)

C-620 mullite is a grade of mullite. The graph bars on the material properties cards below compare C-620 mullite 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

800 MPa 120 x 103 psi

Elastic (Young's, Tensile) Modulus

170 GPa 24 x 106 psi

Flexural Strength

160 MPa 23 x 103 psi

Fracture Toughness

2.0 MPa-m1/2 1.8 x 103 psi-in1/2

Knoop Hardness


Poisson's Ratio


Tensile Strength: Ultimate (UTS)

160 MPa 24 x 103 psi

Electrical Properties

Dielectric Constant (Relative Permittivity) At 1 Hz


Dielectric Constant (Relative Permittivity) At 1 MHz


Dielectric Strength (Breakdown Potential)

17 kV/mm 0.66 V/mil

Electrical Dissipation At 1 MHz


Electrical Resistivity Order of Magnitude

11 10x Ω-m

Other Material Properties


3.0 g/cm3 190 lb/ft3

Maximum Temperature: Mechanical

1680 °C 3060 °F

Maximum Thermal Shock

170 °C 340 °F

Specific Heat Capacity

950 J/kg-K 0.23 BTU/lb-°F

Thermal Conductivity

11 W/m-K 6.1 BTU/h-ft-°F

Thermal Expansion

5.8 µm/m-K

Common Calculations

Stiffness to Weight: Axial

31 points

Stiffness to Weight: Bending

62 points

Strength to Weight: Axial

15 points

Strength to Weight: Bending

22 points

Thermal Diffusivity

3.7 mm2/s

Thermal Shock Resistance

12 points

Followup Questions

Further Reading

Mullite, Hartmut Schneider and Sridhar Komarneni (editors), 2005

Ceramic and Glass Materials: Structure, Properties and Processing, James F. Shackelford and Robert H. Doremus (editors), 2008

ASTM C242: Standard Terminology of Ceramic Whitewares and Related Products

IEC 60672-3: Ceramic and glass-insulating materials - Part 3: Specifications for individual materials

Springer Handbook of Condensed Matter and Materials Data, W. Martienssen and H. Warlimont (editors), 2005