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Mullite

Mullite is an oxide-based engineering ceramic. It has a moderately high heat capacity among the oxide-based engineering ceramics in the database.

The properties of mullite include two common variations. This page shows summary ranges across both of them. For more specific values, follow the links immediately below. The graph bars on the material properties cards further below compare 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

110 to 170 GPa 16 to 24 x 106 psi

Flexural Strength

130 to 160 MPa 18 to 23 x 103 psi

Fracture Toughness

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

Knoop Hardness

750

Poisson's Ratio

0.25

Tensile Strength: Ultimate (UTS)

160 MPa 24 x 103 psi

Electrical Properties

Dielectric Constant (Relative Permittivity) At 1 Hz

8.0

Dielectric Constant (Relative Permittivity) At 1 MHz

6.3

Dielectric Strength (Breakdown Potential)

16 to 17 kV/mm 0.63 to 0.66 V/mil

Electrical Dissipation At 1 MHz

0.0025

Electrical Resistivity Order of Magnitude

10 to 11 10x Ω-m

Other Material Properties

Density

2.7 to 3.0 g/cm3 170 to 190 lb/ft3

Maximum Temperature: Mechanical

1680 °C 3060 °F

Maximum Thermal Shock

170 to 230 °C 340 to 450 °F

Specific Heat Capacity

950 J/kg-K 0.23 BTU/lb-°F

Thermal Conductivity

3.5 to 11 W/m-K 2.0 to 6.1 BTU/h-ft-°F

Thermal Expansion

5.8 µm/m-K

Common Calculations

Stiffness to Weight: Axial

22 to 31 points

Stiffness to Weight: Bending

58 to 62 points

Strength to Weight: Axial

15 to 17 points

Strength to Weight: Bending

22 to 24 points

Thermal Diffusivity

1.4 to 3.7 m2/s

Thermal Shock Resistance

12 to 19 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