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 mm2/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