Silicon Nitride (Si3N4)
Silicon nitride is a non-oxide engineering ceramic. It can have a moderately low thermal conductivity among the non-oxide engineering ceramics in the database.
The properties of silicon nitride include four common variations. This page shows summary ranges across all of them. For more specific values, follow the links immediately below. The graph bars on the material properties cards further below compare silicon nitride to other non-oxide 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
600 to 2950 MPa 87 to 430 x 103 psi
Elastic (Young's, Tensile) Modulus
140 to 310 GPa 20 to 45 x 106 psi
Flexural Strength
130 to 810 MPa 18 to 120 x 103 psi
Fracture Toughness
3.1 to 6.2 MPa-m1/2 2.9 to 5.6 x 103 psi-in1/2
Poisson's Ratio
0.24 to 0.27
Thermal Properties
Maximum Temperature: Mechanical
1000 to 1330 °C 1830 to 2420 °F
Maximum Thermal Shock
290 to 750 °C 550 to 1380 °F
Specific Heat Capacity
720 to 800 J/kg-K 0.17 to 0.19 BTU/lb-°F
Thermal Conductivity
12 to 31 W/m-K 7.0 to 18 BTU/h-ft-°F
Thermal Expansion
2.5 to 3.2 µm/m-K
Other Material Properties
Density
2.2 to 3.4 g/cm3 140 to 210 lb/ft3
Dielectric Constant (Relative Permittivity) At 1 MHz
8.0 to 10
Dielectric Strength (Breakdown Potential)
18 kV/mm 0.7 V/mil
Electrical Resistivity Order of Magnitude
11 to 12 10x Ω-m
Common Calculations
Stiffness to Weight: Axial
34 to 53 points
Stiffness to Weight: Bending
65 to 78 points
Thermal Diffusivity
7.5 to 13 mm2/s
Followup Questions
Further Reading
Silicon Nitride and the Sialons, Vivien Mitchell, 1993
Handbook of Refractory Carbides and Nitrides: Properties, Characteristics, Processing and Applications, Hugh O. Pierson, 1996
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
Sintering of Advanced Materials: Fundamentals and Processes, Zhigang Zak Fang (editor), 2010