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Silicon Nitride

We've just introduced a new Direct Pressure Sintered Silicon Nitride (Si3N4) powder-to-part component manufacturing process that provides a high-performance, cost-effective material solution. The material should be of interest to manufacturers looking for a material with a high strength-to-weight ratio, which compares favorably even with metallic nickel-based “superalloys”. The material also exhibits an unusually low coefficient of thermal expansion, which is a useful property for designers working with high temperature applications.

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PropertyASTM MethodUnitsSilicon Nitride
Crystal Size (Average)Thin SectionMicrons4
Gas Permeability-atms-cc/secgas tight < 10-10
Water AbsorptionC 20-97%0

PropertyASTM MethodUnitsSilicon Nitride
DensityC 20-97g/cc3.25
HardnessVickers 500 gmGPa (kg/mm2)15 (1529)
Fracture ToughnessNotched BeamMPam1/26
Flexural Strength (MOR) (3 point) @ RTºF417-87MPa (psi x 103)900 (130)
Tensile Strength @ RTº-MPa (psi x 103)537 (78)
Compressive Strength @ RTº-MPa (psi x 103)2500 (362)
Elastic ModulusC848GPa (psi x 106)300 (44)
Poisson's RatioC848-0.28

PropertyASTM MethodUnitsSilicon Nitride
C.T.E., 25 - 600°CC 372-96x10-6/°C2.9
Thermal Conductivity @ RTºC 408W/m-K29
Max Use Temperature (Non-Loading)
(at high strength)
-Fahrenheit (°F)2552
Max Use Temperature (Non-Loading) 
(at high strength)
-Celsius (°C)1400

PropertyASTM MethodUnitsSilicon Nitride
Dielectric Strength
(.125" Thick)
D 149-97AV/mil330
Dielectric Constant
@ 1MHz
D 150-98-9.2
Volume Resistivity,
D 257ohms-cm> 1 x 1014

Note: The information in this data sheet is for design guidance only. STC does not warrant this data as absolute values. Forming methods and specific geometry could affect properties. Slight adjustments can be made to some of the properties to accommodate specific customer requirements. Most of the dense materials in the table are resistant to mechanical erosion and chemical attack. STC has performed ASTM testing qualification for certain compositions, in accordance with ASTM D2442. Please consult our technical staff for appropriate material and specifc test results.

Note: In addition to the above compositions, STC offers a wide range of alternative materials. Please contact one of our applications engineers for material requirements that may not be shown above.

Download the chart as shown above.