SiAlON (silicon aluminium oxynitride) SiAlON
Si6-zAlzOzN8-z (beta-SiAlON, z from 0 to 4.2)
SiAlON is a ceramic solid solution based on silicon nitride, in which aluminium and oxygen replace part of the silicon and nitrogen.
Evidence level
2 of 5
Lab-measured
- 0Predicted only. No one has made it, or no measurement exists.
- 1Calculated. Only calculated or predicted values from sources.
- 2Lab-measured. Measured properties with their conditions stated.
- 3Space-relevant tests. Measured in conditions relevant to space, such as vacuum or atomic oxygen.
- 4Ground-qualified. Qualified for an application on the ground.
- 5Flown or field-proven. Flight or field results exist.
Recipe, share of the weight
- Si not statedSilicon
- N not statedNitrogen
- Al not statedAluminium
- O not statedOxygen
- Y2O3, MgO not statedYttria or magnesia (sintering aid)
Best for
Heat-resistant and wear-resistant machine parts and molten-metal handling parts, where toughness is not the main requirement
Weakest at
Thermal shock and fracture toughness; the glassy grain-boundary phase limits strength at high temperature in pressureless-sintered grades
Risk at a glance
- People No data. No hazard data recorded
- If it fails High. Brittle fracture under thermal shock
- Corrosion Low. SiAlON forms a silica-type protective layer in air at high oxygen pressure, but at low oxygen pressure it forms volatile SiO.
Quick facts: SiAlON
| Property | Value | Basis |
|---|---|---|
| Density | 3.1 to 3.7 g/cm³ | 2 sourced values across conditions |
| Tensile strength | 193 MPa | 1 sourced value |
| Young's modulus | 288 GPa | 1 sourced value |
| Thermal conductivity | 18 to 28 W/(m·K) | 2 sourced values across conditions |
| Specific heat | 879 J/(kg·K) | 1 sourced value |
| Maximum service temperature | 1,200 to 1,700 °C | 2 sourced values across conditions |
What is the density of SiAlON?
SiAlON has a density of 3.1 to 3.7 g/cm³. The range covers 2 sourced values across the tempers, forms and test conditions the sources report; room-temperature values are used where a source states a temperature.
What is the thermal conductivity of SiAlON?
SiAlON has a thermal conductivity of 18 to 28 W/(m·K). The range covers 2 sourced values across the tempers, forms and test conditions the sources report; room-temperature values are used where a source states a temperature.
What is the tensile strength of SiAlON?
SiAlON has a tensile strength of 193 MPa. The source and test conditions are listed in the properties table on this page.
What is the Young's modulus of SiAlON?
SiAlON has a Young's modulus of 288 GPa. The source and test conditions are listed in the properties table on this page.
What is the maximum service temperature of SiAlON?
SiAlON has a maximum service temperature of 1,200 to 1,700 °C. The range covers 2 sourced values across the tempers, forms and test conditions the sources report; room-temperature values are used where a source states a temperature.
What is SiAlON used for?
Uses recorded in the sources include Thermocouple sheath for molten metal; Automotive location pin; Semiconductor equipment parts.
Why it exists
SiAlON is a ceramic solid solution of silicon nitride in which aluminium and oxygen replace part of the silicon and nitrogen. The beta form has the same atomic arrangement as beta silicon nitride, and the sources describe it as having better properties than both silicon nitride and alumina. It is used where heat and wear resistance matter, and the sources list molten-metal handling, cutting and machine parts among its applications.
Where it's used
Molten-metal handling
The AZoM article lists Syalon grades as thermocouple sheaths for molten metal, with a stated range of up to 1200 and 1400 °C.
Automotive wear part
In the AZoM article a Syalon 101 location pin lasted a year, against 8 hours for a conventional steel pin with an alumina sleeve.
Semiconductor and industrial parts
Ferrotec lists semiconductor equipment parts, general industry machinery parts, heat-resistant parts and abrasion-resistant parts among SiAlON applications.
Recipe
Si6-zAlzOzN8-z (beta-SiAlON, z from 0 to 4.2)
SiAlON is a solid solution built on silicon nitride (Si3N4). Silicon and nitrogen are partly replaced by aluminium and oxygen, and a sintering aid such as yttria, magnesia or aluminium nitride is added to densify it.
| Ingredient | Share of the weight | What it does |
|---|---|---|
| Silicon Si | not stated | Part of the rigid Si-N framework of silicon nitride; partly replaced by aluminium. |
| Nitrogen N | not stated | Part of the framework; partly replaced by oxygen to keep the charge balanced. |
| Aluminium Al | not stated | Replaces silicon. In SiAlON the aluminium is coordinated as AlO4, not as AlO6 as in alumina. |
| Oxygen O | not stated | Replaces nitrogen, which keeps the charge balanced when aluminium replaces silicon. |
| Yttria or magnesia (sintering aid) Y2O3, MgO | not stated | Forms a liquid during sintering that cools to a refractory intergranular glass. |
Weight shares are as printed in the sources.
What it can do
Molten-metal service
The AZoM article lists thermocouple sheaths for molten metal up to 1200 and 1400 °C.
Wear in a part
A Syalon 101 location pin lasted a year in the AZoM article's automotive example.
Bending load at room temperature
945 MPa for Syalon 101 in the AZoM table.
Strength at high temperature
The NASA review gives 375 MPa as the highest sintered-material MOR at 1370 °C.
How it compares
The sources describe SiAlON as having better properties than both silicon nitride and alumina, but the NASA review says that room-temperature strength of pressureless-sintered beta'-SiAlON is lower than that of hot-pressed silicon nitride. The published density differs by table: 3.1 to 3.7 g/cc in the INSACO table, 3.25 g.cm-3 for Syalon 101. The maximum service temperature runs from 1200 to 1700 °C across the three tables.
The same measurements for each material, so you can compare them. Each row names the key condition under the value; the full conditions and methods are in the numbered notes under Technical details. Other materials are shown beside it; each was measured under its own conditions, so open its page before comparing closely. Compare every grade in the family.
| Measurement | SiAlON | AlN | h-BN | CrN | AlN-BN | Si3N4 | TiN | ZrN |
|---|---|---|---|---|---|---|---|---|
| Thermal behavior and safety | ||||||||
| Thermal conductivity, Syalon 101 | 28 W/m.K6 | 140 to 180 W/m•°K | 30 W/(m·K) | no data | 92 W/mK | 24 W/mK | 26.96 W/(m·K) | no data |
| Thermal conductivity, SiAlON (INSACO table, range) | 18 to 25 W/mK15 | 140 to 180 W/m•°K | 30 W/(m·K) | no data | 92 W/mK | 24 W/mK | 26.96 W/(m·K) | no data |
| Specific heat, SiAlON (INSACO table) | 0.21 cal/g°C16 | 740 J/Kg•°K | no data | no data | no data | 620 J/kgK | no data | no data |
| Physical and electrical | ||||||||
| Density, Syalon 101 | 3.25 g.cm-31 | 3.26 gm/cc | 2 g/cm³ | 5.9 g/cm³ | 2.88 g/cm³ | 3.18 to 3.3 g/cm³ | no data | 7090 kg m-3 |
| Hardness, Syalon 101 (type not printed) | 15 GPa5 | 1100 Kg/mm2 | no data | 22 GPa | no data | 14.5 GPa | 20 GPa | 26.3 GPa |
| Density, SiAlON (INSACO table, range) | 3.1 to 3.7 gm/cc8 | 3.26 gm/cc | 2 g/cm³ | 5.9 g/cm³ | 2.88 g/cm³ | 3.18 to 3.3 g/cm³ | no data | 7090 kg m-3 |
| Hardness, SiAlON (INSACO table, range) | 1600 to 1800 Knoop9 | 1100 Kg/mm2 | no data | 22 GPa | no data | 14.5 GPa | 20 GPa | 26.3 GPa |
| Other measurements | ||||||||
| Young's modulus, Syalon 101 | 288 GPa2 | 330 GPa | 47 GPa | 200 GPa | 176 GPa | 290 GPa | 500 GPa | no data |
| Bend strength, Syalon 101 | 945 MPa3 | 320 MPa | 94 MPa | no data | 300 MPa | 670 MPa | no data | no data |
| Fracture toughness K1c, Syalon 101 | 7.7 MPa.m 0.54 | 2.6 MPa•m1/2 | no data | no data | 2 MPa m1/2 | 6.2 MPa·m1/2 | no data | no data |
| Maximum operating temperature, Syalon 101 | 1200 °C7 | no data | 850 °C | 700 °C | 1000 °C | 1200 °C | no data | no data |
| Tensile strength, SiAlON (INSACO table) | 28 kpsi10 | no data | no data | no data | no data | no data | no data | no data |
| Flexural strength, SiAlON (INSACO table) | 110 kpsi11 | 320 MPa | 94 MPa | no data | 300 MPa | 670 MPa | no data | no data |
| Poisson's ratio, SiAlON (INSACO table) | 0.21 -12 | 0.24 - | no data | 0.2 - | 0.31 - | 0.26 - | 0.237 - | no data |
| Dielectric strength, SiAlON (INSACO table) | 212 ac V/mil13 | 17 ac-kv/mm | 88 kV/mm | no data | 65 kV/mm | no data | no data | no data |
| Dielectric constant, SiAlON (INSACO table) | 9.3 -14 | 9 - | 4.6 - | no data | 6.8 - | no data | no data | no data |
| Maximum working temperature, SiAlON (INSACO table) | 1700 °C17 | no data | 850 °C | 700 °C | 1000 °C | 1200 °C | no data | no data |
| Highest room-temperature MOR, hot-pressed beta'-SiAlON (review) | 648 MPa18 | 320 MPa | 94 MPa | no data | 300 MPa | 670 MPa | no data | no data |
| Highest room-temperature MOR, pressureless-sintered beta'-SiAlON (review) | 483 MPa19 | 320 MPa | 94 MPa | no data | 300 MPa | 670 MPa | no data | no data |
| Highest MOR at 1370 °C, sintered SiAlON (review) | 375 MPa20 | 320 MPa | 94 MPa | no data | 300 MPa | 670 MPa | no data | no data |
Why choose it, and why not
Good for
- Heat-resistant and abrasion-resistant machine parts, which Ferrotec lists among its SiAlON applications.
- Wear parts in hot or abrasive service, such as the Syalon 101 location pin in the AZoM example.
Watch out for
- Thermal shock: low thermal conductivity and poor fracture toughness make cracking on fast temperature change a risk (NASA review).
- Fracture toughness is 7.7 MPa.m 0.5 for Syalon 101 (AZoM table).
- Glassy grain-boundary phase limits high-temperature strength in pressureless-sintered grades (NASA review).
- Density, service temperature and strength differ by grade and by source; check the grade before using a value.
SiAlON is a hard, heat-resistant ceramic whose main weakness is thermal shock. Choose the grade for the service temperature and test for thermal cycling.
Technical details
For scientists and researchers. Everything above comes from the record below: every number with its method, its conditions and its source.
Notes
The method, full conditions and any caveat for the numbered rows above.
| # | Measurement | Method | Conditions | Caveat |
|---|---|---|---|---|
| 1 | Density, Syalon 101 | Typical value in a table of typical physical and mechanical properties | grade Syalon 101 (beta-SiAlON), as named in the table titletest no test conditions printed in the table | — |
| 2 | Young's modulus, Syalon 101 | Typical value in a table of typical physical and mechanical properties | grade Syalon 101 (beta-SiAlON)test no test conditions printed in the table | — |
| 3 | Bend strength, Syalon 101 | Typical value in a table of typical physical and mechanical properties | grade Syalon 101 (beta-SiAlON)test bend test; no test conditions printed in the table | — |
| 4 | Fracture toughness K1c, Syalon 101 | Typical value in a table of typical physical and mechanical properties; property name is not in the canonical list | grade Syalon 101 (beta-SiAlON)test method not printed in the table | — |
| 5 | Hardness, Syalon 101 (type not printed) | Typical value in a table of typical physical and mechanical properties | grade Syalon 101 (beta-SiAlON)test hardness scale and load not printed in the table | — |
| 6 | Thermal conductivity, Syalon 101 | Typical value in a table of typical physical and mechanical properties | grade Syalon 101 (beta-SiAlON)temperature not printed in the table | — |
| 7 | Maximum operating temperature, Syalon 101 | Typical value in a table of typical physical and mechanical properties | grade Syalon 101 (beta-SiAlON)basis maximum operating temperature as printed in the table | — |
| 8 | Density, SiAlON (INSACO table, range) | Range printed in a table of properties attributed to INSACO | product SiAlON, the table names no gradetemperature room temperature, per the table footnote | — |
| 9 | Hardness, SiAlON (INSACO table, range) | Range printed in a table of properties attributed to INSACO | product SiAlON, the table names no gradetemperature room temperature, per the table footnote | — |
| 10 | Tensile strength, SiAlON (INSACO table) | Value printed in a table of properties attributed to INSACO | product SiAlON, the table names no gradetemperature room temperature, per the table footnote | — |
| 11 | Flexural strength, SiAlON (INSACO table) | Value printed in a table of properties attributed to INSACO | product SiAlON, the table names no gradetemperature room temperature, per the table footnote | — |
| 12 | Poisson's ratio, SiAlON (INSACO table) | Value printed in a table of properties attributed to INSACO | product SiAlON, the table names no gradetemperature room temperature, per the table footnote | — |
| 13 | Dielectric strength, SiAlON (INSACO table) | Value printed in a table of properties attributed to INSACO | product SiAlON, the table names no gradetemperature room temperature, per the table footnote | — |
| 14 | Dielectric constant, SiAlON (INSACO table) | Value printed in a table of properties attributed to INSACO | product SiAlON, the table names no gradefrequency 1 MHz | — |
| 15 | Thermal conductivity, SiAlON (INSACO table, range) | Range printed in a table of properties attributed to INSACO | product SiAlON, the table names no gradetemperature room temperature, per the table footnote | — |
| 16 | Specific heat, SiAlON (INSACO table) | Value printed in a table of properties attributed to INSACO | product SiAlON, the table names no gradetemperature room temperature, per the table footnote | — |
| 17 | Maximum working temperature, SiAlON (INSACO table) | Value printed in a table of properties attributed to INSACO | product SiAlON, the table names no gradebasis printed as Maximum Working Temperature | — |
| 18 | Highest room-temperature MOR, hot-pressed beta'-SiAlON (review) | Value stated in the text of a 1979 NASA Lewis state-of-the-art review (cites ref. 17 of that review) | form hot-pressed beta'-SiAlON bodiestemperature room temperaturebasis highest value the 1979 review reports for this form; not one grade | — |
| 19 | Highest room-temperature MOR, pressureless-sintered beta'-SiAlON (review) | Value stated in the text of a 1979 NASA Lewis state-of-the-art review (cites ref. 31 of that review) | form pressureless-sintered beta'-SiAlON bodiestemperature room temperaturebasis highest value the 1979 review reports for this form; not one grade | — |
| 20 | Highest MOR at 1370 °C, sintered SiAlON (review) | Value stated in the text of a 1979 NASA Lewis state-of-the-art review (cites ref. 29 of that review) | form sintered SiAlONtemperature 1370 °C | — |
Corrosion and compatibility
What happens when it meets other materials and environments.
| Environment | Concern | What happens |
|---|---|---|
| Oxidation in air at high temperature | low | SiAlON forms a silica-type protective layer in air at high oxygen pressure, but at low oxygen pressure it forms volatile SiO.1 |
| Molten-metal handling (thermocouple sheaths and level sensors) | not rated | SiAlON parts are used in molten-metal handling; the sources give no corrosion rate for this service.2 |
| # | Environment | Details | Test conditions |
|---|---|---|---|
| 1 | Oxidation in air at high temperature | Cao and Metselaar describe passive oxidation in a related alpha-prime sialon, which forms a protective layer, and active oxidation at lower oxygen partial pressures, which forms volatile SiO. The review does not give a rate for SiAlON in service. | basis description of oxidation mechanisms in an alpha-prime sialon review, not a test of a named gradeatmosphere oxygen-containing gas |
| 2 | Molten-metal handling (thermocouple sheaths and level sensors) | The AZoM article lists Syalon grades as thermocouple sheaths for molten metal up to 1200 and 1400 °C and a level sensor up to 800 °C. It does not report corrosion or wear rates for these parts. | grade Syalon grades named in the molten-metal section (not identified by grade in the text)metal not named in the section |
Risks and side effects
Hazards to people, what happens when a cell overheats, and how the material is handled and stored.
For people
No hazard data for SiAlON itself were found. The closest compound with a PubChem GHS record, silicon nitride, is not classified.
- Silicon nitride GHS
- PubChem reports that silicon nitride (trisilicon tetranitride) does not meet GHS hazard criteria for 97.3% (250 of 257) of reports.
- Dust
- No dust or inhalation data for SiAlON were found in the sources read.
If a part cracks or overheats
These are the failure modes the sources describe. No SiAlON incident data were found.
- Thermal shock
- The NASA review attributes poor thermal shock behaviour to low thermal conductivity and poor fracture toughness.
- Glass phase
- The NASA review says the glassy grain-boundary phase controls high-temperature properties of sintered bodies.
Handling and storage
- Storage
- No storage instructions for SiAlON were found in the sources read.
- Molten metal
- The AZoM article describes molten-metal use but gives no corrosion or wear rate for it.
Test details
The original wording and numbers from the sources, for readers who want them.
Failure risks
| Failure | Trigger and consequence |
|---|---|
| Brittle fracture under thermal shockhigh severity | Rapid temperature change on a SiAlON partThe NASA review attributes poor thermal shock behaviour of beta-SiAlON to its low thermal conductivity and poor fracture toughness. No thermal shock test value is kept here, because the only product page that printed one could not be re-read for verification. |
| Loss of high-temperature strength from grain-boundary glassmoderate severity | Use near the top of the service range in grades sintered without pressureThe NASA review says the glassy grain-boundary phase has a controlling influence on high-temperature properties of sintered bodies. Syalon grades convert this glass to a refractory crystal phase to raise the service temperature. |
| Active oxidation to volatile SiOlow severity | Operation at low oxygen partial pressureCao and Metselaar describe volatile SiO formation under active oxidation, which removes material from the surface. |
Side effects on surrounding parts
| Affects | Effect |
|---|---|
| Surface recession and the furnace or chamber atmosphere | Active oxidation releases volatile SiO gas instead of forming a protective layer. |
Handling and storage
- No handling or storage instructions for SiAlON were found in the sources read; no supplier safety data sheet was retrieved.
Mitigations
- Limit fast temperature changes, since the sources tie thermal shock failure to low conductivity and poor toughness.
Supply and geography
How common the raw materials are and where they come from.
Aluminium
- Top producers (2025)
- China 60.8%, India 5.7%, Russia 5.3%, Canada 4.5%
- Critical mineral lists
- US: listed, EU: listed
- Recycling
- USGS: about 3.6 million tons of aluminum was recovered from purchased scrap in the United States in 2025.
Silicon
- Top producers (2025)
- China 87%, Brazil 3.9%, Norway 2.8%
- Critical mineral lists
- US: listed, EU: listed
- Recycling
- USGS: silicon recycling is insignificant.
- Substitutes
- USGS: gallium arsenide and germanium are the principal substitutes for silicon in semiconductor and infrared applications.
Documents
Datasheets, safety data sheets, papers and standards you can open.
Full record
The complete spore, as stored. Free to reuse under CC-BY-4.0. Images keep the licence shown with each one.
Show the full YAML
spore: profile
id: sialon
spore_version: 0.2
family: carbide-nitride-boride-ceramics
name: SiAlON (silicon aluminium oxynitride)
abbreviation: SiAlON
role: wear-resistant structural ceramic
category: ceramics
type: nitrides
summary: SiAlON is a ceramic solid solution based on silicon nitride, in which aluminium and oxygen replace part of the silicon and nitrogen. The sources give a density of 3.1 to 3.7 g/cc (INSACO table), 3.25 g.cm-3 for the Syalon 101 grade, and maximum service temperatures of 1200 to 1700 degC depending on the table. The Syalon 101 bending strength is printed as 945 MPa. The sources describe it as a wear and heat-resistant material for molten-metal handling and machine parts; its weak point is thermal shock.
best_for: Heat-resistant and wear-resistant machine parts and molten-metal handling parts, where toughness is not the main requirement
weakest_at: Thermal shock and fracture toughness; the glassy grain-boundary phase limits strength at high temperature in pressureless-sintered grades
identity:
formula: Si6-zAlzOzN8-z (beta-SiAlON, z from 0 to 4.2)
source: syalons-guide
where: beta-SiAlON Ceramics section, general formula
designations: []
tags:
environments: []
stresses:
- extreme-heat
- thermal-cycling
- mechanical-wear
applications:
- structures
- mechanisms
- electronics-and-chips
properties:
- benchmark: density
label: Density, Syalon 101
value: 3.25
unit: g.cm-3
scope: material
conditions:
grade: Syalon 101 (beta-SiAlON), as named in the table title
test: no test conditions printed in the table
method: Typical value in a table of typical physical and mechanical properties
status: ground
source: azom-syalon101
where: Table 1 (Key Properties section), Density row
- benchmark: elastic_modulus
label: Young's modulus, Syalon 101
value: 288
unit: GPa
scope: material
conditions:
grade: Syalon 101 (beta-SiAlON)
test: no test conditions printed in the table
method: Typical value in a table of typical physical and mechanical properties
status: ground
source: azom-syalon101
where: Table 1 (Key Properties section), Young's Modulus row
- benchmark: flexural_strength
label: Bend strength, Syalon 101
value: 945
unit: MPa
scope: material
conditions:
grade: Syalon 101 (beta-SiAlON)
test: bend test; no test conditions printed in the table
method: Typical value in a table of typical physical and mechanical properties
status: ground
source: azom-syalon101
where: Table 1 (Key Properties section), Bend Strength row
- benchmark: fracture_toughness
label: Fracture toughness K1c, Syalon 101
value: 7.7
unit: MPa.m 0.5
scope: material
conditions:
grade: Syalon 101 (beta-SiAlON)
test: method not printed in the table
method: Typical value in a table of typical physical and mechanical properties; property name is not in the canonical list
status: ground
source: azom-syalon101
where: Table 1 (Key Properties section), Fracture Toughness K1c row
- benchmark: hardness
label: Hardness, Syalon 101 (type not printed)
value: 15
unit: GPa
scope: material
conditions:
grade: Syalon 101 (beta-SiAlON)
test: hardness scale and load not printed in the table
method: Typical value in a table of typical physical and mechanical properties
status: ground
source: azom-syalon101
where: Table 1 (Key Properties section), Hardness row
- benchmark: thermal_conductivity
label: Thermal conductivity, Syalon 101
value: 28
unit: W/m.K
scope: material
conditions:
grade: Syalon 101 (beta-SiAlON)
temperature: not printed in the table
method: Typical value in a table of typical physical and mechanical properties
status: ground
source: azom-syalon101
where: Table 1 (Key Properties section), Thermal Conductivity row
- benchmark: max_service_temp
label: Maximum operating temperature, Syalon 101
value: 1200
unit: °C
scope: material
conditions:
grade: Syalon 101 (beta-SiAlON)
basis: maximum operating temperature as printed in the table
method: Typical value in a table of typical physical and mechanical properties
status: ground
source: azom-syalon101
where: Table 1 (Key Properties section), Maximum Operating Temperature row
- benchmark: density
label: Density, SiAlON (INSACO table, range)
value: 3.1
value_high: 3.7
bound: range
unit: gm/cc
scope: material
conditions:
product: SiAlON, the table names no grade
temperature: room temperature, per the table footnote
method: Range printed in a table of properties attributed to INSACO
status: ground
source: azom-insaco
where: Mechanical Properties table, Density row
- benchmark: hardness
label: Hardness, SiAlON (INSACO table, range)
value: 1600
value_high: 1800
bound: range
unit: Knoop
scope: material
conditions:
product: SiAlON, the table names no grade
temperature: room temperature, per the table footnote
method: Range printed in a table of properties attributed to INSACO
status: ground
source: azom-insaco
where: Mechanical Properties table, Hardness row
- benchmark: ultimate_tensile_strength
label: Tensile strength, SiAlON (INSACO table)
value: 28
unit: kpsi
scope: material
conditions:
product: SiAlON, the table names no grade
temperature: room temperature, per the table footnote
method: Value printed in a table of properties attributed to INSACO
status: ground
source: azom-insaco
where: Mechanical Properties table, Tensile Strength row
- benchmark: flexural_strength
label: Flexural strength, SiAlON (INSACO table)
value: 110
unit: kpsi
scope: material
conditions:
product: SiAlON, the table names no grade
temperature: room temperature, per the table footnote
method: Value printed in a table of properties attributed to INSACO
status: ground
source: azom-insaco
where: Mechanical Properties table, Flexural Strength row
- benchmark: poissons_ratio
label: Poisson's ratio, SiAlON (INSACO table)
value: 0.21
unit: '-'
scope: material
conditions:
product: SiAlON, the table names no grade
temperature: room temperature, per the table footnote
method: Value printed in a table of properties attributed to INSACO
status: ground
source: azom-insaco
where: Mechanical Properties table, Poisson's Ratio row
- benchmark: dielectric_strength
label: Dielectric strength, SiAlON (INSACO table)
value: 212
unit: ac V/mil
scope: material
conditions:
product: SiAlON, the table names no grade
temperature: room temperature, per the table footnote
method: Value printed in a table of properties attributed to INSACO
status: ground
source: azom-insaco
where: Electrical Properties table, Dielectric Strength row
- benchmark: dielectric_constant
label: Dielectric constant, SiAlON (INSACO table)
value: 9.3
unit: '-'
scope: material
conditions:
product: SiAlON, the table names no grade
frequency: 1 MHz
method: Value printed in a table of properties attributed to INSACO
status: ground
source: azom-insaco
where: Electrical Properties table, Dielectric Constant row
- benchmark: thermal_conductivity
label: Thermal conductivity, SiAlON (INSACO table, range)
value: 18
value_high: 25
bound: range
unit: W/mK
scope: material
conditions:
product: SiAlON, the table names no grade
temperature: room temperature, per the table footnote
method: Range printed in a table of properties attributed to INSACO
status: ground
source: azom-insaco
where: Thermal Properties table, Thermal Conductivity row
- benchmark: specific_heat
label: Specific heat, SiAlON (INSACO table)
value: 0.21
unit: cal/g°C
scope: material
conditions:
product: SiAlON, the table names no grade
temperature: room temperature, per the table footnote
method: Value printed in a table of properties attributed to INSACO
status: ground
source: azom-insaco
where: Thermal Properties table, Specific Heat row
- benchmark: max_service_temp
label: Maximum working temperature, SiAlON (INSACO table)
value: 1700
unit: °C
scope: material
conditions:
product: SiAlON, the table names no grade
basis: printed as Maximum Working Temperature
method: Value printed in a table of properties attributed to INSACO
status: ground
source: azom-insaco
where: Thermal Properties table, Maximum Working Temperature row
- benchmark: flexural_strength
label: Highest room-temperature MOR, hot-pressed beta'-SiAlON (review)
value: 648
unit: MPa
scope: material
conditions:
form: hot-pressed beta'-SiAlON bodies
temperature: room temperature
basis: highest value the 1979 review reports for this form; not one grade
method: Value stated in the text of a 1979 NASA Lewis state-of-the-art review (cites ref. 17 of that review)
status: ground
source: nasa-tm79207
where: Modulus of Rupture section, text
- benchmark: flexural_strength
label: Highest room-temperature MOR, pressureless-sintered beta'-SiAlON (review)
value: 483
unit: MPa
scope: material
conditions:
form: pressureless-sintered beta'-SiAlON bodies
temperature: room temperature
basis: highest value the 1979 review reports for this form; not one grade
method: Value stated in the text of a 1979 NASA Lewis state-of-the-art review (cites ref. 31 of that review)
status: ground
source: nasa-tm79207
where: Modulus of Rupture section, text
- benchmark: flexural_strength
label: Highest MOR at 1370 °C, sintered SiAlON (review)
value: 375
unit: MPa
scope: material
conditions:
form: sintered SiAlON
temperature: 1370 °C
method: Value stated in the text of a 1979 NASA Lewis state-of-the-art review (cites ref. 29 of that review)
status: ground
source: nasa-tm79207
where: Modulus of Rupture section, text
checked_values: 20
corrosion:
- environment: Oxidation in air at high temperature
headline: SiAlON forms a silica-type protective layer in air at high oxygen pressure, but at low oxygen pressure it forms volatile SiO.
effect: Cao and Metselaar describe passive oxidation in a related alpha-prime sialon, which forms a protective layer, and active oxidation at lower oxygen partial pressures, which forms volatile SiO. The review does not give a rate for SiAlON in service.
rating: low
conditions:
basis: description of oxidation mechanisms in an alpha-prime sialon review, not a test of a named grade
atmosphere: oxygen-containing gas
source: cao-metselaar-1991
where: Oxidation Resistance section and Figure 22 (schematic)
- environment: Molten-metal handling (thermocouple sheaths and level sensors)
headline: SiAlON parts are used in molten-metal handling; the sources give no corrosion rate for this service.
effect: The AZoM article lists Syalon grades as thermocouple sheaths for molten metal up to 1200 and 1400 °C and a level sensor up to 800 °C. It does not report corrosion or wear rates for these parts.
rating: unknown
conditions:
grade: Syalon grades named in the molten-metal section (not identified by grade in the text)
metal: not named in the section
source: azom-syalon101
where: Molten Metal Handling section
risks:
hazards:
- text: 'PubChem''s GHS section for silicon nitride (trisilicon tetranitride, CID 3084099) reads Not Classified: the compound does not meet GHS hazard criteria for 97.3% (250 of 257) of reports. This is a related compound, not SiAlON; no SiAlON hazard record was found.'
ghs: []
source: pubchem-sin3n4
where: Safety and Hazards, GHS Classification
failure_risks:
- mode: Brittle fracture under thermal shock
trigger: Rapid temperature change on a SiAlON part
consequence: The NASA review attributes poor thermal shock behaviour of beta-SiAlON to its low thermal conductivity and poor fracture toughness. No thermal shock test value is kept here, because the only product page that printed one could not be re-read for verification.
severity: high
source: nasa-tm79207
where: Thermal Shock section
- mode: Loss of high-temperature strength from grain-boundary glass
trigger: Use near the top of the service range in grades sintered without pressure
consequence: The NASA review says the glassy grain-boundary phase has a controlling influence on high-temperature properties of sintered bodies. Syalon grades convert this glass to a refractory crystal phase to raise the service temperature.
severity: moderate
source: nasa-tm79207
where: Density and Microstructure section, text
- mode: Active oxidation to volatile SiO
trigger: Operation at low oxygen partial pressure
consequence: Cao and Metselaar describe volatile SiO formation under active oxidation, which removes material from the surface.
severity: low
source: cao-metselaar-1991
where: Oxidation Resistance section
side_effects:
- text: Active oxidation releases volatile SiO gas instead of forming a protective layer.
affects: Surface recession and the furnace or chamber atmosphere
source: cao-metselaar-1991
where: Oxidation Resistance section
handling:
- text: No handling or storage instructions for SiAlON were found in the sources read; no supplier safety data sheet was retrieved.
source: pubchem-sin3n4
where: Safety and Hazards (related compound)
mitigations:
- text: Limit fast temperature changes, since the sources tie thermal shock failure to low conductivity and poor toughness.
source: nasa-tm79207
where: Thermal Shock section (implication of the finding)
uses:
- application: structures
device: Thermocouple sheath for molten metal
example: The AZoM article lists Syalon grades as thermocouple sheaths for molten metal, with a stated temperature range of up to 1200 and 1400 °C.
source: azom-syalon101
where: Molten Metal Handling section
- application: mechanisms
device: Automotive location pin
example: In the AZoM article a Syalon 101 pin lasted a year, against 8 hours for a conventional steel pin with an alumina sleeve.
source: azom-syalon101
where: Wear Components section
- application: electronics-and-chips
device: Semiconductor equipment parts
example: Ferrotec lists semiconductor equipment parts, general industry machinery parts, heat-resistant parts and abrasion-resistant parts among SiAlON applications.
source: ferrotec-sialon
where: Applications section
supply:
- subject: Aluminium
producers:
- country: China
share_percent: 60.8
year: 2025
- country: India
share_percent: 5.7
year: 2025
- country: Russia
share_percent: 5.3
year: 2025
- country: Canada
share_percent: 4.5
year: 2025
critical_lists:
- list: USGS 2025 List of Critical Minerals (aluminum)
listed: true
- list: EU critical raw materials list (aluminium and bauxite merged into one entry)
listed: true
recycling: 'USGS: about 3.6 million tons of aluminum was recovered from purchased scrap in the United States in 2025.'
substitutes: []
source: usgs-mcs2026-aluminum
where: 'World smelter production 2025e table (shares calculated by Space Mushroom against the 74,000 thousand t world total); Salient Statistics and Recycling text. Lists: USGS and European Commission pages.'
- subject: Silicon
producers:
- country: China
share_percent: 87
year: 2025
- country: Brazil
share_percent: 3.9
year: 2025
- country: Norway
share_percent: 2.8
year: 2025
critical_lists:
- list: USGS 2025 List of Critical Minerals (silicon added in the 2025 list)
listed: true
- list: EU critical raw materials list (silicon metal entry)
listed: true
recycling: 'USGS: silicon recycling is insignificant.'
substitutes:
- 'USGS: gallium arsenide and germanium are the principal substitutes for silicon in semiconductor and infrared applications.'
source: usgs-mcs2026-silicon
where: 'World Production table, silicon metal 2025 (shares calculated by Space Mushroom against the 4,600 thousand t world total, which excludes U.S. production); Recycling and Substitutes text. Lists: USGS and European Commission pages.'
media: []
documents:
- title: 'International Syalons: Advanced silicon nitride and SiAlON ceramics guide (types of SiAlON)'
type: datasheet
url: https://www.syalons.com/wp-content/uploads/2018/03/guide-to-types-of-sialon-ceramics.pdf
year: 2018
- title: 'AZoM: What are SiAlON ceramics? Syalon 101 typical properties table (article 15727)'
type: datasheet
url: https://www.azom.com/article.aspx?ArticleID=15727
year: 2018
- title: 'AZoM: SiAlON ceramic properties table attributed to INSACO (article 5065)'
type: datasheet
url: https://www.azom.com/article.aspx?ArticleID=5065
year: 2008
- title: 'Ferrotec: SiAlON ceramics product page'
type: datasheet
url: https://ceramics.ferrotec.com/materials/advanced/sialon/
year: 2026
- title: 'NASA TM-79207: State-of-the-Art of SiAlON Materials (Dutta, Lewis Research Center, 1979)'
type: report
url: https://ntrs.nasa.gov/citations/19790022207
year: 1979
- title: 'Cao and Metselaar: alpha-prime sialon ceramics, a review (Chemistry of Materials 3, 242, 1991)'
type: paper
url: https://pure.tue.nl/ws/files/1696947/620117.pdf
year: 1991
- title: 'PubChem: Trisilicon tetranitride (silicon nitride, CID 3084099), GHS classification'
type: database
url: https://pubchem.ncbi.nlm.nih.gov/compound/3084099
year: 2026
- title: 'USGS Mineral Commodity Summaries 2026: Aluminum'
type: report
url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-aluminum.pdf
year: 2026
- title: 'USGS Mineral Commodity Summaries 2026: Silicon'
type: report
url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-silicon.pdf
year: 2026
gaps:
- No space flight, vacuum, radiation or thermal-vacuum result for SiAlON was found in the sources read.
- No UNS, EN or other standard designation for SiAlON was printed in any source read; the only designation listed is the trade name Syalon 101.
- Coefficient of thermal expansion is printed in the sources with an exponent (x 10-6 per degree C) and is left out; volume resistivity (printed as greater than 10^14 ohm-cm) and the INSACO modulus (printed as 46 x 10^6 psi) are left out for the same reason.
- The Ferrotec, INSACO and AZoM 5065 tables name no grade; those rows are labelled as SiAlON without a grade. Only the AZoM Syalon 101 table names a grade.
- No SiAlON-specific safety data sheet was retrieved; the supplier pages for SiAlON sheet (American Elements, Goodfellow) blocked automated access. The hazard entry uses PubChem's record for silicon nitride, a related compound.
- The sources give a composition range (z from 0 to 4.2), not a fixed formula, so the recipe lists elements without atom counts.
- No corrosion or wear rate for molten aluminium was found; the molten-metal rows describe use, not a measured rate.
- The NASA TM-79207 text is an OCR scan with degree signs and superscripts lost; only values that could be read clearly are used. Its density and thermal expansion values are not used.
- The USGS list of critical minerals page confirms aluminum and silicon; the European Commission page lists silicon metal and merges aluminium into the bauxite entry.
- The Wikipedia SiAlON article gives history and composition only and is not cited for any value in this profile.
- Property names fracture_toughness and hardness are not in the canonical list and are used as short names.
- 'The densities disagree by source: 3.1 to 3.7 gm/cc (INSACO table) and 3.25 g.cm-3 (Syalon 101). Each is kept with its source.'
- The Ferrotec SiAlON product page (ceramics.ferrotec.com) is cited only for its applications list. Its property table was read in this run but the verification fetch was blocked by a Cloudflare page, so its nine property rows (density, bending strength, Young modulus, Vickers hardness, service temperature, thermal conductivity, dielectric constant, water absorption, thermal shock) are left out.
sources:
azom-syalon101:
title: 'AZoM article 15727: SiAlON (Syalon 101) typical physical and mechanical properties, molten-metal and wear uses'
id: AZoM article ArticleID=15727
url: https://www.azom.com/article.aspx?ArticleID=15727
year: 2018
kind: web
license: Web article, cited not reproduced
azom-insaco:
title: 'AZoM article 5065: SiAlON properties table attributed to INSACO Inc.'
id: AZoM article ArticleID=5065
url: https://www.azom.com/article.aspx?ArticleID=5065
year: 2008
kind: web
license: Web article, cited not reproduced
ferrotec-sialon:
title: 'Ferrotec: SiAlON ceramics (advanced ceramics product page)'
id: Ferrotec advanced ceramics, SiAlON
url: https://ceramics.ferrotec.com/materials/advanced/sialon/
year: 2026
kind: datasheet
license: Manufacturer page, cited not reproduced
syalons-guide:
title: 'International Syalons: Advanced silicon nitride and SiAlON ceramics, guide to types of SiAlON ceramics'
id: International Syalons (Newcastle) Limited
url: https://www.syalons.com/wp-content/uploads/2018/03/guide-to-types-of-sialon-ceramics.pdf
year: 2018
kind: datasheet
license: Manufacturer guide, cited not reproduced
nasa-tm79207:
title: 'NASA TM-79207: State-of-the-Art of SiAlON Materials (Sunil Dutta, Lewis Research Center)'
id: NTRS 19790022207, N79-30378
url: https://ntrs.nasa.gov/citations/19790022207
year: 1979
kind: report
license: public domain (NASA)
cao-metselaar-1991:
title: 'alpha''-Sialon ceramics: a review (Cao and Metselaar, Chemistry of Materials 3, 242-252)'
id: doi:10.1021/cm00014a009
url: https://pure.tue.nl/ws/files/1696947/620117.pdf
year: 1991
kind: paper
license: repository copy, cited not reproduced
wikipedia-sialon:
title: 'Wikipedia: SiAlON (history and composition only)'
id: en.wikipedia.org/wiki/Sialon
url: https://en.wikipedia.org/wiki/Sialon
year: 2026
kind: web
license: CC BY-SA 4.0
pubchem-sin3n4:
title: PubChem compound record, Trisilicon tetranitride (silicon nitride), CID 3084099
id: CID 3084099
url: https://pubchem.ncbi.nlm.nih.gov/compound/3084099
year: 2026
kind: database
license: public domain (NCBI)
usgs-mcs2026-aluminum:
title: 'Mineral Commodity Summaries 2026: Aluminum'
id: USGS MCS 2026, February 2026
url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-aluminum.pdf
year: 2026
kind: report
license: public domain (USGS)
usgs-mcs2026-silicon:
title: 'Mineral Commodity Summaries 2026: Silicon'
id: USGS MCS 2026, February 2026
url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-silicon.pdf
year: 2026
kind: report
license: public domain (USGS)
usgs-crit2025:
title: About the 2025 List of Critical Minerals (USGS, final list of 60 minerals)
id: Final 2025 List of Critical Minerals
url: https://www.usgs.gov/programs/mineral-resources-program/science/about-2025-list-critical-minerals
year: 2025
kind: web
license: public domain (USGS)
ec-crm:
title: Critical raw materials (European Commission, Regulation (EU) 2024/1252)
id: Regulation (EU) 2024/1252
url: https://single-market-economy.ec.europa.eu/sectors/raw-materials/areas-specific-interest/critical-raw-materials_en
year: 2024
kind: web
license: European Commission web page
license: CC-BY-4.0
updated: '2026-11-01'
review:
status: draft
method: assistant
checked_values: 20
unreachable: 1
caveats: 2
note: Written by an AI assistant on 2026-11-01 from pages fetched in this run. Supplier safety sheets were blocked; the hazard entry uses the PubChem record for silicon nitride. The Ferrotec property table is left out because the verification fetch was blocked.
story:
recipe:
line: SiAlON is a solid solution built on silicon nitride (Si3N4). Silicon and nitrogen are partly replaced by aluminium and oxygen, and a sintering aid such as yttria, magnesia or aluminium nitride is added to densify it.
parts:
- name: Silicon
symbol: Si
role: Part of the rigid Si-N framework of silicon nitride; partly replaced by aluminium.
- name: Nitrogen
symbol: 'N'
role: Part of the framework; partly replaced by oxygen to keep the charge balanced.
- name: Aluminium
symbol: Al
role: Replaces silicon. In SiAlON the aluminium is coordinated as AlO4, not as AlO6 as in alumina.
- name: Oxygen
symbol: O
role: Replaces nitrogen, which keeps the charge balanced when aluminium replaces silicon.
- name: Yttria or magnesia (sintering aid)
symbol: Y2O3, MgO
role: Forms a liquid during sintering that cools to a refractory intergranular glass.
risk_groups:
- title: For people
verdict: Not classified in the closest PubChem record
lead: No hazard data for SiAlON itself were found. The closest compound with a PubChem GHS record, silicon nitride, is not classified.
points:
- label: Silicon nitride GHS
line: PubChem reports that silicon nitride (trisilicon tetranitride) does not meet GHS hazard criteria for 97.3% (250 of 257) of reports.
- label: Dust
line: No dust or inhalation data for SiAlON were found in the sources read.
- title: If a part cracks or overheats
verdict: 'Brittle: thermal shock and grain-boundary glass'
lead: These are the failure modes the sources describe. No SiAlON incident data were found.
points:
- label: Thermal shock
line: The NASA review attributes poor thermal shock behaviour to low thermal conductivity and poor fracture toughness.
- label: Glass phase
line: The NASA review says the glassy grain-boundary phase controls high-temperature properties of sintered bodies.
- title: Handling and storage
verdict: No storage or handling statements found
points:
- label: Storage
line: No storage instructions for SiAlON were found in the sources read.
- label: Molten metal
line: The AZoM article describes molten-metal use but gives no corrosion or wear rate for it.
why: SiAlON is a ceramic solid solution of silicon nitride in which aluminium and oxygen replace part of the silicon and nitrogen. The beta form has the same atomic arrangement as beta silicon nitride, and the sources describe it as having better properties than both silicon nitride and alumina. It is used where heat and wear resistance matter, and the sources list molten-metal handling, cutting and machine parts among its applications.
uses:
- where: Molten-metal handling
line: The AZoM article lists Syalon grades as thermocouple sheaths for molten metal, with a stated range of up to 1200 and 1400 °C.
- where: Automotive wear part
line: In the AZoM article a Syalon 101 location pin lasted a year, against 8 hours for a conventional steel pin with an alumina sleeve.
- where: Semiconductor and industrial parts
line: Ferrotec lists semiconductor equipment parts, general industry machinery parts, heat-resistant parts and abrasion-resistant parts among SiAlON applications.
can_do:
- label: Molten-metal service
line: The AZoM article lists thermocouple sheaths for molten metal up to 1200 and 1400 °C.
- label: Wear in a part
line: A Syalon 101 location pin lasted a year in the AZoM article's automotive example.
- label: Bending load at room temperature
line: 945 MPa for Syalon 101 in the AZoM table.
- label: Strength at high temperature
line: The NASA review gives 375 MPa as the highest sintered-material MOR at 1370 °C.
compare: 'The sources describe SiAlON as having better properties than both silicon nitride and alumina, but the NASA review says that room-temperature strength of pressureless-sintered beta''-SiAlON is lower than that of hot-pressed silicon nitride. The published density differs by table: 3.1 to 3.7 g/cc in the INSACO table, 3.25 g.cm-3 for Syalon 101. The maximum service temperature runs from 1200 to 1700 °C across the three tables.'
compare_rows:
- label: Density
benchmark: density
- label: Maximum service temperature
benchmark: max_service_temp
- label: Thermal conductivity
benchmark: thermal_conductivity
handling:
- No storage or handling instructions for SiAlON were found in the sources read.
- Avoid rapid temperature changes, because the sources tie thermal shock failure to low conductivity and poor toughness.
- Silicon nitride is not classified in the PubChem record; no dust limit was found for SiAlON.
good_for:
- Heat-resistant and abrasion-resistant machine parts, which Ferrotec lists among its SiAlON applications.
- Wear parts in hot or abrasive service, such as the Syalon 101 location pin in the AZoM example.
watch_out:
- 'Thermal shock: low thermal conductivity and poor fracture toughness make cracking on fast temperature change a risk (NASA review).'
- Fracture toughness is 7.7 MPa.m 0.5 for Syalon 101 (AZoM table).
- Glassy grain-boundary phase limits high-temperature strength in pressureless-sintered grades (NASA review).
- Density, service temperature and strength differ by grade and by source; check the grade before using a value.
verdict: SiAlON is a hard, heat-resistant ceramic whose main weakness is thermal shock. Choose the grade for the service temperature and test for thermal cycling.
References
Every number above carries a reference number. Click one to see the source and where in it the value comes from.
Updated