Aluminosilicate ceramic stable to 1700 °C with low thermal expansion. A versatile workhorse for high-temperature service where thermal shock matters.
Used for: furnace tubes · thermocouple sheaths · insulators · kiln furniture · crucibles · heater components
Mullite (3Al₂O₃·2SiO₂) is formed by reaction of alumina with silica during sintering. It exists as a family of materials — dense (impervious) mullite, porous mullite (also called sillimanite at certain compositions) and porous corundum at higher alumina contents.
Mullite combines a low coefficient of thermal expansion (~5 × 10⁻⁶/K) with continuous-use temperatures up to 1700 °C. It is mechanically tough enough for furnace components and far more thermal-shock-tolerant than dense alumina, while remaining chemically stable in most oxidising atmospheres.
Dense (EM60) is specified where strength, gas-tightness or chemical containment is critical. Porous grades (EM60P, EM80P) trade some strength for excellent thermal-shock resistance and lower thermal conductivity — preferred for kiln furniture and rapidly cycled components.
Furnace tubes and thermocouple protection sheaths to 1600–1700 °C, kiln furniture (setters, posts, batts), electrical heater components, wear- and corrosion-resistant tooling and crucibles.
| Grade | Purity | Max temp | Density | Hardness | Typical use | Find products |
|---|---|---|---|---|---|---|
| EM60 | 60% Al₂O₃ min | 1600 °C | 2.9 | — | Impervious dense mullite — tubes, sheaths, structural | → Find products |
| EM60P | 60% Al₂O₃ | 1500 °C | 2.4 | — | Porous mullite (sillimanite) — kiln furniture, thermal-shock duty | → Find products |
| EM80P | 80% Al₂O₃ | 1700 °C | 2.6 | — | Porous corundum — higher temperature, heavy-cycle service | → Find products |
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Mullite costs less than dense alumina and tolerates thermal shock significantly better. Where the operating temperature is below 1700 °C and chemistry is benign, mullite is usually the right specification.
Sillimanite is an Al₂SiO₅ mineral that converts to mullite plus silica on firing. In commercial language, porous Al₂O₃–SiO₂ bodies near 60% alumina are sold under both names; chemically and mechanically they are very similar.
Dense mullite is widely used for glass-tank components and crucibles handling oxidising melts. For aggressive non-oxide melts or alkali glasses, check chemistry with us before specifying.
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