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Alumina 94%
*Click on a Property to see a comparison of up to 10 materials
Property* Value
General
Chemical FormulaAl2O3
Mechanical
Density3.7 gm/cc
Hardness2000 Knoop
Tensile Strength28 kpsi
Modulus of Elasticity41 - 46 x 106 psi
Flexural Strength51 kpsi
Compressive Strength300 - 350 kpsi
Poisson's Ratio0.21
Fracture Toughness4 - 5 MPa m½
Electrical
Dielectric Strength212 - 220 ac V/mil
Dielectric Constant9.3 (@ 1 MHz)
Volume Resistivity> 1014 ohm-cm2
Thermal
Coefficient of Thermal Expansion5.2 - 7.9 x 10-6/°C
Thermal Conductivity18.0 - 28.0 W/mK
Specific Heat0.21 cal/g °C
Maximum Working Temperature1700 °C
Shock Resistance300 °C Diff.
All properties are at room temperature unless otherwise noted.

Engineering data are representative, and are not intended as absolute nor warrantable. Manufacturer’s Data shown is blended from multiple sources and therefore illustrates the marketplace.

Alumina (Al2O3) is one of the most widely specified, general-purpose technical ceramics. All aluminas are very hard and wear resistant, with high-compressive strength even against extreme temperatures and corrosive environments. Aluminas are also excellent electrical insulators and are gas tight.

Alumina is produced by firing a tightly packed powder form of Al2O3 which includes some binder material. Commercially available grades range from 90% up to 99.95% with the higher purity generating somewhat higher hardness. It is possible to machine alumina using diamond grinding techniques. Polishing is also possible, with the degree attainable affected by alumina grain size and production technique, whether pressed or extruded.

90%-97%: Best suited for metalizing (metal deposition which allows brazing) because of large grain structure.

98%-99.95%: Common range for isostatically pressed grades, with extruded shapes also available at low cost.

As-fired tolerances are generally only possible within a few percent of dimension. Extremely tight tolerances are attainable, but only by precision machining the fired part using diamond grinding techniques. This adds considerable cost, but tolerances to millionths of an inch are possible, and are often cost-effective due to the extraordinary stability and durability of the finished piece.

Additional options include blends of zirconia with alumina and silicon nitride with alumina. The result is a performance combination that is tougher than alumina alone, but with improved hardness, strength and thermal properties compared to these other materials, especially at elevated temperature.

SEE ALSO: Zirconia Toughened Alumina (ZrO2-Al2O3), or Sialon (Si3N4-Al2O3)


Wikipedia Reference for Alumina 94%

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