Alumina (Aluminum Oxide)

Alumina, also known as Aluminum Oxide, is a hard wearing advanced technical ceramic material frequently used in a wide variety of industrial applications. Once fired and sintered, it can only be machined using diamond-grinding methods. It features high hardness and wear resistance, low erosion levels, high temperature resistance, corrosion resistance, and bioinertness. Additionally, it can be highly polished making it useful for precision sealing applications like pumps and pistons.

Alumina is an excellent high temperature ceramic material due to its high temperature stability. It is the most commonly used type of advanced ceramic and is available in purities ranging from 95 – 99.9%. Precision Ceramics has access to many different types of Alumina including: injection molded, die pressed, isosostatically pressed, slip cast, and extruded. 

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Alumina Properties

Alumina features high hardness and wear resistance, low erosion levels, high temperature and corrosion resistance and bio-inertness. Its high temperature stability and thermal conductivity make it particularly suitable for high temperature applications such as thermocouple protection in high temperature measurement.

  • Excellent electrical insulation properties
  • High compressive and dielectric strength
  • High hardness and mechanical strength
  • High thermal conductivity and thermal shock resistance
  • Low density
  • Resistant to strong acid and alkali attack at high temperatures
  • Transparent to microwave radio frequencies
  • Very specific thermal conductive and thermal expansion rates
  • Wear and abrasion resistant

Alumina is available is multiple grades including 95%-99.9%  high purity Alumina, high purity re-crystalized Alumina, and Zirconia toughened Alumina (ZTA). The following are the properties for 99.7% grade alumina.

Mechanical Properties

Unit
Density
g/cm3
Compressive Strength
MPa
Tensile Strength
MPa
Flexural Strength @ 20°C
MPa
Flexural Strength @ 800°C
MPa
Fracture Toughness KIc
MPa m^1/2
Young‘s Modulus E
GPa
Poisson Ratio
-
Hardness Knoop (1000g)
GPa
Value
Density
3.9
Compressive Strength
2500
Tensile Strength
260
Flexural Strength @ 20°C
350
Flexural Strength @ 800°C
250
Fracture Toughness KIc
4.5
Young‘s Modulus E
350
Poisson Ratio
0.22
Hardness Knoop (1000g)
14

Thermal Properties

Unit
Maximum Temperature
°C
Thermal Conductivity @ 20°C
W/mK
Thermal Expansion a at 20–100°C
10-6/K
Specific Heat
100°C
Thermal Shock Parameter R1
K
Value
Maximum Temperature
1700
Thermal Conductivity @ 20°C
28
Thermal Expansion a at 20–100°C
8.4
Specific Heat
880
Thermal Shock Parameter R1
200

Electrical Properties

Unit
Dielectric Constant
1 MHz
Dielectric Strength (6.35mm)
ac-kV/mm
Dielectric Loss (tan delta 25° C)
1 MHz
Volume Resistivity @ 25°C
Ωcm
Volume Resistivity @ 500°C
Ωcm
Volume Resistivity @ 1000°C
Ωcm
Value
Dielectric Constant
9.7
Dielectric Strength (6.35mm)
8.7
Dielectric Loss (tan delta 25° C)
0.0001
Volume Resistivity @ 25°C
10^14
Volume Resistivity @ 500°C
2x10^10
Volume Resistivity @ 1000°C
2x10^6

Related Materials

Ceramic Material - CeramAlum (Aluminum Nitride)

Aluminum Nitride

Aluminum Nitride (AlN) is an excellent material to use if high thermal conductivity and electrical insulation properties are required -- an ideal material for use in thermal management and electrical applications.

Ceramic Material - Shapal Hi-M Soft (Machinable Aluminum Nitride)

Shapal Hi-M Soft

Shapal Hi-M Soft is a hybrid type of machinable Aluminum Nitride (AlN) ceramic that offers high mechanical strength and thermal conductivity.

Alumina Manufacturing

Alumina can be produced in a wide range of purities with additives designed to enhance its properties. Typical purities range from 90 to 99.9% although Precision Ceramics generally work with 99.7% material.

It can be injection molded, die pressed, isostatically pressed, slip cast and extruded. Once fired and sintered, it can only be machined using diamondgrinding methods but prior to sintering advanced green and biscuit machining techniques developed by Precision Ceramics allow more complex components to be manufactured using traditional machining methods. In addition Alumina can be readily joined to metals or other ceramics using metallising and brazing techniques.

Alumina can be machined in green, biscuit, or fully dense states. While in the green or biscuit form it can be machined relatively easily into complex geometries. However, the sintering process that is required to fully densify the material causes the alumiuna body to shrink approximately 20%. This shrinkage means that it is impossible to hold very tight tolerances when machining alumina pre-sintering. In order to achieve very tight tolerances, fully sintered material must be machined/ground with diamond tools. In this process a very precise diamond coated tool/wheel is used to abrade away the material until the desired form is created. Due to the inherit toughness and hardness of the material, this can be a time consuming and costly process.

Precision Ceramics specialises in tight tolerance, highly complex work and has extensive in-house machining facilities – including 4th & 5th axis machining centres, drilling, grinding, milling, polishing, sawing, tapping, threading and turning – to enable us to manufacture Alumina components to the highest specifications.

Precision Ceramics is your Alumina machining specialist for your technical ceramic prototyping & manufacturing needs; we are always happy to use our many years of advanced ceramics experience to provide advice on materials, design, and application. If you would like to buy Alumina plates, rods, tubes or custom machined components, please contact us and one of our experts will be happy to assist you.

Frequently Asked Questions

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    What is Aluminum Nitride?

    Aluminum Nitride (AlN) is an excellent material to use if high thermal conductivity and electrical insulation properties are required; making it an ideal material for use in thermal management and electrical applications. Additionally, Aluminum Nitride is common alternative to Beryllium Oxide (BeO) in the semiconductor industry as it is not a health hazard when machined. Aluminum Nitride has a coefficient of thermal expansion and electrical insulation properties that closely matches that of Silicon wafer material, making it an useful material for electronics applications where high temperatures and heat dissipation is often a problem.

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    What is Aluminum Nitride used for?

    Aluminum Nitride (AlN) is an excellent material to use if high thermal conductivity and electrical insulation properties are required. Because of it’s qualities, it is an ideal material for use in thermal management and electrical applications. Some common applications of Aluminum Nitride include the following:

    • Heat sinks & heat spreaders
    • Electrical insulators for lasers
    • Chucks, clamp rings for semiconductor processing equipment
    • Electrical insulators
    • Silicon wafer handling and processing
    • Substrates & insulators for microelectronic devices & opto electronic devices
    • Substrates for electronic packages
    • Chip carriers for sensors and detectors
    • Chiplets
    • Collets
    • Laser heat management components
    • Molten metal fixtures
    • Packages for microwave devices
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    Is Aluminum Nitride a ceramic?

    Aluminum nitride (AlN) is a technical ceramic material that features an extremely interesting combination of very high thermal conductivity and excellent electrical insulation properties.

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    Is Aluminum Nitride toxic?

    Exposure to AlN through mouth, inhalation, or injection may cause bone and lung toxicity. Repeated exposure can irritate the eyes and skin.

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    What's the difference between Shapal vs Aluminum Nitride?

    Pure Aluminum Nitride is often the material of choice for high thermal conductivity applications, however, because it is such a hard material it is often costly to produce in small quantities or non-standard sizes. Shapal Hi-M soft is a machinable Aluminum Nitride/Boron Nitride composite material that can be machined into incredibly tight tolerances and complicated shapes while still providing excellent thermal conductivity.