High Purity Alumina (99.5%, 99.8%, 99.96%)

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> High Purity (99.96%) Alumina Ceramics

Alumina (Al2 O3) is a common workhorse material in the world of technical ceramics and is utilized in an extensive variety of industries and applications. Alumina’s material properties offer electrical isolation, wear resistance, high temperature resistance, and good mechanical strength. STC’s fully dense, 99.5%, 99.8% and 99.96% alumina bodies offer improved performance over lower purity alumina ceramics in demanding operating conditions.

Our High purity aluminas make for improved corrosion resistance due to lower impurity/silica content. Higher hardness, increased dielectric strength, and in some cases, superior flexural strength. Finer grain sizes also allow for smooth surface finishes. The grade of alumina is selected to best fit the application.

Of our high purity aluminas our 99.96% material exhibits superior flexural strength and dielectric strengths making them excellent candidates for thin walled parts in high-voltage applications.

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Prime Features
High Mechanical Strength High Temperature Resistance
High Wear Resistance Excellent Corrosion Resistance
Excellent Dielectric Strength Suitable For food applications
low dielectric loss bio-inert
Typical Applications
High Strength, Thin Walled Components Mass Spec Components
End Effectors Precision Valve Seats And Seals
bio compatible parts pump pistons and sleeves
high voltage dielectric parts food compatible parts
semiconductor components  
Materials Property Chart
  High Purity Alumina
  Property ASTM Method Units AL995 99.5% AL9980 99.8% AL9996 99.96%
General Crystal Size (Average) Thin Section Microns 6 6 2
Color -- -- Ivory - White Ivory Off White/Blush
Gas Permeability -- atms-cc/sec gas tight <10-10 gas tight <10-10 gas tight <10-10
Water Absorption C 20-97 % 0 0 0
Mechanical Density C 20-97 g/cc 3.88 3.91 3.93
Hardness Vickers 500gm GPa (kg/mm2) 14.3 (1459) 15 (1530) 19.6 (2000)
Hardness -- R45N 82 86 90
Fracture Toughness Notched Beam MPam1/2 4 - 5 3 - 4 5 - 6
Flexural Strength (MOR)
(3 point) @ RT
F417-87 MPa (psi x 103 338 (49) 379 (55) 455 (66)
Tensile Strength @ RT -- MPa (psi x 103) 172 (25) 200 (29) 275 (40)
Compressive Strength @ RT -- MPa (psi x 103) 2137 (310) 2240 (325) 2413 (350)
Elastic Modulus C848 GPa (psi x 106) 379 (55) 379 (55) 393 (57)
Poisson's Ratio C848 -- 0.23 0.23 0.23
Thermal C.T.E. 25 - 100° C C 372-96 x 10-6/C 6.3 6.5 6.5
C.T.E. 25 - 300° C C 372-96 x 10-6/C 6.9 7.9 7.9
C.T.E. 25 - 600° C C 372-96 x 10-6/C 7.6 8.1 8.2
Thermal Conductivity @ RT C 408 W/m K 30 30 35
Max Use Temp -- Farenheit (°F) 3047 3047 3100
-- Celsius (°C) 1675 1675 1700
Electrical Dielectric Strength (.125" Thick) D 149-97A V/mil 270 290 422
Dielectric Constant @ 1 MHz D 150-98 -- 9.8 9.8 9.9
Dielectric Constant D 2520-95 -- 9.7 10 --
@ Gigahertz D 2520-95 -- 9.8 9.6 --
Dielectric Loss @ 1 MHz D 150-98 -- 0.0002 < .0001 < .0001
Dielectric Loss D 2520-95 -- < .0001 < .0001 --
@ Gigahertz D 2520-95 -- 9.8 9.6 --
Volume Resistivity, 25°C D 257 ohms-cm > 1 x 1014 > 1 x 1014 > 1 x 1014
Volume Resistivity, 300°C D 1829 ohms-cm 1 x 1012 3 x 1012 1 x 1013
Volume Resistivity, 500°C D 1829 ohms-cm 5 x 1010 6 x 1010 5 x 1012
Volume Resistivity, 700°C D 1829 ohms-cm 2 x 109 6 x 109 1 x 1012
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 specific test results.