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> High Purity (99.96%) Alumina Ceramics

The most common material used for structural ceramic parts is alumina. The versatility of alumina stems from its broadly impressive material properties, ease of manufacture, wide availability, and budget-friendly cost. STC’s fully dense, 74% alumina to 99.96% alumina bodies are work-horse materials for applications that require electrical isolation, wear resistance, high temperature resistance, and good mechanical strength. The grade of alumina is selected to best fit the application.

It is used in applications from aerospace to medical, from bearings to analytical instrumentation. In addition, these materials lend themselves well to be hermetically sealed to metals through metallizing and brazing methods.

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Prime Features
Good Mechanical Strength High Temperature Resistance
High Wear Resistance Good Chemical Resistance
Good Dielectric Strength Suitable for Ceramic-to-Metal Assemblies
High Hardness  
Typical Applications
Igniters Spray Nozzles
Structural Ceramics Parts Ceramic Bearings
Wear Guides Electrical Insulators
Bushings Feed Thru Insulators
Pump Compnents  
Materials Property Chart
  Alumina (Standard) Alumina (High Purity)
  Property ASTM Method Units AL74 74% AL95 95% AL96 96% AL98 98% AL995 99.5% AL9980 99.8% AL9996 99.96%
Electrical Dielectric Strength (.125" Thick) D 149-97A V/mil 225 250 250 260 270 290 422
Dielectric Constant @ 1 MHz D 150-98 -- 7.0 9.0 9.1 9.5 9.8 9.8 9.9
Dielectric Constant D 2520-95 -- -- 9.2 9.1 9.4 9.7 10 --
@ Gigahertz D 2520-95 -- -- 11.0 10.9 9.8 9.8 9.6 --
Dielectric Loss @ 1 MHz D 150-98 -- 0.0012 0.0006 0.0004 0.0006 0.0002 < .0001 < .0001
Dielectric Loss D 2520-95 -- -- 0.0009 0.0007 0.0005 < .0001 < .0001 --
@ Gigahertz D 2520-95 -- -- 12.5 10.9 9.8 9.8 9.6 --
Volume Resistivity, 25°C D 257 ohms-cm < 1 x 1013 > 1 x 1014 > 1 x 1014 > 1 x 1014 > 1 x 1014 > 1 x 1014 > 1 x 1014
Volume Resistivity, 300°C D 1829 ohms-cm 4 x 1010 5 x 1012 3 x 1012 8 x 1011 1 x 1012 3 x 1012 1 x 1013
Volume Resistivity, 500°C D 1829 ohms-cm 3 x 107 3 x 109 7 x 109 2 x 109 5 x 1010 6 x 1010 5 x 1012
Volume Resistivity, 700°C D 1829 ohms-cm 2 x 106 3 x 108 4 x 108 2 x 108 2 x 109 6 x 109 1 x 1012
Thermal C.T.E. 25 - 100° C C 372-96 x 10-6/C 5.5 6.1 6.0 6.2 6.3 6.5 6.5
C.T.E. 25 - 300° C C 372-96 x 10-6/C 5.8 7.0 6.8 6.8 6.9 7.9 7.9
C.T.E. 25 - 600° C C 372-96 x 10-6/C 6.3 7.7 7.5 7.6 7.6 8.1 8.2
Thermal Conductivity @ RT C 408 W/m K 4 19 23 29 30 30 35
Max Use Temp -- Farenheit (°F) 2800 3000 3100 3100 3047 3047 3100
-- Celsius (°C) 1540 1650 1700 1700 1675 1675 1700
Mechanical
Density C 20-97 g/cc 3.03 3.65 3.71 3.78 3.88 3.91 3.93
Hardness Vickers 500gm GPa (kg/mm2) 10.5 (1075) 11.5 (1175) 12.7 (1300) 12.7 (1300) 14.3 (1459) 15 (1530) 19.6 (2000)
Hardness -- R45N 78 79 81 81 82 86 90
Fracture Toughness Notched Beam MPam1/2 2 - 5 3 - 4 4 - 5 4 - 5 4 - 5 3 - 4 5 - 6
Flexural Strength (MOR)
(3 point) @ RT
F417-87 MPa (psi x 103 241 (35) 310 (45) 358 (52) 393 (57) 338 (49) 379 (55) 455 (66)
Tensile Strength @ RT -- MPa (psi x 103) 117 (17) 151 (22) 200 (29) 221 (32) 172 (25) 200 (29) 275 (40)
Compressive Strength @ RT -- MPa (psi x 103) 1378 (200) 1827 (265) 2068 (300) 2241 (325) 2137 (310) 2240 (325) 2413 (350)
Elastic Modulus C848 GPa (psi x 106) 172 (25) 303 (44) 310 (45) 345 (50) 379 (55) 379 (55) 393 (57)
Poisson's Ratio C848 -- 0.22 0.22 0.22 0.23 0.23 0.23 0.23
General Crystal Size (Average) Thin Section Microns 13 11 8 7 6 6 2
Color -- -- White Ivory White Or Purple White Ivory - White Ivory Off White/Blush
Gas Permeability -- atms-cc/sec gas tight <10-10 gas tight <10-10 gas tight <10-10 gas tight <10-10 gas tight <10-10 gas tight <10-10 gas tight <10-10
Water Absorption C 20-97 % 0 0 0 0 0 0 0
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.