Standard Alumina (74%, 95%, 96%, 98%)

Aluminum Oxide, or alumina, is the most common technical ceramic material used today. The versatility of alumina stems from its broadly impressive material properties, ease of manufacture, wide availability, and budget-friendly cost. STC produces a range of alumina purity from 74% alumina to 99.96% alumina - these bodies are the industry work-horse materials for applications that require electrical isolation, wear resistance, high temperature resistance, and good mechanical strength.

Alumina sees application from aerospace to medical, from bearings to analytical instrumentation, from electrical standoffs to semiconductor processing. In addition, these materials lend themselves well to be hermetically sealed to metals through metallizing and brazing methods.

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Prime Features
Performs well in corrosive environments  
Typical Applications
Structural ceramic parts Aerospace
Medical Bearings
Analytical instrumentation  
Materials Property Chart
  Aluminas
  Property ASTM Method Units AL74 74% AL95 95% AL96 96% AL98 98%
Electrical Dielectric Strength (.125" Thick) D 149-97A V/mil 225 250 250 260
Dielectric Constant @ 1 MHz D 150-98 -- 7.0 9.0 9.1 9.5
Dielectric Constant D 2520-95 -- -- 9.2 9.1 9.4
@ Gigahertz D 2520-95 -- -- 11.0 10.9 9.8
Dielectric Loss @ 1 MHz D 150-98 -- 0.0012 0.0006 0.0004 0.0006
Dielectric Loss D 2520-95 -- -- 0.0009 0.0007 0.0005
@ Gigahertz D 2520-95 -- -- 12.5 10.9 9.8
Volume Resistivity, 25°C D 257 ohms-cm < 1 x 1013 > 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
Volume Resistivity, 500°C D 1829 ohms-cm 3 x 107 3 x 109 7 x 109 2 x 109
Volume Resistivity, 700°C D 1829 ohms-cm 2 x 106 3 x 108 4 x 108 2 x 108
Thermal C.T.E. 25 - 100° C C 372-96 x 10-6/C 5.5 6.1 6.0 6.2
C.T.E. 25 - 300° C C 372-96 x 10-6/C 5.8 7.0 6.8 6.8
C.T.E. 25 - 600° C C 372-96 x 10-6/C 6.3 7.7 7.5 7.6
Thermal Conductivity @ RT C 408 W/m K 4 19 23 29
Max Use Temp -- Farenheit (°F) 2800 3000 3100 3100
-- Celsius (°C) 1540 1650 1700 1700
Mechanical Density C 20-97 g/cc 3.03 3.65 3.71 3.78
Hardness Vickers 500gm GPa (kg/mm2) 10.5 (1075) 11.5 (1175) 12.7 (1300) 12.7 (1300)
Hardness -- R45N 78 79 81 81
Fracture Toughness Notched Beam MPam1/2 2 - 5 3 - 4 4 - 5 4 - 5
Flexural Strength (MOR)
(3 point) @ RT
F417-87 MPa (psi x 103 241 (35) 310 (45) 358 (52) 393 (57)
Tensile Strength @ RT -- MPa (psi x 103) 117 (17) 151 (22) 200 (29) 221 (32)
Compressive Strength @ RT -- MPa (psi x 103) 1378 (200) 1827 (265) 2068 (300) 2241 (325)
Elastic Modulus C848 GPa (psi x 106) 172 (25) 303 (44) 310 (45) 345 (50)
Poisson's Ratio C848 -- 0.22 0.22 0.22 0.23
General Crystal Size (Average) Thin Section Microns 13 11 8 7
Color -- -- White Ivory White Or Purple White
Gas Permeability -- atms-cc/sec 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
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.