Silicates

Silicate Ceramics were the first technical ceramics developed to support early electrical technologies, including Magnesium Silicates (Steatite and Cordierite) and Mullite. At STC we import Grade A Lava (Hydrous Aluminum Silicate), a naturally occurring silicate material that is shares many of the performance advantages of the engineered silicates.

In general, Silicates are valuable for their good dielectric properties, resistance to thermal shock and high temperature performance. In recent years, these materials are seeing new applications based on their low RF loss factors and low thermal expansion.

These materials are a low cost alternative based on their simple natural ingredients and relatively simple processing steps.

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Prime Features
Lower Cost Good electrical insulation
Low Coefficient of Thermal Expansion High Thermal Shock Resistance
Typical Applications
Structural ceramic parts Aerospace
Medical Bearings
Analytical instrumentation  
Materials Property Chart
  Silicates
  Property ASTM Method Units Steatite L-4 Steatite L-5 Cordierite Mullite Lava Grade A Fired
General Crystal Size (Average) Thin Section Microns 7 7 -- 7 --
Color -- -- Tan Gray - Green Orange - Tan Gray - Tan Gray - Tan
Gas Permeability -- atms-cc/sec -- -- Porous -- Porous
Water Absorption C 20-97 % 0 0 10 0 3
Mechanical Density C 20-97 g/cc 2.65 2.75 2.00 3.00 2.30
Hardness Vickers 500gm GPa (kg/mm2) 4.9 (500) 4.9 (500) 5.8 (590) 10 (1000) 4.4 (450)
Hardness -- R45N 57 57 50 78 42
Fracture Toughness Notched Beam MPam1/2 -- -- -- 3 --
Flexural Strength (MOR)
(3 point) @ RT
F417-87 MPa (psi x 103 117 (17) 138 (20) 66 (9.5) 206 (30) 69 (10)
Tensile Strength @ RT -- MPa (psi x 103) 103 (15) 103 (15) 19 (2.7) 138 (20) 21 (3)
Compressive Strength @ RT -- MPa (psi x 103) 551 (80) 586 (85) 165 (24) 1034 (150) 172 (25)
Elastic Modulus C848 GPa (psi x 106) 103 (15) 103 (15) 103 (15) 179 (26) --
Poisson's Ratio C848 -- 0.24 0.24 0.31 0.24 --
Thermal C.T.E. 25 - 100° C C 372-96 x 10-6/C 7.3 8.5 2.1 3.6 2.9
C.T.E. 25 - 300° C C 372-96 x 10-6/C 7.4 8.6 2.5 4.1 3.3
C.T.E. 25 - 600° C C 372-96 x 10-6/C 7.5 8.6 3.0 4.8 3.6
Thermal Conductivity @ RT C 408 W/m K 3 3 3 4 2
Max Use Temp -- Farenheit (°F) 2350 2350 2350 3100 2000
-- Celsius (°C) 1290 1290 1290 1700 1100
Electrical Dielectric Strength (.125" Thick) D 149-97A V/mil 260 270 120 250 100
Dielectric Constant @ 1 MHz D 150-98 -- 5.6 5.7 5.5 6.7 5.3
Dielectric Constant D 2520-95 -- 5.6 5.8 -- 6.7 --
@ Gigahertz D 2520-95 -- 9.2 12.5 -- 11.4 --
Dielectric Loss @ 1 MHz D 150-98 -- 0.003 0.0014 -- 0.003 --
Dielectric Loss D 2520-95 -- 0.005 0.0017 -- 0.003 --
@ Gigahertz D 2520-95 -- 9.2 12.5 -- 11.4 --
Volume Resistivity, 25°C D 257 ohms-cm > 1 x 1014 > 1 x 1014 > 1 x 1014 > 1 x 1014 --
Volume Resistivity, 300°C D 1829 ohms-cm 2 x 1010 1 x 1011 -- 4 x 1010 --
Volume Resistivity, 500°C D 1829 ohms-cm 1 x 109 4 x 1010 -- 1 x 109 --
Volume Resistivity, 700°C D 1829 ohms-cm 2 x 108 1 x 109 -- -- --
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.