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 CostGood electrical insulation
Low Coefficient of Thermal ExpansionHigh Thermal Shock Resistance
Typical Applications
Structural ceramic partsAerospace
MedicalBearings
Analytical instrumentation 
Materials Property Chart
 Silicates
 PropertyASTM MethodUnitsSteatite L-4Steatite L-5CordieriteMulliteLava Grade A Fired
GeneralCrystal Size (Average)Thin SectionMicrons77--7--
Color----TanGray - GreenOrange - TanGray - TanGray - Tan
Gas Permeability--atms-cc/sec----Porous--Porous
Water AbsorptionC 20-97%001003
MechanicalDensityC 20-97g/cc2.652.752.003.002.30
HardnessVickers 500gmGPa (kg/mm2)4.9 (500)4.9 (500)5.8 (590)10 (1000)4.4 (450)
Hardness--R45N5757507842
Fracture ToughnessNotched BeamMPam1/2------3--
Flexural Strength (MOR)
(3 point) @ RT
F417-87MPa (psi x 103117 (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 ModulusC848GPa (psi x 106)103 (15)103 (15)103 (15)179 (26)--
Poisson's RatioC848--0.240.240.310.24--
ThermalC.T.E. 25 - 100° CC 372-96x 10-6/C7.38.52.13.62.9
C.T.E. 25 - 300° CC 372-96x 10-6/C7.48.62.54.13.3
C.T.E. 25 - 600° CC 372-96x 10-6/C7.58.63.04.83.6
Thermal Conductivity @ RTC 408W/m K33342
Max Use Temp--Farenheit (°F)23502350235031002000
--Celsius (°C)12901290129017001100
ElectricalDielectric Strength (.125" Thick)D 149-97AV/mil260270120250100
Dielectric Constant @ 1 MHzD 150-98--5.65.75.56.75.3
Dielectric ConstantD 2520-95--5.65.8--6.7--
@ GigahertzD 2520-95--9.212.5--11.4--
Dielectric Loss @ 1 MHzD 150-98--0.0030.0014--0.003--
Dielectric LossD 2520-95--0.0050.0017--0.003--
@ GigahertzD 2520-95--9.212.5--11.4--
Volume Resistivity, 25°CD 257ohms-cm> 1 x 1014> 1 x 1014> 1 x 1014> 1 x 1014--
Volume Resistivity, 300°CD 1829ohms-cm2 x 10101 x 1011--4 x 1010--
Volume Resistivity, 500°CD 1829ohms-cm1 x 1094 x 1010--1 x 109--
Volume Resistivity, 700°CD 1829ohms-cm2 x 1081 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.