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.

Property Charts & Safety Data Sheets

Property Charts: Silicates

Master Ceramics Property Chart: Full Color
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Safety Data Sheets: Cordierite Ceramic (Refractory Grade)
Unfired Cordierite Lava (Grade “A”) Ceramic
Lava (Grade “A”) Powder
Lava (Grade “S”) Ceramic
Unfired Lava (Grade “A”)
Unfired Lava (Grade “S”)
Dense Mullite Ceramic
Dense Steatite Ceramic
Unfired Steatite

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
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 10 ¹⁰	1 x 10 ¹¹	--	4 x 10 ¹⁰	--
	Volume Resistivity, 500°C	D 1829	Ohms-cm	1 x 10 ⁹	4 x 10 ¹⁰	--	1 x 10 ⁹	--
	Volume Resistivity, 700°C	D 1829	Ohms-cm	2 x 10 ⁸	1 x 10 ⁹	--	--	--
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	4.8	3.6
	Thermal Conductivity @ RT	C 408	W/m K	3	3	3	4	2
	Max Use Temp	--	Fahrenheit (°F)	2350	2350	2350	3100	2000
	Max Use Temp	--	Celsius (°C)	1290	1290	1290	1700	1100
Mechanical	Density	C 20-97	G/Cc	2.65	2.75	2	3	2.3
	Hardness	Vickers 500gm	GPa (kg/mm ² )	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	MPam ^1/2	--	--	--	3	--
	Flexural Strength (MOR) (3 point) @ RT	F417-87	MPa (psi X 10 ³)	117 (17)	138 (20)	66 (9.5)	206 (30)	69 (10)
	Tensile Strength @ RT	--	MPa (psi X 10 ³)	103 (15)	103 (15)	19 (2.7)	138 (20)	21 (3)
	Compressive Strength @ RT	--	MPa (psi X 10 ³)	551 (80)	586 (85)	165 (24)	1034 (150)	172 (25)
	Elastic Modulus	C848	GPa (psi X 10 ⁶)	103 (15)	103 (15)	103 (15)	179 (26)	--
	Poisson's Ratio	C848	--	0.24	0.24	0.31	0.24	--
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

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.

Cordierite

Its good thermal shock properties lend this material to be used in refractory applications. Its low thermal expansion and thermal conductivity make it a good choice for fixtures and other applications.

Property Charts & Safety Data Sheets

Property Charts: Cordierite

Master Ceramics Property Chart: Full Color
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Safety Data Sheets: Cordierite Ceramic (Refractory Grade)
Unfired Cordierite

Materials Property Chart

		Silicates
	Property	ASTM Method	Units	Cordierite
Electrical	Dielectric Strength (.125" Thick)	D 149-97A	V/mil	120
	Dielectric Constant @ 1 MHz	D 150-98	--	5.5
	Volume Resistivity, 25°C	D 257	Ohms-cm	> 1 X 10¹⁴
Thermal	C.T.E. 25 - 100° C	C 372-96	X 10 ^-6 /C	2.1
	C.T.E. 25 - 300° C	C 372-96	X 10 ^-6 /C	2.5
	C.T.E. 25 - 600° C	C 372-96	X 10 ^-6 /C	3
	Thermal Conductivity @ RT	C 408	W/m K	3
	Max Use Temp	--	Fahrenheit (°F)	2350
	Max Use Temp	--	Celsius (°C)	1290
Mechanical	Density	C 20-97	G/Cc	2
	Hardness	Vickers 500gm	GPa (kg/mm ² )	5.8 (590)
	Hardness	--	R45N	50
	Flexural Strength (MOR) (3 point) @ RT	F417-87	MPa (psi X 10 ³)	66 (9.5)
	Tensile Strength @ RT	--	MPa (psi X 10 ³)	19 (2.7)
	Compressive Strength @ RT	--	MPa (psi X 10 ³)	165 (24)
	Elastic Modulus	C848	GPa (psi X 10 ⁶ )	103 (15)
	Poisson's Ratio	C848	--	0.31
General	Color	--	--	Orange-Tan
	Gas Permeability	--	atms-cc/sec	Porous
	Water Absorption	C 20-97	%	10

Lava (Grade "A")

Grade A Lava is a machinable ceramic that exhibits good electrical and heat resistance. Excellent thermal shock properties allow it to be used in applications where long term thermal cycling is a consideration. Low thermal conductivity is also a highlight of this material.

Lava is a natural, mined stone known as hydrous aluminum silicate. This machinable ceramic material has many applications in both the unfired and fully fired state. We offer unfired feedstock in block, rod, plate or bar form and also provide fired, finished components manufactured to your technical specifications.

Unfired lava is a free machining material, easily worked with normal tooling and methods. It can be milled, turned, drilled, tapped and threaded. Commonly used as a prototyping material and for fixturing used in high temperature applications.

Unfired machined parts are hardened by kiln firing and once fired they are only workable by diamond grinding. This material has a predictable expansion of about 2% which must be taken into consideration while machining if the part is to be fired. Lava is capable of maintaining very close tolerances from the unfired to fired state, often eliminating the need for additional after firing grinding.

Fully fired lava becomes very hard and has superb thermal shock and excellent electrical properties. It is well suited to applications demanding repeated thermal cycling.

Lava is a natural material with a range of color and texture. Texture ranges from smooth/glossy to rough/dull. Color varies from light tan to dark black. Texture and color can be uniform or mottled in the same part or batch of parts. This variation is to be expected as a normal characteristic of the material.

Property Charts & Safety Data Sheets

Property Charts: Lava (Grade “A”)

Master Ceramics Property Chart: Full Color
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Safety Data Sheets: Lava (Grade “A”) Ceramic
Lava (Grade “A”) Powder
Lava (Grade “S”) Ceramic
Unfired Lava (Grade “A”)
Unfired Lava (Grade “S”)

Materials Property Chart

		Lava
	Property	ASTM Method	Units	Lava Grade A Fired
General	Color	--	--	Gray-Tan
	Gas Permeability	--	atms-cc/sec	Porous
	Water Absorption	C 20-97	%	3
Mechanical	Density	C 20-97	G/Cc	2.3
	Hardness	Vickers 500gm	GPa (kg/mm ² )	4.4 (450)
	Hardness	--	R45N	42
	Flexural Strength (MOR) (3 point) @ RT	F417-87	MPa (psi X 10 ³)	69 (10)
	Tensile Strength @ RT	--	MPa (psi X 10 ³)	21 (3)
	Compressive Strength @ RT	--	MPa (psi X 10 ³)	172 (25)
Thermal	C.T.E. 25 - 100° C	C 372-96	X 10 ^-6 /C	2.9
	C.T.E. 25 - 300° C	C 372-96	X 10 ^-6 /C	3.3
	C.T.E. 25 - 600° C	C 372-96	X 10 ^-6 /C	3.6
	Thermal Conductivity @ RT	C 408	W/m K	2
	Max Use Temp	--	Fahrenheit (°F)	2000
	Max Use Temp	--	Celsius (°C)	1100
Electrical	Dielectric Strength (.125" Thick)	D 149-97A	V/mil	100
Electrical	Dielectric Constant @ 1 MHz	D 150-98	--	5.3

Mullite

Mullite is an excellent material due to its high temperature stability, strength and creep resistance. It is similar to Cordierite, although it is not as good an insulator and has a higher coefficient of thermal expansion. It is commonly used in heater exchange parts and electrical insulators.

Property Charts & Safety Data Sheets

Property Charts: Mullite

Master Ceramics Property Chart: Full Color
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Safety Data Sheets: Dense Mullite Ceramic

Materials Property Chart

		Silicates
	Property	ASTM Method	Units	Mullite
Electrical	Dielectric Strength (.125" Thick)	D 149-97A	V/mil	250
	Dielectric Constant @ 1 MHz	D 150-98	--	6.7
	Dielectric Constant	D 2520-95	--	6.7
	@ Gigahertz	D 2520-95	--	11.4
	Dielectric Loss @ 1 MHz	D 150-98	--	0.003
	Dielectric Loss	D 2520-95	--	0.003
	@ Gigahertz	D 2520-95	--	11.4
	Volume Resistivity, 25°C	D 257	Ohms-cm	> 1 x 10¹⁴
	Volume Resistivity, 300°C	D 1829	Ohms-cm	4 x 10 ¹⁰
	Volume Resistivity, 500°C	D 1829	Ohms-cm	1 x 10 ⁹
Thermal	C.T.E. 25 - 100° C	C 372-96	X 10 ^-6 /C	3.6
	C.T.E. 25 - 300° C	C 372-96	X 10 ^-6 /C	4.1
	C.T.E. 25 - 600° C	C 372-96	X 10 ^-6 /C	4.8
	Thermal Conductivity @ RT	C 408	W/m K	4
	Max Use Temp	--	Fahrenheit (°F)	3100
	Max Use Temp	--	Celsius (°C)	1700
Mechanical	Density	C 20-97	G/Cc	3
	Hardness	Vickers 500gm	GPa (kg/mm ² )	10 (1000)
	Hardness	--	R45N	78
	Fracture Toughness	Notched Beam	MPam ^1/2	3
	Flexural Strength (MOR) (3 point) @ RT	F417-87	MPa (psi X 10 ³)	206 (30)
	Tensile Strength @ RT	--	MPa (psi X 10 ³)	138 (20)
	Compressive Strength @ RT	--	MPa (psi X 10 ³)	1034 (150)
	Elastic Modulus	C848	GPa (psi X 10 ⁶ )	179 (26)
	Poisson's Ratio	C848	--	0.24
General	Crystal Size (Average)	Thin Section	Microns	7
	Color	--	--	Gray-Tan
	Water Absorption	C 20-97	%	0

Steatite

Steatite is a low cost material with high electrical resistance at high temperatures, good mechanical strength and a very low dielectric loss factor. Such properties make it ideal for high frequency, low loss, and high voltage insulation. Moreover, steatite is an excellent material for electrical engineering as it can be readily shape sintered into a wide variety of forms such as washers, bushings, resistor forms, spaces and beads.

Steatite has been used for many years in large-scale industrial systems, household electronic appliances, aerospace and automotive applications, and specialized eletro-technical instruments such as cathode-ray tubes.

Property Charts & Safety Data Sheets

Property Charts: Steatite

Master Ceramics Property Chart: Full Color
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Safety Data Sheets: Dense Steatite Ceramic
Unfired Steatite

Prime Features

Low Cost Material: High Electrical Resistance At High Temperatures

Good Mechanical Strength: Very Low Dielectric Loss Factor

Typical Applications

Excellent Material For Electrical Engineering: Large-Scale Industrial Systems

Household Electronic Appliances: Aerospace And Automotive Engineering

Specialized Eletro-Technical Instruments (E.G. Cathode-Ray Tubes)

Materials Property Chart

		Silicates
	Property	ASTM Method	Units	Steatite L-4	Steatite L-5
Electrical	Dielectric Strength (.125" Thick)	D 149-97A	V/mil	260	270
	Dielectric Constant @ 1 MHz	D 150-98	--	5.6	5.7
	Dielectric Constant	D 2520-95	--	5.6	5.8
	@ Gigahertz	D 2520-95	--	9.2	12.5
	Dielectric Loss @ 1 MHz	D 150-98	--	0.003	0.0014
	Dielectric Loss	D 2520-95	--	0.005	0.0017
	@ Gigahertz	D 2520-95	--	9.2	12.5
	Volume Resistivity, 25°C	D 257	Ohms-cm	> 1 x 10¹⁴	> 1 x 10¹⁴
	Volume Resistivity, 300°C	D 1829	Ohms-cm	2 x 10 ¹⁰	1 x 10 ¹¹
	Volume Resistivity, 500°C	D 1829	Ohms-cm	1 x 10 ⁹	4 x 10 ¹⁰
	Volume Resistivity, 700°C	D 1829	Ohms-cm	2 x 10 ⁸	1 x 10 ⁹
Thermal	C.T.E. 25 - 100° C	C 372-96	X 10 ^-6 /C	7.3	8.5
	C.T.E. 25 - 300° C	C 372-96	X 10 ^-6 /C	7.4	8.6
	C.T.E. 25 - 600° C	C 372-96	X 10 ^-6 /C	7.5	8.6
	Thermal Conductivity @ RT	C 408	W/m K	3	3
	Max Use Temp	--	Fahrenheit (°F)	2350	2350
	Max Use Temp	--	Celsius (°C)	1290	1290
Mechanical	Density	C 20-97	G/Cc	2.65	2.75
	Hardness	Vickers 500gm	GPa (kg/mm ² )	4.9 (500)	4.9 (500)
	Hardness	--	R45N	57	57
	Flexural Strength (MOR) (3 point) @ RT	F417-87	MPa (psi X 10 ³)	117 (17)	138 (20)
	Tensile Strength @ RT	--	MPa (psi X 10 ³)	103 (15)	103 (15)
	Compressive Strength @ RT	--	MPa (psi X 10 ³)	551 (80)	586 (85)
	Elastic Modulus	C848	GPa (psi X 10 ⁶ )	103 (15)	103 (15)
	Poisson's Ratio	C848	--	0.24	0.24
General	Crystal Size (Average)	Thin Section	Microns	7	7
	Color	--	--	Tan	Gray-Green
	Water Absorption	C 20-97	%	0	0

Certifications

Click below to view our Quality Certifications, Registrations and Compliance

AS9100 & ISO 9001

STC RoHS Compliance Statement

Superior Technical Ceramics (STC) makes no stand-alone electronic or electrical products but is proud to be a subcontractor of ceramics used in electronic and electrical products. STC has been asked by numerous customers to confirm that our ceramics are RoHS Compliant.

After a complete bi-annual review of the materials used in our parts and the manufacturing process, we can advise you, our customers, that STC is RoHS & RoHS 3 compliant.

January 24, 2024

RoHS stands for Restriction of Hazardous Substances and impacts the entire electronics industry and many electrical products as well. The original RoHS, also known as Directive 2002/95/EC, originated in the European Union in 2002 and restricts the use of six hazardous materials found in electrical and electronic products. All applicable products in the EU market from July 1, 2006, must pass RoHS compliance.

Directive 2011/65/EU was published in 2011 by the EU, which is known as RoHS-Recast or RoHS 2. RoHS 2 includes a CE-marking directive, with RoHS compliance now being required for CE marking of products. RoHS 2 also added Categories 8 and 9 and has additional compliance recordkeeping requirements.

Directive 2015/863 is known as RoHS 3. RoHS 3 adds four additional restricted substances (phthalates) to the list of six.

EU RoHS specifies maximum levels for the following 10 restricted substances. The first six applied to the original RoHS while the last four were added under RoHS 3, which took effect July 22, 2019.

Cadmium (Cd): < 100 ppm
Lead (Pb): < 1000 ppm
Mercury (Hg): < 1000 ppm
Hexavalent Chromium: (Cr VI) < 1000 ppm
Polybrominated Biphenyls (PBB): < 1000 ppm
Polybrominated Diphenyl Ethers (PBDE): < 1000 ppm
Bis(2-Ethylhexyl) phthalate (DEHP): < 1000 ppm
Benzyl butyl phthalate (BBP): < 1000 ppm
Dibutyl phthalate (DBP): < 1000 ppm
Diisobutyl phthalate (DIBP): < 1000 ppm

RoHS 3 (EU Directive 2015/863) adds Category 11 (catch-all) products and adds four new restricted substances – all phthalates. The four phthalates are mainly used as insulation plasticizers and are on the REACH list of SVHC (Substances of Very High Concern). The expanded list for RoHS 3 is thus as follows:

Cadmium (0.01 %)
Lead (0.1 %)
Mercury (0.1 %)
Hexavalent chromium (0.1 %)
Polybrominated biphenyls (PBB) (0.1 %)
Polybrominated diphenyl ethers (PBDE) (0.1 %)
Bis(2-ethylhexyl) phthalate (DEHP) (0.1 %)
Butyl benzyl phthalate (BBP) (0.1 %)
Dibutyl phthalate (DBP) (0.1 %)
Diisobutyl phthalate (DIBP) (0.1 %)

Download a PDF of our registration letter here.

Silicates

Property Charts & Safety Data Sheets

Prime Features

Typical Applications

Materials Property Chart

Cordierite

Property Charts & Safety Data Sheets

Materials Property Chart

Lava (Grade "A")

Property Charts & Safety Data Sheets

Materials Property Chart

Mullite

Property Charts & Safety Data Sheets

Materials Property Chart

Steatite

Property Charts & Safety Data Sheets

Prime Features

Typical Applications

Materials Property Chart

Certifications

ITAR Registered

View our ITAR Registration Letter

ITAR Registered

View our ITAR Registration Letter