SCHOTT Technical Glasses
Apart from its application in optics, glass as a technical material has exerted a formative influence on the development of important technological fields such as chemistry, pharmaceutics, automotive, optics, optoelectronics and information technology. SCHOTT Technical Glasses offers pertinent information in concise form. It contains general information for the determination and evaluation of important glass properties and also informs about specific chemical and physical characteristics and possible applications of the commercial technical glasses produced by SCHOTT. With this brochure, we hope to assist scientists, engineers, and designers in making the appropriate choice and make optimum use of SCHOTT products.
Apart from its application in optics, glass as a technical material has exerted a formative influence on the development of important technological fields such as chemistry, pharmaceutics, automotive, optics, optoelectronics and information technology. SCHOTT Technical Glasses offers pertinent information in concise form. It contains general information for the determination and evaluation of important glass properties and also informs about specific chemical and physical characteristics and possible applications of the commercial technical glasses produced by SCHOTT. With this brochure, we hope to assist scientists, engineers, and designers in making the appropriate choice and make optimum use of SCHOTT products.
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51<br />
9.2 Glass and glass-ceramic sealants for<br />
technical ceramics<br />
Dielectrically superior and highly insulating ceramics such<br />
as hard porcelain, steatite, Al 2 O 3 ceramics, and forsterite<br />
exhaust almost the complete expansion range offered by<br />
technical glasses. Hard porcelain can generally be sealed<br />
with alkaline earth borosilicate glasses, which are also compatible<br />
with tungsten. Glass seals with Al 2 O 3 ceramics and<br />
steatite are possible with special glasses such as 8436, which<br />
will also seal with 28 Ni/18 Co/Fe alloy. Soft glasses with<br />
thermal expansions around 9 x 10 –6 /K are suitable for sealing<br />
to forsterite.<br />
Aluminum oxide, zirconium oxide and silicon carbide have<br />
high temperature resistance. Hence, these ceramics are commonly<br />
used in high-temperature sensor applications such as<br />
in the combustion chamber or exhaust track of automobiles.<br />
<strong>SCHOTT</strong> has developed special glasses and glass-ceramics<br />
for the joining of these technical ceramics. The sealants are<br />
stable at elevated temperatures and are chemically resistant,<br />
thereby contributing to the stability of the ceramic applications<br />
over an extended period of time.<br />
Joining of SiC ceramic with <strong>SCHOTT</strong> sealing glass<br />
Advantages<br />
• CTE-matched sealing glasses for Al 2 O 3 , ZrO 2 and SiC<br />
substrates<br />
• Sealing glasses are available for operating temperatures<br />
in the range 530 – 1040 °C and CTE in the range<br />
4.6 – 9.8 x 10 –6 /K<br />
• Seals can be achieved through conventional heating<br />
(in a furnace) as well as through laser welding<br />
• Glass sealants have excellent electrical insulation<br />
• Sealants are available in powder, paste and preform<br />
formats<br />
Sealing partner<br />
<strong>SCHOTT</strong><br />
glass number<br />
CTE* (10 –6 /K<br />
for 20 – 300 °C)<br />
T g (°C)<br />
Sealing<br />
temperature (°C)<br />
SiC 8253 4.6 785 1320 735<br />
AIN G018-200 4.6 557 665 550<br />
G018-266 6.9 585 770 530<br />
G018-346 7.3 720 1270 670<br />
Al 2 O 3<br />
G018-358<br />
658 940<br />
8.5<br />
8.8 **<br />
Maximum operating<br />
temperature (°C)<br />
600<br />
1040 **<br />
G018-385 8.4 ** 992 950 950 °C (1000)<br />
G018-339 9.2 ** 627 990 760 **<br />
ZrO 2 9.1<br />
560<br />
G018-311<br />
622 850<br />
9.9 **<br />
880 **<br />
9<br />
* CTE = coefficient of thermal expansion ** p.c. = partially crystalline<br />
Table 14. Sealing glasses for high-temperature applications
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