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Ceramic Transparent to Infrared
Name: Sumit
Status: student
Grade: 12+
Location: NH
Country: USA
Date: Spring 2010
Question:
What are the different types of 'glass" that are
transparent to infrared spectrum?
Replies:
Hi Sumit,
The materials used for infrared transparent windows are often
ceramic materials but are not typically glasses. The term glass
refers to an amorphous material meaning that it has no regular
crystal structure.
There are two common approaches to improve the mechanical properties
of transparent ceramic materials. One is to make a single crystal
material, meaning that the entire structure is essentially perfectly
ordered at the atomic level. These single crystals are expensive to
make and very labor intensive to produce. In other cases, it is
possible to make a polycrystalline material. Basically, a powder
consisting of small crystals of the material are compacted using
very high pressures and temperatures to form a solid. Depending on
the application, either single crystalline materials or
polycrystalline materials could be used.
To actually answer your question now, aluminum oxide (sapphire) is
commonly used in both single and polycrystalline forms. Yttrium
oxide is also used. A combination of the two materials called
yttrium aluminum garnet (YAG) is also very common. Aluminum oxynitride
(AlON), magnesium oxide, zinc sulfide, zirconium oxide, cadmium sulfide,
and spinel (MgAl2O4) are also options. Recently there has also been
some attention to developing nanocomposite combinations using silicon
carbide as a particulate reinforcement to improve mechanical properties.
Special thanks to Dr. Michael Rauscher, who provided the information in
this response.
Hope this helps,
Burr Zimmerman
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Update: June 2012
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