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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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