Interacting with and Generating Light

In this chapter we examine four key properties of ceramic materials all of which we can classify as optical. (1) Ceramics can be transparent, translucent, or opaque for one particular composition. (2) The color of many ceramics can be changed by small additions additives, dopants, or point defects. (3) Ceramics can emit light in response to an electric field or illumination by light of another wavelength. (4) Ceramics can reflect and/or refract light. We will discuss why these effects are special for ceramics and how we make use of them. 

The optical properties of ceramics result in some of their most important applications. In their pure form, most dielectric single crystals and glasses are transparent to visible light. This behavior is very different from that of metals and semiconductors, which, unless they are very thin ( 1 pm), are opaque. Many ceramics and glasses also show good transparency to infrared (IR) radiation. This property has led to the use of glasses for optical fibers for high-speed communications. 

We can produce polycrystalline ceramics that are highly transparent. The ability to make translucent and transparent polycrystalline ceramics was developed in the 1960s when it was discovered that small additions of MgO to AI2O3 powder could produce a fully dense ceramic by sintering. This product is widely used in streetlights (the golden glow). 

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The interaction of sulphur trioxide with water is highly exothermic. The heat that is generated is substantial and sometimes light is produced as well. This is a cause of accidents involving this oxide. 

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