Why can porous ceramic materials scatter optical and infrared radiation?

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optical ceramics High-pressure sodium-vapour lamp bulb.

Porous ceramic materials scatter optical and infrared radiation primarily due to the presence of air spaces within their structure. When light or infrared radiation encounters these internal pores, it undergoes scattering because of the difference in the refractive index between the solid ceramic material and the air trapped within the voids.

This interaction occurs because the boundaries between the ceramic matrix and the air pockets act as scattering centers. In materials science, when radiation travels through a medium containing multiple phases with different optical properties, the mismatch at these interfaces causes the radiation to change direction repeatedly. This phenomenon is why many porous ceramics appear opaque or translucent rather than transparent, as the incident radiation is diffused throughout the material rather than passing through it directly.1