By nature, advanced ceramics do not have reflective properties, either because their dark colours absorb light or due to their chemical instability under light energy. There are, however, some groups of alumina, magnesia or silica-based advanced ceramics that offer this property.
Optical reflection is the physical property corresponding to the ability of a material to reflect light waves emitted on its surface.
A distinction should be made between specular reflection, which sends a single light ray (mirror effect) in one direction, and diffuse reflection, which reflects light in a broad range of directions and is made up of many light rays.
Special ceramics with a high silica content offer specular reflection, and with a highly polished surface finish enable the creation of perfectly reflecting mirrors.
Alumina and magnesia polycrystalline ceramics with an intense white colour, slightly or partially densified, offer diffusing reflection as the light is reflected on the grain boundaries that are distributed in a random fashion. They are used for the manufacture of diffusing reflectors.
The ceramics that have light-reflective properties are mainly used in photonic systems (optics, optoelectronics, lasers) intended for the medical, defence and aeronautical and spatial markets.