Rare-earth-doped alpha'-Sialon ceramics with novel optical properties

A new phenomenon in the field of Sialon ceramics is reported which may lead to applications based on their optical or electronic properties in combination with their mechanical and thermal properties. For the first time a colored alpha'-Sialon ceramic has been synthesized, with relatively high optical transparency by careful control of the sintering atmosphere, and adding suitable rare earths as stabilizing cations. This compares with normal Sialons and silicon nitrides which are grey-black in color and are opaque. Oxidation/reduction mechanisms have been identified as an influence on the valence of the stabilizing cation, which is responsible for the unusual optical properties.