Transparent Ceramics: general characteristics and manufacturing processes

Transparent polycrystalline ceramics are materials produced by shaping powders and sintering crucibles. By their very nature and the manufacturing processes used, transparent ceramics combine the properties of single-crystals (compactness, purity, homogeneity) with the characteristics of ceramics (ease of shaping, large-sized parts, flexibility of composition). They also offer enhanced thermomechanical performance (toughness, thermal shock resistance).

Since the first development work on transparent ceramics in the 1950s, a great deal of research has been carried out to gain better control over their manufacture. Drastic control of the manufacturing process is essential to master the microstructures of the ceramics produced and, consequently, their optical performance. The main challenge in this case lies in the complete elimination of porosity and the control of impurities that can alter their optical properties. These two objectives can be achieved through the synthesis of pure, homogeneous nanopowders, the use of liquid shaping processes, and the development of controlled-atmosphere sintering techniques (vacuum, pressure, etc.).

The aim of this article is to clarify the relationship between the structural, microstructural and optical characteristics of transparent ceramics, so as to ultimately guide the choice of suitable ceramic processes for their manufacture. The key stages of the process are described in detail, with examples of actual applications.

At the end of the article, readers will find a glossary and a list of the symbols used.