Transparent Ceramics Characterization, properties and applications

By their very nature and the manufacturing processes used, transparent ceramics must be able to combine the properties of single crystals (compactness, purity, homogeneity) with the characteristics of ceramics (ease of shaping, large parts, flexibility of composition). They also offer enhanced thermo-mechanical performance (mechanical strength, toughness, resistance to thermal shock), making them particularly well-suited to applications involving high thermal and/or mechanical stress.

Several compositions are now being developed in the form of transparent polycrystalline ceramics, such as alumina, YAG Y ₃ Al ₅ O ₁₂ , spinel MgAl ₂ O ₄ , calcium fluoride CaF ₂ or zinc selenide. The variety of materials available makes it possible to cover a wide range of applications, such as lighting, watchmaking, shielding or power lasers. Nevertheless, one of the main limitations of transparent polycrystalline ceramics obtained by powder sintering remains the presence of residual defects, in particular porosity, which alter their optical transparency through light scattering. The characterization of these defects, which remains difficult due to their very low proportion in transparent ceramics (< 0.1% vol.), requires the use of adapted techniques.

The first section of this article aims to present characterization methods that provide access to the nature and, possibly, quantity of residual defects in transparent ceramics with a view to optimizing their manufacture. A second section details the physico-chemical properties of the most common transparent ceramics, along with examples of industrial and scientific applications.

The general properties and manufacturing processes of transparent ceramics are described in detail in [E 6 418] .

At the end of the article, readers will find a glossary and a table of the notations used.