An overview on transparent ceramics with pyrochlore and fluorite structures

Transparent ceramics have potential applications in various areas, including aerospace, relativistic optics industries, medical cares and defense. Specifically, they can be used as laser gain media, armor windows, IR domes, solid-state phosphors, scintillators and electro-optical components. From crystal structure point of view, transparent ceramic materials should have high crystallographic symmetries (cubic, tetragonal and hexagonal), which have minimal birefringent effect. Currently, transparent ceramics are dominantly based on oxide materials, although there are also nonoxides, such as fluorides and nitrides (oxynitrides). Transparent ceramics with pyrochlore and fluorite structures have attracted much attention in recent years, whereas fluorides are not well described in the open literature. Therefore, this paper is aimed to deliver an overview on the progress of the two categories of transparent ceramics, from material processing and characterization point of view.