Transparent ceramics: The material of next generation

In the first half of the 20th century, ceramics were supposed to be an opaque material only. Transparent ceramics seemed to be a fantasy before the 1960s. However, the advancement in sintering technologies and continuous research in solid-state materials form a relationship between transparency and ceramics. Now, transparent ceramics are a reality, and they are fabricated using advanced sintering technologies such as vacuum sintering, hot pressing, hot isostatic pressing, spark plasma sintering, and microwave sintering. Furthermore, sintering aids are additional assets to produce completely dense, transparent ceramics with optimum grain size. The use of cold isostatic pressing further ensures the high densification of ceramics. Transparent ceramics based on oxides are leading in research as well as industry owing to their better mechanical strength and chemical stability, along with an easier synthesis process compared to nonoxide ceramics. Nevertheless, nonoxide-based ceramics are also emerging, and some quantum amount of research is also taking place in this arena. Transparent ceramics exhibit a unique fusion of high optical transmittance and toughness. Initially, these ceramics were developed for high-power solid-state laser applications and replaced single crystals. However, with time and progress in fabrication technologies, these ceramics also find their applications in various other fields, such as lighting, scintillating, protective windows, transparent armor, optical lenses, and biomedical. This chapter sheds some light on factors affecting transparency, types of transparent materials, and their applications in different fields.