Discussion on polycrystals over single crystals for optical devices
Résumé
Conventional transparent materials have a strong absorption in the infrared region making them unsuitable in the spectral range. Crystal growth processes are usually very time‐consuming and needs sophisticated/expensive machines. Polycrystalline nature of the ceramics is prone to diffusing light, which primarily arises from residual pores, grain boundaries, secondary phases and birefringency (anisotropic materials). Rapid sintering techniques such as Spark Plasma Sintering (SPS) helps in obtaining maximum densification in short duration of time at comparatively lesser sintering temperatures in comparison to other classical sintering. With the recent technological advances in sintering technology and nanopowders fabrication, it is possible to obtain a dense ceramic that is transparent. Transparent ceramics processing with nanosized ceramic powders and advanced densification technology provides an alternative approach to overcome the disadvantages/limits of conventional single‐crystal growth process. Most of the current transparent ceramics are limited only to cubic materials, currently extended to non‐cubic materials as well though in early stages. Conventionally, either Hot‐Isostatic Pressing (HIP), or Hot Pressing (HP) or vacuum sintering at very high temperatures using ultrapure ultrafine powders often fabricates optically transparent ceramics. This paper demonstrates the fabrication of transparent ceramics of both cubic and non‐cubic crystal structured materials by Spark Plasma Sintering (SPS) for materials without any additives/sintering aids.
Domaines
Matériaux
Origine : Fichiers produits par l'(les) auteur(s)