Tellurium based glasses:: A ruthless glass to crystal competition

Although selenium and tellurium are very close in the periodic table, their ability to form glasses is totally different. Indeed, selenium based glasses are very common and stable whereas pure tellurium glasses need an extremely fast quenching such as splash cooling. Consequently, tellurium glasses are very suitable for the fast and reversible glass to crystal transformation for optical storage applications. In particular, glasses of the ternary system Ge/Sb/Tc are the most appropriate to observe phase transformation under laser beam irradiation for the Digital Versatile Disk (DVD) technology. Also, Te based glasses could be very interesting to produce optics for the far infrared, thanks to their low phonon character due to the high atomic weight of Te. Especially, some new tellurium glasses of the system Ge/Ga/Te/I are currently in development for infrared detection of exoplanet within the framework of the Darwin mission. In this contribution an overview covering the past two decades is proposed on the chemistry and the potential applications of these original glasses. (C) 2007 Elsevier Masson SAS. All rights reserved.