Nonoxide tellurium-based glasses

Telluride glasses, i.e., nonoxide glasses based on the chalcogen element tellurium, constitute a particular class of materials used in numerous technological applications. While many telluride systems are not intrinsically good glass formers, a wide range of telluride glass compositions have been developed and offer a unique set of optical and electrical properties. Telluride glasses possess a very broad transparency in the infrared, which can range up to more than 20 μm, making them particularly interesting for optical applications in the far-infrared range. Several families of telluride glasses (e.g., ternary and quaternary systems based on tellurium, germanium, and gallium) have been explored and optimized in order to further develop these applications. Indeed, a large number of organic compounds have their specific spectral signature (or “fingerprint”) in the far-infrared, making telluride glasses materials of choice for the fabrication of sensing devices. Tellurides are also found in the fabrication of rewritable optical disks and phase-change memory devices, as some compositions exhibit fast and reversible conversion between crystalline and amorphous (glassy) phases. More recently, telluride glasses have been demonstrated to be promising candidates as thermoelectric materials, due to their semiconducting nature. In this chapter, the fundamentals of the telluride glasses and of their structure are presented. An overview of the different families of telluride glasses, as well as their specific properties, is given. The considerations related to their relatively complex fabrication processes are also described.