An aqueous-chemistry approach to nano-bismuth telluride and nano-antimony telluride as thermoelectric materials

Chemical synthesis of bismuth telluride Bi2Te3 and other chalcogenide thermoelectric materials is possible by many different routes. Most often, the chalcogenide material is produced as nanocrystals of various morphologies in attempts to achieve better thermoelectric performance in the nanocomposite because of enhanced grain boundary scattering. However, publications dealing with the synthesis of large amounts of cheap nanomaterials are still very rare. We present an aqueous chemical synthesis in alkaline solution as well as in an NH3/NH4Cl buffer medium producing nanocrystalline bismuth telluride in high quantities. For the precipitation process, different Bi and Sb salts can be used as precursors resulting in a variety of product morphologies. The use of a buffer medium for the reaction solution makes it possible to dissolve the precursors in acidic medium, adding a solution instead of dispersion to the reaction medium. The powders from the reactions were sintered to give nanocomposites using spark plasma sintering. Only a small influence of sintering on the nanostructure could be detected. Room-temperature thermoelectric properties of these nanocomposites are within the range or slightly worse than the values for bulk material.