Comparative growth mechanism study for two thermoelectric compounds

Abstract

Reaction pathways have been determined for the formation of two thermoelectric materials, bismuth telluride and lead telluride, fabricated by solution-phase, solid-state synthesis. The fabrication of these compounds by way of a modified polyol process has been investigated because this bottom-up approach has a proclivity for tailoring nanoscale features and has the potential to reduce manufacturing costs. These thermoelectric nanomaterials were characterized by powder X-ray diffractometry, scanning electron microscopy and energy-dispersive X-ray spectroscopy. By generating a range of samples as a function of temperature, mechanisms of formation were determined by mapping out changes in crystal structure, morphology and elemental composition. Growth mechanisms for both materials were compared to investigate which growth stages are unique to the compound being fabricated and which are common to the synthetic method. Findings showed that the formation of intermediate stages was dependent on variables beyond temperature and time, such as reduction rate, conjugate anion of the starting reagent and the reaction atmosphere. These types of experimental investigations of wet-chemical methods to fabricate nanomaterials with energy-related applications are fundamental to determine the feasibility of this approach to fabricate thermoelectric materials with reduced production costs and improved energy transport properties.