Electrodeposition of bismuth telluride thin films containing silica nanoparticles for thermoelectric applications

The electrodeposition of bismuth telluride (Bi2Te3) with incorporated silica nanoparticles (diameter = 16 nm) was studied in ethylene glycol using a rotating disk electrode. "By matching the refractive index of the silica nanoparticles to the refractive index of the electrolyte i.e. "refractive index matching", the attractive van der Waals force between particles was minimized. Refractive index matching was used to avoid agglomeration of the silica particles in solution due to the attractive van der Waals forces and resulted in Bi2Te3 coatings that contain up to 8 vol% of individual silica particles as verified by TEM. The concentration of the incorporated silica nanoparticles was found to be influenced by several parameters: the applied current density, rotation speeds and silica concentration in the electrolyte. A model was developed to predict the amount of incorporated particles. The effect of each parameter was predicted by this model and verified experimentally. The Seebeck coefficient and thermal diffusivity of bismuth telluride films with and without silica nanoparticles were measured.