Thermoelectric Properties of Ultralong Silver Telluride Hollow Nanofibers

Ultralong AgxTey nanofibers were synthesized for the first time by galvanically displacing electrospun Ni nanofibers. Control over the nanofiber morphology, composition, and crystal structure was obtained by tuning the Ag+ concentrations in the electrolytes. While Te-rich branched p-type AgxTey nanofibers were synthesized at low Ag+ concentrations, Ag-rich nodular AgxTey nanofibers were obtained at high Ag+ concentrations. The Te-rich nanofibers consist of coexisting Te and Ag7Te4 phases, and the Ag-rich fibers consist of coexisting Ag and Ag2Te phases. The energy barrier height at the phase interface is found to be a key factor affecting the thermoelectric power factor of the fibers. A high barrier height increases the Seebeck coefficient, S, but reduces the electrical conductivity, σ, due to the energy filter effect. The Ag7Te4/Te system was not competitive with the Ag2Te/Ag system due to its high barrier height where the increase in S could not overcome the severely diminished electrical conductivity. ...