Thermoelectric Properties of Ultralong Silver Telluride Hollow Nanofibers

Abstract

Ultralong Ag_<i>x</i>Te_<i>y</i> 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 Ag_<i>x</i>Te_<i>y</i> nanofibers were synthesized at low Ag⁺ concentrations, Ag-rich nodular Ag_<i>x</i>Te_<i>y</i> 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, <i>S</i>, 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 <i>S</i> could not overcome the severely diminished electrical conductivity. The highest power factor was found in the Ag₂Te/Ag-rich nanofibers with an energy barrier height of 0.054 eV