Influence Na in GeTe for thermoelectric applications

Abstract

Germanium telluride (GeTe), a semiconductor material, is a complex solid state system with interesting fundamental properties and it serves as a base for high-efficiency thermoelectric materials. Generally, thermoelectric conversion efficiency can be enhanced with appropriate strategies such as doping, alloying, and nanostructuring in the thermoelectric materials. Since there is a significant discrepancy between the electronic and thermal transport data for GeTe-based materials reported in the literature obscuring the baseline knowledge and preventing a clear understanding of the effect of alloying GeTe with various elements, we introduce pentavelant ions into GeTe to enhance the Seebeck coefficient and reduction of thermal conductivity to overcome the discrepancy between the electronic and thermal transport data. A complete study including XRD, Seebeck coefficient, electrical resistivity, and thermal conductivity on Ge rich Ge1-xNaxTe (x = 0.01, 0.02 &0.03) samples was conducted. All compounds were prepared by solid state reaction and hot press method. From the results, Na doping enhances the Seebeck coefficient in the low temperature range and drastically decreased at high temperature. Our data show that at 723 K, Ge0.99Na0.01 Te & Ge0.98Na0.02Te has power factor about 25 µWcm-1K−2. In addition the influence of Na in GeTe to enhance the electrical conductivity.