The effect of Ag concentration on the structural, electrical and thermal transport behavior of Pb:Te:Ag:Se mixtures and improvement of thermoelectric performance via Cu doping

摘要

Pb, Te, Ag and Se, when reacted in a 1:1 :x: 1 (x = 1.9,2.0, 2.01) molar ratio, form a two phase composite which consists of a phase which crystallizes in the fee cubic PbSe structure and a phase that crystallizes in the Ag_2Te structure. In this article, we demonstrate that by varying the Ag concentration, we can manipulate which variant of the Ag_2Te structure stabilizes at room temperature (monoclinic ct-Ag_2Te or cubic P-Ag_(1.9)Te) and can consequently manipulate the electrical and thermal transport behavior of the composite and hence the thermoelectric performance. Additionally, we show that Cu-doping results in an overall improvement in thermoelectric performance. Our results suggest that formation of composites is a viable path for achieving a phonon-glass-electron-crystal (PGEC) alloy.