**Abstract**

The demand for energy efficiency has motivated many researchers to seek for novel methods capable of enhancing the conversion of heat to electricity. Most of the recently published methods for thermoelectric (TE) efficiency enhancement discuss on the reduction of the lattice thermal conductivity, with a minor focus on improved electronic optimization. This is attributed mainly to the fact that the electronic properties are correlated and opposing each other upon increasing the carrier concentration. It has been reported that the system of PbTe-BiTe has potentially high TE performance; this chapter is focused on a detailed investigation of the co-effect of bismuth as an effective electronic dopant and at the same time, as a second phase promoter in the PbTe matrix. (PbTe)*x*(BiTe)1−*<sup>x</sup>* alloys were thermoelectrically examined and the values were analyzed analytically by the general effective media (GEM) approach.

**Keywords:** thermoelectric, PbTe, BiTe, solubility, GEM
