**Acknowledgements**

*Advanced Thermoelectric Materials for Energy Harvesting Applications*

level, the GEM evaluation can predict the transport properties in a very reliable way, since the transport properties of the composite are expected to act as a com-

*Calculated GEM curves at room temperature of (a) effective Seebeck coefficient, (b) effective electrical resistivity and (c) effective thermal conductivity as a function of the embedded bismuth percentage, under* 

considering the thermal conductivity increment, the overall room temperature thermoelectric efficiency is decreased. On the other hand, the "series" morphological alignment condition at room temperature, exhibits more moderate changes that might allow bigger introduction of bismuth to the matrix, which will reduce the lattice contribution to the thermal conductivity, and at the same time will not affect as drastically the electronic properties. This finding implies on a potential method for enhancing the thermoelectric efficiency by an artificial "series" morphological

alignment of the secondary phase which can lead to possible further study.

The reason for the small mismatches observed in our GEM calculations, might be related to the fact that the matrix was represented by alloy *iii*; it is well known that even a slight change in impurity content, affect substantially the transport properties.

The co-effect of bismuth as an effective electronic dopant and at the same time, as a second phase promoter in the PbTe matrix was investigated and explained in details with regard to the dissolution pattern transition. These two effects on the

In our homogeneous distribution level and morphological alignment conditions, it can be seen that up to 0.1%, a slight change in bismuth concentration is accompanied with a drastic change in the electronic properties of the composite. A drastic degradation in the absolute Seebeck coefficient along with a great improvement in

> 2 *ρ*<sup>−</sup><sup>1</sup>

); yet while

posite with an increasing amount of a secondary metallic phase.

*different morphological alignment and uneven distribution conditions (t = 0.5).*

the electrical conductivity, sums up in an increased power factor (*α*

**58**

**4. Conclusions**

**Figure 6.**

The work was supported by the Israel Science Foundation (ISF) Individual Research Grant No. 455/16. The authors would like to thank Mr. Yair George for the synthesis of the alloys and specimens preparation.
