Insight into the transport properties and enhanced thermoelectric performance of n-type Pb1−xSbxTe

Highlights: • Effect of Sb substitution on the microstructural properties of PbTe was studied. • Electronic transport model was developed to characterize the scattering mechanisms. • Role of the grain boundaries on the transport properties of n-type PbTe was estimated. • High-efficient n-type thermoelectric segmented leg has been proposed for module fabrication. -- Abstract: Lead telluride is one of the best materials for the fabrication of a medium-temperature thermoelectric modules. In this work, a detailed experimental and theoretical study is carried out to understand the effect of Sb substitution in PbTe semiconductor. The combined structural and transport investigation indicate a possible amphoteric effect of Sb in Pb_1−xSb_xTe; however, this effect was significant just for the lowest Sb-doped sample (x = 0.001) considered in this work. We develop an electronic transport model based on transport relaxation time approximation that accurately describes the main scattering mechanisms in n-type PbTe. By comparison of theoretical and experimental data, we found that both acoustic phonons, as well as scattering at grain boundaries mostly defines the electronic transport in Sb-doped PbTe over the temperature range of 300–800 K. Furthermore, the maximal dimensionless figure of merit ZT= 1.1 was obtained for samples with the nominal Sb concentration of x = 0.01 and x = 0.02 at different temperatures, making these materials promising for the fabrication of a segmented or functionally graded n-type PbTe-based thermoelectric leg. Thermoelectric efficiency η of the sample with the nominal Sb concentration of x = 0.01 reaches the value of η = 11.7% which is one of the best values, obtained for a single-doped n-type PbTe material.