Transport properties of the SnBi2Te4–PbBi2Te4 solid solution

Abstract

We report on the electrical and thermal transport properties of the Sn1−xPbxBi2Te4 series and we discuss the potential of these materials for thermoelectric conversion applications. From the evolution of the XRD patterns, we can confidently conclude that a complete solid solution exists between SnBi2Te4 and PbBi2Te4, with no miscibility gap. A crossover from p-type conduction in Sn-rich samples to n-type conduction in Pb-rich ones has been observed, with a transition between x=0.3 and 0.4. A concomitant increase of the electrical resistivity and of the Seebeck coefficient has been observed in the solid solution, which leads to almost constant values of the thermoelectric power factor. Moreover, the thermal conductivity is slightly reduced in the solid solution. The best figure of merit ZT values at room temperature have been observed for p-type Sn0.8Pb0.2Bi2Te4 with ZT=0.25 and for n-type Sn0.3Pb0.7Bi2Te4 with ZT=0.15.