Tuning of thermoelectric properties with changing Se content in Sb

Polycrystalline Sb2Te3−xSex $(0.0\leq x\leq1.0)$ samples were synthesized by the solid-state reaction method. The structural analysis showed that up to the maximal concentration of Se, the samples possess rhombohedral crystal symmetry (space group $R\bar{3}m$ ). The increase of Se content increases the resistivity of the samples. The variation of phonon frequencies, observed from the Raman spectroscopic study, depicts an anomalous behaviour around $x=0.2$ . The sample Sb2Te2.8Se0.2 also shows maximum Seebeck coefficient, carrier concentration and thermoelectric power factor. The nature of the scattering mechanism controlling the thermopower data has been explored. The thermoelectric properties of the synthesized materials have been analyzed theoretically in the frame of the Boltzmann equation approach