  Polycrystalline Sb 2 Te 3-x Se x (0.0 < x < 1.0) samples were synthesized by
the solid state reaction method. The structural analysis showed that up to the
maximal concentration of Se, the samples possess the Rhombohedral crystal
symmetry (space group R 3 m ). Increase of Se content increases the resistivity
of the samples. Variation of phonon frequencies, observed from Raman
spectroscopic study, depict anomalous behaviour around x = 0.2. The sample Sb 2
Te 2.8 Se 0.2 also shows maximum Seebeck coefficient, carrier concentration and
thermoelectric power factor. Nature of scattering mechanism controlling the
thermopower data has been explored. The thermoelectric properties of the
synthesized materials have been analyzed theoretically in the frame of
Boltzmann equation approach.
