Effects of PbTe doping on the thermoelectric properties of (Bi2Te3)0.2(Sb2Te3)0.8

We have investigated the thermoelectric properties of p-type Bi-Te thermoelectric material doped with PbTe. The samples (Bi₂Te₃)_0.2(Sb₂Te₃)_0.8+xwt%PbTe (x=0, 0.05, 0.1, 0.3, 0.5) were fabricated by the mechanical alloying (MA) and spark plasma sintering (SPS) method. The Seebeck coefficient (α), the electric conductivity (σ), the Hall carrier concentration (n_p) and the thermal conductivity (K) were measured in the temperature range 323-523 K. The maximum value of the Seebeck coefficient shifted toward a higher temperature with increasing PbTe content. The electric conductivity increased with increasing PbTe content. Although, the values of thermal conductivity of x=0.05, 0.1 samples were increased monotonously with increasing temperature, x=0.3, 0.5 samples showed minimum value then increased with temperature. The dimensionless figure of merit ZT and average ZT were calculated in temperature range 323-523 K. The maximum ZT of 1.12 was obtained for x=0.3 sample at 373 K. The maximum value of the average ZT was 1.02 for x=0.3 sample.