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 (alpha), the electric conductivity (sigma), the Hall carrier concentration (n(p)) and the thermal conductivity (ic) were measured in the temperature range 323-523K. 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 323-523K. The maximum ZT of 1.12 was obtained for x=0.3 sample at 373K. The maximum value of the average ZT was 1.02 for x=0.3 sample.