Thermoelectric properties of stoichiometric Ag1−xPb18SbTe20 (x = 0, 0.1, 0.2)

Polycrystalline-sintered samples of stoichiometric Ag1−xPb18SbTe20 (x = 0, 0.1, 0.2) were prepared by a solid-state reaction. The electrical resistivity and Seebeck coefficient were measured from room temperature to about 700 K. The electrical resistivity of stoichiometric Ag1−xPb18SbTe20 decreases with increasing temperature. The values of the electrical resistivity are of the order of 10−5 to 10−4 (Ω m). The Seebeck coefficient of stoichiometric Ag1−xPb18SbTe20 is negative, which shows n-type behavior. The absolute value of the Seebeck coefficient at 373 K is −337 μV K−1 for Ag0.6Pb18SbTe20. The thermal diffusivity was measured from room temperature to about 700 K. The thermal conductivity was evaluated from the thermal diffusivity and heat capacity. The value of thermal conductivity is 0.916 Wm−1 K−1 at 373 K for Ag0.6Pb18SbTe20. The dimensionless figure of merit ZT of Ag1−xPb18SbTe20 was evaluated by using the data of the electrical resistivity, Seebeck coefficient, thermal conductivity obtained in the present study. The maximum value of ZT is 1.07 at 673 K for Ag0.6Pb18SbTe20.