Reduction of thermal conductivity in PbTe:Tl by alloying with TlSbTe2

A series of single-phase polycrystalline (TlSbTe2)x(Tl0.02Pb0.98Te)1−x (x= 0, 0.05, 0.1) compounds were made to reduce thermal conductivity while maintaining the enhanced Seebeck coefficients found in PbTe doped with Tl. Transport property measurements confirmed that high Seebeck coefficients from doping with Tl are retained by alloying with TlSbTe2. At the same time, a thermal conductivity as low as 0.8 W/mK at room temperature, and 0.6 W/mK at 673 K was observed, corresponding to a 30% reduction in lattice thermal conductivity at 673 K compared with 2%Tl-PbTe. However, the maximum zT in this system is 0.8 (at 623 K), which is lower than that of 2%Tl-PbTe prepared in this work (1.2 at 673 K) owing to a decrease of the charge-carrier mobility when alloying with TlSbTe2. Possible influences on the mobility are discussed.