Thermoelectric properties of the TlBiS2-PbS alloys

High efficiency of thermoelectric conversion can be achieved by using materials with a high Seebeck coefficient, high electrical conductivity, and low thermal conductivity. Mass-difference-scattering of the phonons is one of the most effective way for reducing the thermal conductivity in bulk thermoelectric materials. Investigations of transport phenomena in (TIBiS2)(1-x)(2PbS)(x) alloys system have shown that in solid solutions of the (A(3)B(5)C(2)(6))(1-x) (2A(4)B(6))(x) type at cation substitution according to scheme 2A(4(+2)) -> A(3(+1)) +B5(+3) occurs a strong decrease of the lattice thermal conductivity. In the vicinity of x 0.50 the lattice part of thermal conductivity of (TIBiS2)1-x(2PbS)x alloys decreases down to 0.26 W/mK, i.e., it approaches the theoretical minimum. As a result, the thermoelectric figure of merit for these alloys (approximate to 25%) exceeds the respective value for lead sulfide at room temperature.