Electrical and thermal transport properties of (TlBiS2)1-x(2PbS)x alloys

A high efficiency of thermoelectric conversion can be achieved by using materials with a maximum figure of merit Z, i.e. materials with a high Seebeck coefficient S, high electrical conductivity Q and low thermal conductivity K. Investigations of transport phenomena in alloys of the (TlBiS2)(1-z)(2PbS)(x) system have shown that in solid solutions of type (A(3)B(5)C(2)(6))(1-x)(2A(4)B(6))(x) cation substitution according to the scheme 2A(4(+2))-->A(3(+I)) + B5(+3) leads to a strong decrease in lattice thermal conductivity K-L. In an area (X = 0.50) of the K-L=f (C) curve the lattice part of the thermal conductivity of (TIBiS2)(1-x)(2PbS)(X) alloys decreases to 0.26 W m(-1) K-1, which is approaching the theoretical minimum. As a result, the dependence of the thermoelectric figure of merit on composition Z = f (C) of alloys of the (TIBiS2)(1-x)(2PbS)(x) system passes through a maximum in the area X = 0.50, exceeding by similar to25% the respective value of Z for lead sulfide at room temperature.