Thermoelectrical figure of merit ofPbTe-based solid solutions with phonon scattering by off‑centerimpurities

E.A. Gurieva¹, P.P. Konstantinov¹,L.V. Prokofieva¹, M.I. Fedorov¹, Yu.I. Ravich²

¹A.F. Ioffe Physicotechnical InstituteRAS. 194021 St. Petersburg, Russia

²St.Petersburg State PolytechnicalUniversity. 195251 St. Petersburg, Russia

Thethermopower, electroconductivity and thermal conductivity coefficients (S, s and k) have been studied for ternary solid solutionsPbTe_1-xSe_x, and quaternary one PbTe_1‑2xSe_xS_x.Considerable decrease in mobility and anomalousrunning of s(x) in the vicinity of77 K have been found out for quaternary alloys with x ³ 0.1. For composition with x =0.15 the unusual behavior k(T) has been also marked:with lowering temperature thermal conductivity at first weakly grows thenslightly drops. According to estimations, in the latter material lattice heatconductivity has a constant value in the range of (80-300) K. It means, thatwith lowering temperature the reduction of phonon scattering on phonons iscompletely compensated by increase of phonon scattering on impurities. Thefound out anomalies in s(x) and k(T) dependencies are discussedtaking into account a possibility for the S atoms to occupy off-center latticesites.

In the range of (80-300) K, thermoelectric figure of merit Z of alloysstudied has been determined.. The quaternary composition with x = 0.1: has themaximum value of Z despite of the marked reduction of mobility. The Sn atoms, as the S ones, may getoff the central sites, in this connection one could expect the appearance ofthe same influence of these atoms on thermoelectric properties of appropriatesolid solutions. Experimental data on thermoelectric figure of merit ofPb(Sn)Te(Se) solid solutions at room temperature are discussed.