Melt-slow Cooling Synthesis and Thermoelectric Properties of Pb_(9.6)Sb_mTe_3Se_7 Alloys

Pb9.6SbmTe3Se7 alloys(m=0.15,0.2,0.25,0.267,0.3,0.35,0.4) have been synthesized by slow cooling followed smelting in evacuated tubes and powder hot pressing,and the effect of Sb doping on the thermoelectric performance was investigated.As the Sb content increases,except for the alloy of m=0.4,carrier mobility decreases,electrical conductivity decreases,and thermal conductivity shows a decreasing trend,significantly lower than the thermal conductivity of PbTe.HRTEM images suggest the Pb9.6Sb0.3Te3Se7 phases are inhomogeneous with widely distributed nanosized islands with different shapes,which are favorable to the strong suppression of the lattice thermal conductivity.Finally,the thermoelectric properties of the materials have been improved by Sb doping.It is noteworthy that Pb9.6Sb0.3Te3Se7 exhibits a high thermoelectric figure of merit,with the highest ZT ～1.14 at 673 K,which is about 50% higher than that of the state-of-the-art n-type PbTe reported previously.