Enhanced Thermoelectric Performance and Thermal Stability in β-Zn4Sb3 by Slight Pb-Doping

We report a systematic study of the thermoelectric properties and thermal stability of Pb-doped (Zn1- Pb )(4)Sb-3 ( = 0.0 to 0.02) bulk samples prepared by melting-quenching followed by subsequent spark plasma sintering, as a function of Pb-doping content and temperature. With introduction of Pb at Zn sites, the lattice parameters show an anomalous decrease which can be interpreted by preferential occupation of Pb at interstitial Zn sites. The exciting simultaneous enhancements of both electrical conductivity and Seebeck coefficient lead to a significant improvement in power factor for samples with low doping content. This improvement is mainly ascribed to the abnormal increase in hole mobility, which is realized by a decreased degree of disorder following introduction of heavier and larger Pb atoms, hampering the migration of liquid Zn in local disordered structure. Therefore, the improved power factors combined with intrinsic low thermal conductivity result in > 1.1 for lightly doped samples for > 600 K, with peak of 1.2 for the sample doped with 0.5 at.% Pb, representing an approximately 20% improvement compared with the undoped sample. What is more important here is the apparent improvement of high-temperature thermal stability by light Pb-doping, which is beneficial for commercial applications of this promising and cheap material for intermediate-temperature waste heat recovery.