Preparation and Properties of Zn4Sb2.94In0.06/ZnO Composite Thermoelectric Materials

Abstract

Zn4Sb2.94In0.06/x wt.% ZnO (x = 0, 0.5, 1, 2) composite thermoelectric (TE) materials were prepared with ZnO as additive. The materials were characterized by x-ray diffraction analysis, electron probe microanalysis, and use of TE transport measurements. The ZnO additive, distributed throughout the interior of intact part of the bulk material, interacts with diffusing elemental Zn at elevated temperatures, which is beneficial to the thermal stability of the composite TE materials. The electrical conductivity is increased by addition of the ZnO, because of increased carrier mobility, even though the carrier concentration decreases slightly. The Seebeck coefficients are nearly the same for all the composite TE materials below 560 K, and the presence of the decomposition product ZnSb increases the Seebeck coefficient at high temperatures. All the composite TE materials have lower thermal conductivity than pure Zn4Sb2.94In0.06, as a result of the lower lattice thermal conductivity, because of the enhanced phonon scattering induced by the ZnO additive. The maximum ZT is 1.16 at 700 K for the sample with x = 1, an increase of 86% compared with that of pure Zn4Sb2.94In0.06. Therefore, addition of ZnO can increase the thermal stability and TE performance of Zn4Sb3-based composite TE materials.