Influence of Preparation Processing on the Transport Properties of Melt-Spun Sb2−xBixTe3+y

In this work, we present our attempt to improve the thermoelectric performance of melt-spun (MS) Sb2−xBixTe3+y samples densified by spark plasma sintering (SPS) through two different methods: (1) alignment of the MS ribbons in the SPS die; (2) repetitive SPS sintering. A microstructural study of the dense samples was performed by scanning electron microscopy supported by x-ray diffraction analyses. The thermoelectric and galvanomagnetic properties were measured in the direction perpendicular to the uniaxial pressing direction of SPS. Alignment of the ribbons gives rise to improved thermoelectric performances with an increase of up to 26% with respect to the reference sample, yielding a peak dimensionless figure of merit ZT value of 1.1 at 355 K. Yet, in contrast to recent studies, we observed a decrease in the thermoelectric efficiency of ∼10% in the Sb1.5Bi0.5Te3.1 sample prepared by double-SPS compared to the sample densified with a single SPS process. Nevertheless, all MS samples possess improved thermal and electrical properties compared to the reference samples, proving the positive influence of this method.