Nanostructured Thermoelectric Materials for Temperatures of 200–1200 K Obtained by Spark Plasma Sintering

The broad application of thermoelectricity is constrained by the low efficiency of thermoelectric elements, which is mainly determined by the thermoelectric figure of merit of thermoelectric materials (TEMs) used for their manufacture. At present, the main direction of increasing the figure of merit is to reduce the phonon thermal conductivity of TEMs due to their nanostructuring. The phase composition and fine structure of TEM nanopowders are studied using a JEM-2100 transmission electron microscope. The elemental composition of the starting components for the synthesis of TEMs, ground powders, and bulk nanostructured TEMs (NTEMs) is determined using a JSM-6480LV scanning electron microscope. Methods are developed and modes for obtaining nanodispersed powders and NTEMs based on Bi2Te3, Sb2Te3, PbTe, GeTe and SiGe with operating temperatures in the range of 200–1200 K are optimized. The powders are obtained using a planetary ball mill. The average size of coherent-scattering regions in powders is in the range of 12–47 nm. Bulk NTEMs are made by powder compaction by spark plasma sintering. It is shown that the regions of coherent scattering in bulk samples increase in comparison with the powder structure by an average of 2–3 times and range from 20 to 120 nm. In NTEM, due to a decrease in the thermal conductivity, an increase in the parameter ZT from 10 to 20