Bulk Nanocrystalline Thermoelectrics Based on Bi-Sb-Te Solid Solution

TL;DR

This paper reports the fabrication of bulk nanocrystalline Bi-Sb-Te thermoelectric materials with enhanced efficiency, achieved through various consolidation methods and nanostructuring, supported by theoretical analysis of transport properties.

Contribution

It introduces a new method for producing bulk nanostructured Bi-Sb-Te thermoelectrics with high ZT and provides a theoretical model correlating nanograin size with thermoelectric performance.

Findings

Achieved ZT=1.22 at 360 K in nanostructured Bi-Sb-Te.

Nanograin size reduction improves thermoelectric efficiency.

Theoretical models match experimental conductivity and power data.

Abstract

A nanopowder from p-Bi-Sb-Te with particles ~ 10 nm were fabricated by the ball milling using different technological modes. Cold and hot pressing at different conditions and also SPS process were used for consolidation of the powder into a bulk nanostructure and nanocomposites. The main factors allowing slowing-down of the growth of nanograins as a result of recrystallization are the reduction of the temperature and of the duration of the pressing, the increase of the pressure, as well as addition of small value additives (like MoS2, thermally expanded graphite or fullerenes). It was reached the thermoelectric figure of merit ZT=1.22 (at 360 K) in the bulk nanostructure Bi0,4Sb1,6Te3 fabricated by SPS method. Some mechanisms of the improvement of the thermoelectric efficiency in bulk nanocrystalline semiconductors based on BixSb2-xTe3 are studied theoretically. The reduction of nanograin size can lead to improvement of the thermoelectric figure of merit. The theoretical dependence of the electric and heat conductivities and the thermoelectric power as the function of nanograins size in BixSb2-xTe3 bulk nanostructure are quite accurately correlates with the experimental data.