Computationally Modelling the Use of Nanotechnology to Enhance the Performance of Thermoelectric Materials

Abstract

The increased focus on global climate change has meant that the thermoelectric market has received considerably more attention. There are many processes producing large amounts of waste heat that can be utilised to generate electrical energy. Thermoelectric devices have long suffered with low efficiencies, but this can be addressed in principle by improving the performance of the thermoelectric materials these devices are manufactured with. This paper investigates the thermoelectric performance of market standard thermoelectric materials before analysing how this performance can be improved through the adoption of various nanotechnology techniques. This analysis is carried out through the computational simulation of the materials over low-, mid- and high-temperature ranges. In the low-temperature range, through the use of nanopores and full frequency phonon scattering, Mg0.97Zn0.03Ag0.9Sb0.95 performed best with a ZT value of 1.45 at 433 K. Across the mid-temperature range a potentially industry leading ZT value of 2.08 was reached by AgSbTe1.85Se0.15. This was carried out by simulating the effect of band engineering and the introduction of dense stacking faults due to the addition of Se into AgSbTe2. AgSbTe1.85Se0.15 cannot be implemented in devices operating above 673 K because it degrades too quickly. Therefore, for the top 200 K of the mid-temperature range a PbBi0.002Te–15% Ag2Te nanocomposite performed best with a maximum ZT of 2.04 at 753 K and maximum efficiency of 23.27 at 813 K. In the high-temperature range, through the doping of hafnium (Hf) the nanostructured FeNb0.88Hf0.12Sb recorded the highest ZT value of 1.49 at 1273 K. This was closely followed by Fe1.05Nb0.75Ti0.25Sb, which recorded a ZT value of 1.31 at 1133 K. This makes Fe1.05Nb0.75Ti0.25Sb an attractive substitute for FeNb0.88Hf0.12Sb due to the much lower cost and far greater abundance of titanium (Ti) compared with hafnium.