Impact of fermi surface shape engineering on calculated electronic transport properties of Bi-Sb-Te

Sang Il Kim, Jong Chan Lim, Heesun Yang, Hyun Sik Kim

Research output: Contribution to journalArticlepeer-review

6 Scopus citations

Abstract

Using thermoelectric refrigerators can address climate change because they do not utilize harmful greenhouse gases as refrigerants. To compete with current vapor compression cycle refrigerators, the thermoelectric performance of materials needs to be improved. However, improving thermoelectric performance is challenging because of the trade-off relationship between the Seebeck coefficient and electrical conductivity. Here, we demonstrate that decreasing conductivity effective mass by engineering the shape of the Fermi surface pocket (non-parabolicity factor) can decouple electrical conductivity from the Seebeck coefficient. The effect of engineering the non-parabolicity factor was shown by calculating the electronic transport properties of a state-of-the-art Bi-Sb-Te ingot via two-band model with varying non-parabolicity. The power factor (the product of the Seebeck coefficient squared and electrical conductivity) was calculated to be improved because of enhanced electrical conductivity, with an approximately constant Seebeck coefficient, using a non-parabolicity factor other than unity. Engineering the non-parabolicity factor to achieve lighter conductivity effective mass can improve the electronic transport properties of thermoelectric materials because it only improves electrical conductivity without decreasing the Seebeck coefficient (which is directly proportional to the band mass of a single Fermi surface pocket and not to the conductivity effective mass). Theoretically, it is demonstrated that a thermoelectric figure-of-merit zT higher than 1.3 can be achieved with a Bi-Sb-Te ingot if the non-parabolicity factor is engineered to be 0.2. Engineering the non-parabolicity factor is another effective band engineering approach, similar to band convergence, to achieve an effective improvement in power factor.

Original languageEnglish
Pages (from-to)54-60
Number of pages7
JournalJournal of Korean Institute of Metals and Materials
Volume59
Issue number1
DOIs
StatePublished - Jan 2021

Keywords

  • Band mass of a single Fermi pocket
  • Conductivity effective mass
  • Non-parabolicity factor
  • Power factor
  • Thermoelectric

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