Na Doping in PbTe: Solubility, Band Convergence, Phase Boundary Mapping, and Thermoelectric Properties

Priyanka Jood, James P. Male, Shashwat Anand, Yoshitaka Matsushita, Yoshiki Takagiwa, Mercouri G. Kanatzidis, G. Jeffrey Snyder, Michihiro Ohta

Research output: Contribution to journalArticle

Abstract

Many monumental breakthroughs in p-type PbTe thermoelectrics are driven by optimizing a Pb0.98Na0.02Te matrix. However, recent works found that x > 0.02 in Pb1-xNaxTe further improves the thermoelectric figure of merit, zT, despite being above the expected Na solubility limit. We explain the origins of improved performance from excess Na doping through computation and experiments on Pb1-xNaxTe with 0.01 ≤ x ≤ 0.04. High temperature X-ray diffraction and Hall carrier concentration measurements show enhanced Na solubility at high temperatures when x > 0.02 but no improvement in carrier concentration, indicating that Na is entering the lattice but is electrically compensated by high intrinsic defect concentrations. The higher Na concentration leads to band convergence between the light L and heavy ς valence bands in PbTe, suppressing bipolar conduction and increasing the Seebeck coefficient. This results in a high temperature zT nearing 2 for Pb0.96Na0.04Te, ∼25% higher than traditionally reported values for pristine PbTe-Na. Further, we apply a phase diagram approach to explain the origins of increased solubility from excess Na doping and offer strategies for repeatable synthesis of high zT Na-doped materials. A starting matrix of simple, high performing Pb0.96Na0.04Te synthesized following our guidelines may be superior to Pb0.98Na0.02Te for continued zT optimization in p-type PbTe materials.

Original languageEnglish
Pages (from-to)15464-15475
Number of pages12
JournalJournal of the American Chemical Society
Volume142
Issue number36
DOIs
Publication statusPublished - Sep 9 2020

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

Fingerprint Dive into the research topics of 'Na Doping in PbTe: Solubility, Band Convergence, Phase Boundary Mapping, and Thermoelectric Properties'. Together they form a unique fingerprint.

  • Cite this