Achieving zT > 1 in Inexpensive Zintl Phase Ca9Zn4+ xSb9 by Phase Boundary Mapping

Saneyuki Ohno, Umut Aydemir, Maximilian Amsler, Jan Hendrik Pöhls, Sevan Chanakian, Alex Zevalkink, Mary Anne White, Sabah K. Bux, Chris Wolverton, G. Jeffrey Snyder

Research output: Contribution to journalArticlepeer-review

68 Citations (Scopus)

Abstract

Complex multinary compounds (ternary, quaternary, and higher) offer countless opportunities for discovering new semiconductors for applications such as photovoltaics and thermoelectrics. However, controlling doping has been a major challenge in complex semiconductors as there are many possibilities for charged intrinsic defects (e.g., vacancies, interstitials, antisite defects) whose energy depends on competing impurity phases. Even in compounds with no apparent deviation from a stoichiometric nominal composition, such defects commonly lead to free carrier concentrations in excess of 1020 cm−3. Nevertheless, by slightly altering the nominal composition, these defect concentrations can be tuned with small variation of the chemical potentials (composition) of each element. While the variation of chemical composition is undetectable, it is shown that the changes can be inferred by mapping (in nominal composition space) the boundaries where different competing impurity phases form. In the inexpensive Zintl compound Ca9Zn4+ xSb9, the carrier concentrations can be finely tuned within three different three-phase regions by altering the nominal composition (x = 0.2–0.8), enabling the doubling of thermoelectric performance (zT). Because of the low thermal conductivity, the zT can reach as high as 1.1 at 875 K, which is one of the highest among the earth abundant p-type thermoelectrics with no ion conducting.

Original languageEnglish
Article number1606361
JournalAdvanced Functional Materials
Volume27
Issue number20
DOIs
Publication statusPublished - May 25 2017
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Biomaterials
  • Chemistry(all)
  • Materials Science(all)
  • Condensed Matter Physics
  • Electrochemistry

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