Effect of excess Na on the morphology and thermoelectric properties of Na x Pb1-x Te0.85Se0.15

Chanyoung Kang, Hongchao Wang, Heejin Kim, Sung Jin Kim, Woochul Kim

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Abstract

The thermoelectric properties of p-Na x Pb1-x Te 0.85Se0.15, which possesses a high thermoelectric figure of merit due to band convergence, have been systematically investigated for increasing Na concentration (x = 0.01, 0.02, 0.03, 0.05, and 0.07) from room temperature to 773 K. For x values up to 0.03, the hole concentration increases with the Na concentration; however, for x ≥ 0.03, excess Na forms separate microstructures with needle- and plate-like shapes. At high concentrations (x = 0.05 and 0.07) both the number and size of these structures increase (over 10 μm). Differential scanning calorimetry identifies a phase change near 660 K in samples with x = 0.05 and 0.07, confirming the formation of microstructures; this phase change leads to a decrease in electrical resistivity. However, these microstructures do not significantly affect thermal transport, probably because they are too large to scatter phonons. The highest thermoelectric figure of merit, zT, value is 1.6, which is obtained at 760 K for x = 0.05, due to the low thermal conductivity and electrical resistivity.

Original languageEnglish
Pages (from-to)353-358
Number of pages6
JournalJournal of Electronic Materials
Volume43
Issue number2
DOIs
Publication statusPublished - 2014 Jan 1

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Electrical and Electronic Engineering
  • Materials Chemistry

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