Effects of Co-doping and Microstructure on Charge Carrier Energy Filtering in Thermoelectric Titanium-Doped Zinc Aluminum Oxide

Chhatrasal Gayner, Yuriy Natanzon, Yaron Amouyal

Research output: Contribution to journalArticlepeer-review


ZnO is a promising thermoelectric (TE) material for high-temperature applications; however, its TE performance is limited by strong coupling between electrical and thermal transport. In this study, we synthesized Al and Ti co-doped ZnO by a solid-state reaction and air sintering at 1500 °C and analyzed the microstructure to establish its correlation with TE properties. The TE transport properties were measured between room temperature and 800 °C, and electronic properties were calculated from first principles calculations. Herein, we introduced second and third phases into a ZnO-based matrix to enhance its power factor (PF) by charge carrier energy filtering by applying co-doping with Al and Ti. Although multiphase materials usually do not exhibit high PF, in this study, it is observed that three-phase ZnO-based materials exhibit higher PF values compared to the two-phase materials. We observed unusual behavior, in which the Seebeck coefficient (S) and electrical conductivity (σ) values increased simultaneously with temperature for Zn1-x-yAlxTiyO, originating from energy filtering of charge carriers due to both co-doping and the peculiar multiphase structure. High σ values were associated with the increase of electron concentration, while high S values were due to Fermi energy tuning and heavier effective masses initiated by Al and Ti co-doping. Besides increasing the PF, the multiphase structure played an essential role in reducing lattice thermal conductivity due to phonon scattering by the Umklapp, point defect, and second-phase mechanisms. Our approach yielded an increase of the TE figure of merit upon formation of a three-phase 2 wt % Ti-doped Zn0.98Al0.02O compound of ca. 10 times compared to the corresponding value attained for its two-phase ZnAl0.02O counterpart.

Original languageEnglish
Pages (from-to)4035-4050
Number of pages16
JournalACS Applied Materials and Interfaces
Issue number3
StatePublished - 26 Jan 2022


  • charge carrier energy filtering
  • electron and phonon transport
  • multiphase oxides
  • thermoelectric materials
  • zinc oxide

All Science Journal Classification (ASJC) codes

  • Materials Science(all)


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