Observations of Co4+ in a Higher Spin State and the Increase in the Seebeck Coefficient of Thermoelectric Ca3Co4O9

Klie R. F. , Qiao Q., Paulauskas T., Gulec A., Rebola A., Oeguet S., ...More

PHYSICAL REVIEW LETTERS, vol.108, no.19, 2012 (Journal Indexed in SCI) identifier identifier

  • Publication Type: Article / Article
  • Volume: 108 Issue: 19
  • Publication Date: 2012
  • Doi Number: 10.1103/physrevlett.108.196601
  • Title of Journal : PHYSICAL REVIEW LETTERS


Ca3Co4O9 has a unique structure that leads to exceptionally high thermoelectric transport. Here we report the achievement of a 27% increase in the room-temperature in-plane Seebeck coefficient of Ca3Co4O9 thin films. We combine aberration-corrected Z-contrast imaging, atomic-column resolved electron energy-loss spectroscopy, and density-functional calculations to show that the increase is caused by stacking faults with Co4+-ions in a higher spin state compared to that of bulk Ca3Co4O9. The higher Seebeck coefficient makes the Ca3Co4O9 system suitable for many high temperature waste-heat-recovery applications.