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ACS Omega. 2018 Sep 7;3(9):10798-10810. doi: 10.1021/acsomega.8b01552. eCollection 2018 Sep 30.

Nanoscale Texturing and Interfaces in Compositionally Modified Ca3Co4O9 with Enhanced Thermoelectric Performance.

Author information

1
Center for Energy Harvesting Materials and Systems (CEHMS), Department of Materials Science and Engineering, Department of Mechanical Engineering, and Department of Physics, Virginia Tech, Blacksburg, Virginia 24061, United States.
2
Department of Materials Science and Engineering, Pennsylvania State University, State College, Pennsylvania 16802, United States.

Abstract

Oxide thermoelectric materials are nontoxic, chemically and thermally stable in oxidizing environments, cost-effective, and comparatively simpler to synthesize. However, thermoelectric oxides exhibit comparatively lower figure of merit (ZT) than that of metallic alloy counterparts. In this study, nanoscale texturing and interface engineering were utilized for enhancing the thermoelectric performance of oxide polycrystalline Ca3Co4O9 materials, which were synthesized using conventional sintering and spark plasma sintering (SPS) techniques. Results demonstrated that nanoscale platelets (having layered structure with nanoscale spacing) and metallic inclusions provide effective scattering of phonons, resulting in lower thermal conductivity and higher ZT. Thermoelectric measurement direction was found to have a significant effect on the magnitude of ZT because of the strong anisotropy in the transport properties induced by the layered nanostructure. The peak ZT value for the Ca2.85Lu0.15Co3.95Ga0.05O9 specimen measured along both perpendicular and parallel directions with respect to the SPS pressure axis is found be 0.16 at 630 °C and 0.04 at 580 °C, respectively. The peak ZT of 0.25 at 670 °C was observed for the spark plasma-sintered Ca2.95Ag0.05Co4O9 sample. The estimated output power of 2.15 W was obtained for the full size model, showing high-temperature thermoelectric applicability of this nanostructured material without significant oxidation.

Conflict of interest statement

The authors declare no competing financial interest.

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