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Influence of pressure assisted sintering and reaction sintering on microstructure and thermoelectric properties of bi-doped and undoped calcium cobaltite

Title data

Bresch, Sophie ; Mieller, Bjoern ; Schönauer-Kamin, Daniela ; Moos, Ralf ; Giovanelli, Fabien ; Rabe, Torsten:
Influence of pressure assisted sintering and reaction sintering on microstructure and thermoelectric properties of bi-doped and undoped calcium cobaltite.
In: Journal of Applied Physics. Vol. 126 (2019) Issue 7 . - No. 075102.
ISSN 1089-7550
DOI: https://doi.org/10.1063/1.5107476

Abstract in another language

Calcium cobaltite (Ca3Co4O9) is considered as one of the most promising thermoelectric p-type oxides for energy harvesting applications at temperatures above 500 °C. It is challenging to sinter this material as its stability is limited to 920 °C. To facilitate a practicable and scalable production of Ca3Co4O9 for multilayer generators, a systematic study of the influence of powder calcination, Bi doping, reaction sintering, and pressure-assisted sintering (PAS) on microstructure and thermoelectric properties is presented. Batches of doped, undoped, calcined, and not calcined powders were prepared, tape-cast, and sintered with and without uniaxial pressure at 900 °C. The resulting phase compositions, microstructures, and thermoelectric properties were analyzed. It is shown that the beneficial effect of Bi doping observed on pressureless sintered samples cannot be transferred to PAS. Liquid phase formation induces distortions and abnormal grain growth. Although the Seebeck coefficient is increased to 139 μV/K by Bi doping, the power factor is low due to poor electrical conductivity. The best results were achieved by PAS of calcined powder. The dense and textured microstructure exhibits a high power factor of 326 μW/m K2 at 800 °C but adversely high thermal conductivity in the relevant direction. The figure of merit is higher than 0.08 at 700 °C.

Further data

Item Type: Article in a journal
Refereed: Yes
Institutions of the University: Faculties > Faculty of Engineering Science
Faculties > Faculty of Engineering Science > Chair Functional Materials > Chair Functional Materials - Univ.-Prof. Dr.-Ing. Ralf Moos
Profile Fields > Advanced Fields > Advanced Materials
Research Institutions > Research Centres > Bayreuth Center for Material Science and Engineering - BayMAT
Result of work at the UBT: Yes
DDC Subjects: 600 Technology, medicine, applied sciences > 620 Engineering
Date Deposited: 16 Sep 2019 08:09
Last Modified: 16 Sep 2019 08:09
URI: https://eref.uni-bayreuth.de/id/eprint/52132