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Schönauer-Kamin, Daniela ; Stephan, Rebekka ; Paulus, Daniel ; Moos, Ralf:
Thermoelectric and Morphological Properties of Powder-Aerosol Deposited Textured Calcium Cobaltite Ca₃Co₄O₉ Films.
2024
Veranstaltung: 40th International Conference on Thermoelectrics - ICT/ECT2024
, June 30 - July 4, 2024
, Krakow, Poland.
(Veranstaltungsbeitrag: Kongress/Konferenz/Symposium/Tagung
,
Vortrag
)
Abstract
Thermoelectric oxides are widely discussed as cost-effective, unlimitedly available, and long-term stable materials especially with a high oxidation stability. The thermoelectric oxide calcium cobaltite Ca3Co4O9 (CCO) is a promising p-type conducting material for conversion of waste heat into electrical energy by a thermoelectric generator (TEG). First studies of CCO laminates, prepared from mixed-oxide powders, tape-casted and then pressure-assisted sintered show a textured CCO microstructure with the thermoelectrically favorable ab-direction perpendicular to the pressing direction. The thermoelectric properties show a maximum figure of merit and power factor PF as required for energy harvesting. Flexible and planar TEGs in film or multilayer technology are getting more important. The powder aerosol deposition (PAD) method to obtain dense ceramic films directly from the synthesized starting powders without a subsequent high-temperature step is emerging recently for thermeoelctric materials, too. In this work, CCO powders, prepared by a mixed-oxide route, are processed by PAD to ceramic films at room temperature. The PF of the CCO films (film thickness 10 - 30 μm) are characterized in synthetic air atmosphere from room temperature to 900 °C. Additionally, the morphology of the CCO-PAD films is investigated by SEM and XRD to characterize texture and anisotropy of the resulting films after the thermal treatment. It is typical for PAD films that a moderate thermal annealing of the films results in improved electrical properties due to the release of microstrain. Additionally, crystallite growth effects will occur during thermal treatment and can also contribute to changes in the power factor. The results show that thermally annealed CCO films provide a dense textured microstructure with a preferred crystallite orientation in the favorable ab-direction. During thermal annealing, the microstrain releases and the particles grow. The PF increases strongly and surpasses the known-properties of CCO-bulk materials. The PF approaches single cystal values, especially due to a strong improvement of the electrical conductivity in-plane (ab- direction) during the thermal treatment, whereby the Seebeck coefficent remains almost unaffected. The relationship between the thermoelectric properties and the film morphology as a function of the thermal annealing parameters will be shown. The evaluated high PF confirms the great potential of CCO-PAD films for the p-leg of planar TEGs.
Weitere Angaben
| Publikationsform: | Veranstaltungsbeitrag (Vortrag) |
|---|---|
| Begutachteter Beitrag: | Ja |
| Institutionen der Universität: | Fakultäten > Fakultät für Ingenieurwissenschaften Fakultäten > Fakultät für Ingenieurwissenschaften > Lehrstuhl Funktionsmaterialien > Lehrstuhl Funktionsmaterialien - Univ.-Prof. Dr.-Ing. Ralf Moos Profilfelder > Advanced Fields > Neue Materialien Forschungseinrichtungen > Zentrale wissenschaftliche Einrichtungen > Bayreuther Materialzentrum - BayMAT |
| Titel an der UBT entstanden: | Ja |
| Themengebiete aus DDC: | 600 Technik, Medizin, angewandte Wissenschaften > 620 Ingenieurwissenschaften |
| Eingestellt am: | 08 Aug 2024 11:41 |
| Letzte Änderung: | 08 Aug 2024 11:41 |
| URI: | https://eref.uni-bayreuth.de/id/eprint/90165 |