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Pressure assisted sintering of tape casted calcium cobaltite


Bresch, Sophie ; Mieller, Bjoern ; Moos, Ralf ; Rabe, Torsten:
Pressure assisted sintering of tape casted calcium cobaltite.
Veranstaltung: 15th International Conference of the European Ceramic Society , July 9-13, 2017 , Budapest, Hungary.
(Veranstaltungsbeitrag: Kongress/Konferenz/Symposium/Tagung , Vortrag )


Thermoelectric materials can convert waste heat directly into electrical power by utilizing the Seebeck effect. Calcium cobaltite Ca3Co4O9 is a promising p-type oxide thermoelectric material for applications between 600 °C and 900 °C in air. The properties and morphology of Ca3Co4O9 are strongly anisotropic because of its crystal structure of alternating layers of CoO2 and Ca2CoO3. The electrical conductivity is for example 13.5 times higher in a/bdirection than in c-direction. 1 By aligning the plate-like grains, the anisotropic properties can be assigned to the component. Hot-pressing of tablets is a well-known technology for grain alignment of Ca3Co4O9 and increases the thermoelectric properties in a/b-direction remarkably. It also increases the relative density. However, hot-pressing of tablets is limited by the tablet size. An interesting alternative for larger components is the pressure assisted sintering of panels from tape casted layers. Tape casting already leads to a grain alignment during green body forming. By combining tape casting and pressure assisted sintering 50kN maximum force) of Ca3Co4O9, high densities and high thermoelectric properties can be reached for large components up to 200 mm edge length. Ca3Co4O9 was successfully tape casted with the doctor blade technique (binder: polyvinyl butyral, organic solvent). Several layers of tape were stacked and laminated to 5 cm × 5 cm panels. These panels were sintered with different applied pressures in a LTCC sintering press with combined in-situ shrinkage measurement. Pressure-less sintered panels have a 2.5 times higher electrical conductivity at room temperature than test bars with randomly orientated particles. By applying a uniaxial pressure of 10 MPa during sintering, the electrical conductivity increases by the factor of 6 compared to the pressure-less sintered panels. About 40% linear shrinkage are reached in pressing direction. The Seebeck coefficient (S25°C=146 μV/K)and the electrical conductivity (σ25°C=15100 S/m) are in good agreement with the values published in literature for hot-pressed tablets.

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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 > Forschungszentren > Bayreuther Materialzentrum - BayMAT
Fakultäten > Fakultät für Ingenieurwissenschaften > Lehrstuhl Funktionsmaterialien
Profilfelder > Advanced Fields
Forschungseinrichtungen > Forschungszentren
Titel an der UBT entstanden: Ja
Themengebiete aus DDC: 600 Technik, Medizin, angewandte Wissenschaften > 620 Ingenieurwissenschaften
Eingestellt am: 24 Jul 2017 08:14
Letzte Änderung: 24 Jul 2017 08:15
URI: https://eref.uni-bayreuth.de/id/eprint/38739