Influence of pressure and dwell time on pressure-assisted sintering of calcium cobaltite

Titelangaben

Bresch, Sophie ; Mieller, Bjoern ; Schönauer-Kamin, Daniela ; Moos, Ralf ; Reimann, Timmy ; Giovannelli, Fabien ; Rabe, Torsten:
Influence of pressure and dwell time on pressure-assisted sintering of calcium cobaltite.
In: Journal of the American Ceramic Society. Bd. 104 (2021) Heft 2 . - S. 917-927.
ISSN 1551-2916
DOI: https://doi.org/10.1111/jace.17541

Volltext

Link zum Volltext (externe URL):

Abstract

Calcium cobaltite Ca3Co4O9, abbreviated Co349, is a promising thermoelectric material for high‐temperature applications in air. Its anisotropic properties can be assigned to polycrystalline parts by texturing. Tape casting and pressure‐assisted sintering (PAS) are a possible future way for a cost‐effective mass‐production of thermoelectric generators. This study examines the influence of pressure and dwell time during PAS at 900°C of tape‐cast Co349 on texture and thermoelectric properties. Tape casting aligns lentoid Co349. PAS results in a textured Co349 microstructure with the thermoelectrically favorable ab‐direction perpendicular to the pressing direction. By pressure variation during sintering, the microstructure of Co349 can be tailored either toward a maximum figure of merit as required for energy harvesting or toward a maximum power factor as required for energy harvesting. Moderate pressure of 2.5 MPa results in 25% porosity and a textured microstructure with a figure of merit of 0.13 at 700°C, two times higher than the dry‐pressed, pressureless‐sintered reference. A pressure of 7.5 MPa leads to 94% density and a high power factor of 326 µW/mK2 at 800°C, which is 11 times higher than the dry‐pressed reference (30 MPa) from the same powder.