abstract
This work presents a comparative analysis of pure and Ag-intercalated Ca3Co4O9 multilayer thermoelectric materials prepared through the hot-uniaxial pressing technique. Samples were prepared by attrition milling and hot-pressed at 900 degrees C and 55 MPa for 1 h. They were mirror polished, and some of them were stacked with and without intermediate Ag foil and hot-pressed again at 900 degrees C and 52 MPa for 1 h. Out-of-plane XRD showed that samples are nearly single-phase, and the grains are well oriented with their ab-plane perpendicular to the pressure direction. Microstructural studies confirmed perfect welding in the multilayer samples accompanied by the formation of a very thin layer containing larger grains and notable Ag diffusion close to the Ca3Co4O9/Ag interface. Three-point bending stresses have been increased in Ag-containing samples, while microhardness has been raised in all samples hot-pressed twice. Thermoelectric measurements showed a decrease of thermal gradient along the Ag-containing sample, together with a drastic decrease of electrical resistivity when compared to the Ag-free ones. However, the Ag-layers have promoted a drastic decrease in the Seebeck coefficient, reflected in a notable reduction of the power factor of Ca3Co4O9/Ag multilayer composites. Nevertheless, these results show that it is possible to use these materials to reduce Joule heating and increasing the compatibility with the welding compounds when building thermoelectric modules. Moreover, they open a new research line searching for larger S compounds to be intercalated with Ag foils.
keywords
MECHANICAL-PROPERTIES; PHASE-EQUILIBRIA; ENHANCEMENT; PERFORMANCE; CA3CO4O9+DELTA; GENERATORS; COBALTITE; OXIDE; POWER; CA
subject category
Materials Science
authors
Amirkhizi, P; Madre, MA; Wang, H; Li, Z; Torres, MA; Sotelo, A; Hedayati, M; Kovalevsky, AV; Rasekh, S
our authors
Andrei Kavaleuski
Principal Researcher
Parisa Amir Khizi
PhD Student
Shahed Rasekh
Junior ResearcherProjects
CICECO - Aveiro Institute of Materials (UIDB/50011/2020)
CICECO - Aveiro Institute of Materials (UIDP/50011/2020)
Associated Laboratory CICECO-Aveiro Institute of Materials (LA/P/0006/2020)
acknowledgements
The authors wish to thank the Gobierno de Aragon (Grupo de Investigacion T54_23R) and Universidad de Zaragoza (UZ2022-IAR-09) for financial support. Sh. Rasekh acknowledges the support of the Research Employment Contract FCT-CEECIND/02608/2017. This work was also developed within the scope of the PhD project of P. Amirkhizi (grant 2020.08051.BD funded by FCT) and the project CICECO-Aveiro Institute of Materials, UIDB/50011/2020, UIDP/50011/2020 & LA/P/0006/2020, financed by national funds through the FCT/MCTES (PID-DAC) . Authors would like to acknowledge the use of Servicio General de Apoyo a la Investigacion-SAI, Universidad de Zaragoza.