resumo
In this study, hybrid microwave sintering of Ca3Co4O9 thermoelectric materials was implemented for the first time. Thermoelectric properties of samples sintered in different conditions and in conventional electrical furnace, using the same temperatures and dwell times, were assessed and compared. Microwave processing was found to promote densification and grain texturing in Ca3Co4O9 bulk ceramics, leading to a significant increase of the electrical conductivity. Seebeck coefficient and thermal conductivity were essentially unaffected by the microstructural changes. Prolonged exposure to microwave radiation at 800 degrees C led to partial phase decomposition and consequent formation of Ca3Co2O6 and Co3O4 impurities, with minor effect on the charge transport. Still, the significant presence of residual porosity suggests the need for further optimization of powder and microwave processing conditions. (C) 2016 Elsevier Ltd and Techna Group S.r.l. All rights reserved.
palavras-chave
GRAIN-SIZE; CERAMICS; PERFORMANCE; TEXTURE; OXIDES; DENSIFICATION; SUBSTITUTION; ENHANCEMENT; IMPROVEMENT; SCATTERING
categoria
Materials Science
autores
Miyazawa, K; Amaral, F; Kovalevsky, AV; Graca, MPF
nossos autores
Andrei Kavaleuski
Investigador principalProjectos
agradecimentos
This work was supported by the project RECI/CTM-CER/0336/2012 co-financed by FEDER, QREN reference COMPETE: FCOMP-01-0124-FEDER-027465.; A.V. Kovalevsky acknowledges the support from FCT/MEC (IF/00302/2012) Grant and the project CICECO-Aveiro Institute of Materials (ref. UID/CTM/50011/2013) financed by national funds through the FCT/MEC and when applicable co-financed by FEDER under the PT2020 Partnership Agreement.; This work is funded by FEDER funds through the COMPETE 2020 Programme and National Funds through FCT - Portuguese Foundation for Science and Technology under the project UID/CTM/50025/2013