Improvement of thermoelectric properties of Ca.sub.0.9Gd.sub.0.1MnO.sub.3 by powder engineering through K.sub.2CO.sub.3 additions

• Published in: Journal of materials science Vol. 54; no. 4; pp. 3252 - 3261
• Main Authors: Ferreira, N. M, Ferro, M. C, Sarabando, A. R, Ribeiro, A, Davarpanah, A, Amaral, V, Madre, M. A
• Format: Journal Article
• Language: English
• Published: Springer 01.02.2019
• ISSN: 0022-2461; 1573-4803
• DOI: 10.1007/s10853-018-3058-x

Oxide materials based on calcium manganite show clear prospects as thermoelectrics, provided by their stability at high temperatures and inherent flexibility in tuning the relevant electrical and thermal transport properties. Donor-doped CaMnO.sub.3 is an n-type semiconductor with a perovskite structure and relatively high thermoelectric performance. In this work, the precursor powders have been modified through potassium carbonate additions to produce Ca.sub.0.9Gd.sub.0.1MnO.sub.3 pellets without the usual delamination problems occurring during the compaction process. In order to demonstrate the relevant effects, several samples with different amounts of potassium carbonate (0-15 wt%) have been prepared. The results showed that potassium additions significantly facilitate the compaction procedure, while also improving the thermoelectric performances. The results also highlight the importance of porosity control for improving ZT, by decreasing the thermal conductivity without reduction of the electrical performance. The highest ZT values were observed for the samples processed at 15 wt% of potassium carbonate addition, exhibiting an improvement at least 30% at 800 °C when compared to the pure samples.