Tuning the Thermoelectric Performance of CaMnO3-Based Ceramics by Controlled Exsolution and Microstructuring
| Autor: | Nikola Kanas, Benjamin A. D. Williamson, Frank Steinbach, Richard Hinterding, Mari-Ann Einarsrud, Sverre M. Selbach, Armin Feldhoff, Kjell Wiik |
|---|---|
| Jazyk: | angličtina |
| Rok vydání: | 2022 |
| Předmět: |
oxide thermoelectrics
Dewey Decimal Classification::500 | Naturwissenschaften::540 | Chemie composite CaMnO 3-δ electrical conductivity ddc:540 Materials Chemistry Electrochemistry Energy Engineering and Power Technology Chemical Engineering (miscellaneous) thermal conductivity Electrical and Electronic Engineering heterostructuring |
| Zdroj: | ACS Applied Energy Materials 5 (2022), Nr. 10 ACS Applied Energy Materials |
| DOI: | 10.15488/13994 |
| Popis: | The thermoelectric properties of CaMnO3−δ/CaMn2O4 composites were tuned via microstructuring and compositional adjustment. Single-phase rock-salt-structured CaO–MnO materials with Ca:Mn ratios larger than unity were produced in reducing atmosphere and subsequently densified by spark plasma sintering in vacuum. Annealing in air at 1340 °C between 1 and 24 h activated redox-driven exsolution and resulted in a variation in microstructure and CaMnO3−δ materials with 10 and 15 vol % CaMn2O4, respectively. The nature of the CaMnO3−δ/CaMn2O4 grain boundary was analyzed by transmission electron microscopy on short- and long-term annealed samples, and a sharp interface with no secondary phase formation was indicated in both cases. This was further complemented by density functional theory (DFT) calculations, which confirmed that the CaMnO3−δ indeed is a line compound. DFT calculations predict segregation of oxygen vacancies from the bulk of CaMnO3−δ to the interface between CaMnO3−δ and CaMn2O4, resulting in an enhanced electronic conductivity of the CaMnO3−δ phase. Samples with 15 vol % CaMn2O4 annealed for 24 h reached the highest electrical conductivity of 73 S·cm–1 at 900 °C. The lowest thermal conductivity was obtained for composites with 10 vol % CaMn2O4 annealed for 8 h, reaching 0.56 W·m–1K–1 at 700 °C. However, the highest thermoelectric figure-of-merit, zT, was obtained for samples with 15 vol % CaMn2O4 reaching 0.11 at temperatures between 800 and 900 °C, due to the enhanced power factor above 700 °C. This work represents an approach to boost the thermoelectric performance of CaMnO3−δ based composites. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|