Significant enhancement of the thermoelectric performance in Ca3Co4O9 thermoelectric materials through combined strontium substitution and hot-pressing process
This work explores the possibilities for a further enhancement of the thermoelectric properties of Ca3Co4O9 by Sr-doping combined with hot-pressing. Modified hot-pressing process resulted in highly-textured and dense ceramics. Sr-doping significantly improves electrical properties, resulting in extr...
| Autores: | , , , , , , , , , , |
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| Tipo de recurso: | artículo |
| Estado: | Versión aceptada para publicación |
| Fecha de publicación: | 2019 |
| País: | España |
| Institución: | Consejo Superior de Investigaciones Científicas (CSIC) |
| Repositorio: | DIGITAL.CSIC. Repositorio Institucional del CSIC |
| OAI Identifier: | oai:digital.csic.es:10261/181636 |
| Acceso en línea: | http://hdl.handle.net/10261/181636 |
| Access Level: | acceso abierto |
| Palabra clave: | Ceramics Oxides Hot-pressing Texture Electrical properties |
| Sumario: | This work explores the possibilities for a further enhancement of the thermoelectric properties of Ca3Co4O9 by Sr-doping combined with hot-pressing. Modified hot-pressing process resulted in highly-textured and dense ceramics. Sr-doping significantly improves electrical properties, resulting in extremely large power factor (1.2 mW/K2m at 800 °C) due to simultaneous electrical resistivity decrease and Seebeck coefficient increase. The main effect on cumulative electrical performance is provided by the Seebeck coefficient, reaching 270μV/K at 800 °C. XPS revealed relatively high average cobalt oxidation state at room temperature (+3.3), compared to materials produced by conventional sintering. The results of combined XPS and Auger electron spectroscopy emphasize the importance of high densification in Ca3Co4O9-based ceramics for preventing phase decomposition and interaction with CO2 and moisture. Still, despite the exceptional electrical performance, the calculated figure-of-merit (estimated as 0.29 at 800 °C) is around the best reported in the literature due to a high thermal conductivity (4.4 W/K m at room temperature). |
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