Laser processing of calcium manganite-based materials for thermoelectric generators

abstract

Thermoelectric oxides are emerging as a promising alternative to traditional thermoelectric materials due to their high-temperature stability, low cost, and abundance. In this work, we investigate the Laser Floating Zone (LFZ) technique for processing Ca1-xNdxMnO3 with different Nd concentrations (x = 0, 0.05, 0.1, 0.2), grown at various pulling rates (25 and 100 mm h- 1). The impact of the sample's composition and processing conditions on the microstructure and thermoelectric performance was analysed. X-ray diffraction results confirmed the formation of the major perovskite-type structure, favoured by the slower pulling rate. Scanning electron microscopy/energy dispersive spectroscopy showed high-density, nonporous structure of the samples, with uniform Nd distribution. Electrical conductivity and Seebeck coefficient measurements, conducted in air from 500 K to 1200 K, demonstrated an expected correlated trend between these properties, with electrical conductivity increasing and the Seebeck coefficient decreasing upon doping. Similar measurements were made for the thermal conductivity, from 500 to 1100 K, which showed a decrease with increasing Nd content, an expected behaviour. The highest power factor (168.6 mu W m- 1K- 2) and the highest figure of merit (0.14) were achieved for Ca0.95Nd0.05MnO3 grown at a 100 mm h- 1 at 1173 K. These values are within those reported for conventional solid-state reaction samples. A prototype unileg thermoelectric module based on Ca0.95Nd0.05MnO3 was fabricated and tested, yielding a maximum power output of 298 mu W under a thermal gradient of 483 K. These findings demonstrate that LFZ growth is a viable method for producing efficient oxide thermoelectrics for intermediate-to high-temperature energy harvesting applications.

keywords

TRANSPORT-PROPERTIES; CAMNO3 PEROVSKITES; ENERGY-CONVERSION; OXIDE; TEMPERATURE; PERFORMANCE; FABRICATION; IMPROVEMENT; HEAT

subject category

Materials Science

authors

Batista, FQ; Lopes, DJ; Dura, OJ; Mikhalev, SM; Constantinescudd, G; Costa, FM; Kovalevsky, AV; Ferreira, NM

Groups

G3 - Electrochemical Materials, Interfaces and Coatings

Projects

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)

Collaboratory for Emerging Technologies, CoLab (EMERGING TECHNOLOGIES)

Thermoelectric oxide composites: design through controlled interactions (TEOsINTE)

acknowledgements

The authors acknowledge the support of the project i3N (LA/P/0037/2020, UID-B/50025/2020 and UID-P/50025/2020) and CICECO-Aveiro Institute of Materials, UIDB/50011/2020 (DOI 10.54499/UIDB/50011/2020) , UIDP/50011/2020 (DOI 10.54499/UIDP/50011/2020) & LA/P/0006/2020 (DOI 10.54499/LA/P/0006/2020) , financed by national funds through the FCT/MCTES (PIDDAC) . Diogo Lopes ac-knowledges the PhD scholarship by FCT (grant https://doi.org/10. 54499/2020.06454.BD) . This work is funded by national funds through FCT - Fundacao para a Ciencia e a Tecnologia, I.P., under the project/contract UID 00481 - Centre for Mechanical Technology and Automation. G.C. acknowledges the support of the TEOsINTE project (Grant Agreement ID: 101003375) , funded under the H2020-EU.4. Programmes (Funding Scheme: MSCA-IF-EF-ST - Standard EF) . This work is also funded by National Funds (OE) , through FCT - Fundacao para a Ciencia e a Tecnologia, I.P., in the scope of the framework contract foreseen in the numbers 4, 5 and 6 of article 23, of the Decree-Law 57/2016, of August 29, changed by Law 57/2017, of July 19.