High thermoelectric performances of Bi–AE–Co–O compounds directionally growth from the melt

Abstract

Bi2AE2Co2Ox (AE = Ca, Sr, and Ba) thermoelectric compounds were grown from the melt by the laser floating zone technique. Microstructural analysis of as-grown samples has shown the formation of well-aligned thermoelectric grains together with a relative high amount of secondary phases. On the other hand, a short (24 h) thermal treatment (810 °C for Sr, 800 °C for Ca, and 750 °C for Ba) under air, raises of thermoelectric phase content through the recombination of the secondary ones. These microstructural modifications led to a large decrease of electrical resistivity, improving the power factor. These results have been compared with samples prepared by the conventional solid state method and with the best values reported in the literature. From these data, it is possible to deduce that the high thermoelectric characteristics obtained in these samples make them very attractive for practical applications.

Keywords

• Thermoelectric
• Oxide
• Directional growth
• Electrical properties