Abstract
Although BiCuSeO has become of interest as a high-performance thermoelectric material, it is reported to be unstable in air above 548 K. However, about details of time dependence of thermoelectric ptoperties for BiCuSeO at high temperatures in air have not yet been determined. In this study, the time dependence of the thermoelectric properties for BiCuSeO in tair was investigated. The relationship between the temperature difference AT and the thermoelectromotive force E in air was measured using the large temperature difference method. Variations in p and a over time at 550 K were determined using the DC four terminals method and small temperature difference method. From the result of large temperature difference method, the thermoelectromotive force at 723 K was actually less than the value obtained at 673 K. The results of thermoelectric properties measurements over time showed that p abruptly increased between 135 and 182 min then decreased from 182 to 210 min, while the a exhibited a opposite tendency for p. The result of XPS and XRD suggested that BiCuSeO was pyrolyzed upon heating at 550 K for 6 h in air. In contrast, the risult of TG analysis demonstrated that BiCuSeO was stable below 800 K under an inert gas flow, thus the pyrolysis observed at 550 K was the result of reaction with atmospheric oxygen.
