Ba_1/3CoO₂: An Oxide Thermoelectric Material showing ZT = 0.55 at 600 °C in air

Abstract

  Oxide-based thermoelectric materials that show a high figure of merit are promising because of their good chemical and thermal stability as well as their harmless nature compared to chalcogenide-based state-of-the-art thermoelectric materials. Although several high-ZT thermoelectric oxides (ZT > 1) have been reported thus far, the reliability is low due to a lack of careful observation of their stability at elevated temperatures. Recently, we found a reliable high-ZT thermoelectric oxide, Ba_1/3CoO₂. The crystal structure and electrical resistivity of the Ba_1/3CoO₂ epitaxial films were found to be maintained up to 600 °C. The power factor gradually increased to ~1.2 mW m⁻¹ K⁻² and the thermal conductivity gradually decreased to ~1.9 W m⁻¹ K⁻¹ with increasing temperature up to 600 °C. Consequently, the ZT reached ~0.55 at 600 °C in air, the highest among oxides and comparable to that of p-type PbTe and p-type SiGe.