High temperature oxidation behavior of cobalt triantimonide thermoelectric material

The oxidation behavior of CoSb3 thermoelectric material in air has been studied from 500 degrees C to 650 degrees C. The present work showed that the growth of oxide scale on CoSb3 material obeyed a parabolic law from 500 degrees C to 600 degrees C, while tremendous weight loss occurred at 650 degrees C owing to the sublimation of Sb2O3. The oxidation activation energy of CoSb3 was estimated to be 37.4 kJ/mol. SEM and XRD results showed that the oxide scale of CoSb3 was the mixture of Sb2O3 and CoSb2O6 when CoSb3 was oxidized below 600 degrees C; whereas the oxide scale consisted of an outer layer of Sb2O3 and an inner layer, which was composed of Sb2O3 and CoSb2O6, when CoSb3 was oxidized at 650 degrees C. Cracks appeared at the scale/CoSb3 interface after a certain oxidation time. The oxidation mechanism of CoSb3 material was discussed. After oxidation at 650 degrees C for 48 h, thermoelectric performance of CoSb3 declined obviously and ZT value decreased from 0.24 to 0.17 at 327 degrees C. (C) 2010 Elsevier B.V. All rights reserved.