High-temperature oxidation kinetics of nanostructured thermoelectric skutterudite CoSb3 under different environments

Abstract

Skutterudite CoSb₃ is an n-type thermoelectric material used in thermoelectric generators (TEGs) to recover and convert heat from various sources into electricity. For TEGs, such as CoSb₃, thermal stability is crucial, especially when exposed to high temperatures and varying environments. To synthesize high-purity nanostructured CoSb₃, an optimized solvothermal method was developed with detailed investigation of the influence of stoichiometry, solvent choice, and reaction duration on the formation mechanism, as revealed by Powder X-ray diffraction (PXRD). The thermal degradation behavior of the synthesized CoSb₃ was systematically analyzed in air and nitrogen atmosphere. The oxidation products were identified using PXRD, the microstructural changes and morphological evolution during oxidation were examined using SEM (Scanning Electron Microscopy) and TEM (Transmission Electron Microscopy). Oxidation kinetics were determined using a nonlinear integral isoconversional method. This study revealed the formation of multiple oxides of Co and Sb at higher temperature and interconversion of these oxides after secondary reaction and follows a different kinetics in air and N₂ atmosphere due to the changes in the degradation mechanism.