Abstract: The mixed conductor La_0.8Sr_0.2(Ga_0.8Mg_0.2)_1-○xFe_○xO_3-○δ (LSGMF) samples were prepared by solid-state reaction. The performances were researched by scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). The influence of doped Fe content on the thermal weight loss process and kinetics of LSGMF was investigated， and the apparent activation energy for the process was calculated with the Coats-Redfem method. The results showed that the thermal weight loss process of LSGMF can be divided into three stages. In the low-temperature region， the thermal weight loss is mainly caused by desorption of H₂O and CO₂ adsorbed on the surface of LSGMF， and the apparent activation energy is 0.154~0.227eV. In the medium and high temperature region， it mainly attributes to some of the lattice oxygen atoms becoming O₂， and the apparent activation energy is 0.280~0.350eV. When the doped Fe content x is 0.9， the peak value of weight loss rate is the smallest (0.0137/s)， and the apparent activation energy E_○2+3 is the highest. It indicates that the weight loss rate is the slowest and the stability of LSGMF is the highest.

Key words: mixed conductor, LSGMF, thermal analysis, kinetics, Coats-Redfem