Sol-gel synthesis and characterization of Co-doped LSGM perovskites

One of the major requirements for the development and commercialization of low-cost SOFCs is the reduction in the operating temperature. One of the methods to reach this aim is the use of solid electrolytes which exhibit superior ionic conductivity at intermediate temperatures (IT, T < 800 °C). Among these ionic conductors, doped LaGaO₃ materials show high oxide ionic conductivity in the 600-800 °C range. These perovskites are usually prepared by time- and energy-consuming solid state reaction. In this paper, La_0.8 Sr_0.2Ga_0.8Mg_0.2O_2.8 (LSGM) and La_0.8Sr_0.20Ga_0.8Mg_0.2-x Co_xO_3-δ (LSGMC) powders containing different amounts of Co (x = 0.05, 0.085 and 0.10) were prepared from precursors synthesised by citrate sol-gel method. The precursors were calcined at 1000 °C (10 h) and dense high-purity pellets were obtained by pressing (300 MPa) and sintering in air at 1475 °C (5, 10 and 20 h). Sintered pellets of LSGM and LSGMC contained very small amounts (<1%) of SrLaGa₃O₇ and SrLaGaO₄, respectively, as detected by X-ray diffraction (XRD) and by the combined use of scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The data clearly showed the feasibility of sol-gel methods to produce Co-doped LSGM perovskite type oxides.