Development by Mechanochemistry of La(0.8)Sr(0.2)Ga(0.8)Mg(0.2)O(2.8) Electrolyte for SOFCs

In this work, a mechanochemical process using high-energy milling conditions was employed to synthesize La(0.8)Sr(0.2)Ga(0.8)Mg(0.2)O(3-δ) (LSGM) powders from the corresponding stoichiometric amounts of La(2)O(3), SrO, Ga(2)O(3), and MgO in a short time. After 60 min of milling, the desired final product was obtained without the need for any subsequent annealing treatment. A half solid oxide fuel cell (SOFC) was then developed using LSGM as an electrolyte and La(0.8)Sr(0.2)MnO(3) (LSM) as an electrode, both obtained by mechanochemistry. The characterization by X-ray diffraction of as-prepared powders showed that LSGM and LSM present a perovskite structure and pseudo-cubic symmetry. The thermal and chemical stability between the electrolyte (LSGM) and the electrode (LSM) were analyzed by dynamic X-ray diffraction as a function of temperature. The electrolyte (LSGM) is thermally stable up to 800 and from 900 °C, where the secondary phases of LaSrGa(3)O(7) and LaSrGaO(4) appear. The best sintering temperature for the electrolyte is 1400 °C, since at this temperature, LaSrGaO(4) disappears and the percentage of LaSrGa(3)O(7) is minimized(.) The electrolyte is chemically compatible with the electrode up to 800 °C. The powder sample of the electrolyte (LSGM) at 1400 °C observed by HRTEM indicates that the cubic symmetry Pm-3m is preserved. The SOFC was constructed using the brush-painting technique; the electrode–electrolyte interface characterized by SEM presented good adhesion at 800 °C. The electrical properties of the electrolyte and the half-cell were analyzed by complex impedance spectroscopy. It was found that LSGM is a good candidate to be used as an electrolyte in SOFC, with an Ea value of 0.9 eV, and the LSM sample is a good candidate to be used as cathode.