Preparation and characterisation of supported La0.83Sr 0.17Ga0.83Mg0.17O2.83 thick films for application in IT-SOFCs

In order to perform the electrical characterisation of the electrolyte thick (about 100 μm) films, layers of La0.83Sr 0.17Ga0.83Mg0.17O2.83 (LSGM) were sandwiched between a pellet and a film of La0.83Sr 0.2MnO3 (LSM). Both LSGM and LSM coatings were deposited on the porous LSM sintered substrate one after the other by screen printing technique; the proper thermal treatment followed each deposition process. The average grain size of the LSGM films was about 3 μm. The electrolyte and the electrode powders were prepared following solgel and solid-state route, respectively. Electrical characterisation was carried out by the complex impedance spectroscopy (IS) technique in air and in the temperature range 300-800°C. The results were compared with those previously obtained on pellets, in the same operating condition. The film and the pellet show about the same value of the bulk conductivity, while total electrical resistivity of the former is two orders of magnitude higher than that of the latter. The large difference between the two resistivity values is due to the high grain boundary contribution of the film, which may be accounted for by either the smaller average grain size of the LSGM layer compared to those of the pellets (on average, about 25 μm) or for the Mn cations diffusion into the electrolyte material at the LSGM/LSM interface; experimental evidences would suggest the latter.