Fabrication and tests of anode supported IT-SOFCs based on doped-lanthanum Gallate electrolyte film prepared by electrophoretic deposition

The aim of this work of thesis is the fabrication and test of SOFCs based on an anode supported doped Lanthanum Gallate film. Dense electrolyte films made of La0.8Sr0.2Ga0.8Mg0.2O3-δ (LSGM 2020), La0.83Sr0.17Ga0.83Mg0.17O3-δ (LSGM 1717), La0.8Sr0.2Ga0.8Mg0.115Co0.085O3-δ (LSGMC) were fabricated by electrophoretic deposition (EPD). LSGM 2020 powders were supplied by Praxair, LSGM 1717 were supplied by the Department of Industrial Engineering, University of Bergamo, while pure LSGMC powders were prepared in our laboratories by sol-gel synthesis. Single-phase LSGMC powders were obtained at a calcination temperature of 1450°C, using PVA and a molar ratio between the hydroxylic groups and the total cations of 3:1 Electrophoretic deposition was achieved employing a solution of acetone + I2 + H2O as powder suspending medium. A systematic study using platinum substrate were performed on the effect of water and iodine content, of the applied voltage, and of powder loading on the EPD rate. This allowed us to identify the suitable set of EPD process parameters that were used to deposit LSGM 2020, LSGM 1717 and LSGMC films on green tape-cast composite anodes, made of lanthanum-doped ceria (La0.4Ce0.6O2-x, LDC), polyvinylidene difluoride (PVDF), and carbon powders. The bilayer of EPD deposited films and green anode support were co-fired in air at 1490 °C to obtain dense and crack-free thick LSGM 2020, LSGM 1717 and LSGMC films on porous LDC. Line profile analysis performed by energy dispersive X-ray spectroscopy (EDS) did not reveal any ion interdiffusion across the LSGM/LDC or LSGMC/LDC interfaces. The chemical and structural compatibility of LSGM with LDC was also checked by heat treating a mixture of the two powders (1:1 weight ratio) using the same thermal cycle as that of the LDC/LSGM bi-layer co-firing at 1490 °C. The prototype SOFCs were prepared first depositing by slurry coating an La0.8Sr0.2Fe0.5Co0.5 cathode on the electrolyte film and firing at 1100°C, then the porous LDC layer was infiltrated with Ni2+ salts and calcined at 900°C, to obtain a NiO/LDC composite anode. A maximum power density output of over 0.750 W/cm2 and 0.250 W/cm2 at 700°C and 600°C, respectively, were obtained using H2 as fuel and air as oxidant.