Controlling Yttria-stabilized zirconia/gadolinia-doped ceria interdiffusion layer in the solid oxide fuel cell electrolyte via flash sintering method

Yttria-stabilized zirconia (YSZ)/gadolinia-doped ceria (GDC) dual-layered electrolytes have promising potential in solid oxide fuel cells (SOFCs) to prevent the destroying reaction of the lanthanum-containing cathode with ZrO2 base electrolyte and improve ionic conduction by blocking ceria based electrolyte electronic conduction. Preparation of the YSZ/GDC electrolyte is problematic due to the formation of a high electrical resistance interdiffusion layer at high sintering temperatures. Flash sintering (FS) is a promising method for sintering materials at low temperatures and short times. Herein, FS is used to limit the interdiffusion layer. The green dual-layered electrolytes are prepared by YSZ tape casting and coating the GDC layer on the binder-burnout YSZ layer by wet spraying method. The effect of electric field strength (E) and current density (J) on the interdiffusion layer thickness is investigated by the response surface methodology (RSM). The interdiffusion layer thickness in the electrolytes is determined using elemental distribution curves across the YSZ/GDC interface using a scanning electron microscope (SEM) equipped with an energy-dispersive X-ray spectrometer (EDS). Response surface of interdiffusion layer thickness shows that the electric field strength is more effective in the interdiffusion layer propagation than the current density. By controlling the electric field strength and current density, the interdiffusion layer is limited and descends from 45 µm for E = 300 V/cm and J = 200 mA/mm2 to 1 µm for E = 80 V/cm and J = 200 mA/mm2 as the optimum FS parameters. Electrochemical impedance spectroscopy (EIS) results show improved electrical conduction in optimal flash sintered electrolytes compared with conventionally sintered ones due to the thinner interdiffusion layer. The SOFC single cell is made using the optimal flash sintered YSZ/GDC electrolyte, which shows a performance of 0.3 W/cm2 at 800 °C, about 15% higher than the SOFC single cell made by conventionally sintered YSZ/GDC electrolyte.