Preparation of YSZ electrolyte coatings for SOFC by electron beam physical vapor deposition combined with a sol infiltration treatment

Yttria-stabilized zirconia (YSZ) electrolyte coatings for planar solid oxide fuel cell were prepared on porous NiO-YSZ substrates with a high deposition rate of 1 μm/min by electron beam physical vapor deposition (EB-PVD) technique. A sol infiltration treatment was conducted to improve the gas tightness of EB-PVD coating through infiltrating the coating sample in a zirconium and yttrium sol bath followed by a heat treatment. The parameters of heat treatment were determined according to thermogravimetric analysis and X-ray diffraction result of precursor powders obtained from the sol. After infiltration treatment, the sol had penetrated into the coating and the impregnation depth reached up to 3 μm. At the same time, the intergranular pores and gaps of as-deposited coating had been stuffed by the decomposed products from the sol. The coefficient of gas permeability dropped from 6.78 × 10^-5 cm⁴ N^-1 s^-1 for as-deposited coating to 6.54 × 10^-6 cm⁴ N^-1 s^-1 for the coating after eight times of infiltration treatment. Then unit cells were assembled and the open circuit voltage increased from 0.820 V for unit cell with as-deposited electrolyte coating to 1.036 V for cell with electrolyte coating after eight times of infiltration treatment. For unit cell with electrolyte coating after eight times of sol infiltration, the maximum output powder density of 150 mW/cm² was obtained at 800 °C.