A novel approach for substantially improving the sinterability of BaZr_0.4Ce_0.4Y_0.2O_3-δ electrolyte for fuel cells by impregnating the green membrane with zinc nitrate as a sintering aid

BaZr_0.4Ce_0.4Y_0.2O_3-δ (BZCY4) has been widely considered to be a promising electrolyte material for H⁺-SOFC, but it is restricted to commercial applications due to its poor densification behavior. A dense BZCY4 pellet was obtained by sintering at 1250°C after impregnating the material with a zinc nitrate solution. The dilatometer curves and scanning electron microscopy (SEM) images indicated that the sinterability of the BZCY4 material is effectively improved by impregnating the green membrane with 4wt% Zn. Moreover, EDX mapping indicated that the Ba, Zr and Ce elements were homogeneously distributed in the BZCY4+4wt% Zn sample sintered at 1250°C. In addition, an integrated SOFC employing a BZCY4+4wt% Zn electrolyte was successfully fabricated without any cracks and delamination by impregnating the BZCY4 electrolyte membrane with zinc nitrate as a sintering aid. This single cell with a 25mm thick BZCY4+4wt% Zn electrolyte membrane exhibited power densities as high as 360 and 276mWcm^-2 at 700 and 600°C, respectively. Electrical conductivity measurements demonstrated that the total conductivities of BZCY4+4wt% Zn were 0.46×10^-2Scm^-1, 0.56×10^-2Scm^-1, 0.20×10^-2Scm^-1 and 0.40×10^-2Scm^-1 at 600°C in air, wet air, 10% H₂-Ar and wet 10% H₂-Ar, respectively.