Preparation and properties of Zn doped BaZr_0.7Pr_0.1 Y_0.2O_3-δ proton-conducting used for solid electrolytes oxide fuel cells

BaZr_0.7Pr_0.1 Y_0.2O_3-δ (BZPY) and BaZr_0.7Pr_0.1 Y_0.16Zn_0.04O_3-δ (BZPYZn) proton-conducting solid oxide fuel cells (SOFC) electrolytes were synthesized by a citrate-nitrate combustion method. The influence of Zn doped on the sintering, coefficient of thermal expansion (TEC) and electrical properties of sample were investigated. The phase and microstructure of the sintered samples were characterized by X-ray diffraction and scanning electron microscope, respectively. The results showed that BZPYZn exhibits a single perovskite structure after the calcination at 1100°C for 5 h. With increasing of sintering temperatures (from 1300°C to 1400°C), the grain size of BZPYZn ceramic sample increases, and porosity decreases. The high relative density of 97.3% is obtained for the BZPYZn sample sintered at 1350°C for 5 h. The BZPYZn sample exhibit a high ionic conductivity (10^-3 to 10^-2 S/cm) at 500-800°C. The average TEC of the BZPYZn is 9.2 × 10^-6/K from room temperature up to 1000°C, which fits well with those of electrode materials (e.g. Ni). It is indicated that BZPYZn is a promising candidate as a stable and easily sintered electrolyte for intermediate-temperature SOFC.