Y, Gd, and Pr tri-doped perovskite-type proton conducting electrolytes with improved sinterability and chemical stability

Abstract Tri-doping of barium cerium zirconate with rare earth elements praseodymium (Pr), gadolinium (Gd), and yttrium (Y) as dopants was followed to mitigate sinterability issues while improving the chemical stability and proton conductivity. The effect of the concentration of dopants was focused by varying the concentration of Pr and Y, and keeping the concentration of Gd, Zr and Ce constant in the ‘B’ site of perovskite structure (BaCe0.5Zr0.2Y0.1Gd0.1Pr0.1O3-δ and BaCe0.5Zr0.2Y0.15Gd0.1Pr0.05O3-δ). The sintering behavior, morphology, and grain boundary growth of the proton conducting electrolyte materials were systematically studied. The BaCe0.5Zr0.2Y0.1Gd0.1Pr0.1O3-δ electrolyte shows high relative density and large grain size (20 µm) after sintering at a relatively low temperature (1350 °C). X-ray diffraction (XRD) and Raman spectroscopic analysis demonstrated the excellent chemical stability of the Pr-doped proton-conducting electrolyte in a moisture-rich argon atmosphere for over 200 h at 600 °C. The conductivity measurements revealed that the tri-doped electrolyte materials have high conductivity values, 3.11, and 15.09 mS cm-1 in wet Argon at 400, and 600 °C, respectively. The obtained values of conductivity of the electrolytes were found to be stable over 240 h in 50% wet argon atmosphere at 600 °C demonstrating the higher chemical stability of the electrolyte.