Reduction in sintering temperature of stable proton conductor BaCe0.35Zr0.5Y0.15O3-δ prepared by sol-gel method and its transport properties

Reducing the sintering temperature of proton conducting solid electrolytes, without deteriorating their conductivities, is a great challenge in the field of solid oxide fuel cells. In this work, BaCe0.35Zr0.5Y0.15O3-delta (BCZY) prepared by sol-gel method exhibited a lowest sintering temperature (i.e., 1100 degrees C, after adding 2 wt.% of ZnO) compared to the other ceramic proton conductors developed so far. Bulk conductivity (sigma(gi)) of the Zn-doped sample is decreased by one order of magnitude due to sever trapping of protons,. whereas its grain boundary conductivity (sigma(gi)) remained similar to that of parent sample. Both the samples exhibited a transition in conductivity above 300 degrees C, due to dissociation of protons from defect pairs such as Y-OH. Dielectric constant (epsilon(r)) of the Zn-doped sample is reduced by two orders of magnitude, which lead to a stronger coulombic interaction between dopants and protons. As a result, the association energy of protons (0.43 eV) in Zn-doped sample is found to be much higher than that of protons in the parent sample (BCZY). Higher electronegativity of Y (compared to that of Ce) is expected to be the reason for the lower association energy of protons in clusters than that in isolated octahedra (0.14 and 0.22 eV, respectively) of BCZY. (C) 2015 Elsevier B.V. All rights reserved.