  Among various perovskite proton conducting oxides, Y-doped BaZrO3 perovskite
is a promising material for electrochemical hydrogen devices due to the good
chemical stability and higher proton conductivity at higher operating
temperatures like 500-800 {\deg}C. For the practical application of the
functional BaZrO3 proton conductor in the electrochemical hydrogen devices, its
necessary to understand the isotopic effect of proton conductivity. To
understand the isotopic effect of proton conductivity in the barium zirconates,
in this study, the proton conductivity in the Ar, (Ar + 4% H2), (Ar + 4% D2),
(Ar + H2O), (Ar + D2O), and O2 atmospheres were measured for two different
compositions: BaZr0.9Y0.1O2.95 (BZY), and BaZr0.955Y0.03Co0.015O2.97 (BZYC) in
the temperature range from 500 {\deg}C to 1000 {\deg}C. By comparing the
obtained results, a significant difference in sinterability, conductivity, and
the isotopic effect was observed due to the co-doping of the Co element in the
BaZr1-xYxO3-a proton conductor.
