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The proton conductivities of BaZr 1-x Y x O 3-δ (BYZ) pellet samples with x = 0.06 to 0.4 were studied. The analysis showed that the optimum doping concentrations for bulk and grain boundary proton conductivity were at x = 0.1 and 0.2, respectively. The activation energies of the proton conductivity in bulk were between 0.42-0.47 eV, and 0.68-0.82 eV in the grain boundary. To gain more insight into the ionic conductivity mechanism in BYZ, quantum simulations complemented with kinetic Monte Carlo technique was employed to simulate proton and oxide ion migration processes in 8-30 at.% BYZ supercell. The results reveal the effect of defect associations on the proton and oxide ion migration and confirm the domination of proton conductivity on the overall ionic conductivity at all doping concentrations throughout the temperature range of this study. The optimum doping concentrations for the proton and oxide ion conductivities were extracted and compared with the experimental results.

Y-doped BaZrO3 (BYZ) pellets and thin films were fabricated by solid state reaction and co-sputtering technique, respectively. The conductivity of BYZ samples was measured using electrochemical impedance spectroscopy technique in the atmospheres of air, dry H2, and wet H2. As Y content increases from 6 at.% to 20 at.%, the increase of bulk and grain boundary conductivity is observed, while at 30 at.%, the conductivity starts to degrade. The activation energies in bulk and grain boundary are in the range of 0.28-0.40 eV and 0.91-0.96 eV, respectively. BYZ pellets have the highest proton conductivity at the Y doping concentration of 20 at.%. Furthermore, the dense and uniform BYZ thin films of 130-140 nm in thickness were obtained by co-sputtering technique. The conductivities of the BYZ thin films are about 10^3 - 10^4 times those of the pellet samples. The reason of the observed high conductivity is still under further investigation.

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