Orbital hybridization and polarization resistance of Cu-doped PrBaCo2O5+δ

The effects of Cu doping of PrBaCo2O5+δ layered perovskite oxide (PBCCux, x = 0, 0.1, 0.2, and 0.5) were investigated in terms of local atomic structure change and polarization resistance. As the copper doping concentration in PBCCux increased, the peaks in the XRD patterns of the samples shifted to lower angle which indicates lattice expansion by oxygen vacancy formation and larger ion doping. O K-edge XANES was used to determine the change in orbital hybridization with Cu doping, and it was confirmed that the O2− species decreased and the monoxidic species increased with the addition of Cu resulting in covalency increase. As the Cu content increased, the Co–O first shell intensity decreased in the Co K-edge EXAFS spectra because of the formation of oxygen vacancies by Cu doping. The impedance at 600 °C decreased by approximately 73% from 0.91 Ω cm2 (PBCO) to 0.23 Ω cm2 (PBCCu0.5) by the synergetic effect of oxygen vacancy formation and the increase in covalency.