Electrical conductivity relaxation of polycrystalline PrBaCo2O5 + δ thin films

Thin films of PrBaCo2O5 + δ (PBCO) were prepared on SrTiO3 substrates by spray pyrolysis. Electrical conductivity relaxation was performed to measure the surface exchange coefficient, kchem, from 650 to 850 K, in the pO2 range 0.05–100% at a total pressure of 1 atm. The measured values fell in the range from 3.4 × 10− 9 cm/s to 8.6 × 10− 7 cm/s, with an activation energy of 1.30 eV. These values are significantly lower, and the activation energy higher, than previous reports. This discrepancy, and the discrepancies between prior reports in the literature, are attributed to surface composition. The film samples used in this study are shown to be enriched in (Pr + Ba) when compared with the bulk composition.