Electrode properties of Ln[sub 2]NiO[sub 4+δ] (Ln=La, Nd, Pr)

The perovskite-type materials, , were prepared by a modified Pechini method and their electrochemical properties investigated using ac impedance and dc polarization methods from 300 to under different oxygen partial pressures. Schouler methodology based on the frequency relaxation has been used to assign different electrochemical processes. A transfer process related to oxygen ions moving between the electrolyte and electrode interface was found in the mixed ionic and electronic conducting electrode/electrolyte system. The study shows that the compound exhibits promising electrode properties due to its high chemical stability and low polarization resistance. The oxygen diffusion process is the rate-limiting step at low oxygen partial pressure, whereas the charge-transfer process becomes more important at higher oxygen partial pressure.