Oxygen exchange kinetics and nonstoichiometry of pristine La0.6Sr0.4CoO3−δ thin films unaltered by degradation

Abstract

La_0.6Sr_0.4CoO_3−δ thin films grown on YSZ single crystals were investigated directly in the stage of deposition by means of in situ impedance spectroscopy during pulsed laser deposition (IPLD). This method allows the observation of dense thin films unaltered by degradation and provides information about the oxygen exchange kinetics as well as the defect chemistry of pristine LSC thin films. These measurements revealed remarkably low surface resistance values (1.3 Ω cm² at 600 °C and 0.04 mbar O₂) compared to films measured outside the PLD chamber (∼20 Ω cm² at 600 °C and 0.04 mbar O₂). Also the activation energy of the surface exchange resistance at 0.04 mbar p(O₂) is significantly lower than at ambient conditions (∼1 eV vs. ∼1.3 eV) and degradation happens considerably slower. Furthermore, the grain size of the LSC thin film does not affect its initial surface resistance directly after deposition. The chemical capacitance of LSC thin films was linked to the concentration of oxygen vacancies and shows that LSC thin films exhibit lower oxygen vacancy concentrations than the corresponding bulk material.