In situ oxygen surface exchange coefficient measurements on lanthanum strontium ferrite thin films via the curvature relaxation method

•Oxygen surface exchange coefficients k˜'s were measured via the curvature relaxation (κR) method.•Sputtered La0.6Sr0.4FeO3−δk˜'s agreed with literature bulk sample k˜'s.•Sputtered La0.6Sr0.4FeO3−δk˜'s were different than literature thin film k˜'s.•The in-situ, electrode-free (κR) method measures k˜ and film stress simultaneously.•The (κR) method can measure the k˜ of any mechano-chemically active thin film.

Here, an in situ   curvature relaxation (κR) method was used to measure chemical oxygen surface exchange coefficients (k˜'s) under well-characterized stress, temperature, and oxygen partial pressure conditions. These k˜'s were measured by analyzing the transient curvature of yttria stabilized zirconia supported La0.6Sr0.4FeO3 − δ thin films reacting to oxygen partial pressure step changes. The sputtered thin film k˜'s measured here were consistent with extrapolated bulk sample k˜'s, but larger than those reported for pulsed laser deposited thin films. This is the first time that the curvature response of a system has been used to characterize thin film oxygen surface exchange kinetics. The simultaneous measurement of film stress and k˜ provided by the curvature relaxation method may help explain the large k˜ discrepancies observed in the literature.