Fig. 9. Relative concentrations of Fe²⁺ as a function of the reduction temperature (left panel) after treatment for 1 h each, and (right panel) the reduction time at 673 K. The small schemes serve as model perovskite surfaces to explain the respective oxidation state changes. Blue-dashed line: limited growth model. Orange-dashed line: linear temperature-dependence of Fe(ii). Red-dashed line: Avrami-type fit model for the isothermal increase of the Fe(ii) at 673 K reduction temperature.