Fig. 4: Quantitative analysis of the electroforming process to determine the dynamic characteristics associated with oxygen-vacancy migration in BCFO.
From: Ultrafast collective oxygen-vacancy flow in Ca-doped BiFeO3
a The real-time monitoring current acquired at a bias of 25 V while varying the temperature from 250 °C to 390 °C. A green-dashed guideline indicates the transition time from the as-grown phase (T0) to the intermediate phase (T). The black line represents the time to fulfill the T to Mc transition. b Transition time and saturation current for the T to Mc transition. c The position of the boundary between the T and Mc phases is plotted as a function of elapsed time. The error bar is defined as the full-width-at-half-maximum of differential color change. The green lines represent the fitting curves that match the experimental results. d Simplified model assuming that the applied bias is only across the left region of the front. e The fitting parameters, i.e., ionic mobility and time offset are determined by fitting the data in c to the model addressed in the main text. Diffusivity can be derived from mobility. f Instantaneous velocity of the front propagation of the Mc phase obtained by differentiation of the experimental data in c. g Arrhenius plot for the ionic conductivities
