Extended Data Figure 6 : Stability tests for HSrCoO2.5 and SrCoO3−δ.

From: Electric-field control of tri-state phase transformation with a selective dual-ion switch

Extended Data Figure 6

a, b, XRD θ scans for thin films of a, HSrCoO2.5 and b, SrCoO3−δ grown on LSAT(001) substrate, as a function of time after ILG-induced formation followed by storage at room temperature (25 °C) and in a 1 atm air environment with relative humidity of 40%. The diffraction peaks of HSrCoO2.5 remain nearly unchanged even after 11 days, suggesting that this phase is a robust equilibrium state. Meanwhile, for SrCoO3−δ, a negligible shift in the peak position (of about 0.1°) was observed after 11 days, suggesting that this phase still holds the structure of perovskite, with the occurrence of a tiny amount of oxygen vacancies. (Interestingly, with a similar hydrogenated system (HVO2), the structure gradually returns to that of the dehydrogenated VO2 phase after 8 days at room temperature, owing to the slow release of hydrogen18.) c, d, In situ temperature-dependent XRD θ scans for thin films of c, HSrCoO2.5 and d, SrCoO3−δ around the LSAT(002) peak, annealed in a 1 atm oxygen gas (oxidizing) or a 1 atm argon gas (reducing) environment, respectively. The crystalline structures of both phases remain stable up to 175–195 °C, above which they change into the brownmillerite SrCoO2.5. The SrCoO2.5 phase is a thermodynamic equilibrium state, which is stable at temperatures up to 350 °C in mild oxidizing or reducing environments, owing to the robustness of the Co3+ valence state.