Migration Kinetics of Surface Ions in Oxygen‐Deficient Perovskite During Topotactic Transitions

Abstract

Oxygen diffusivity and surface exchange kinetics underpin the ionic, electronic, and catalytic functionalities of complex multivalent oxides. Towards understanding and controlling the kinetics of oxygen transport in emerging technologies, it is highly desirable to reveal the underlying lattice dynamics and ionic activities related to oxygen variation. In this study, the evolution of oxygen content is identified in real‐time during the progress of a topotactic phase transition in La0.7Sr0.3MnO3‐δ epitaxial thin films, both at the surface and throughout the bulk. Using polarized neutron reflectometry, a quantitative depth profile of the oxygen content gradient is achieved, which, alongside atomic‐resolution scanning transmission electron microscopy, uniquely reveals the formation of a novel structural phase near the surface. Surface‐sensitive X‐ray spectroscopies further confirm a significant change of the electronic structure accompanying the transition. The anisotropic features of this novel phase enable a distinct oxygen diffusion pathway in contrast to conventional observation of oxygen motion at moderate temperatures. The results provide insights furthering the design of solid oxygen ion conductors within the framework of topotactic phase transitions.

Enhancing magneto-ionic effects in cobalt oxide films by electrolyte engineering

“…Finally, Ca(BF 4 ) 2 was chosen since it is typically dissolved in alkyl carbonates like PC in calcium ion batteries. 24 Our work reveals that improvements in oxygen ion motion [25][26][27] in cobalt oxide are accomplished by adding these salts to PC. Specifically, the fastest magneto-ionic rate is observed when using PC + 2.5 Â 10 À4 M KI electrolyte, which is 35 times larger than the rate observed for bare PC electrolyte under À1.5 V.…”

Effect of capping layers on the near-surface region of SrVO3 films

“…This broader component is attributed to other chemical states of Sr that can form as a result of Sr excess near the surface of the film. Such Sr enrichment has been observed in many perovskite oxides 51 and can result from segregation of Sr-rich phases to the surface; 52 these could be SrO precipitates, as was shown, for example, in strontium titanate-based perovskites [53][54][55][56][57] and in SVO. 43 In other cases, the formation of surface Sr-rich Ruddlesden-Popper (RP) phases 58 has been reported in different perovskite oxides 19,59 and in SVO films, where structures of Sr 3 V 2 O 8 60,61 were identified.…”

Research Progress on the Application of Topological Phase Transition Materials in the Field of Memristor and Neuromorphic Computing

“…Common topological phase transition metal oxide (TMO) materials include ironbased materials (e.g., SrFeO x (SFO) [18]), cobalt-based materials (e.g., LaCoO x [19,20], SrCoO x (SCO) [21,22], and La 1-x Sr x CoO x [23,24]), and manganese-based materials (e.g., La x Sr 1-x MnO x [25,26], and SrMnO x [27,28]). Typically, controllable arrangements of oxygen vacancies in the materials can be achieved through methods such as annealing in hightemperature vacuum (or oxygen) atmospheres [29], ion liquid gating [30], and electron beam irradiation [31].…”