Facile Pathways to Synthesize Perovskite Strontium Cobalt Oxides

Abstract

Topotactic phase transition obtains extensive research attention due to its associated rich physics as well as a promising potential application. Particularly, the oxygen incorporation into brownmillerite oxides leads to the structural transition into perovskite oxides with distinct magnetic and electronic properties. Using brownmillerite SrCoO 2.5 (BM-SCO), two novel pathways are revealed to achieve the topotactic phase transition into its corresponding perovskite SrCoO 3 (P-SCO). It is demonstrated that by using aqueous alkali as the electrolyte during gating, the negative biased voltage triggers a rapid transition into P-SCO, which is attributed to the presence of strong oxidizing hydroxyl radicals. While surprisingly, it is observed that the acid solution with rich protons can also trigger an unexpected phase transition from BM-SCO into P-SCO in a much faster manner. With density functional theory calculations, this transition is elucidated as a proton-assist ionic disproportionation, in which the Co ions are simultaneously oxidized and reduced, while the latter one is dissolved within the solution. These case studies not only achieve a deep understanding of the structural phase transition in BM-SCO but also shed new light on the topotactic phase transition of complex oxides.

Strain-Induced Uphill Hydrogen Distribution in Perovskite Oxide Films

“…Therefore, the uphill distribution does not necessarily depend on the method to introduce hydrogen, which can be maintained in the absence of an electric field. This is also the first successful attempt of hydrogenation to perovskite oxides via metal-alkaline treatment, which avoids the use of electric gating or H 2 gas at high temperatures. , Note that metal-acid processing can also inject hydrogen into NNO via proton–electron codoping, but acid will inevitably corrode the surface of oxides. , Since most perovskite oxides are stable in alkaline conditions, the metal-alkaline protocol provides opportunities for exploring new hydrogenated phases of perovskite oxides.…”

Highly efficient and fast modulation of magnetic coupling interaction in the SrCoO2.5/La0.7Ca0.3MnO3 heterostructure

“…single B-SCO films into HAc solution for 2 seconds, the active oxygen species would be produced, which is attributed to the reaction between the proton in the acidic solutions and the surface of the B-SCO layer. 17,18 Then, the active oxygen species migrate to the inner of the B-SCO layer to fill possible oxygen vacancies, inducing the transformation to a perovskite structure. The changes in the magnetic and structural properties before and after the treatment with acid confirm the structural transition (see ESI, † Fig.…”

“…Very recently, an acid solution with rich protons has been reported to trigger the rapid phase transition within seconds, 17,18 which is attributed to the migration of the active oxygen species into the materials assisted by protons. The brownmillerite SrCoO 2.5 (B-SCO) with an oxygen-vacancies channel exhibits an oxygen-dependent topotactic phase transition.…”

“…This enables B-SCO to be transformed to the perovskite SrCoO 3Àx (P-SCO, 0 p x p 0.25) accompanied by a change from antiferromagnetic insulator to ferromagnetic metal. 14,17,19,20 In this work, the B-SCO/LCMO bilayer was fabricated on a SrTiO 3 substrate. The exchange bias effect is observed because of the interaction of the antiferromagnetic layer with the ferromagnetic layer.…”

Realizing Metastable Cobaltite Perovskite via Proton-Induced Filling of Oxygen Vacancy Channels

“…53 Note: During the revision of the manuscript, we are aware of a relevant work that realized topotactic phase transition via acidic solution processing. 54 Differently, we mainly focus on the oxide−proton interaction and provide direct observation of active oxygen release in our work.…”