Perovskite nickelates as electric-field sensors in salt water

Abstract

Designing materials to function in harsh environments, such as conductive aqueous media, is a problem of broad interest to a range of technologies, including energy, ocean monitoring and biological applications. The main challenge is to retain the stability and morphology of the material as it interacts dynamically with the surrounding environment. Materials that respond to mild stimuli through collective phase transitions and amplify signals could open up new avenues for sensing. Here we present the discovery of an electric-field-driven, water-mediated reversible phase change in a perovskite-structured nickelate, SmNiO. This prototypical strongly correlated quantum material is stable in salt water, does not corrode, and allows exchange of protons with the surrounding water at ambient temperature, with the concurrent modification in electrical resistance and optical properties being capable of multi-modal readout. Besides operating both as thermistors and pH sensors, devices made of this material can detect sub-volt electric potentials in salt water. We postulate that such devices could be used in oceanic environments for monitoring electrical signals from various maritime vessels and sea creatures.

Electron‐Doping Mottronics in Strongly Correlated Perovskite

“…In previous reports, the hydrogenation is (first, i.e., at low H concentrations) expected to trigger a sharp electronic phase transition of the SmNiO 3 from the electron itinerant t e 2g 6 g 1 state to the electron localized t e 2g 6 g 2 state [1,2,4,5] to open a wider bandgap (the extra electrons fill into the p-d hybridized orbits with strong p character since perovskite nickelates carry strong covalency; whether this is a negative or positive transfer insulator [11,12] does not change the characteristic proposed here). Now, what happens if the SmNiO 3 is doped with higher concentration of hydrogen?…”

“…[7] As a typical example, the hydrogenation of the perovskite-structured SmNiO 3 d-band electron-correlated system results in an abrupt electronic transition of the e g orbital from the electron-itinerant Ni 3+ t e www.advmat.de www.advancedsciencenews.com state. [1][2][3][4][5] This was reported to sharply increase the electronic resistivity by several orders of magnitude, [1,2,4,5] while hydrogenated SmNiO 3 is expected to be proton conductive. [4] Although a considerable understanding of the transport properties has been established for single crystalline H x SmNiO 3 (Ni 2+ t e 2g 6 g 2 ) and other proton-doped correlated materials, it remains entirely unclear how doping-controlled transport properties behave in the presence of interfaces and microstructure.…”

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Hydrogen (proton) induced switchable multiphase transformations in d-band electron-correlated materials recently opened a new field for exploring merging multifunctional proton-gated electronic devices, [1] synaptic plasticity, [2,3] sensors, [4] and novel energy conversion devices. [5] Compared to other dopant elements, hydrogen is small in radius and has high ionic mobility.

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“…[5] Compared to other dopant elements, hydrogen is small in radius and has high ionic mobility. [1,[4][5][6] Therefore, the proton distribution is highly adjustable via external electric fields, and the respective tuning of the physical properties of materials is feasible. This is, in particular, the case for the hydrogen-induced sharp transitions in electron orbital configurations and the magnetoelectric/spintronic states for d-band electron-correlated materials, such as SmNiO 3 , [1][2][3][4][5] SrCoO 3−δ , [6] and VO 2 .…”

“…[1,[4][5][6] Therefore, the proton distribution is highly adjustable via external electric fields, and the respective tuning of the physical properties of materials is feasible. This is, in particular, the case for the hydrogen-induced sharp transitions in electron orbital configurations and the magnetoelectric/spintronic states for d-band electron-correlated materials, such as SmNiO 3 , [1][2][3][4][5] SrCoO 3−δ , [6] and VO 2 . [7] As a typical example, the hydrogenation of the perovskite-structured SmNiO 3 d-band electron-correlated system results in an abrupt electronic transition of the e g orbital from the electron-itinerant Ni 3+ t e 2g 6 g 1 state to the electron-localized Ni 2+ t e 2g 6 g 2 The discovery of hydrogen-induced electron localization and highly insulating states in d-band electron correlated perovskites has opened a new paradigm for exploring novel electronic phases of condensed matters and applications in emerging field-controlled electronic devices (e.g., Mottronics).…”