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The search for low temperature super protonic conductivity

English title The search for low temperature super protonic conductivity
Applicant Lippert Thomas
Number 159198
Funding scheme Project funding (Div. I-III)
Research institution Paul Scherrer Institut
Institution of higher education Paul Scherrer Institute - PSI
Main discipline Other disciplines of Physics
Start/End 01.09.2015 - 31.08.2019
Approved amount 506'828.00
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All Disciplines (2)

Discipline
Other disciplines of Physics
Material Sciences

Keywords (6)

thin films ; interfaces ; first-principles molecular dynamics ; high temperature proton conductors; pulsed laser deposition ; strain

Lay Summary (German)

Lead
Festoxidbrennstoffzellen (solid oxide fuel cells, “SOFCs”) sind hocheffiziente elektrochemische Energieumwandler mit einer potentiell bedeutsamen Rolle für die Entwicklung umweltfreundlicher Eneriequellen. Der Einsatz von alternativen Materialien im Design und in der Fabrikation von SOFCs könnte helfen die momentanen technologischen Beschränkungen zu umgehen, wodurch die schnelle und weitverbreitete Entwicklung dieser Technologie gefördert würde.
Lay summary

Hintergrund

Aktuelle SOFC Technologien verwenden Sauerstoffionenleiter als Elektrolyten. Diese Materialien erfordern typischerweise Betriebstemperaturen weit über 800°C. Tiefere Betriebstemperaturen könnten enorme Vorteile bringen. Allerdings nimmt die Ionenleitfähigkeit von Standartelektrolyten mit sinkender Temperatur rapide ab. Protonenleitende Oxide sind alternative Elektrolytmaterialien welche den SOFC Betrieb bei tiefen Temperaturen erlauben würden, da eine tiefere thermische Energie für eine effiziente Ionenleitung erforderlich ist. Der Mechanismus der Protonenleitung in Oxiden ist allerdings noch nicht komplett verstanden, da es einen grossen Unterschied für die Werte der Aktivierungsenergie aus Theorie und Experiment gibt.

Ziel

Das Ziel dieses theoretischen und experimentellen Forschungsprojektes ist die Fabrikation und Charakterisierung von Modellproben. Diese werden durch Dünnschichttechnologien hergestellt und erlauben die Untersuchung des Effektes von Gitterverzerrungen (Dehnung) auf die Protonenleitfähigkeit. Streckende oder komprimierende  Gitterverzerrungen könnten zu unterschiedlichen Werten für die Migrationsenergie führen durch veränderte interatomare abstände, insbesondere den durchschnittlichen Abstand zwischen Protonen und Dotieratomen.

Bedeutung

Verdehnte Dünnfilme könnten “Superprotonenleitfähigkeit” besitzen dank der durch die Verdehnung gesenkten thermischen Energien für den Ladungstransport. Indem das Dotierungselement und die Verdehnung variiert werden, werden theoretische Simulationen und die Charakterisierung der Mikrostruktur es erlauben die lokale Mikrostrukturumgebung zu identifizieren die schnelle Protonenleitung bei tiefen Temperaturen erlaubt. Die Stabilisation metastabiler protonenleitender Phasen durch Gitterverzerrungen könnten in der Tat eine vielversprechende Forschungsrichtung sein: Die Entwicklung neuer Materialien für einen hoch effizienten Betrieb von SOFCs bei tiefen Temperaturen wird durch protonenleitende Oxide ermöglicht.

Direct link to Lay Summary Last update: 05.08.2015

Responsible applicant and co-applicants

Employees

Publications

Publication
Unsupervised landmark analysis for jump detection in molecular dynamics simulations
Kahle Leonid, Musaelian Albert, Marzari Nicola, Kozinsky Boris (2019), Unsupervised landmark analysis for jump detection in molecular dynamics simulations, in Physical Review Materials, 3(5), 055404-055404.
Real-time monitoring of stress evolution during thin film growth by in situ substrate curvature measurement
Gilardi Elisa, Fluri Aline, Lippert Thomas, Pergolesi Daniele (2019), Real-time monitoring of stress evolution during thin film growth by in situ substrate curvature measurement, in Journal of Applied Physics, 125(8), 082513-082513.
Modeling lithium-ion solid-state electrolytes with a pinball model
Kahle Leonid, Marcolongo Aris, Marzari Nicola (2018), Modeling lithium-ion solid-state electrolytes with a pinball model, in Physical Review Materials, 2(6), 065405-065405.
Stress generation and evolution in oxide heteroepitaxy
Fluri Aline, Pergolesi Daniele, Wokaun Alexander, Lippert Thomas (2018), Stress generation and evolution in oxide heteroepitaxy, in Physical Review B, 97(12), 125412-125412.
In situ stress measurements of metal oxide thin films
Fluri A., Schneider C.W., Pergolesi D. (2018), In situ stress measurements of metal oxide thin films, Elsevier, The Netherlands, 109-132.
Enhanced Proton Conductivity in Y-Doped BaZrO 3 via Strain Engineering
Fluri Aline, Marcolongo Aris, Roddatis Vladimir, Wokaun Alexander, Pergolesi Daniele, Marzari Nicola, Lippert Thomas (2017), Enhanced Proton Conductivity in Y-Doped BaZrO 3 via Strain Engineering, in Advanced Science, 4(12), 1700467-1700467.
Anisotropic Proton and Oxygen Ion Conductivity in Epitaxial Ba 2 In 2 O 5 Thin Films
Fluri Aline, Gilardi Elisa, Karlsson Maths, Roddatis Vladimir, Bettinelli Marco, Castelli Ivano E., Lippert Thomas, Pergolesi Daniele (2017), Anisotropic Proton and Oxygen Ion Conductivity in Epitaxial Ba 2 In 2 O 5 Thin Films, in The Journal of Physical Chemistry C, 121(40), 21797-21805.

Collaboration

Group / person Country
Types of collaboration
Imperial College London, Department of Materials, Prof. J. A. Kilner Great Britain and Northern Ireland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Research Infrastructure
Department for Advanced Materials and Surfaces, Dr. Arthur Braun Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
Institut für Materialphysik, Universität Göttingen, Dr. Vladimir Roddatis Germany (Europe)
- Publication
- Research Infrastructure
ETH Zurich, High Energy Physics, Dr. M. Döbeli Switzerland (Europe)
- Publication
- Research Infrastructure
Electrochemistry Laboratory, Paul Scherrer Institute, Dr. E. Fabbri Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
EPFL Lausanne, Laboratory for Computational Science and Modelling, Prof. M. Ceriotti Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Research Infrastructure
Laboratory for Micro and Nanotechnology, Paul Sherrer Institute, Prof. L. Heyderman Switzerland (Europe)
- Publication
- Research Infrastructure

Associated projects

Number Title Start Funding scheme
172708 Laser interaction with materials for thin film deposition: From fundamentals to functional films 01.08.2017 Project funding (Div. I-III)
170743 An ultra-high resolution scanning electron microscope (SEM) for low-energy imaging and analysis 01.02.2017 R'EQUIP
147190 Influence of Strain and Interfaces on the Properties of Ion Conducting Thin Films for micro-Solid-Oxide-Fuel-Cells 01.05.2013 Project funding (Div. I-III)

Abstract

Proton-conducting oxides have been investigated for decades, especially for their application as electrolyte materials in solid-oxide fuel cells (SOFC). Current SOFC technology is based on oxygen-ion conducting electrolytes, such as Y2O3-stabilized ZrO2, and requires very high operating temperatures (above 800°C) to achieve suitable ionic conductivity. Such high temperatures require stringent and challenging material specifications that up to now have represented the key drawback for this technology. The use of proton-conducting electrolytes, as alternative to oxygen-ion conductors, shows great potential for a significant reduction of the SOFC operating temperature, due to the much smaller activation energies for charge transport. Among proton conducting oxides, Y-doped BaZrO3 (BZY) is a particularly interesting material due to its chemical stability in the fuel-cell operating environments and its good proton conductivity in the grains’ interior. However, difficult sintering and poor conducting properties for its grain-boundary regions have precluded so far the use of BZY in the form of sintered ceramic membranes. Only in 2009 a relatively large average-grain size was achieved for BZY sintered pellets, while in 2010 highly textured grain-boundary-free BZY thin films were grown, showing the largest proton conductivity ever reported for solid electrolytes. These recent results have revitalized the search for materials displaying fast protonic conduction pathways at low temperatures (below 500°C); in addition, very recent literature reports that the lattice strain of proton conductors seems to have a large influence on their conductivity. In particular, it has been observed that compressive strains significantly decrease the conductivity by increasing the activation energy for charge transfer, whereas the opposite effect, i.e. a lower activation energy, had been expected from theoretical considerations, with a tensile strain leading to enhanced conductivity in these lower-temperature range. In this project we will combine state-of-the-art experimental synthesis, thin-film growth and characterization, and first-principles calculations to determine the driving force and the microscopic origin for enhanced conductivities, and engineer optimal materials and microstructures for deployment in lower-temperature SOFCs. In particular, biaxially textured thin films of BZY will be fabricated by pulsed laser deposition, where different strain states of the films can be tuned by suitable insulating buffer layers with the same crystalline symmetry but different lattice parameter. Moreover, the growth of highly ordered epitaxial multi-layered heterostructures comprising a proton conducting and an insulating phase will allow investigating the potential contribution of the interfaces to the total conductivity. The conducting properties of the films will be measured and correlated with the microstructural characteristics and the residual strain state of the depositions. In close feedback with these experimental results, extensive simulations will be performed, to elucidate the mechanisms of proton migration in distorted lattices. These will involve the determination of reaction pathways, activation energies, and diffusion coefficients for the protons using a combination of static transition-state finding methods and first-principles Car-Parrinello molecular dynamics; these latter also able to take into account nuclear quantum effects via non-Markovian Langevin equations of motion. Last, an accelerated-dynamics framework will also be developed to rapidly screen diffusion of light nuclei into the solid matrix. The main target of this investigation is the discovery and identification of low-temperature superprotonic conductivity resulting from strain-engineering. The existence of such a superprotonic state has been strongly suggested as an extrapolation of reported experimental results, but has never been observed to date.
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