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Helmholtz-Institut Münster (HI MS), IEK-12, Forschungszentrum Jülich

Research Topic:

Melilites of composition La_1+x Sr_1-x Ga₃O_7+0.5 consist of alternating layers of La/Sr cations and anionic GaO4 unit which form pentagonal rings. Oxygen interstitials (x > 1) and oxygen vacancies (x < 0) are accommodated by local relaxation and high mobility is enabled by structural flexibility. The site energies of the defects and their migration barriers depend on the local cation environment. In my research, I investigate the structure based on density functional theory (DFT) calculations and Monte Carlo simulations to predict and optimize the ionic conductivity. An energy model based on the DFT results is created and applied in Monte Carlo simulations of the ionic conductivity, thus, linking the microscopic ionic motion to the macroscopic ionic conductivity.

 

 

NASICON materials are promising candidates for solid state electrolytes. Especially the composition Na_1+x+y Zr_2-y Sc _y Si _x P_3-x O₁₂ shows high ionic conductivity. Therefore, I investigate monoclinic and rhombohedral structure regarding stability and configurational energy. Site energies as well as migration pathways of sodium ions are studied by means of DFT calculations and molecular dynamics simulations.

 

Publications:

J. Schuett, T.K. Schultze, S. Grieshammer, Oxygen Ion Migration and Conductivity in LaSrGa3O7 Melilites from First Principles, Chem. Mater., 2020, 32, 11, 4442-4450.

Conference contributions:

KMC Simulations in Oxygen Ion Conducting Melilites, Judith Schütt, Steffen Grieshammer, 2019, 118th Bunsentagung, Jena, Germany (poster)