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KFM: Fachverband Kristalline Festkörper und deren Mikrostruktur

KFM 25: Materials for Storage and Conversion of Energy (joint session MM/KFM)

KFM 25.1: Vortrag

Donnerstag, 21. März 2024, 11:45–12:00, C 264

Unraveling, with ab initio modeling, the connection between electronic structure and dynamical properties of the sodium bismuth titanate. — •Marcin Kryński — Warsaw University of Technology, Warsaw, Poland

Oxide ion solid electrolytes has have drawn significant attention as they find applications in many electrochemical devices like oxygen sensors, oxygen pumps and solid oxide fuel cells [1]. Recently, ceramic compounds based on the perovskite Na0.5Bi0.5TiO3 (NBT) attracted major attention due to its high Curie temperature (~325 °C), large remnant polarization (38 μC*cm-2) and exceptional fast oxygen-ion conduction. Interestingly, NBT shows high ionic conductivity only if the molar ration between Na and Bi atoms is above unity. Below this value, a sudden drop of conductivity is observed. In this project we employ state of the art Density Functional Theory, using Strongly Constrained and Appropriately Normed functional (SCAN) together with Dudarev approach of on-site Coulombic interaction to model oxide ion dynamics of NBT electrolyte. For the first time, we correlate dynamical properties of mobile ions with the composition-dependent presence of small polarons. Furthermore, we look at the charge transfer during dynamical processes, change of the dipole moment as well as the bond strength. All this allows us to form a coherent picture of the diffusion processes being strongly correlated to the electronic structure of the NBT and how those two aspects of this compound are modulated by the composition. This work was supported by the National Science Centre, Poland under grant number UMO-2018/30/M/ST3/00743.

Keywords: ab initio; solid electrolytes; molecular dynamics; polarons; diffusion