Designing Optimal Perovskite Structure for High Ionic Conduction

Abstract

Solid‐oxide fuel/electrolyzer cells are limited by a dearth of electrolyte materials with low ohmic loss and an incomplete understanding of the structure–property relationships that would enable the rational design of better materials. Here, using epitaxial thin‐film growth, synchrotron radiation, impedance spectroscopy, and density‐functional theory, the impact of structural parameters (i.e., unit‐cell volume and octahedral rotations) on ionic conductivity is delineated in La0.9Sr0.1Ga0.95Mg0.05O3–δ. As compared to the zero‐strain state, compressive strain reduces the unit‐cell volume while maintaining large octahedral rotations, resulting in a strong reduction of ionic conductivity, while tensile strain increases the unit‐cell volume while quenching octahedral rotations, resulting in a negligible effect on the ionic conductivity. Calculations reveal that larger unit‐cell volumes and octahedral rotations decrease migration barriers and create low‐energy migration pathways, respectively. The desired combination of large unit‐cell volume and octahedral rotations is normally contraindicated, but through the creation of superlattice structures both expanded unit‐cell volume and large octahedral rotations are experimentally realized, which result in an enhancement of the ionic conductivity. All told, the potential to tune ionic conductivity with structure alone by a factor of ≈2.5 at around 600 °C is observed, which sheds new light on the rational design of ion‐conducting perovskite electrolytes.

Defects in complex oxide thin films for electronics and energy applications: challenges and opportunities

“…9e). 220 This provides a new pathway for the rational design of ion-conducting perovskite electrolytes via controlling BO 6 octahedral rotations.…”

Correlating Surface Crystal Orientation and Gas Kinetics in Perovskite Oxide Electrodes

“…For instance, epitaxial strain has been found to influence both the surfacegas kinetics and ionic conductivity of perovskites, where the B-O-B bond strength and angle have been identified as important factors affecting both oxygen exchange and mobility. [7][8][9][10][11] Other studies have focused on the relative importance of both surface-termination and sub-surface chemistry of (001)-oriented perovskite surfaces in dictating electrochemical reaction rates. [12][13][14][15] Perovskite electrodes with different exposed crystallographic orientations have also been reported to have different electrochemical reaction rates.…”

A Database of Ionic Transport Characteristics for Over 29 000 Inorganic Compounds

“…Thus, it is imperative to find a precise and efficient computational method to establish a database that can integrate the data as well as unify their retrievable formats. The First-principles calculation is the preferred method to evaluate transport channel and migration energy of systems, [18][19][20] however, much more time-consuming density functional theory (DFT)-based methods are obviously not an effective solution for screening solid electrolytes. Efforts aimed at developing a method combining geometric configuration analysis based on Voronoi decomposition and bond valence site energy (BVSE) calculations to identify the interstitial positions and transport channels have been undertaken in our previous work.…”