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Designing Optimal Perovskite Structure for High Ionic Conduction.

  • Author(s): Gao, Ran
  • Jain, Abhinav CP
  • Pandya, Shishir
  • Dong, Yongqi
  • Yuan, Yakun
  • Zhou, Hua
  • Dedon, Liv R
  • Thoréton, Vincent
  • Saremi, Sahar
  • Xu, Ruijuan
  • Luo, Aileen
  • Chen, Ting
  • Gopalan, Venkatraman
  • Ertekin, Elif
  • Kilner, John
  • Ishihara, Tatsumi
  • Perry, Nicola H
  • Trinkle, Dallas R
  • Martin, Lane W
  • et al.
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 La0.9 Sr0.1 Ga0.95 Mg0.05 O3- 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.

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