Influence of Native Defects on the Structural, Electronic, Thermal, and Ionic Transport Properties of YBO3 ± δ Perovskites

TL;DR

This study explores how native defects affect the properties of YBO3±δ perovskites, which are promising materials for solid oxide fuel cells.

Contribution

The paper introduces a combined DFT and MD approach to analyze defect effects in YBO3±δ perovskites for SOFC cathode design.

Findings

YCrO3 and YTiO3 show thermal expansion compatible with YSZ electrolytes.

Native defects reduce bandgaps in most YBO3±δ compounds.

Interstitial oxygen defects enhance ionic conductivity more than oxygen vacancies.

Abstract

The development of cathode materials with high ionic
conductivity
and thermomechanical compatibility remains a major challenge for advancing
solid oxide fuel cells (SOFCs), especially at intermediate operating
temperatures. In this work, we present a comprehensive computational
study of orthorhombic YBO3±δ perovskites, where
B = Sc, Ti, V, Cr, Mn, Fe, Co, or Ni, using a combined approach of
density functional theory (DFT) and molecular dynamics (MD). We evaluate
the influence of native defects, oxygen vacancies (VO),
and interstitial oxygen (Oi) on the structural, electronic,
thermal, and ionic transport properties. Our results show that YCrO3 and YTiO3 exhibit thermal expansion coefficients
(TECs) compatible with widely used electrolytes such as YSZ. Hybrid
DFT calculations reveal that pristine compounds, except for YNiO3, behave as moderate-to-wide bandgap semiconductors, with
native defects generally reducing the bandgap. MD simulations indicate
that pristine (Pr) materials show negligible oxygen ion mobility,
while the presence of defects substantially enhances ionic conductivity.
Oi defects are particularly effective, yielding lower activation
energies and higher self-diffusion coefficients compared to VO. These findings demonstrate the critical role of defect engineering
and highlight the potential of combined MD and DFT methodologies for
the analysis and design of SOFC cathodes.

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