Quasi-In Situ 4D-STEM Mapping of Exsolution Driven Parent Matrix Restructuring in Sr₂FeMoO_6-δ

Area of Science:

• Materials Science
• Electrochemistry
• Nanotechnology

Background:

• Double-perovskites are promising for solid oxide cells (SOCs) due to in situ exsolution of catalytic particles.
• Previous studies focused on isolated particles, neglecting realistic electrode architectures and matrix effects.

Purpose of the Study:

• Investigate the impact of exsolution on a realistic Sr2FeMoO6-δ (SFM) electrode.
• Understand the structural transformations within the host matrix during exsolution.
• Differentiate exsolution effects from electron-beam-induced artifacts.

Main Methods:

• Quasi-in situ S/TEM approach on a bulk SOC electrode.
• Plasma-FIB lamella extraction for identical-location characterization.
• EDS, 4D-STEM, iDPC, and radial Fourier analysis (RFA) before and after reduction.

Main Results:

• Surface exsolution is linked to significant crystallographic reorganization in the SFM matrix.
• Observed domain shrinkage and localized phase gradients along grain facets.
• Realistic electrode geometry shows higher exsolution density than isolated particles.

Conclusions:

• Exsolution in double-perovskites involves substantial matrix modification, not just particle formation.
• Studying realistic electrode architectures is essential for understanding SOC material behavior.
• This quasi-in situ method provides critical insights into the exsolution process in SOC electrodes.