Probing oxygen vacancy concentration and homogeneity in solid-oxide fuel-cell cathode materials on the subunit-cell...

Area of Science:

• Materials Science
• Solid-State Chemistry
• Nanotechnology

Background:

• Oxygen vacancies critically influence solid-oxide fuel cell (SOFC) operation, affecting magnetic, electronic, and transport properties of oxides.
• Understanding atomistic mechanisms requires precise knowledge of oxygen vacancy distribution at the unit-cell scale.

Purpose of the Study:

• To develop a method for direct mapping of oxygen vacancy concentrations.
• To investigate the relationship between oxygen vacancy distribution and magnetic properties in thin films.

Main Methods:

• Utilized scanning transmission electron microscopy (STEM) for local lattice parameter measurements.
• Applied the concept of chemical expansivity to quantify local stoichiometry variations and lattice expansion.
• Investigated lanthanum strontium cobaltite (LSC) thin films epitaxially grown on substrates with different symmetries.

Main Results:

• Successfully mapped oxygen vacancy concentrations on the subunit-cell level.
• Demonstrated that local stoichiometry variations correlate with measurable lattice expansion.
• Observed distinct magnetic properties in LSC films with varying vacancy content, as revealed by polarized neutron reflectometry.

Conclusions:

• The developed STEM-based approach enables direct quantification of oxygen vacancy distributions.
• Changes in oxygen chemical potential, reflected in vacancy content, are a source of distinct magnetic properties.
• This work opens avenues for tuning vacancy concentrations and gradients through structural modifications for advanced SOFC design.