Isn't the space-charge potential in ceria-based solid electrolytes largely overestimated?

Area of Science:

• Solid-state chemistry
• Materials science
• Electrochemistry

Background:

• Polycrystalline solid electrolytes exhibit lower ionic conductivity than single crystals.
• Grain boundaries create potential barriers due to charge carrier depletion, impeding ion transport.
• Accurate barrier height estimation is crucial for understanding ionic conduction mechanisms.

Purpose of the Study:

• To investigate the accuracy of resistivity ratio methods for determining grain boundary barrier heights.
• To challenge the assumption that space charge is the sole cause of current obstruction in ceria-based solid electrolytes.

Main Methods:

• Analysis of ionic conductivity in polycrystalline ceria solid solutions.
• Comparison of barrier height estimations using resistivity ratios versus other potential factors.
• Evaluation of space charge effects at grain boundaries.

Main Results:

• The resistivity ratio method significantly overestimates grain boundary barrier heights in ceria solid solutions.
• Even in diluted solutions, the overestimation is considerable.
• Space charge effects alone do not fully explain the observed current obstruction.

Conclusions:

• The resistivity ratio is an unreliable metric for accurately quantifying grain boundary barrier heights.
• Alternative or additional mechanisms beyond space charge must be considered to explain current obstruction in ceria-based solid electrolytes.
• Rethinking grain boundary characterization is essential for developing advanced solid electrolytes.