How space-charge behaviour at grain boundaries in electroceramic oxides is modified by two restricted equilibria

Area of Science:

• Materials Science
• Solid-State Chemistry
• Surface Science

Background:

• Space-charge potential at grain boundaries is crucial for understanding interfacial defect chemistry in oxides.
• Experimental methods like impedance spectroscopy and Scanning Probe Microscopy (SPM) measure this potential but at different temperatures.
• Unifying these measurements is essential for a comprehensive description.

Purpose of the Study:

• To investigate the discrepancies in space-charge potential measurements at grain boundaries in oxides across different temperature ranges.
• To reconcile data from elevated-temperature electrical methods and room-temperature imaging techniques.
• To understand the impact of restricted equilibria on experimental results.

Main Methods:

• Continuum simulations were employed to calculate space-charge potential (Φ₀) in acceptor-doped SrTiO₃.
• Simulations considered restricted equilibrium effects on acceptor-dopant profiles and oxygen-vacancy concentrations.
• Comparison of simulated results with experimental data from electrical methods and imaging techniques.

Main Results:

• Non-trivial differences were observed between space-charge potentials obtained from electrical and imaging methods.
• These differences are attributed to varying measurement temperatures and are exacerbated by restricted equilibria.
• Grain boundary widths derived from elemental profiles differ fundamentally from those obtained via electrical impedance spectroscopy.

Conclusions:

• Direct comparison of space-charge potential data from different temperature regimes requires careful consideration of measurement conditions.
• Restricted equilibria significantly influence the interpretation of experimental data, leading to apparent discrepancies.
• The concept of grain boundary width is method-dependent, with electrical and compositional definitions yielding different results.