Regulating the metal-insulator transition of REBaCo 2 O 5+ δ combining RE-substitution and anion control

Key Points

• The research aims to understand how changes in rare-earth (RE) substitution and anion control can influence metal-insulator transitions (MITs) in REBaCo2O5+δ.
• Analyzed the impact of RE ionic radius on CoO6 octahedral distortion.
• Examined how oxygen vacancies modulate Co valence state.
• Investigated the relationship between structural symmetry and MIT occurrence.
• Demonstrated a clear link between RE ionic radius and octahedral distortion effect on MIT.
• Found that optimal oxygen vacancy levels lead to lower structural symmetry necessary for MIT.
• Showed that δ values approaching 0.5 are critical for inducing abrupt MITs.