The determining factor for interstitial oxygen formation in Ruddlesden-Popper type La2NiO4-based oxides

Area of Science:

• Materials Science
• Solid-State Chemistry
• Surface Science

Background:

• La2NiO4-based oxides are promising materials for various applications.
• Understanding interstitial oxygen formation is crucial for optimizing their properties.
• Existing mechanisms for interstitial oxygen formation require further clarification.

Purpose of the Study:

• To elucidate the interstitial oxygen formation mechanism in La2NiO4-based oxides.
• To investigate the role of ligand oxygen in the formation process.
• To identify key factors controlling interstitial oxygen formation.

Main Methods:

• Soft X-ray absorption spectroscopy was employed.
• O K-edge and Ni L-edge spectra were analyzed.
• Changes in spectral features were correlated with interstitial oxygen concentration.

Main Results:

• An increase in interstitial oxygen concentration correlated with a rise in the O K-edge pre-edge peak.
• Ni L-edge spectra remained largely unchanged, indicating minimal direct involvement of Ni.
• Spectral changes suggest ligand oxygen plays a significant role via electronic charge carrier exchange.

Conclusions:

• Interstitial oxygen formation is primarily governed by the electronic charge carrier exchange involving ligand oxygen.
• The equilibrium unoccupied partial density of states (pDOS) of ligand oxygen determines interstitial oxygen formation.
• Modulating the electronic structure of La2NiO4-based oxides is essential for controlling interstitial oxygen formation capability.