Modulating the Electronic Structures of Co-Based Spinel Compounds via Rare Earth Tetrad Effect

Area of Science:

• Materials Science
• Inorganic Chemistry
• Solid State Physics

Background:

• Rare earths (RE) are vital strategic resources for material modification.
• The electronic structure regulation mechanism of RE elements is not fully understood, hindering their optimal use.
• The RE tetrad effect categorizes RE elements based on 4f electron filling.

Purpose of the Study:

• To develop a systematic strategy for regulating the electronic structure of Co-based spinel compounds using the RE tetrad effect.
• To investigate the impact of the RE tetrad effect on the electronic structure of Co3O4 and Co3S4.
• To establish a relationship between RE electronic structure regulation and oxygen-containing species adsorption.

Main Methods:

• Systematic doping of Co-based spinel compounds (Co3O4, Co3S4) with various rare earth elements.
• Analysis of electronic structure modifications, including Co spin and valence states.
• Investigation of RE-induced strain effects (XY-plane and Z-direction).
• Exploration of orbital hybridization (4f-5d-6s-5p) for valence state regulation.

Main Results:

• The RE tetrad effect regulates Co spin states at 1/4 and 3/4 positions and Co valence states at the 1/2 position.
• RE-induced strain in the XY-plane and Z-direction influences the spin states of Co3O4 and Co3S4, respectively.
• Dual-periodic regulation of Co valence state is achieved via orbital hybridization when 4f orbitals are nearly half-filled.
• A clear relationship between the RE tetrad effect's electronic structure regulation and oxygen-containing species adsorption was established.

Conclusions:

• The RE tetrad effect provides a viable strategy for precisely controlling the electronic structure of Co-based spinel compounds.
• This understanding facilitates the accurate selection and efficient utilization of RE elements in advanced material design.
• The study presents a design strategy for RE composite systems based on the tetrad effect.