Ag₅Pd₂O₄, a New Subvalent Silver Oxide, Obtained from Ag₂PdO₂ via a High-pressure Synthesis

Area of Science:

• Materials Science
• Solid-State Chemistry
• Inorganic Chemistry

Background:

• Subvalent silver oxides, with silver in a 0 to +1 oxidation state, are challenging to synthesize systematically.
• Previous discoveries relied on serendipity due to a lack of understanding in synthesis and bonding.
• A need exists for purposeful methods to explore these unique materials.

Purpose of the Study:

• To present a novel, purposeful approach for synthesizing multinary subvalent silver oxides.
• To investigate the formation and structure of a new subvalent silver compound under high pressure.
• To explore the electronic properties and potential applications of the synthesized material.

Main Methods:

• High-pressure techniques involving hydrostatic pressure of approximately 30 GPa.
• Laser heating at 1500 K applied to the precursor material Ag2PdO2.
• In situ single-crystal X-ray diffraction for crystal structure determination.
• Electronic structure calculations to confirm oxidation states and electronic properties.

Main Results:

• Successful synthesis of subvalent silver palladium oxide, Ag5Pd2O4, alongside PdO.
• Determination of the crystal structure of Ag5Pd2O4, featuring layered cationic silver aggregates and anionic oxopalladate units.
• Electronic structure calculations confirmed the subvalent nature of silver, a vanished band gap, and increased electron density on silver atoms.

Conclusions:

• A purposeful high-pressure synthesis route for multinary subvalent silver oxides has been established.
• The novel compound Ag5Pd2O4 exhibits unique structural and electronic characteristics.
• The interplay between subvalent silver and transition metal cations in Ag5Pd2O4 suggests potential for developing materials with rich magneto-electronic functionalities.