Is La₃Ni₂O_6.5 a Bulk Superconducting Nickelate?

Area of Science:

• Materials Science
• Condensed Matter Physics
• Solid State Chemistry

Background:

• Superconductivity observed in RE NIO₂ thin films and La₃Ni₂O_7-δ at high pressures.
• Nickelates are a promising class of materials for high-temperature superconductivity.

Purpose of the Study:

• To investigate the reduction profile of La₃Ni₂O₇.
• To isolate and characterize intermediate phases in the La₃Ni₂O_7-δ system.
• To understand the relationship between oxygen content and superconductivity in nickelates.

Main Methods:

• Reduction of La₃Ni₂O₇ using a 5% H₂/Ar gas stream.
• Isolation and characterization of the metastable intermediate phase La₃Ni₂O_6.45.
• Testing for superconductivity at ambient and high pressures.

Main Results:

• Successfully reduced La₃Ni₂O₇ to isolate the metastable phase La₃Ni₂O_6.45.
• The isolated phase is based on Ni²⁺.
• La₃Ni₂O_6.45 did not exhibit superconductivity under tested conditions.

Conclusions:

• The reduced nickelate phase La₃Ni₂O_6.45 provides valuable insights into the La₃Ni₂O_7-δ system.
• Further research into nickelates as a function of oxygen content is encouraged.
• Understanding oxygen stoichiometry is crucial for exploring superconductivity in these materials.