Topotactic Reduction-Induced Stabilization of β-La₂Mo₂O_8.68 Phase: Structure, Static Oxygen Disorder, and Electrical...

Area of Science:

• Solid-state chemistry
• Materials science
• Oxide ion conductors

Background:

• La₂Mo₂O₉ is a known oxide ion conductor with a phase transition at 580 °C.
• The high-temperature cubic phase exhibits high ionic conductivity.
• Understanding La₂Mo₂O₉ under reducing conditions is crucial for its applications.

Purpose of the Study:

• To stabilize a novel cubic phase of La₂Mo₂O₉ at ambient temperature.
• To investigate the structural and conductive properties of this novel phase.
• To explore potential applications in areas requiring mixed conduction.

Main Methods:

• Topotactic reduction of α-La₂Mo₂O₉ using calcium hydride (CaH₂).
• X-ray diffraction for structural analysis.
• Conductivity measurements to determine transport properties.

Main Results:

• A novel cubic phase of La₂Mo₂O₉ was successfully stabilized at ambient temperature.
• This phase contains approximately 3 atom % oxygen vacancies (La₂Mo₂O_8.68(1)).
• The material exhibits mixed ionic-electronic conduction due to a static distribution of oxygen vacancies.

Conclusions:

• Topotactic reduction offers a route to stabilize new phases of La₂Mo₂O₉ at room temperature.
• The stabilized cubic phase presents a unique static vacancy distribution.
• The mixed ionic-electronic conductivity broadens the potential applications of La₂Mo₂O₉.