A Metastable Crystalline Phase in Two-Dimensional Metallic Oxide Nanoplates

Area of Science:

• Materials Science
• Nanotechnology
• Solid-State Chemistry

Background:

• Cerium oxide nanoparticles exhibit unique properties influenced by their crystal structure and surface characteristics.
• Phase transformations in metal oxides are crucial for developing advanced materials with tailored functionalities.

Purpose of the Study:

• To synthesize ultrathin cerium oxide nanoplates (<1.4 nm) and investigate their phase transformation.
• To explore the role of surface energy in stabilizing metastable phases in nanomaterials.
• To establish a generalizable method for manipulating and stabilizing novel oxide materials.

Main Methods:

• Synthesis of cerium oxide nanoparticles with varying thicknesses (1.2 nm, 2.2 nm, 5.4 nm).
• Characterization using transmission electron microscopy (TEM) and X-ray diffraction (XRD).
• Thermodynamic energy analysis to determine phase stability.

Main Results:

• Ultrathin cerium oxide nanoplates (<1.4 nm) exhibited a phase transformation from face-centered cubic (fcc) to body-centered tetragonal (bct).
• The metastable bct phase was exclusively observed in the ultrathin nanoplates (1.2 nm).
• Thermodynamic analysis confirmed that increased surface energy in ultrathin nanoplates stabilizes the bct phase.

Conclusions:

• Surface energy is a critical factor in stabilizing metastable phases in cerium oxide nanostructures.
• The developed method of surface energy regulation can be applied to other metallic oxides.
• This approach provides a novel pathway for creating and stabilizing new materials under ambient conditions.