Multi-stoichiometric quasi-two-dimensional W_nO_3n-1 tungsten oxides

Area of Science:

• Materials Science
• Solid State Chemistry
• Nanotechnology

Background:

• Tungsten oxides exhibit diverse crystallographic structures and non-stoichiometric phases.
• Oxygen deficiency in metal oxides is often accommodated by crystallographic shear (CS) planes.
• Epitaxial growth offers a route to control nanostructure formation.

Purpose of the Study:

• To identify and characterize novel quasi-two-dimensional tungsten oxide structures.
• To investigate the role of crystallographic shear planes in accommodating oxygen deficiency.
• To explore the formation of multi-stoichiometric phases within these structures.

Main Methods:

• Epitaxial growth of tungsten oxide platelets on W19O55 nanowires (NW).
• Transmission Electron Microscopy (TEM) for structural analysis.
• X-ray Diffraction (XRD) for phase identification.

Main Results:

• Identification of quasi-two-dimensional tungsten oxide platelets grown epitaxially on W19O55 NW.
• Observation of crystallographic shear planes in both NW and platelets, accommodating oxygen deficiency.
• Discovery of syntactically grown, multi-stoichiometric phases (W18O53 to W9O26) within single platelets.
• Demonstration of a new form of polycrystallinity where CS planes stabilize the multi-stoichiometric structure.

Conclusions:

• Quasi-two-dimensional tungsten oxide platelets represent a novel material structure.
• Crystallographic shear planes are crucial for accommodating oxygen deficiency and stabilizing complex non-stoichiometric phases.
• This work reveals a new polycrystallinity mechanism in layered oxide crystals.