Two-Step Synthesis of VO₂ (M) with Tuned Crystallinity

Area of Science:

• Materials Science
• Solid State Chemistry
• Nanotechnology

Background:

• Vanadium dioxide (VO2) exhibits a metal-insulator transition (MIT) with potential applications in electronics and thermochromic devices.
• Controlling the crystallinity and phase purity of VO2 is crucial for optimizing its MIT properties.
• Existing synthesis methods often face challenges in achieving high crystallinity and phase purity.

Purpose of the Study:

• To develop a facile two-step synthesis method for highly crystallized monoclinic vanadium dioxide (VO2 (M)).
• To investigate the role of residual carbon content in the post-crystallization of VO2.
• To explore the preparation of other vanadium oxides (V2O3, V2O5) with controlled microstructures.

Main Methods:

• Two-step thermal treatment: thermolysis of vanadyl ethylene glycolate (VEG) followed by postannealing.
• Characterization techniques: X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM).
• Quantitative analysis of crystalline VO2 using the Fullprof program and differential scanning calorimetry (DSC) for MIT behavior.

Main Results:

• A two-step method successfully synthesized highly crystallized VO2 (M).
• Residual carbon content was identified as a critical factor in VO2 (M) crystallization.
• Postannealing significantly increased the weight percent of crystalline VO2 from 44% to 100%.
• Improved crystallinity enhanced the sharpness and intensity of DSC peaks, indicating better MIT behavior.
• V2O3 and V2O5 with unique microstructures were also prepared using modified postannealing conditions.

Conclusions:

• The developed two-step thermal treatment is effective for synthesizing highly crystallized VO2 (M).
• Control over residual carbon content is key for achieving optimal VO2 crystallization.
• The method offers a pathway for preparing various vanadium oxides with tailored microstructures and properties.