Temperature-dependent phase stability of nanocrystalline SiO2

Area of Science:

• Materials Science
• Solid-State Chemistry

Background:

• Nanocrystalline silicon dioxide (SiO2) powders are synthesized via gas phase condensation.
• Understanding the phase transformations of SiO2 is crucial for materials applications.

Purpose of the Study:

• To characterize the structural and phase evolution of nanocrystalline SiO2 powder.
• To investigate the effects of annealing on the amorphous and crystalline phases of SiO2.

Main Methods:

• X-ray diffraction (XRD) analysis.
• Electron diffraction techniques.
• Gas phase condensation synthesis.

Main Results:

• As-synthesized SiO2 powder is predominantly amorphous with a minor alpha-crystobalite phase.
• Annealing leads to the gradual transformation of the amorphous phase into alpha-crystobalite crystallites.
• Further annealing results in the formation of beta-crystobalite domains from existing crystallites.

Conclusions:

• The annealing process induces significant phase transformations in nanocrystalline SiO2.
• The study elucidates the structural evolution pathway from amorphous SiO2 to alpha- and beta-crystobalite.