Ultra-Low-Bubble-Density Quartz Glass Enabled by Stepwise Calcination of High-Purity Synthetic Quartz Powder

Area of Science:

• Materials Science
• Chemical Engineering
• Glass Science

Background:

• High-purity synthetic quartz powders are crucial for semiconductor manufacturing, particularly for quartz crucibles and ware.
• Sol-gel derived quartz powders contain hydrogen bonds that cause bubble formation during glass fusion, compromising product quality.

Purpose of the Study:

• To investigate the behavior of hydrogen bond removal in synthetic quartz powders as a function of calcination temperature.
• To establish an optimized calcination process for minimizing hydrogen content and subsequent bubble formation in fused quartz glass.

Main Methods:

• Investigated hydrogen bond removal using mass loss, Brunauer-Emmett-Teller (BET) specific surface area, tap density, and Fourier transform infrared (FT-IR) spectroscopy.
• Analyzed the removal temperatures for physisorbed water, vicinal/geminal silanols, and isolated silanols.

Main Results:

• Physisorbed water and weakly bonded hydroxyl groups (~3350 cm⁻¹) were removed between 200-600 °C.
• Vicinal/geminal silanols (~3650 cm⁻¹) were removed between 700-1000 °C.
• Isolated silanols (~3745 cm⁻¹) were removed above 1100 °C.

Conclusions:

• A stepwise calcination process (300 °C for 5h, 700 °C for 5h, 1200 °C for 10h) was developed based on observed hydrogen bond removal behavior.
• This optimized process reduced hydroxyl (OH) concentration to 3.6 ppm.
• The developed process significantly decreased bubble density in fused quartz glass to 0.6 bubbles cm⁻³.