Fused Quartz Vs Fused Silica Key Differences for Glass Selection

At first glance, "quartz glass" might seem like a straightforward term, but the price differences between products can be staggering—sometimes varying by several hundred percent. The secret lies in understanding the two distinct types: fused quartz and fused silica glass.

Fused quartz is created by melting natural quartz crystals at temperatures around 2000°C (3632°F). While this process is relatively simple and cost-effective, the resulting material contains impurities from the natural crystals, limiting its purity. Key characteristics include:

• Purity: Contains trace metals, hydroxyl groups, and other impurities.
• Optical Performance: Lower light transmission, especially in UV wavelengths (below ~220 nm).
• Bubbles/Inclusions: Visible imperfections are common.
• Cost: Significantly cheaper than fused silica.

Fused silica is synthesized from ultra-pure silicon dioxide powder at lower temperatures (~1700°C/3092°F). This meticulous process yields exceptional purity and optical clarity:

• Purity: 99.999% SiO₂ with minimal contaminants (often <1 ppm).
• Optical Performance: Maintains >90% UV transmission down to 180 nm.
• Bubbles/Inclusions: Nearly defect-free structure.
• Cost: Priced at a premium due to complex manufacturing.

Fused Quartz is Ideal For:

• Industrial viewports (furnaces, reactors)
• UV lamp housings for disinfection
• Thermal insulation components

Fused Silica is Essential For:

• Precision optics (lenses, prisms, mirrors)
• Semiconductor manufacturing equipment
• Advanced scientific instruments

Thermal Resistance: Both withstand continuous operation at 1000°C (1832°F) with excellent thermal shock resistance.

Chemical Resistance: Nearly identical—resistant to most acids except hydrofluoric acid and hot phosphoric acid.

UV Transmission: Fused silica transmits ~90% at 190 nm vs. fused quartz's ~50% at the same wavelength.

Myth 1: "Fused silica is always better."
Reality: For non-critical applications like observation windows, fused quartz provides adequate performance at lower cost.

Myth 2: "The materials differ chemically."
Reality: Both are SiO₂—the differences lie in purity and microstructure, not base chemistry.