Quartz glass, widely referred to in precision engineering as fused silica or fused quartz, is an ultra-pure amorphous glass made by melting naturally occurring or synthetic silicon dioxide (SiO₂) at temperatures exceeding 1700°C. Unlike conventional architectural float glass or borosilicate glass, it contains virtually zero flux additives or alkali oxides.
Thanks to its single-component SiO₂ chemical structure, quartz glass delivers remarkable thermal shock stability, broad optical transmission ranging from deep ultraviolet (DUV) to the mid-infrared spectrum, and near-absolute chemical inertness, making it an irreplaceable substrate across semiconductor, photonics, and high-temperature processing industries worldwide.
What is Quartz Glass Made of?
Quartz glass is manufactured from high-purity silica raw feedstock with an overall SiO₂ purity exceeding 99.99%. Feedstocks typically include refined natural crystal sand or synthetic chemical precursors such as silicon tetrachloride (SiCl₄).
Under ultra-high melting temperatures, crystalline quartz completely transforms into an isotropic, non-crystalline vitreous state without internal grain boundaries. Tight impurity control is critical during purification: even trace metallic contaminants (iron, sodium, potassium) at parts-per-million (ppm) levels will degrade optical transmission, induce devitrification (crystallization) under heat, and lower laser damage thresholds. For comprehensive technical definitions, refer to the fused quartz scientific reference.
Key Material Grades: JGS1 vs. JGS2 vs. JGS3
In global optics and semiconductor procurement, transparent quartz glass is standardized into three primary optical grades:
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JGS1 (Synthetic UV Fused Silica): Synthesized chemically from SiCl₄. It features Class 0 bubble-free purity, deep ultraviolet transmission down to 185 nm, minimal hydroxyl (OH) content, and negligible autofluorescence. It is the premier substrate for excimer laser optics, lithography blanks, and DUV inspection windows.
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JGS2 (Optical Grade Fused Quartz): Produced by high-temperature melting of refined natural crystal in a vacuum furnace. It maintains continuous thermal resistance up to 1100°C and stable transparency across visible and near-infrared bands (220 nm to 2500 nm), ideal for laser debris shields, pyrometer viewports, and optical blanks.
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JGS3 (Infrared Fused Quartz): Fused under specific vacuum reducing conditions to eliminate the fundamental OH absorption band at 2.73 µm. It delivers extended optical transmission deep into the infrared spectrum (up to 3500 nm), serving infrared thermal detectors and gas spectroscopy instruments.
Comprehensive Material Property Comparison
To clearly highlight the engineering superiority of fused quartz over conventional technical glasses, review the physical and thermal parameters below:
| Material Property / Parameter | Optical Quartz Glass (Fused Silica) | High Borosilicate 3.3 Glass | Standard Soda-Lime Float Glass |
| SiO₂ Chemical Purity | > 99.99% | Approx. 81% | Approx. 72% |
| Continuous Operating Temp | Up to 1100°C | Up to 450°C | Up to 150°C |
| Short-Term Peak Temp | Up to 1250°C | Up to 500°C | Up to 200°C |
| Coefficient of Thermal Expansion (CTE) | 5.5 × 10⁻⁷ / K (0°C to 300°C) | 3.3 × 10⁻⁶ / K | 9.0 × 10⁻⁶ / K |
| Thermal Shock Resistance (ΔT) | Over 1000°C (Quenched to cold water) | 150°C | 50°C |
| Usable Optical Transmission | 185 nm to 3500 nm (DUV through IR) | 310 nm to 2500 nm | 380 nm to 2000 nm |
| Acid & Hydrolytic Resistance | Unaffected by all acids (except HF) | High acid resistance (Class 1) | Moderate (Leaches under acid exposure) |
| Dielectric Strength | 25 to 40 kV/mm | 15 to 20 kV/mm | 10 kV/mm |
Precision Fabrication & CNC Capabilities
Because quartz glass has an extremely high softening point (1730°C) and high hardness (Mohs 7), secondary processing requires diamond-tooled CNC machinery and specialized pitch polishing:
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Precision CNC Sizing: High-speed waterjet cutting, core drilling, rectangular stepped ledges, and 45-degree safety arrises with dimensional tolerances within ±0.02 mm to ±0.05 mm.
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Planetary Double-Sided Polishing: Achieves transmitted wavefront distortions up to λ/10, parallelism under 10 arcseconds, and surface roughness Ra under 0.5 nm for precision laser windows.
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Thin-Film Dielectric Coatings: Single-layer MgF₂ and broadband anti-reflective (BBAR) vacuum coatings maximizing visible and laser line throughput to over 98.5%.
Explore our custom optical quartz glass plates for industrial thermal viewports, or select our fused silica windows & optical flats for high-power laser beam diagnostics.
Primary Industrial Applications
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Semiconductor & Photovoltaics: High-temperature furnace diffusion tubes, wafer carrier boats, vacuum chamber viewports, and plasma etching observation plates.
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Laser Systems & Photonics: High-power fiber laser protective debris windows, cavity output couplers, beam splitters, and interferometry reference flats.
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UV Sterilization & Analytical Metrology: Germicidal lamp envelopes, HPLC flow cells, spectrophotometer cuvettes, and chromatography detection windows.
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Industrial Furnace Engineering: Explosion-proof thermal sight glasses, metallurgical furnace inspection ports, and chemical reactor observation windows.
Frequently Asked Questions (FAQ)
Q: What is the operational difference between fused quartz and fused silica?
A: “Fused quartz” typically denotes glass manufactured by melting natural crystal sands (such as JGS2), which contains slight bubble inclusions and residual trace elements. “Fused silica” describes synthetic glass synthesized chemically (such as JGS1), which guarantees Class 0 bubble-free purity, negligible autofluorescence, and extended deep-UV transmission.
Q: Can quartz glass be chemically tempered like regular soda-lime glass?
A: No. Chemical ion-exchange strengthening requires alkali ions (like sodium) in the glass composition to exchange with potassium in a molten salt bath. Because high-purity quartz glass consists of virtually 100% pure SiO₂ with zero alkali content, it cannot be chemically strengthened. However, its natural tensile and thermal shock endurance far exceeds tempered glass.
Q: Why does hydrofluoric acid corrode quartz glass?
A: Hydrofluoric acid (HF) is one of the few chemical agents capable of breaking the stable silicon-oxygen (Si-O-Si) bond network in quartz glass, converting it into soluble hexafluorosilicic acid. All other mineral acids (hydrochloric, sulfuric, nitric) have zero corrosive effect on quartz glass.
Get Custom Quartz Glass Solutions
Whether you require standard optical disc blanks, stepped viewport windows, or custom-machined quartz prototypes, Chenshi Tech manufactures and tests every component strictly to your technical CAD, STEP, or DXF drawings.
Contact our technical sales team at sales@chenshi-tech.com to request material certifications, engineering evaluations, and factory-direct quotations.