Fused quartz
A high-purity glass used in optics, semiconductors, and high-temperature applications.
Fused quartz, also known as fused silica or quartz glass, is a glass composed of almost pure silica (silicon dioxide, SiO₂) in amorphous (non-crystalline) form. It differs from other commercial glasses by having no added ingredients, resulting in high working and melting temperatures, greater strength, higher chemical resistance, and lower thermal expansion, making it suitable for specialized uses in lighting, scientific applications, semiconductor fabrication, and laboratory equipment.
- composition
- Almost pure silica (SiO₂) in amorphous form
- common_impurities
- Aluminium, titanium, and hydroxyl (OH) groups
- key_properties
- High strength, chemical resistance, low thermal expansion, wide UV-to-IR transparency
Lore & Background
Fused quartz is produced by fusing high-purity silica sand, which consists of quartz crystals. There are four basic types of commercial silica glass: Type I is produced by electrically melting natural quartz in a vacuum or inert atmosphere; Type II by fusing quartz crystal powder in a high-temperature flame; Type III by burning SiCl₄ in a hydrogen-oxygen flame; and Type IV by burning SiCl₄ in a water vapor-free plasma flame. The manufacturing process determines trace impurities, such as aluminium and titanium, which affect ultraviolet transmission, and hydroxyl groups, which reduce infrared transmission.
Reader's Guide
Fused quartz is significant for its unique combination of properties: extreme thermal shock resistance due to a very low coefficient of thermal expansion, high melting point, and broad optical transparency from the ultraviolet to the near-mid infrared. These qualities make it essential for specialized applications such as lenses and optics for UV and IR wavelengths, envelopes for halogen and high-intensity discharge lamps, windows in spacecraft and deep-diving vessels, substrates for photolithography masks and EPROMs, and precision mirror substrates for telescopes. In the semiconductor industry, its thermal stability and UV transparency are critical for projection masks and furnace components. Fused quartz also serves as a refractory material for crucibles and furnace tubes, and as a low-damping material for high-Q resonators in gyroscopes and musical instruments like the glass harmonica. Its legacy lies in enabling technologies that require high purity, thermal stability, and optical performance beyond the capabilities of ordinary glass.
Did You Know?
- Fused quartz is used as the envelope for halogen lamps and high-intensity discharge lamps due to its strength and high melting point.
- Fused quartz was used in the windows of crewed spacecraft, including the Space Shuttle and International Space Station.
- EPROMs (erasable programmable read-only memory) use a transparent fused quartz window to transmit UV light for erasing the chip.
Frequently Asked Questions
Who is Fused quartz?
Fused quartz is a glass built from nearly pure silicon dioxide (SiO₂) locked into a non-crystalline, amorphous lattice. Unlike everyday commercial glasses, it carries no added fluxes or colorants, which is the root of its unusual physical and chemical behavior.
What are Fused quartz's powers/role?
It boasts very low thermal expansion (roughly 5.5×10⁻⁷ per kelvin), outstanding chemical resistance, high mechanical strength, and transparency stretching from the ultraviolet through the infrared. Those traits make it the material of choice for precision optics, semiconductor photolithography, and high-temperature lab glassware.
Why is Fused quartz important?
Because it pairs near-total silica purity with a broad UV-to-IR transmission window, it is indispensable in laser systems, chip-fabrication optics, and scientific instrumentation where even microscopic thermal drift or surface corrosion would invalidate measurements. No other common glass replicates that combination of stability and clarity.
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