What is the difference between fused silica and quartz?
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Difference Between Fused Silica and Quartz
Fused silica and quartz are both forms of silicon dioxide (SiO2), a common chemical compound that occurs naturally and can also be manufactured for various industrial, scientific, and technical applications. Despite their chemical similarities, there are distinct differences in their properties, origin, and uses that set them apart.
Origin and Manufacture
Fused Silica: It is a synthetic material produced by the high-temperature fusion of high-purity silica sand. The process typically involves using either an electric arc or a flame to melt the silica particles, resulting in a non-crystalline (amorphous) glass with very low levels of impurities.
Quartz: In contrast, quartz is a naturally occurring crystalline form of silicon dioxide. It can also be manufactured as a crystal through a hydrothermal process, which involves a growth technique from a high-temperature aqueous solution at high pressures.
Physical Properties
Fused Silica: Fused silica has exceptional optical properties, including high transmission of ultraviolet light and a very low coefficient of thermal expansion, making it resistant to thermal shock. Its amorphous nature contributes to its excellent insulation characteristics and chemical purity.
Quartz: Natural quartz crystals are highly structured at the molecular level, making them less transparent to UV but more resistant to high pressures. Manufactured quartz can have properties tailored to specific applications, but it tends to hold more impurities than fused silica.
Thermal Properties
Fused Silica: Exhibits extremely low thermal expansion and high thermal shock resistance, making it an excellent material for high-temperature applications.
Quartz: While also resistant to thermal variations, quartz has a higher thermal expansion coefficient compared to fused silica, and therefore, it is somewhat less resistant to rapid temperature changes.
Applications
Fused Silica: Used in semiconductor manufacturing, precision optics like lenses and mirrors, UV light transmission, and optical fibers.
Quartz: Utilized in electronic components such as oscillators and filters, as well as in the fabrication of glassware, lab equipment, and timekeeping devices that require precise crystal lattice structures.
In summary, while both fused silica and quartz are forms of silicon dioxide, they differ mainly in their production process, physical structure, purity levels, optical and thermal properties, and their range of applications. Fused silica with its exceptional purity and thermal properties finds usage in high-precision and high-temperature environments, whereas quartz's structured crystalline form is preferred for electronic and specialty glass applications. These disparities underscore the importance of choosing the right material based on the specific requirements of the application.