Quartz glass is made by melting natural quartz crystals of exceptional purity with an SiO2 content of 99.9% and allowing the melt to cool down in the shape and dimensions required. The source material has particularly low iron, potassium and sodium oxides, and as a result very low trace element content. It is the material of choice for a variety of applications in several industries because of its exceptional properties, which are listed below:
- very high purity
- excellent elasticity
- superior compressive strength
- withstands extremely high temperature
- extremely low thermal expansion
- high thermal shock resistance
- low thermal conductivity
- essentially impermeable to gases
- outstanding optical transmission properties
- extraordinary chemical resistance
- high resistivity
- high dielectric strength
Major applications of quartz glass products include both the lighting and the semiconductor industry. In the lighting products, quartz glass is widely used in high-temperature arc and filament lamps requiring high purity to minimize devitrification and provide optimum sag resistance. The properties of Quarts glass contribute to the long life of these lamps at high operating temperatures.
Quartz glass is also utilized in various ways by major semiconductor manufacturers worldwide. Common applications include furnace tubes for oxidation, CVD (Chemical Vapor Deposition) and diffusion processes, end caps, transfer carriers, thermocouple tubes, wafer carriers, end plates, baffles and bell-jars for epitaxial reactors. Crucibles from which single crystal silicon is pulling up; bell jars for CVD; cleaning baths after etching and machining; tubes, boats, and other jigs for heat treatments.
Fused quartz is used for its high chemical purity, high-temperature resistance, and precise dimensional tolerances. In addition, it has numerous desirable properties, such as superior heat resistance, light transparency, electrical insulation and chemical stability.