1. What is Quartz Glass: Its Basic Definition
Quartz glass is one of the essential materials in modern advanced industries, and its unique properties make it used in a wide range of fields. Its properties that set it apart from ordinary glass come from its main components and its structure.
The main component of quartz glass is silicon dioxide (SiO₂), one of the most abundant compounds on Earth. This silicon dioxide is obtained by melting it at a very high purity and solidifying it without crystallizing it when cooled. Therefore, quartz glass is an “amorphous” solid with no crystal structure, and this amorphous structure is the root of its excellent properties. It is also often referred to as “silica glass”.
In understanding its basic definition, it is important to note that “quartz” and “quartz glass” are different substances. The table below clearly shows the differences.
| item | Quartz (Crystal) | Quartz Glass (Silica Glass) |
|---|---|---|
| Principal component | Silicon dioxide (SiO₂) | Silicon dioxide (SiO₂) |
| Crystal structure | Have a crystal structure (regular atomic arrangement) | Has an amorphous structure (irregular atomic arrangement) |
| transparency | transparent | transparent |
| Manufacturing method | Naturally occurring or artificially crystal grown | Melting and amorphizing silicon dioxide with high purity |
| Main applications | Watches, oscillators, jewelry, etc. | Semiconductors, optics, lighting, medical, etc. |
Quartz glass exhibits unique physical and chemical properties that are not found in other types of glass due to its amorphous structure and extremely high purity (typically above 99.99%). Specifically, they offer extremely high heat resistance, very low coefficient of thermal expansion, excellent light transmission over a wide range of wavelengths (especially in the ultraviolet region), high chemical stability, and excellent electrical insulation. These properties are what make quartz glass an essential material in the modern field of advanced technology.
2. Outstanding performance of quartz glass
Quartz glass has become an essential material in modern industries due to its exceptional physical and chemical properties. Its unique properties that set it apart from ordinary glass determine its value. Here, we will delve into the key properties of quartz glass.
2.1 Incredible Heat Resistance and Low Coefficient of Thermal Expansion
One of the biggest features of quartz glass is its exceptional heat resistance. It has a very high softening point of about 1700°C and can maintain a continuous service temperature of more than 1000°C. This allows for stable use in high-temperature environments.
In addition, it has an extremely low coefficient of thermal expansion. The change in volume is very small when the temperature changes, so it exhibits strong resistance to sudden temperature changes (thermal shock). This is an essential element in optics and semiconductor manufacturing equipment that require precise dimensional accuracy to maximize its performance.
Compared to general soda-lime glass and borosilicate glass, the difference is obvious.
| Types of glass | Softening point (approximate) | Coefficient of Thermal Expansion (Approximate) | Thermal shock resistant |
|---|---|---|---|
| Quartz Glass | Approx. 1700°C | Approx. 0.5 x 10-6 /°C | Extremely high |
| Borosilicate Glass | Approx. 820°C | Approx. 3.3 x 10-6 /°C | high |
| Soda-lime glass | Approx. 700°C | Approx. 9.0 x 10-6 /°C | low |
2.2 Excellent Transmittance from UV to Infrared
Quartz glass boasts excellent light transmission over a wide wavelength range. It is particularly noteworthy for its very high transmittance in the ultraviolet region, which many other optical materials would absorb. This is why it is useful in various fields that utilize ultraviolet light, such as UV lamps, sterilization equipment, semiconductor exposure equipment, and spectrophotometers.
It has good transmittance not only in the visible light region but also in the infrared region, so it is used in a wide range of optical applications. For example, its properties are also used as a core material for optical fibers for communications.
2.3 High Chemical Stability and Corrosion Resistance
Quartz glass has very high chemical stability and excellent resistance to most acids and alkalis. In particular, it is almost invulnerable to acidic or neutral solutions and water vapor even at high temperatures, so it is widely used in chemical plants, laboratory laboratory equipment, and etching equipment in semiconductor manufacturing processes.
However, it is sensitive to hydrofluoric acid (HF), high temperature and concentration of phosphoric acid, and alkaline solutions, so care must be taken in the operating environment. However, with that exception, it can be said that it is a material with extremely excellent corrosion resistance. This property makes it ideal for use in processes where high purity needs to be maintained and in highly corrosive environments.
2.4 Electrical Properties and Mechanical Strength
Quartz glass also plays an important role in the electrical and electronics industry due to its excellent electrical properties.
Firstly, it has a very high dielectric breakdown strength and low dielectric loss, making it an excellent electrical insulating material. In particular, because of its stable electrical properties in the high-frequency range, it is used in high-frequency heating equipment, insulating components of semiconductor manufacturing equipment, and communication equipment.
Next, regarding mechanical strength, quartz glass is a brittle material common to glass in general, and it is vulnerable to impact. However, the tensile strength and compressive strength are relatively high. It also has the characteristics of high surface hardness and resistance to scratches. This is advantageous in enhancing the durability of parts that have undergone precision machining.
The balance between these electrical properties and mechanical strength makes quartz glass an indispensable material in a wide range of advanced technology fields.
3. Types of quartz glass and how to make them
Quartz glass is utilized in a wide range of sectors due to its exceptional properties, but its properties can vary widely depending on the raw material and production method. Here, we will delve into the main types of quartz glass and how they are produced.
3.1 Difference Between Natural and Synthetic Quartz Glass
Quartz glass can be broadly classified into two types due to the difference in raw materials: natural quartz glass and synthetic quartz glass. There are distinct differences in their characteristics, production methods, and primary applications.
Natural quartz glass is manufactured from naturally occurring quartz (quartz). Synthetic quartz glass, on the other hand, is produced from chemically synthesized high-purity silica compounds (e.g., silicon tetrachloride: SiCl4). This difference in raw materials significantly impacts the purity, properties, and cost of the final product.
| item | Natural Quartz Glass | Synthetic quartz glass |
|---|---|---|
| raw materials | Natural Crystal (Quartz) | High-purity synthetic silica compounds (e.g., silicon tetrachloride SiCl4) |
| purity | Relatively low (including metal impurities, etc.) | Very high (high purity) |
| OH base content | low | High (OH-free type also exists) |
| Bubbles | Relatively many | Very little |
| UV Transmittance | Low transmittance in the short wavelength range | Very high (good transmittance up to deep ultraviolet) |
| Manufacturing Costs | Relatively low | high |
| Main applications | General optical components, protective tubes, lamp tubes, crucibles | Components for semiconductor manufacturing, high-precision optical lenses, optical fiber substrates, ultraviolet lamps |
Synthetic quartz glass is an essential material for semiconductor manufacturing equipment and high-precision optical equipment that require extremely high purity and excellent UV transmittance. On the other hand, natural quartz glass is widely used in applications where the basic properties of quartz glass (heat resistance, chemical resistance, etc.) are required at a lower cost.
3.2 Main Manufacturing Processes of Quartz Glass
The production methods of quartz glass vary depending on the type of raw material and the properties desired in the final product. Here is an explanation of the main manufacturing processes.
3.2.1 Melting Method (Production of Natural Quartz Glass)
The melting method is mainly used to produce natural quartz glass made from natural quartz. It is the process of melting and shaping natural quartz powder at high temperatures. There are several variations of this method.
- Electromelting methodIt is a method of melting quartz powder in an electric furnace by electric heating. Although it is a relatively simple process, it is characterized by the fact that impurities (especially metal impurities) contained in the raw material crystal are easy to remain in the product, and air bubbles are easily mixed in during melting. Therefore, it is mainly utilized in general industrial applications and components where high optical purity is not required.
- Flame MeltingIt is a method of melting quartz powder using a high-temperature flame such as a hydrogen-oxygen flame. Compared to the electromelting method, it can melt at a high temperature, so some impurities can be volatilized, but it is characterized by the fact that the hydrogen contained in the flame is easily taken up as a hydroxyl group (OH group) in the glass. Since OH groups affect the absorption of infrared light, managing OH group content is important in some applications.
3.2.2 Synthesis Method (Production of Synthetic Quartz Glass)
The synthesis method is used to produce high-purity synthetic quartz glass. It is a process that uses a chemical vapor phase reaction to produce extremely pure silica (silicon dioxide) and vitrify it. This method results in high-performance quartz glass with very few impurities and air bubbles.
- Flame hydrolysis (VAD, OVD, etc.)Raw gas such as silicon tetrachloride (SiCl4) is hydrolyzed and oxidized in a hydrogen-oxygen flame to produce high-purity silica particles (soot). This soot is deposited on the target rod or substrate, which is then transparently vitrified (sintered) at high temperatures.
- VAD method (Vapor-phase Axial Deposition): Mainly used in the production of optical fiber base metals, soot is deposited axially to grow the base metal.
- OVD method (Outside Vapor Deposition): This method deposits soot around the periphery of the target rod.
These methods tend to have a higher OH group content, but it is also possible to reduce the OH group by subsequent dewatering treatment.
- Plasma methodThis is a method of decomposing and oxidizing raw gas such as silicon tetrachloride (SiCl4) to produce silica and vitrify it in plasma flames such as high-frequency plasma and microwave plasma. Because the plasma is very hot, it can produce high-purity silica more efficiently and with extremely low OH group contamination. For this reason, it is used in optical materials for semiconductor lithography equipment where high transmittance in the deep ultraviolet region is required.
- MCVD (Modified Chemical Vapor Deposition)This method involves passing raw gas through the inside of a glass tube and depositing a silica layer while heating it from the outside. It is mainly used in the production of optical fiber base metals. It is suitable for the production of high-performance optical fibers with multi-layer structure.
With the evolution of these manufacturing techniques, quartz glass is designed and manufactured to have optimal properties depending on its application.
4. Main Applications of Quartz Glass
Quartz glass is utilized as an indispensable material in a wide range of sectors of modern society due to its exceptional properties. It is particularly valuable in cutting-edge technology fields where high-temperature resistance, excellent optical properties, high chemical stability, and electrical insulation are required.
4.1 The Role of Quartz Glass in Semiconductor Manufacturing
The semiconductor manufacturing process requires extremely high purity and precise temperature control, which is why quartz glass is widely adopted as the primary material. Quartz glass is essential for ensuring the quality and reliability of semiconductor devices due to its excellent stability and chemical inertness at high temperatures.
Some of the main applications include:
- Core tubes (process tubes): Used in heat treatment processes such as oxidation, diffusion, and CVD (chemical vapor deposition) of semiconductor wafers. It can withstand high temperatures and elute very little impurities, allowing it to maintain a high-purity environment.
- Wafer carriers and boats: Used to hold and transport wafers within the heat treatment furnace. It has low deformation at high temperatures and does not contaminate the wafer.
- Various jigs and reaction vessels: Components and vessels used in etching, cleaning, and thin film formation processes rely on their high chemical resistance and purity.
- Gas Distribution Plate (Shower Plate): Used in CVD equipment, for example, to uniformly deliver reactive gas to the wafer surface.
Thus, quartz glass plays a crucial role in every stage of semiconductor manufacturing, making it a fundamental material for miniaturization and higher performance.
4.2 For Advanced Optics
Quartz glass is widely utilized in advanced optical instruments and optical communication technologies due to its excellent optical properties. In particular, its high transmittance over a wide wavelength range, from ultraviolet to infrared, is a significant advantage that other glass materials do not have.
Key optical applications include:
| Application Categories | Specific Applications | Advantages of quartz glass |
|---|---|---|
| Lenses, prisms, window materials | UV lithography equipment lens, spectrometer prism, laser machine protective window | High transmittance over a wide wavelength range, dimensional stability due to low thermal expansion |
| optical fiber | Long-distance optical communication cable, image transmission of medical endoscope | Low loss, high purity, excellent optical transmission characteristics |
| Laser Optics | Oscillators and transmission system components of high-power lasers, and optical systems of laser machines | High laser resistance, low thermo-optical distortion |
| Measuring and analytical instruments | Spectrophotometer Cell, UV Detector Window | UV permeability, low impact on the sample due to chemical stability |
In these applications, quartz glass’s high light transmission, thermal stability, and chemical purity are key factors in determining device performance and reliability.
4.3 Contribution to the Medical Field and Research and Development
Whether in the medical field or research and development, quartz glass has made significant contributions due to its unique properties. Its high purity, chemical stability, and UV permeability are particularly useful in these areas.
- Medical Equipment:
- Endoscope optics: Enables high-resolution image transmission, contributing to improved diagnostic accuracy.
- Protective tube for ultraviolet germicidal lamps: It efficiently transmits the light of ultraviolet lamps and is used to sterilize medical instruments and air and water.
- Analyzer cells and window materials: They are used to analyze biological samples and chemicals, such as blood testing devices and DNA analyzers, allowing for highly accurate measurements with less reaction with reagents.
- Research and Development:
- Laboratory equipment: They are widely used in beakers, flasks, reaction vessels, and other experiments that require chemical reactions at high temperatures and high purity.
- Spectroscopic Analysis Cells: As measurement cells such as UV-Vis spectrophotometers and fluorescence spectrophotometers, they enable accurate light absorption and emission measurements of samples.
- As part of :D biotechnology sector NA sequencing and cell culture equipment, high purity and optical properties are required.
- Plasma Research: As a window or reaction vessel in plasma generators, their resistance to high-temperature plasmas and chemical stability are leveraged.
Quartz glass is also highly biocompatible and is an important material for safe and high-precision operation in a wide range of fields, from medical diagnostics to basic research.
4.4 Lighting Industry and Other Applications
In the lighting industry, quartz glass is also an essential material for the production of certain high-performance lamps. Its excellent properties are also used in a variety of other industrial fields.
4.4.1 Application in the Lighting Industry
Due to its high temperature resistance, excellent UV permeability, and low coefficient of thermal expansion, quartz glass is used as an envelope (outer tube) for the following high-performance lamps:
- Halogen lamps: Capable of operating at high temperatures, providing high luminous efficiency and long service life.
- High-pressure mercury lamps, metal halide lamps: These lamps emit ultraviolet light, making the most of UV transmittance and enabling efficient light emitting.
- UV Germicidal Lamps, UV Curing Lamps: They serve as an essential source of UV light for sterilization and resin curing processes in medical, food processing, and industrial sectors.
4.4.2 Other Diverse Application Areas
The unique properties of quartz glass make it valuable in a wide range of fields beyond the lighting industry.
| Areas of application | Specific use cases | Why quartz glass? |
|---|---|---|
| Aerospace Industry | Spacecraft windows, telescope mirror boards | Resistance to the harsh environment of space (high temperature, radiation), dimensional stability due to low thermal expansion |
| Solar Cell Manufacturing | Silicon melting crucible, diffusion furnace parts | High purity, high temperature resistance, chemical stability |
| Vacuum Technology | Vacuum Chamber Window, Vacuum Pump Parts | Low outgassing and high vacuum can be maintained |
| Thermocouple Protection Tube | Temperature measurement in a high-temperature furnace | Corrosion resistance at high temperatures, electrical insulation, thermal shock resistance |
| Industrial furnaces and heating equipment | Protective tube of heating heater, observation window in the furnace | Durability in high-temperature environments, thermal shock resistance |
| Measuring Equipment | Water Level Gauge Float, High Precision Flow Meter Parts | Chemical stability, precision machinability |
These diverse applications demonstrate that quartz glass offers unique value that is hard to replace with other materials in extreme environments and situations where high precision is required.
5. Comparison with Other Glass: Advantages of quartz glass.
The excellent properties of quartz glass can be understood more clearly by comparing it with other common glasses. Here, we will explain how quartz glass is a special and high-performance material, comparing it with soda-lime glass, which is the most widely used in our daily lives, and borosilicate glass, which has excellent heat resistance.
5.1 Comparison of Quartz Glass and Soda-Lime Glass
Soda-lime glass is the most common glass used in many products around us, such as window glass and beverage bottles. However, its properties are very different from quartz glass.
- Heat resistance and thermal expansion rate: Soda-lime glass is sensitive to heat and is prone to cracking under sudden temperature changes. This is due to its high coefficient of thermal expansion. Quartz glass, on the other hand, has extremely high heat resistance and has a very low coefficient of thermal expansion, which means it can withstand rapid temperature changes.
- Optical properties: Soda-lime glass transmits visible light well, but it hardly transmits ultraviolet light. In contrast, quartz glass boasts high transmittance over a wide range of wavelengths, from deep ultraviolet to near-infrared, particularly ultraviolet transmittance.
- Chemical stability: Soda-lime glass is relatively weak to acids and alkalis, especially strong alkalis. Quartz glass exhibits excellent resistance to most acids and alkalis.
- Electrical Insulation: Soda-lime glass also has electrical insulation, but quartz glass has even better electrical insulation properties, making it suitable for high-voltage and high-frequency applications.
5.2 Comparison of Quartz Glass and Borosilicate Glass
Borosilicate glass is a glass that has better heat resistance and chemical stability than soda-lime glass, which is used in laboratory equipment and heat-resistant tableware. But it still doesn’t match the performance of quartz glass.
- Heat Resistance and Thermal Expansion Rate: Borosilicate glass is also heat-resistant, but the continuous service temperature is generally around 500°C. Quartz glass can be used at high temperatures above 1000°C, and its coefficient of thermal expansion is even lower than borosilicate glass, making it suitable for use in more severe temperature environments.
- Optical Properties: Borosilicate glass transmits a portion of ultraviolet light, while quartz glass’s transmittance in the deep ultraviolet region is overwhelmingly superior. This is a decisive difference in applications that require specific wavelengths of light, such as lithography equipment in semiconductor manufacturing.
- Chemical stability: Borosilicate glass exhibits high resistance to acids and alkalis, while quartz glass has even higher purity and excellent chemical stability.
- Mechanical strength: Borosilicate glass is relatively strong, while quartz glass combines high compressive strength and hardness.
5.3 Comparison Table of Properties of Key Glass Materials
In the table below, you can compare the properties of the main glass materials and see at a glance where the advantages of quartz glass lie.
| Features | Quartz Glass | Borosilicate Glass | Soda-Lime Glass |
|---|---|---|---|
| Principal component | Silicon dioxide (SiO₂) 99.9% or more | Silicon dioxide, boron oxide, aluminum oxide, etc. | Silicon dioxide, sodium oxide, calcium oxide, etc. |
| Softening point (approximate) | Approx. 1600°C | Approx. 820°C | Approx. 700°C |
| Continuous service temperature (approximate) | Approx. 1000°C~1200°C | Approx. 500°C | Approx. 250°C |
| Coefficient of Thermal Expansion (Approximate) | Very low (0.5 x 10⁻⁶ /°C) | Low (3.3 x 10⁻⁶ /°C) | High (9.0 x 10⁻⁶ /°C) |
| UV Transmittance | Extremely high (up to deep ultraviolet) | Relatively high (partially transmitted) | Low (almost impermeable) |
| Chemical stability | Extremely high | high | Relatively low |
| Electrical insulation | Extremely high | high | Medium |
| Manufacturing Costs | high price | Medium | low price |
| Main applications | Semiconductor manufacturing equipment, optical lenses, optical fibers, lamps | Laboratory Equipment, Heat-Resistant Tableware, Medical Containers | Window glass, bottles, tableware |
5.4 Advantages and Importance of Quartz Glass
Thus, quartz glass has properties that far surpass other common glasses in terms of heat resistance, coefficient of thermal expansion, optical properties, chemical stability, and electrical insulation. In particular, its extremely high purity and excellent transmittance in the deep ultraviolet region make it an indispensable material in cutting-edge technology fields such as semiconductor manufacturing, advanced optical instruments, and optical communications.
While its production cost is expensive compared to other glasses, the technical benefits it brings to its unique performance are immense. Quartz glass continues to grow in importance as an “unsung hero” that supports the development of modern society.
6. Conclusion
Quartz glass is a specialized glass primarily composed of high-purity silicon dioxide (silica), and its outstanding physical and chemical properties make it an indispensable material in a wide range of fields in modern society. In this article, we have explained the full picture of quartz glass, from its basic definition to its unique properties not found in other glasses, its diverse types and manufacturing methods, and its wide range of applications that support cutting-edge technology.
6.1 Reaffirming the Features and Diverse Applications of Quartz Glass
The unique properties of quartz glass make it truly valuable in many situations where other materials are difficult to replace. In particular, the following key properties determine their use in areas that require advanced technology, such as semiconductor manufacturing, optics, and medical fields.
| Key characteristics | Concrete Advantages | Typical application areas |
|---|---|---|
| Excellent heat resistance and low thermal expansion | Shape stability in high-temperature environments, resistance to thermal shock | Semiconductor manufacturing equipment (core tubes, jigs), high-temperature reactor windows, aerospace and aerospace fields |
| High transmittance over a wide wavelength range | Excellent light transmission from ultraviolet to infrared | Optical Lenses, Prisms, Spectrometers, Lithography Equipment, Optical Fibers |
| High chemical stability | Excellent corrosion resistance to acids and alkalis | Laboratory equipment, chemical plants, chemical storage containers, semiconductor cleaning tanks |
| Excellent electrical insulation | Stable insulation performance under high voltages | Semiconductor manufacturing processes, electrical and electronic components, high-frequency devices |
| High mechanical strength | High hardness and scratch resistance | Precision parts, protective covers, wear-resistant parts |
The combination of these properties positions quartz glass not just as a transparent material but as a strategic material that underpins the foundation of modern industries.
6.2 The Potential of Quartz Glass to Open Up the Future
Quartz glass will continue to be at the center of further innovations in the years to come due to its exceptional properties. In particular, fields such as 5G/6G communication, quantum computing, renewable energy technologies, and next-generation medical devices are expected to drive demand for higher-performance and higher-purity quartz glass. The evolution of manufacturing technology is expected to develop quartz glass products with even more complex shapes and functions, bringing new value to our lives and industries. Quartz glass is an important material that continues to evolve with the advancement of science and technology and continue to contribute to the development of future society.