Fused quartz

Fused quartz or fused silica is glass consisting of silica in amorphous (non-crystalline) form. It differs from traditional glasses in containing no other ingredients, which are typically added to glass to lower the melt temperature. Fused silica, therefore, has high working and melting temperatures. Although the terms fused quartz and fused silica are used interchangeably, the optical and thermal properties of fused silica are superior to those of fused quartz and other types of glass due to its purity.[1] For these reasons, it finds use in situations such as semiconductor fabrication and laboratory equipment. It transmits ultraviolet better than other glasses, so is used to make lenses and optics for the ultraviolet spectrum. The low coefficient of thermal expansion of fused quartz makes it a useful material for precision mirror substrates.[2]

Einstein gyro gravity probe b
This fused quartz sphere was manufactured for use in a gyroscope in the Gravity Probe B experiment. It is one of the most accurate spheres ever manufactured, deviating from a perfect sphere by no more than 40 atoms of thickness. Only neutron stars are thought to be smoother.


Fused quartz is produced by fusing (melting) high-purity silica sand, which consists of quartz crystals. There are four basic types of commercial silica glass:

  • Type I is created by the electric melting of natural quartz in a vacuum, or in an inert gas at low pressure.
  • Type II is the result of quartz crystal powder by flame fusion.
  • Type III is a synthetic variety; it is produced by the hydrolyzation of SiCl4 when sprayed into an OH flame.
  • Type IV is a synthetic produced from SiCl4 in a water vapor-free plasma flame.[3]

Quartz contains only silicon and oxygen, although commercial quartz glass often contains impurities. The most dominant impurities are aluminium and titanium.[4]


Melting is effected at approximately 1650°C (3000°F) using either an electrically heated furnace (electrically fused) or a gas/oxygen-fuelled furnace (flame-fused). Fused silica can be made from almost any silicon-rich chemical precursor, usually using a continuous process which involves flame oxidation of volatile silicon compounds to silicon dioxide, and thermal fusion of the resulting dust (although alternative processes are used). This results in a transparent glass with an ultra-high purity and improved optical transmission in the deep ultraviolet. One common method involves adding silicon tetrachloride to a hydrogen–oxygen flame, but this precursor results in environmentally unfriendly byproducts including chlorine and hydrochloric acid.

Product quality

Fused quartz is normally transparent. The material can, however, become translucent if small air bubbles are allowed to be trapped within. The water content (and therefore infrared transmission of fused quartz and fused silica) is determined by the manufacturing process. Flame-fused material always has a higher water content due to the combination of the hydrocarbons and oxygen fuelling the furnace, forming hydroxyl [OH] groups within the material. An IR grade material typically has an [OH] content of <10 parts per million.


Most of the applications of fused silica exploit its wide transparency range, which extends from the UV to the near IR. Fused silica is the key starting material for optical fiber, used for telecommunications.

Because of its strength and high melting point (compared to ordinary glass), fused silica is used as an envelope for halogen lamps and high-intensity discharge lamps, which must operate at a high envelope temperature to achieve their combination of high brightness and long life. Vacuum tubes with silica envelopes allowed for radiation cooling by incandescent anodes.

Because of its strength, fused silica was used in deep diving vessels such as the bathysphere and benthoscope. Fused silica is also used to form the windows of manned spacecraft, including the Space Shuttle and International Space Station.[5]

The combination of strength, thermal stability, and UV transparency makes it an excellent substrate for projection masks for photolithography.

EPROM Intel C1702A
An EPROM with fused quartz window in the top of the package

Its UV transparency also finds uses in the semiconductor industry; an EPROM, or erasable programmable read only memory, is a type of memory chip that retains its data when its power supply is switched off, but which can be erased by exposure to strong ultraviolet light. EPROMs are recognizable by the transparent fused quartz window which sits on top of the package, through which the silicon chip is visible, and which permits exposure to UV light during erasing.

Due to the thermal stability and composition, it is used in semiconductor fabrication furnaces.

Fused quartz has nearly ideal properties for fabricating first surface mirrors such as those used in telescopes. The material behaves in a predictable way and allows the optical fabricator to put a very smooth polish onto the surface and produce the desired figure with fewer testing iterations. In some instances, a high-purity UV grade of fused quartz has been used to make several of the individual uncoated lens elements of special-purpose lenses including the Zeiss 105mm f/4.3 UV Sonnar, a lens formerly made for the Hasselblad camera, and the Nikon UV-Nikkor 105mm f/4.5 (presently sold as the Nikon PF10545MF-UV) lens. These lenses are used for UV photography, as the quartz glass has a lower extinction rate than lenses made with more common flint or crown glass formulas.

Fused quartz can be metallised and etched for use as a substrate for high-precision microwave circuits, the thermal stability making it a good choice for narrowband filters and similar demanding applications. The lower dielectric constant than alumina allows higher impedance tracks or thinner substrates.

Fused quartz is also the material used for modern glass instruments such as the glass harp and the verrophone, and is also used for new builds of the historical glass harmonica. Here, the superior strength and structure of fused quartz gives it a greater dynamic range and a clearer sound than the historically used lead crystal.

Refractory material applications

Fused silica as an industrial raw material is used to make various refractory shapes such as crucibles, trays, shrouds, and rollers for many high-temperature thermal processes including steelmaking, investment casting, and glass manufacture. Refractory shapes made from fused silica have excellent thermal shock resistance and are chemically inert to most elements and compounds, including virtually all acids, regardless of concentration, except hydrofluoric acid, which is very reactive even in fairly low concentrations. Translucent fused-silica tubes are commonly used to sheathe electric elements in room heaters, industrial furnaces, and other similar applications.

Owing to its low mechanical damping at ordinary temperatures, it is used for high-Q resonators, in particular, for wine-glass resonator of hemispherical resonator gyro.[6][7]

Quartz glassware is occasionally used in chemistry laboratories when standard borosilicate glass cannot withstand high temperatures or when high UV transmission is required. The cost of production is significantly higher, limiting its use; it is usually found as a single basic element, such as a tube in a furnace, or as a flask, the elements in direct exposure to the heat.

Physical properties

The extremely low coefficient of thermal expansion, about 5.5×10−7/°C (20–320°C), accounts for its remarkable ability to undergo large, rapid temperature changes without cracking (see thermal shock).

Fused silica phosphorescence from a 24 million watt flash
Phosphorescence in fused quartz from an extremely intense pulse of ultraviolet light, centered at 170 nm, in a flashtube

Fused quartz is prone to phosphorescence and "solarisation" (purplish discoloration) under intense UV illumination, as is often seen in flashtubes. "UV grade" synthetic fused silica (sold under various tradenames including "HPFS", "Spectrosil", and "Suprasil") has a very low metallic impurity content making it transparent deeper into the ultraviolet. An optic with a thickness of 1 cm has a transmittance around 50% at a wavelength of 170 nm, which drops to only a few percent at 160 nm. However, its infrared transmission is limited by strong water absorptions at 2.2 μm and 2.7 μm.

"Infrared grade" fused quartz (tradenames "Infrasil", "Vitreosil IR", and others), which is electrically fused, has a greater presence of metallic impurities, limiting its UV transmittance wavelength to around 250 nm, but a much lower water content, leading to excellent infrared transmission up to 3.6 μm wavelength. All grades of transparent fused quartz/fused silica have nearly identical physical properties.

Phosphorescence of the quartz ignition tube of an air-gap flash

Optical properties

The optical dispersion of fused silica can be approximated by the following Sellmeier equation:[8]

where the wavelength is measured in micrometers. This equation is valid between 0.21 and 3.71 micrometers and at 20 °C.[8] Its validity was confirmed for wavelengths up to 6.7 µm.[9] Experimental data for the real (refractive index) and imaginary (absorption index) parts of the complex refractive index of fused quartz reported in the literature over the spectral range from 30 nm to 1000 µm have been reviewed by Kitamura et al.[9] and are available online.

Typical properties of clear fused silica

See also


  1. ^ "Quartz vs. Fused Silica: What's the Difference?". Swift Glass. 2015-09-08. Retrieved 2017-08-18.
  2. ^ De Jong, Bernard H. W. S.; Beerkens, Ruud G. C.; Van Nijnatten, Peter A. (2000). "Glass". Ullmann's Encyclopedia of Industrial Chemistry. doi:10.1002/14356007.a12_365. ISBN 3-527-30673-0.
  3. ^ Kitamura, Rei (2007-09-25). "Optical constants of silica glass from extreme ultraviolet to far infrared at near room temperature" (PDF). UCLA Engineering. Retrieved 2017-08-18.
  4. ^ Chemical purity of fused quartz / fused silica, www.heraeus-quarzglas.com
  5. ^ Salem, Jonathan (2012). "Transparent Armor Ceramics as Spacecraft Windows". Journal of the American Ceramic Society.
  6. ^ An Overview of MEMS Inertial Sensing Technology, February 1, 2003
  7. ^ Penn, Steven D.; Harry, Gregory M.; Gretarsson, Andri M.; Kittelberger, Scott E.; Saulson, Peter R.; Schiller, John J.; Smith, Joshua R.; Swords, Sol O. (2001). "High quality factor measured in fused silica". Review of Scientific Instruments. 72 (9): 3670. arXiv:gr-qc/0009035. Bibcode:2001RScI...72.3670P. doi:10.1063/1.1394183.
  8. ^ a b c Malitson, I. H. (October 1965). "Interspecimen Comparison of the Refractive Index of Fused Silica" (PDF). Journal of the Optical Society of America. 55 (10): 1205–1209. doi:10.1364/JOSA.55.001205. Retrieved 2014-07-12.
  9. ^ a b Kitamura, Rei; Pilon, Laurent; Jonasz, Miroslaw (2007-11-19). "Optical Constants of Silica Glass From Extreme Ultraviolet to Far Infrared at Near Room Temperatures" (PDF). Applied Optics. 46 (33): 8118–8133. Bibcode:2007ApOpt..46.8118K. doi:10.1364/AO.46.008118. Retrieved 2014-07-12.
  10. ^ Wapler, M. C.; Leupold, J.; Dragonu, I.; von Elverfeldt, D.; Zaitsev, M.; Wallrabe, U. (2014). "Magnetic properties of materials for MR engineering, micro-MR and beyond". JMR. 242: 233–242. arXiv:1403.4760. Bibcode:2014JMagR.242..233W. doi:10.1016/j.jmr.2014.02.005.
  11. ^ "Keysight Technologies GENESYS Concepts" (PDF). Keysight Technologies.
  12. ^ "Fused Silica". OpticsLand. Archived from the original on 2013-06-02. Retrieved 2016-02-27.
  13. ^ Surface tension and viscosity measurement of optical glasses using a scanning CO2 laser
  14. ^ "Refractive Index of Fused Silica (Fused Quartz)". Refractive Index. Retrieved 2017-08-18.

External links


The Benthoscope was a deep sea submersible designed by Otis Barton after the Second World War. He hired the Watson-Stillman Company, who had earlier constructed his and William Beebe's bathysphere to produce the new design of deep diving vessel, which was named from the Greek benthos, meaning "bottom".

The Benthoscope was essentially similar to the bathysphere, but was built to withstand higher pressures, with a crush depth of 10,000 feet (3,048 m). Its internal diameter was 4.5 feet (1.4 m), and its wall thickness was 1.75 inches (44.5 mm). It weighed 7 tons (6,350 kg), an increase in weight of 1,600 pounds (726 kg) over the bathysphere. Two windows of fused quartz were installed, one facing straight ahead and the other diagonally down. Other arrangements followed the bathysphere, with oxygen supplied from cylinders, and calcium chloride and soda lime used to absorb moisture and CO2 respectively.

In August 1949, Barton established a new world depth record with a solo descent to 4,500 feet, which remains the deepest dive by a submersible suspended by a cable.

The Benthoscope is now on display in front of the Los Angeles Maritime Museum in San Pedro, California.

Color reaction

In chemistry, a color reaction or colour reaction is a chemical reaction that is used to transform colorless chemical compounds into colored derivatives which can be detected visually or with the aid of a colorimeter.

The concentration of a colorless solution cannot normally be determined with a colorimeter. The addition of a color reagent leads to a color reaction and the absorbance of the colored product can then be measured with a colorimeter.

A change in absorbance in the ultraviolet range cannot be detected by eye but can be measured by a suitably equipped colorimeter. A special colorimeter is required because standard colorimeters cannot operate below a wavelength of 400 nanometers. It is also necessary to use fused quartz cuvettes because glass is opaque to ultraviolet.


A cuvette (French: cuvette = "little vessel") is a small tube-like container with straight sides and a circular or square cross section. It is sealed at one end, and made of a clear, transparent material such as plastic, glass, or fused quartz. Cuvettes are designed to hold samples for spectroscopic measurement, where a beam of light is passed through the sample within the cuvette to measure the absorbance, transmittance, fluorescence intensity, fluorescence polarization, or fluorescence lifetime of the sample. This measurement is done with a spectrophotometer.


An EPROM (rarely EROM), or erasable programmable read-only memory, is a type of memory chip that retains its data when its power supply is switched off. Computer memory that can retrieve stored data after a power supply has been turned off and back on is called non-volatile. It is an array of floating-gate transistors individually programmed by an electronic device that supplies higher voltages than those normally used in digital circuits. Once programmed, an EPROM can be erased by exposing it to strong ultraviolet light source (such as from a mercury-vapor light). EPROMs are easily recognizable by the transparent fused quartz window in the top of the package, through which the silicon chip is visible, and which permits exposure to ultraviolet light during erasing.

Hemispherical resonator gyroscope

The Hemispherical Resonator Gyroscope (HRG), also called wine-glass gyroscope or mushroom gyro, is a compact, low noise, high performance angular rate or rotation sensor. An HRG is made using a thin solid-state hemispherical shell, anchored by a thick stem. This shell is driven to a flexural resonance by electrostatic forces generated by electrodes which are deposited directly onto separate fused-quartz structures that surround the shell. The gyroscopic effect is obtained from the inertial property of the flexural standing waves. Although the HRG is a mechanical system, it has no moving parts, and can be very compact.

High-intensity discharge lamp

High-intensity discharge lamps (HID lamps) are a type of electrical gas-discharge lamp which produces light by means of an electric arc between tungsten electrodes housed inside a translucent or transparent fused quartz or fused alumina arc tube. This tube is filled with noble gas and often also contains suitable metal or metal salts. The noble gas enables the arc's initial strike. Once the arc is started, it heats and evaporates the metallic admixture. Its presence in the arc plasma greatly increases the intensity of visible light produced by the arc for a given power input, as the metals have many emission spectral lines in the visible part of the spectrum. High-intensity discharge lamps are a type of arc lamp.

Brand new high-intensity discharge lamps make more visible light per unit of electric power consumed than fluorescent and incandescent lamps, since a greater proportion of their radiation is visible light in contrast to infrared. However, the lumen output of HID lighting can deteriorate by up to 70% over 10,000 burning hours.

Many modern vehicles use HID bulbs for the main lighting systems, some applications are now moving from HID bulbs to LED and laser technology. However, this HID technology is not new and was first demonstrated by Francis Hauksbee in 1705.

Mercury-vapor lamp

A mercury-vapor lamp is a gas discharge lamp that uses an electric arc through vaporized mercury to produce light. The arc discharge is generally confined to a small fused quartz arc tube mounted within a larger borosilicate glass bulb. The outer bulb may be clear or coated with a phosphor; in either case, the outer bulb provides thermal insulation, protection from the ultraviolet radiation the light produces, and a convenient mounting for the fused quartz arc tube.

Mercury vapor lamps are more energy efficient than incandescent and most fluorescent lights, with luminous efficacies of 35 to 65 lumens/watt. Their other advantages are a long bulb lifetime in the range of 24,000 hours and a high intensity, clear white light output. For these reasons, they are used for large area overhead lighting, such as in factories, warehouses, and sports arenas as well as for streetlights. Clear mercury lamps produce white light with a bluish-green tint due to mercury's combination of spectral lines. This is not flattering to human skin color, so such lamps are typically not used in retail stores. "Color corrected" mercury bulbs overcome this problem with a phosphor on the inside of the outer bulb that emits white light, offering better color rendition.

They operate at an internal pressure of around one atmosphere and require special fixtures, as well as an electrical ballast. They also require a warm-up period of 4 – 7 minutes to reach full light output. Mercury vapor lamps are becoming obsolete due to the higher efficiency and better color balance of metal halide lamps.

Metal-halide lamp

A metal-halide lamp is an electrical lamp that produces light by an electric arc through a gaseous mixture of vaporized mercury and metal halides (compounds of metals with bromine or iodine). It is a type of high-intensity discharge (HID) gas discharge lamp. Developed in the 1960s, they are similar to mercury vapor lamps, but contain additional metal halide compounds in the quartz arc tube, which improve the efficiency and color rendition of the light.

The most common metal halide compound used is sodium iodide. Once the arc tube reaches its running temperature, the sodium dissociates from the iodine, adding orange and reds to the lamp's spectrum from the sodium D line as the metal ionizes.

As a result, metal-halide lamps have high luminous efficacy of around 75–100 lumens per watt, which is about twice that of mercury vapor lights and 3 to 5 times that of incandescent lights and produce an intense white light. Lamp life is 6,000 to 15,000 hours. As one of the most efficient sources of high CRI white light, metal halides as of 2005 were the fastest growing segment of the lighting industry. They are used for wide area overhead lighting of commercial, industrial, and public spaces, such as parking lots, sports arenas, factories, and retail stores, as well as residential security lighting and automotive headlamps (xenon headlights).

The lamps consist of a small fused quartz or ceramic arc tube which contains the gases and the arc, enclosed inside a larger glass bulb which has a coating to filter out the ultraviolet light produced. They operate at a pressure between 4 and 20 atmospheres, and require special fixtures to operate safely, as well as an electrical ballast. Metal atoms produce most of the light output. They require a warm-up period of several minutes to reach full light output.

Nicholas U. Mayall Telescope

The Nicholas U. Mayall Telescope, also known as the Mayall 4-meter Telescope, is a four-meter reflector telescope located at the Kitt Peak National Observatory in Arizona and named after Nicholas U. Mayall. It saw first light on February 27, 1973, and was the second-largest telescope in the world at that time. Initial observers included: David Crawford, Nicholas Mayall, and Arthur Hoag. It was dedicated on June 20, 1973 after Mayall's retirement as director. The mirror has an f/2.7 hyperboloidal shape. It is made from a two-foot (61 cm (24 in)) thick fused quartz disk that is supported in an advanced-design mirror cell. The prime focus has a field of view six times larger than that of the Hale reflector. An identical reflector was later built at Cerro Tololo Inter-American Observatory, in Chile. It is host to the Dark Energy Spectroscopic Instrument.

Quartz tube furnace

A quartz tube furnace is an electric heating device extensively used in material research. For example, ceramic research, wafer sintering and annealing and powder baking and the quartz tube lengths will differ. For experiments in laboratories the size of tube is from 1" to 13", typically controlled by S-type thermocouples. The temperature controllers often allow the operator to program the heating, dwelling and cooling rates.

Silicon dioxide

Silicon dioxide, also known as silica, silicic acid or silicic acid anydride is an oxide of silicon with the chemical formula SiO2, most commonly found in nature as quartz and in various living organisms. In many parts of the world, silica is the major constituent of sand. Silica is one of the most complex and most abundant families of materials, existing as a compound of several minerals and as synthetic product. Notable examples include fused quartz, fumed silica, silica gel, and aerogels. It is used in structural materials, microelectronics (as an electrical insulator), and as components in the food and pharmaceutical industries.

Inhaling finely divided crystalline silica is toxic and can lead to severe inflammation of the lung tissue, silicosis, bronchitis, lung cancer, and systemic autoimmune diseases, such as lupus and rheumatoid arthritis.

Uptake of amorphous silicon dioxide, in high doses, leads to non-permanent short-term inflammation, where all effects heal.

Silicone resin

Silicone resins are a type of silicone material which is formed by branched, cage-like oligosiloxanes with the general formula of RnSiXmOy, where R is a non reactive substituent, usually Methyl (Me) or Phenyl (Ph), and X is a functional group Hydrogen (H), Hydroxyl group (OH), Chlorine (Cl) or Alkoxy group (OR). These groups are further condensed in many applications, to give highly crosslinked, insoluble polysiloxane networks.When R is methyl, the four possible functional siloxane monomeric units are described as follows:

"M" stands for Me3SiO,

"D" for Me2SiO2,

"T" for MeSiO3 and

"Q" for SiO4.Note that a network of only Q groups becomes fused quartz.

The most abundant silicone resins are built of D and T units (DT resins) or from M and Q units (MQ resins), however many other combinations (MDT, MTQ, QDT) are also used in industry.

Silicone resins represent a broad range of products. Materials of molecular weight in the range of 1000–10,000 are very useful in pressure-sensitive adhesives, silicone rubbers, coatings and additives. Polysiloxane polymers with reactive side group functionality such as vinyl, acrylate, epoxy, mercaptan or amine, are used to create thermoset polymer matrix composites, coatings and adhesives.Silicone resins are prepared by hydrolytic condensation of various silicone precursors. In early processes of preparation of silicone resins sodium silicate and various chlorosilanes were used as starting materials. Although the starting materials were the least expensive ones (something typical for industry), structural control of the product was very difficult. More recently, a less reactive tetraethoxysilane - (TEOS) or ethyl polysilicate and various disiloxanes are used as starting materials.


Sitall aka Sitall CO-115M or Astrositall, is a crystalline glass-ceramic with ultra-low coefficient of thermal expansion (CTE). It was originally manufactured in the former Soviet Union and was used in the making of primary mirrors for the Russian Maksutov telescopes, but since dissolution has diminished in quality.Sitall has a CTE of only 0 ± 1.5×10−7 °C−1 in the temperature range −60 to 60 °C, placing it in a rather small group of transparent materials with low CTE such as Vycor, Zerodur, Cervit and fused quartz.Materials of low coefficient of thermal expansion are critical in the manufacture of optical elements for telescopes. In segmented mirror telescopes, it is desirable to have this coefficient as near zero as possible, and to have a high degree of homogeneity in the material. The Southern African Large Telescope (SALT) selected Sitall for the manufacture of its 91 primary mirror segments by Lytkarino Optical Glass Factory (LZOS). Using this company was a direct result of increased scientific collaboration between Russia and South Africa since 1994.Sitall was used for the primary and secondary mirrors of the VLT Survey Telescope.

Sitall has been ballistically tested by The Pentagon for use as a complex composite armour system, intended to resist chemical and kinetic assault.

Soda–lime glass

Soda–lime glass, also called soda–lime–silica glass, is the most prevalent type of glass, used for windowpanes and glass containers (bottles and jars) for beverages, food, and some commodity items. Glass bakeware is often made of borosilicate glass. Soda–lime glass accounts for about 90% of manufactured glass.Soda–lime glass is relatively inexpensive, chemically stable, reasonably hard, and extremely workable. Because it can be resoftened and remelted numerous times, it is ideal for glass recycling. It is used in preference to chemically-pure silica, which is silicon dioxide (SiO2), otherwise known as fused quartz. Whereas pure silica has excellent resistance to thermal shock, being able to survive immersion in water while red hot, its high melting temperature (1723 °C) and viscosity make it difficult to work with. Other substances are therefore added to simplify processing. One is the "soda", or sodium carbonate (Na2CO3), which lowers the glass-transition temperature. However, the soda makes the glass water-soluble, which is usually undesirable. To provide for better chemical durability, the "lime" is also added. This is calcium oxide (CaO), generally obtained from limestone. In addition, magnesium oxide (MgO) and alumina, which is aluminium oxide (Al2O3), contribute to the durability. The resulting glass contains about 70 to 74% silica by weight.

The manufacturing process for soda–lime glass consists in melting the raw materials, which are the silica, soda, lime (in the form of (Ca(OH)2), dolomite (CaMg(CO3)2, which provides the magnesium oxide), and aluminium oxide; along with small quantities of fining agents (e.g., sodium sulfate (Na2SO4), sodium chloride (NaCl), etc.) in a glass furnace at temperatures locally up to 1675 °C. The temperature is only limited by the quality of the furnace structure material and by the glass composition. Relatively inexpensive minerals such as trona, sand, and feldspar are usually used instead of pure chemicals. Green and brown bottles are obtained from raw materials containing iron oxide. The mix of raw materials is termed batch.

Soda–lime glass is divided technically into glass used for windows, called flat glass, and glass for containers, called container glass. The two types differ in the application, production method (float process for windows, blowing and pressing for containers), and chemical composition. Flat glass has a higher magnesium oxide and sodium oxide content than container glass, and a lower silica, calcium oxide, and aluminium oxide content. From the lower content of highly water-soluble ions (sodium and magnesium) in container glass comes its slightly higher chemical durability against water, which is required especially for storage of beverages and food.


A strainmeter is an instrument used by geophysicists to measure the

deformation of the Earth.

Linear strainmeters measure the changes in the distance between two points,

using either a solid piece of material (over a short distance)

or a laser interferometer (over a long distance, up to several hundred meters).

The type using a solid length standard was invented by Benioff in 1932,

using an iron pipe; later instruments used rods made of fused quartz.

Modern instruments of this type can make measurements of length changes over

very small distances, and are commonly placed in boreholes to measure

small changes in the diameter of the borehole.

Another type of borehole instrument detects changes in a volume filled with

fluid (such as silicone oil).

The most common type is the dilatometer invented by Sacks and Evertson in the USA

(patent 3,635,076);

a design that uses specially shaped volumes to measure the strain tensor

has been developed by Sakata in Japan.

All these types of strainmeters can measure deformation over frequencies

from a few Hz to periods of days, months, and years. This allows them to measure

signals at lower frequencies than can be detected with seismometers.

Most strainmeter records show signals from the earth tides, and seismic waves

from earthquakes.

At longer periods, they can also record the gradual accumulation of stress (physics)

caused by plate tectonics, the release of this stress in earthquakes,

and rapid changes of stress following earthquakes.

The most extensive network of strainmeters is installed in Japan;

it includes mostly quartz-bar instruments in tunnels and borehole strainmeters,

with a few laser instruments.

Starting in 2003 there has been a major effort (the Plate Boundary Observatory)

to install many more strainmeters along the Pacific/North-America plate boundary

in the United States.

The aim is to install about 100 borehole strainmeters,

primarily in Washington, Oregon and California, and five laser strainmeters,

all in California.

Tellurite glass

Tellurite glasses contain tellurium oxide (TeO2) as the main component.

Tube furnace

A tube furnace is an electric heating device used to conduct syntheses and purifications of inorganic compounds and occasionally in organic synthesis. One possible design consists of a cylindrical cavity surrounded by heating coils that are embedded in a thermally insulating matrix. Temperature can be controlled via feedback from a thermocouple. More elaborate tube furnaces have two (or more) heating zones useful for transport experiments. Some digital temperature controllers provide an RS232 interface, and permit the operator to program segments for uses like ramping, soaking, sintering, and more. Advanced materials in the heating elements, such as molybdenum disilicide offered in certain models can now produce working temperatures up to 1800 °C. This facilitates more sophisticated applications. Common material for the reaction tubes include alumina, Pyrex, and fused quartz.

The tube furnace was invented in the first decade of the 20th century and was originally used to manufacture ceramic filaments for Nernst lamps and glowers.

Xenon arc lamp

A xenon arc lamp is a highly specialized type of gas discharge lamp, an electric light that produces light by passing electricity through ionized xenon gas at high pressure. It produces a bright white light that closely mimics natural sunlight, which extends its applications into the film, and daylight simulation industries. Xenon arc lamps are used in movie projectors in theaters, in searchlights, and for, as mentioned previously, specialized uses in industry and research to simulate sunlight, often for product testing.

Xenon headlamps in automobiles are actually metal-halide lamps, where a xenon arc is only used during start-up to correct the color temperature.


Zerodur (notation of the manufacturer: ZERODUR®), a registered trademark of Schott AG, is a lithium-aluminosilicate glass-ceramic produced by Schott AG since 1968. It has been used for a number of very large telescope mirrors including Keck I, Keck II, and SOFIA, as well as some smaller telescopes (such as the GREGOR Solar Telescope). With its very low coefficient of thermal expansion it can be used to produce mirrors that retain acceptable figures in extremely cold environments such as deep space. Although it has advantages for applications requiring a coefficient of thermal expansion less than that of borosilicate glass, it remains very expensive as compared to borosilicate. The tight tolerance on CTE, ±0.007×10−6 K−1, allows highly accurate applications that require high-precision.

This page is based on a Wikipedia article written by authors (here).
Text is available under the CC BY-SA 3.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.