Silicon carbide (SiC), also known as carborundum (), is a hard chemical compound containing

silicon Silicon is a chemical element; it has symbol Si and atomic number 14. It is a hard, brittle crystalline solid with a blue-grey metallic lustre, and is a tetravalent metalloid (sometimes considered a non-metal) and semiconductor. It is a membe ...

and

carbon Carbon () is a chemical element; it has chemical symbol, symbol C and atomic number 6. It is nonmetallic and tetravalence, tetravalent—meaning that its atoms are able to form up to four covalent bonds due to its valence shell exhibiting 4 ...

. A wide bandgap

semiconductor A semiconductor is a material with electrical conductivity between that of a conductor and an insulator. Its conductivity can be modified by adding impurities (" doping") to its crystal structure. When two regions with different doping level ...

, it occurs in nature as the extremely rare mineral moissanite, but has been mass-produced as a powder and crystal since 1893 for use as an abrasive. Grains of silicon carbide can be bonded together by

sintering Sintering or frittage is the process of compacting and forming a solid mass of material by pressure or heat without melting it to the point of liquefaction. Sintering happens as part of a manufacturing process used with metals, ceramics, plas ...

to form very hard

ceramic A ceramic is any of the various hard, brittle, heat-resistant, and corrosion-resistant materials made by shaping and then firing an inorganic, nonmetallic material, such as clay, at a high temperature. Common examples are earthenware, porcela ...

s that are widely used in applications requiring high endurance, such as car brakes, car clutches and ceramic plates in

bulletproof vest A bulletproof vest, also known as a ballistic vest or bullet-resistant vest, is a type of body armor designed to absorb impact and prevent the penetration of firearm projectiles and explosion fragments to the torso. The vest can be either soft ...

s. Large single crystals of silicon carbide can be grown by the Lely method and they can be cut into gems known as synthetic moissanite. Electronic applications of silicon carbide such as

light-emitting diode A light-emitting diode (LED) is a semiconductor device that emits light when current flows through it. Electrons in the semiconductor recombine with electron holes, releasing energy in the form of photons. The color of the light (corre ...

s (LEDs) and detectors in early radios were first demonstrated around 1907. SiC is used in semiconductor electronics devices that operate at high temperatures or high voltages, or both.

Natural occurrence

Naturally occurring moissanite is found in only minute quantities in certain types of

meteorite A meteorite is a rock (geology), rock that originated in outer space and has fallen to the surface of a planet or Natural satellite, moon. When the original object enters the atmosphere, various factors such as friction, pressure, and chemical ...

, corundum deposits, and

kimberlite Kimberlite is an igneous rock and a rare variant of peridotite. It is most commonly known as the main host matrix for diamonds. It is named after the town of Kimberley, Northern Cape, Kimberley in South Africa, where the discovery of an 83.5-Car ...

. Virtually all the silicon carbide sold in the world, including moissanite jewels, is synthetic. Natural moissanite was first found in 1893 as a small component of the Canyon Diablo meteorite in

Arizona Arizona is a U.S. state, state in the Southwestern United States, Southwestern region of the United States, sharing the Four Corners region of the western United States with Colorado, New Mexico, and Utah. It also borders Nevada to the nort ...

by Ferdinand Henri Moissan, after whom the material was named in 1905. Moissan's discovery of naturally occurring SiC was initially disputed because his sample may have been contaminated by silicon carbide saw blades that were already on the market at that time. While rare on Earth, silicon carbide is remarkably common in space. It is a common form of stardust found around carbon-rich stars, and examples of this stardust have been found in pristine condition in primitive (unaltered) meteorites. The silicon carbide found in space and in meteorites is almost exclusively the beta-polymorph. Analysis of SiC grains found in the Murchison meteorite, a carbonaceous chondrite meteorite, has revealed anomalous isotopic ratios of carbon and silicon, indicating that these grains originated outside the

Solar System The Solar SystemCapitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Sola ...

History

Early experiments

Non-systematic, less-recognized and often unverified syntheses of silicon carbide include: * César-Mansuète Despretz's passing an electric current through a carbon rod embedded in sand (1849) * Robert Sydney Marsden's dissolution of silica in molten silver in a graphite crucible (1881) * Paul Schuetzenberger's heating of a mixture of silicon and silica in a graphite crucible (1881) * Albert Colson's heating of silicon under a stream of ethylene (1882).

Wide-scale production

Wide-scale production is credited to Edward Goodrich Acheson in 1891. Acheson was attempting to prepare artificial diamonds when he heated a mixture of clay (aluminium silicate) and powdered coke (carbon) in an iron bowl. He called the blue crystals that formed ''carborundum'', believing it to be a new compound of carbon and aluminium, similar to corundum. Henri Moissan also synthesized SiC by several routes, including dissolution of carbon in molten silicon, melting a mixture of calcium carbide and silica, and by reducing silica with carbon in an electric furnace. Acheson patented the method for making silicon carbide powder on February 28, 1893. Acheson also developed the electric batch furnace by which SiC is still made today and formed the Carborundum Company to manufacture bulk SiC, initially for use as an abrasive. In 1900 the company settled with the Electric Smelting and Aluminum Company when a judge's decision gave "priority broadly" to its founders "for reducing ores and other substances by the incandescent method". The first use of SiC was as an abrasive. This was followed by electronic applications. In the beginning of the 20th century, silicon carbide was used as a detector in the first radios. In 1907 Henry Joseph Round produced the first LED by applying a voltage to a SiC crystal and observing yellow, green and orange emission at the cathode. The effect was later rediscovered by O.V. Losev in the

Soviet Union The Union of Soviet Socialist Republics. (USSR), commonly known as the Soviet Union, was a List of former transcontinental countries#Since 1700, transcontinental country that spanned much of Eurasia from 1922 until Dissolution of the Soviet ...

, in 1923.

Production

Because natural moissanite is extremely scarce, most silicon carbide is synthetic. Silicon carbide is used as an abrasive, as well as a

and diamond simulant of gem quality. The simplest process to manufacture silicon carbide is to combine

silica Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula , commonly found in nature as quartz. In many parts of the world, silica is the major constituent of sand. Silica is one of the most complex and abundant f ...

sand Sand is a granular material composed of finely divided mineral particles. Sand has various compositions but is usually defined by its grain size. Sand grains are smaller than gravel and coarser than silt. Sand can also refer to a textural ...

and

in an Acheson graphite electric resistance furnace at a high temperature, between and . Fine SiO₂ particles in plant material (e.g. rice husks) can be converted to SiC by heating in the excess carbon from the organic material. The silica fume, which is a byproduct of producing silicon metal and ferrosilicon alloys, can also be converted to SiC by heating with graphite at . The material formed in the Acheson furnace varies in purity, according to its distance from the

graphite Graphite () is a Crystallinity, crystalline allotrope (form) of the element carbon. It consists of many stacked Layered materials, layers of graphene, typically in excess of hundreds of layers. Graphite occurs naturally and is the most stable ...

resistor heat source. Colorless, pale yellow and green crystals have the highest purity and are found closest to the resistor. The color changes to blue and black at greater distance from the resistor, and these darker crystals are less pure. Nitrogen and aluminium are common impurities, and they affect the electrical conductivity of SiC. Lely SiC Crystal

Pure silicon carbide can be made by the Lely process, in which SiC powder is sublimed into high-temperature species of silicon, carbon, silicon dicarbide (SiC₂), and disilicon carbide (Si₂C) in an

argon Argon is a chemical element; it has symbol Ar and atomic number 18. It is in group 18 of the periodic table and is a noble gas. Argon is the third most abundant gas in Earth's atmosphere, at 0.934% (9340 ppmv). It is more than twice as abu ...

gas ambient at 2,500 °C and redeposited into flake-like single crystals, sized up to 2 × 2 cm, at a slightly colder substrate. This process yields high-quality single crystals, mostly of 6H-SiC phase (because of high growth temperature). A modified Lely process involving induction heating in graphite crucibles yields even larger single crystals of 4 inches (10 cm) in diameter, having a section 81 times larger compared to the conventional Lely process. Silicon carbide wafers are often grown using this method, known in the industry as physical vapor transport with a seed wafer made of SiC. SiC powder is heated until it sublimes and then the SiC vapor cools and deposits below the seed crystal. Cubic SiC is usually grown by the more expensive process of

chemical vapor deposition Chemical vapor deposition (CVD) is a vacuum deposition method used to produce high-quality, and high-performance, solid materials. The process is often used in the semiconductor industry to produce thin films. In typical CVD, the wafer (electro ...

(CVD) of silane, hydrogen and nitrogen. Homoepitaxial and heteroepitaxial SiC layers can be grown employing both gas and liquid phase approaches. To form complexly shaped SiC, preceramic polymers can be used as precursors which form the ceramic product through

pyrolysis Pyrolysis is a process involving the Bond cleavage, separation of covalent bonds in organic matter by thermal decomposition within an Chemically inert, inert environment without oxygen. Etymology The word ''pyrolysis'' is coined from the Gree ...

at temperatures in the range 1,000–1,100 °C. Precursor materials to obtain silicon carbide in such a manner include polycarbosilanes, poly(methylsilyne) and polysilazanes. Silicon carbide materials obtained through the pyrolysis of preceramic polymers are known as polymer derived ceramics or PDCs. Pyrolysis of preceramic polymers is most often conducted under an inert atmosphere at relatively low temperatures. Relative to the CVD process, the pyrolysis method is advantageous because the polymer can be formed into various shapes prior to thermalization into the ceramic. SiC can also be made into wafers by cutting a single crystal either using a diamond wire saw or by using a laser. SiC is a useful semiconductor used in power electronics.

Structure and properties

Silicon carbide exists in about 250 crystalline forms. Through inert atmospheric pyrolysis of preceramic polymers, silicon carbide in a glassy amorphous form is also produced. The polymorphism of SiC is characterized by a large family of similar crystalline structures called polytypes. They are variations of the same chemical compound that are identical in two dimensions and differ in the third. Thus, they can be viewed as layers stacked in a certain sequence. Alpha silicon carbide (α-SiC) is the most commonly encountered polymorph, and is formed at temperatures greater than 1,700 °C and has a

hexagonal In geometry, a hexagon (from Greek , , meaning "six", and , , meaning "corner, angle") is a six-sided polygon. The total of the internal angles of any simple (non-self-intersecting) hexagon is 720°. Regular hexagon A regular hexagon is d ...

crystal structure In crystallography, crystal structure is a description of ordered arrangement of atoms, ions, or molecules in a crystalline material. Ordered structures occur from intrinsic nature of constituent particles to form symmetric patterns that repeat ...

(similar to

Wurtzite Wurtzite is a zinc and iron sulfide mineral with the chemical formula , a less frequently encountered Polymorphism (materials science), structural polymorph form of sphalerite. The iron content is variable up to eight percent.Palache, Charles, H ...

). The beta modification (β-SiC), with a zinc blende crystal structure (similar to

diamond Diamond is a Allotropes of carbon, solid form of the element carbon with its atoms arranged in a crystal structure called diamond cubic. Diamond is tasteless, odourless, strong, brittle solid, colourless in pure form, a poor conductor of e ...

), is formed at temperatures below 1,700 °C. Until recently, the beta form has had relatively few commercial uses, although there is now increasing interest in its use as a support for heterogeneous catalysts, owing to its higher surface area compared to the alpha form. Pure SiC is colorless. The brown to black color of the industrial product results from

iron Iron is a chemical element; it has symbol Fe () and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, forming much of Earth's o ...

impurities. The rainbow-like luster of the crystals is due to the thin-film interference of a passivation layer of

silicon dioxide Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula , commonly found in nature as quartz. In many parts of the world, silica is the major constituent of sand. Silica is one of the most complex and abundan ...

that forms on the surface. The high sublimation temperature of SiC (approximately 2,700 °C) makes it useful for bearings and furnace parts. Silicon carbide does not melt but begins to sublimate near 2,700 °C like graphite, having an appreciable vapor pressure near that temperature. It is also highly inert chemically, partly due to the formation of a thin passivated layer of SiO₂. There is currently much interest in its use as a

semiconductor material A semiconductor is a material with electrical conductivity between that of a Electrical conductor, conductor and an Insulator (electricity), insulator. Its conductivity can be modified by adding impurities ("doping (semiconductor), doping") to ...

in electronics, where its high thermal conductivity, high

electric field An electric field (sometimes called E-field) is a field (physics), physical field that surrounds electrically charged particles such as electrons. In classical electromagnetism, the electric field of a single charge (or group of charges) descri ...

breakdown strength and high maximum current density make it more promising than silicon for high-powered devices. SiC has a very low coefficient of thermal expansion of about 2.3 × 10⁻⁶ K⁻¹ near 300 K (for 4H and 6H SiC) and experiences no

phase transition In physics, chemistry, and other related fields like biology, a phase transition (or phase change) is the physical process of transition between one state of a medium and another. Commonly the term is used to refer to changes among the basic Sta ...

s in the temperature range 5 K to 340 K that would cause discontinuities in the thermal expansion coefficient.

Electrical conductivity

Silicon carbide is a

, which can be doped n-type by

nitrogen Nitrogen is a chemical element; it has Symbol (chemistry), symbol N and atomic number 7. Nitrogen is a Nonmetal (chemistry), nonmetal and the lightest member of pnictogen, group 15 of the periodic table, often called the Pnictogen, pnictogens. ...

phosphorus Phosphorus is a chemical element; it has Chemical symbol, symbol P and atomic number 15. All elemental forms of phosphorus are highly Reactivity (chemistry), reactive and are therefore never found in nature. They can nevertheless be prepared ar ...

and p-type by

beryllium Beryllium is a chemical element; it has Symbol (chemistry), symbol Be and atomic number 4. It is a steel-gray, hard, strong, lightweight and brittle alkaline earth metal. It is a divalent element that occurs naturally only in combination with ...

, boron,

aluminium Aluminium (or aluminum in North American English) is a chemical element; it has chemical symbol, symbol Al and atomic number 13. It has a density lower than that of other common metals, about one-third that of steel. Aluminium has ...

, or

gallium Gallium is a chemical element; it has Chemical symbol, symbol Ga and atomic number 31. Discovered by the French chemist Paul-Émile Lecoq de Boisbaudran in 1875, elemental gallium is a soft, silvery metal at standard temperature and pressure. ...

. Metallic conductivity has been achieved by heavy doping with boron, aluminium or nitrogen. Superconductivity has been detected in 3C-SiC:Al, 3C-SiC:B and 6H-SiC:B at similar temperatures ~1.5 K. A crucial difference is however observed for the magnetic field behavior between aluminium and boron doping: 3C-SiC:Al is type-II. In contrast, 3C-SiC:B is type-I, as is 6H-SiC:B. Thus the superconducting properties seem to depend more on dopant (B vs. Al) than on polytype (3C- vs 6H-). In an attempt to explain this dependence, it was noted that B substitutes at C sites in SiC, but Al substitutes at Si sites. Therefore, Al and B "see" different environments, in both polytypes.

Uses

Abrasive and cutting tools

In manufacturing, it is used for its hardness in abrasive machining processes such as grinding, honing, water-jet cutting and sandblasting. SiC provides a much sharper and harder alternative for sand blasting as compared to

aluminium oxide Aluminium oxide (or aluminium(III) oxide) is a chemical compound of aluminium and oxygen with the chemical formula . It is the most commonly occurring of several Aluminium oxide (compounds), aluminium oxides, and specifically identified as alum ...

. Particles of silicon carbide are laminated to paper to create sandpapers and the grip tape on

skateboard A skateboard is a type of sports equipment used for skateboarding. It is usually made of a specially designed 7–8-ply maple plywood deck and has polyurethane wheels attached to the underside by a pair of skateboarding trucks. The skateboard ...

s. In the arts, silicon carbide is a popular abrasive in modern lapidary due to the durability and low cost of the material. In 1982 an exceptionally strong composite of

and silicon carbide whiskers was discovered. Development of this laboratory-produced composite to a commercial product took only three years. In 1985, the first commercial cutting tools made from this alumina and silicon carbide whisker-reinforced composite were introduced into the market.

Structural material

In the 1980s and 1990s, silicon carbide was studied in several research programs for high-temperature gas turbines in

Europe Europe is a continent located entirely in the Northern Hemisphere and mostly in the Eastern Hemisphere. It is bordered by the Arctic Ocean to the north, the Atlantic Ocean to the west, the Mediterranean Sea to the south, and Asia to the east ...

Japan Japan is an island country in East Asia. Located in the Pacific Ocean off the northeast coast of the Asia, Asian mainland, it is bordered on the west by the Sea of Japan and extends from the Sea of Okhotsk in the north to the East China Sea ...

and the

United States The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...

. The components were intended to replace

nickel Nickel is a chemical element; it has symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel is a hard and ductile transition metal. Pure nickel is chemically reactive, but large pieces are slo ...

superalloy

turbine A turbine ( or ) (from the Greek , ''tyrbē'', or Latin ''turbo'', meaning vortex) is a rotary mechanical device that extracts energy from a fluid flow and converts it into useful work. The work produced can be used for generating electrical ...

blades or nozzle vanes. However, none of these projects resulted in a production quantity, mainly because of its low impact resistance and its low fracture

toughness In materials science and metallurgy, toughness is the ability of a material to absorb energy and plastically deform without fracturing.boron carbide), silicon carbide is used in composite armor (e.g. Chobham armor), and in ceramic plates in bulletproof vests. Dragon Skin, which was produced by Pinnacle Armor, used disks of silicon carbide. Improved fracture toughness in SiC armor can be facilitated through the phenomenon of abnormal grain growth or AGG. The growth of abnormally long silicon carbide grains may serve to impart a toughening effect through crack-wake bridging, similar to whisker reinforcement. Similar AGG-toughening effects have been reported in Silicon nitride (Si₃N₄). Silicon carbide is used as a support and shelving material in high temperature kilns such as for firing ceramics, glass fusing, or glass casting. SiC kiln shelves are considerably lighter and more durable than traditional alumina shelves. In December 2015, infusion of silicon carbide nano-particles in molten

magnesium Magnesium is a chemical element; it has Symbol (chemistry), symbol Mg and atomic number 12. It is a shiny gray metal having a low density, low melting point and high chemical reactivity. Like the other alkaline earth metals (group 2 ...

was mentioned as a way to produce a new strong and plastic alloy suitable for use in aeronautics, aerospace, automobile and micro-electronics.

Automobile parts

Silicon-infiltrated carbon-carbon composite is used for high performance "ceramic" brake discs, as they are able to withstand extreme temperatures. The silicon reacts with the graphite in the carbon-carbon composite to become carbon-fiber-reinforced silicon carbide (C/SiC). These brake discs are used on some road-going sports cars, supercars, as well as other performance cars including the

Porsche Carrera GT The Porsche Carrera GT (Project Code 980) is a mid-engine sports car that was manufactured by German automobile manufacturer Porsche from 2003 to 2006. ''Sports Car International'' named the Carrera GT number one on its list of Sports Car Intern ...

, the Bugatti Veyron, the Chevrolet Corvette ZR1, the McLaren P1,

Bentley Bentley Motors Limited is a British designer, manufacturer and marketer of Luxury vehicle, luxury cars and Sport utility vehicle, SUVs. Headquartered in Crewe, England, the company was founded by W. O. Bentley (1888–1971) in 1919 in Crickle ...

Ferrari Ferrari S.p.A. (; ) is an Italian luxury sports car manufacturer based in Maranello. Founded in 1939 by Enzo Ferrari (1898–1988), the company built Auto Avio Costruzioni 815, its first car in 1940, adopted its current name in 1945, and be ...

, Lamborghini and some specific high-performance

Audi Audi AG () is a German automotive manufacturer of luxury vehicles headquartered in Ingolstadt, Bavaria, Germany. A subsidiary of the Volkswagen Group, Audi produces vehicles in nine production facilities worldwide. The origins of the compa ...

cars. Silicon carbide is also used in a sintered form for

diesel particulate filter A diesel particulate filter (DPF) is a device designed to remove diesel exhaust#Particulates, diesel particulate matter or soot from the exhaust gas of a diesel engine.Tom Nash (May 2003) "Diesels: The Smoke is clearing", ''Motor '' Vol.199 No. ...

s. It is also used as an oil additive to reduce friction, emissions, and harmonics.

Foundry crucibles

SiC is used in crucibles for holding melting metal in small and large foundry applications.

Electric systems

The earliest electrical application of SiC was as a surge protection in lightning arresters in electric power systems. These devices must exhibit high resistance until the

voltage Voltage, also known as (electrical) potential difference, electric pressure, or electric tension, is the difference in electric potential between two points. In a Electrostatics, static electric field, it corresponds to the Work (electrical), ...

across them reaches a certain threshold V_T at which point their resistance must drop to a lower level and maintain this level until the applied voltage drops below V_T flushing current into the ground. It was recognized early on that SiC had such a voltage-dependent resistance, and so columns of SiC pellets were connected between high-voltage power lines and the earth. When a

lightning strike A lightning strike or lightning bolt is a lightning event in which an electric discharge takes place between the atmosphere and the ground. Most originate in a cumulonimbus cloud and terminate on the ground, called cloud-to-ground (CG) lightning ...

to the line raises the line voltage sufficiently, the SiC column will conduct, allowing strike current to pass harmlessly to the earth instead of along the power line. The SiC columns proved to conduct significantly at normal power-line operating voltages and thus had to be placed in series with a

spark gap A spark gap consists of an arrangement of two Conductor (material), conducting electrodes separated by a gap usually filled with a gas such as air, designed to allow an electric spark to pass between the conductors. When the potential differenc ...

. This spark gap is ionized and rendered conductive when lightning raises the voltage of the power line conductor, thus effectively connecting the SiC column between the power conductor and the earth. Spark gaps used in lightning arresters are unreliable, either failing to strike an arc when needed or failing to turn off afterwards, in the latter case due to material failure or contamination by dust or salt. Usage of SiC columns was originally intended to eliminate the need for the spark gap in lightning arresters. Gapped SiC arresters were used for lightning-protection and sold under the GE and Westinghouse brand names, among others. The gapped SiC arrester has been largely displaced by no-gap varistors that use columns of

zinc oxide Zinc oxide is an inorganic compound with the Chemical formula, formula . It is a white powder which is insoluble in water. ZnO is used as an additive in numerous materials and products including cosmetics, Zinc metabolism, food supplements, rubbe ...

pellets.

Electronic circuit elements

Silicon carbide was the first commercially important semiconductor material. A crystal radio "carborundum" (synthetic silicon carbide) detector diode was patented by Henry Harrison Chase Dunwoody in 1906. It found much early use in shipboard receivers.

Power electronic devices

In 1993, the silicon carbide was considered a

in both research and early

mass production Mass production, also known as mass production, series production, series manufacture, or continuous production, is the production of substantial amounts of standardized products in a constant flow, including and especially on assembly lines ...

providing advantages for fast, high-temperature and/or high-voltage devices. The first devices available were Schottky diodes, followed by junction-gate FETs and

MOSFET upright=1.3, Two power MOSFETs in amperes">A in the ''on'' state, dissipating up to about 100 watt">W and controlling a load of over 2000 W. A matchstick is pictured for scale. In electronics, the metal–oxide–semiconductor field- ...

s for high-power switching.

Bipolar transistor A bipolar junction transistor (BJT) is a type of transistor that uses both electrons and electron holes as charge carriers. In contrast, a unipolar transistor, such as a field-effect transistor (FET), uses only one kind of charge carrier. A ...

s and thyristors were described. A major problem for SiC commercialization has been the elimination of defects: edge dislocations, screw dislocations (both hollow and closed core), triangular defects and basal plane dislocations. As a result, devices made of SiC crystals initially displayed poor reverse blocking performance, though researchers have been tentatively finding solutions to improve the breakdown performance. Apart from crystal quality, problems with the interface of SiC with silicon dioxide have hampered the development of SiC-based power MOSFETs and insulated-gate bipolar transistors. Although the mechanism is still unclear,

nitriding Nitriding is a heat treating process that diffusion, diffuses nitrogen into the surface of a metal to create a case-hardening, case-hardened surface. These processes are most commonly used on low-alloy steels. They are also used on titanium, alum ...

has dramatically reduced the defects causing the interface problems. In 2008, the first commercial JFETs rated at 1,200 V were introduced to the market, followed in 2011 by the first commercial MOSFETs rated at 1200 V. JFETs are now available rated 650 V to 1,700 V with resistance as low as 25 mΩ. Beside SiC switches and SiC Schottky diodes (also Schottky barrier diode, SBD) in the popular TO-247 and TO-220 packages, companies started even earlier to implement the bare chips into their power electronic modules. SiC SBD diodes found wide market spread being used in PFC circuits and IGBT power modules. Conferences such as the International Conference on Integrated Power Electronics Systems (CIPS) report regularly about the technological progress of SiC power devices. Major challenges for fully unleashing the capabilities of SiC power devices are: * Gate drive: SiC devices often require gate drive voltage levels that are different from their silicon counterparts and may be even unsymmetric, for example, +20 V and −5 V. * Packaging: SiC chips may have a higher power density than silicon power devices and are able to handle higher temperatures exceeding the silicon limit of 150 °C. New die attach technologies such as

are required to efficiently get the heat out of the devices and ensure a reliable interconnection. Beginning with Tesla Model 3 the inverters in the drive unit use 24 pairs of silicon carbide (SiC)

chips rated for 650 volts each. Silicon carbide in this instance gave Tesla a significant advantage over chips made of silicon in terms of size and weight. A number of automobile manufacturers are planning to incorporate silicon carbide into power electronic devices in their products. A significant increase in production of silicon carbide is projected, beginning with a large plant opened 2022 by Wolfspeed, in upstate New York. Uv-LED

LEDs

The phenomenon of

electroluminescence Electroluminescence (EL) is an optical phenomenon, optical and electrical phenomenon, in which a material emits light in response to the passage of an electric current or to a strong electric field. This is distinct from black body light emission ...

was discovered in 1907 using silicon carbide and some of the first commercial LEDs were based on this material. When General Electric of America introduced its SSL-1 Solid State Lamp in March 1967, using a tiny chip of semi-conducting SiC to emit a point of yellow light, it was then the world's brightest LED. By 1970 it had been usurped by brighter red LEDs, but yellow LEDs made from 3C-SiC continued to be manufactured in the Soviet Union in the 1970s and blue LEDs (6H-SiC) worldwide in the 1980s. Carbide LED production soon stopped when a different material, gallium nitride, showed 10–100 times brighter emission. This difference in efficiency is due to the unfavorable indirect bandgap of SiC, whereas GaN has a direct bandgap which favors light emission. However, SiC is still one of the important LED components: It is a popular substrate for growing GaN devices, and it also serves as a heat spreader in high-power LEDs.

Astronomy

The low thermal expansion coefficient, high hardness, rigidity and thermal conductivity make silicon carbide a desirable

mirror A mirror, also known as a looking glass, is an object that Reflection (physics), reflects an image. Light that bounces off a mirror forms an image of whatever is in front of it, which is then focused through the lens of the eye or a camera ...

material for

astronomical Astronomy is a natural science that studies celestial objects and the phenomena that occur in the cosmos. It uses mathematics, physics, and chemistry in order to explain their origin and their overall evolution. Objects of interest include ...

telescopes. The growth technology (

) has been scaled up to produce disks of polycrystalline silicon carbide up to in diameter, and several telescopes like the Herschel Space Telescope are already equipped with SiC optics, as well the Gaia

space observatory A space telescope (also known as space observatory) is a telescope in outer space used to observe astronomical objects. Suggested by Lyman Spitzer in 1946, the first operational telescopes were the American Orbiting Astronomical Observatory, OAO ...

spacecraft subsystems are mounted on a rigid silicon carbide frame, which provides a stable structure that will not expand or contract due to heat.

Thin-filament pyrometry

Silicon carbide fibers are used to measure gas temperatures in an optical technique called thin-filament pyrometry. It involves the placement of a thin filament in a hot gas stream. Radiative emissions from the filament can be correlated with filament temperature. Filaments are SiC fibers with a diameter of 15 micrometers, about one fifth that of a human hair. Because the fibers are so thin, they do little to disturb the flame and their temperature remains close to that of the local gas. Temperatures of about 800–2,500 K can be measured.

Heating elements

References to silicon carbide heating elements exist from the early 20th century when they were produced by Acheson's Carborundum Co. in the U.S. and EKL in Berlin. Silicon carbide offered increased

operating temperature An operating temperature is the allowable temperature range of the local ambient environment at which an electrical or mechanical device operates. The device will operate effectively within a specified temperature range which varies based on the de ...

s compared with metallic heaters. Silicon carbide elements are used today in the melting of glass and non-ferrous metal, heat treatment of metals, float glass production, production of ceramics and electronics components, igniters in pilot lights for gas heaters, etc.

Heat shielding

The outer thermal protection layer of NASA's LOFTID inflatable heat shield incorporates a woven ceramic made from silicon carbide, with fiber of such small diameter that it can be bundled and spun into a yarn.

Nuclear applications

Due to SiC's exceptional

neutron The neutron is a subatomic particle, symbol or , that has no electric charge, and a mass slightly greater than that of a proton. The Discovery of the neutron, neutron was discovered by James Chadwick in 1932, leading to the discovery of nucle ...

absorption capability, it is used as fuel cladding in nuclear reactors and as nuclear waste containment material. It is also used in producing radiation detectors for monitoring radiation levels in nuclear facilities, environmental monitoring, and

medical imaging Medical imaging is the technique and process of imaging the interior of a body for clinical analysis and medical intervention, as well as visual representation of the function of some organs or tissues (physiology). Medical imaging seeks to revea ...

. Again, SiC sensors and electronics for nuclear reactor applications are being developed potentially for future Martian nuclear power and the emerging terrestrial micro nuclear power plants.

Nuclear fuel particles and cladding

Silicon carbide is an important material in TRISO-coated fuel particles, the type of

nuclear fuel Nuclear fuel refers to any substance, typically fissile material, which is used by nuclear power stations or other atomic nucleus, nuclear devices to generate energy. Oxide fuel For fission reactors, the fuel (typically based on uranium) is ...

found in high temperature gas cooled reactors such as the Pebble Bed Reactor. A layer of silicon carbide gives coated fuel particles structural support and is the main diffusion barrier to the release of fission products. Silicon carbide

composite material A composite or composite material (also composition material) is a material which is produced from two or more constituent materials. These constituent materials have notably dissimilar chemical or physical properties and are merged to create a ...

has been investigated for use as a replacement for Zircaloy cladding in light water reactors. One of the reasons for this investigation is that, Zircaloy experiences hydrogen embrittlement as a consequence of the corrosion reaction with water. This produces a reduction in fracture toughness with increasing volumetric fraction of radial hydrides. This phenomenon increases drastically with increasing temperature to the detriment of the material. Silicon carbide cladding does not experience this same mechanical degradation, but instead retains strength properties with increasing temperature. The composite consists of SiC fibers wrapped around a SiC inner layer and surrounded by an SiC outer layer. Problems have been reported with the ability to join the pieces of the SiC composite.

Jewelry

As a

gemstone A gemstone (also called a fine gem, jewel, precious stone, semiprecious stone, or simply gem) is a piece of mineral crystal which, when cut or polished, is used to make jewellery, jewelry or other adornments. Certain Rock (geology), rocks (such ...

used in

jewelry Jewellery (or jewelry in American English) consists of decorative items worn for personal adornment such as brooches, ring (jewellery), rings, necklaces, earrings, pendants, bracelets, and cufflinks. Jewellery may be attached to the body or the ...

, silicon carbide is called "synthetic moissanite" or just "moissanite" after the mineral name. Moissanite is similar to

in several important respects: it is transparent and hard (9–9.5 on the

Mohs scale The Mohs scale ( ) of mineral hardness is a qualitative ordinal scale, from 1 to 10, characterizing scratch resistance of minerals through the ability of harder material to scratch softer material. The scale was introduced in 1812 by the Ger ...

, compared to 10 for diamond), with a

refractive index In optics, the refractive index (or refraction index) of an optical medium is the ratio of the apparent speed of light in the air or vacuum to the speed in the medium. The refractive index determines how much the path of light is bent, or refrac ...

between 2.65 and 2.69 (compared to 2.42 for diamond). Moissanite is somewhat harder than common cubic zirconia. Unlike diamond, moissanite can be strongly birefringent. For this reason, moissanite jewels are cut along the optic axis of the crystal to minimize birefringent effects. It is lighter (density 3.21 g/cm³ vs. 3.53 g/cm³), and much more resistant to heat than diamond. This results in a stone of higher luster, sharper facets, and good resilience. Loose moissanite stones may be placed directly into wax ring moulds for lost-wax casting, as can diamond, as moissanite remains undamaged by temperatures up to . Moissanite has become popular as a diamond substitute, and may be misidentified as diamond, since its

thermal conductivity The thermal conductivity of a material is a measure of its ability to heat conduction, conduct heat. It is commonly denoted by k, \lambda, or \kappa and is measured in W·m−1·K−1. Heat transfer occurs at a lower rate in materials of low ...

is closer to diamond than any other substitute. Many thermal diamond-testing devices cannot distinguish moissanite from diamond, but the gem is distinct in its

birefringence Birefringence, also called double refraction, is the optical property of a material having a refractive index that depends on the polarization and propagation direction of light. These optically anisotropic materials are described as birefrin ...

and a very slight green or yellow fluorescence under ultraviolet light. Some moissanite stones also have curved, string-like inclusions, which diamonds never have.

Steel production

Silicon carbide, dissolved in a basic oxygen furnace used for making

steel Steel is an alloy of iron and carbon that demonstrates improved mechanical properties compared to the pure form of iron. Due to steel's high Young's modulus, elastic modulus, Yield (engineering), yield strength, Fracture, fracture strength a ...

, acts as a

fuel A fuel is any material that can be made to react with other substances so that it releases energy as thermal energy or to be used for work (physics), work. The concept was originally applied solely to those materials capable of releasing chem ...

. The additional energy liberated allows the furnace to process more scrap with the same charge of hot metal. It can also be used to raise tap temperatures and adjust the carbon and silicon content. Silicon carbide is cheaper than a combination of

ferrosilicon Ferrosilicon is an ferroalloy, alloy of iron and silicon. It has a typical silicon content of 15–90% by weight and a high proportion of iron silicides. Production and reactions Ferrosilicon is produced by reduction of silica or sand with coke ...

and carbon, produces cleaner steel and lower emissions due to low levels of trace elements, has a low gas content, and does not lower the temperature of steel.

Catalyst support

The natural resistance to oxidation exhibited by silicon carbide, as well as the discovery of new ways to synthesize the cubic β-SiC form, with its larger surface area, has led to significant interest in its use as a heterogeneous

catalyst support In chemistry, a catalyst support or carrier is a material, usually a solid with a high surface area, to which a catalyst is affixed. The activity of heterogeneous catalysts is mainly promoted by atoms present at the accessible surface of the ma ...

. This form has already been employed as a catalyst support for the oxidation of

hydrocarbon In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons are examples of group 14 hydrides. Hydrocarbons are generally colourless and Hydrophobe, hydrophobic; their odor is usually fain ...

s, such as n-

butane Butane () is an alkane with the formula C4H10. Butane exists as two isomers, ''n''-butane with connectivity and iso-butane with the formula . Both isomers are highly flammable, colorless, easily liquefied gases that quickly vaporize at ro ...

, to maleic anhydride.

Carborundum printmaking

Silicon carbide is used in carborundum printmaking – a

collagraph Collagraphy (sometimes spelled collography) is a printmaking process in which materials are glued or sealed to a rigid substrate (such as paperboard or wood) to create a plate. Once inked, the plate becomes a tool for imprinting the design onto p ...

printmaking Printmaking is the process of creating work of art, artworks by printing, normally on paper, but also on fabric, wood, metal, and other surfaces. "Traditional printmaking" normally covers only the process of creating prints using a hand proces ...

technique. Carborundum grit is applied in a paste to the surface of an aluminium plate. When the paste is dry, ink is applied and trapped in its granular surface, then wiped from the bare areas of the plate. The ink plate is then printed onto paper in a rolling-bed press used for intaglio printmaking. The result is a print of painted marks embossed into the paper. Carborundum grit is also used in stone Lithography. Its uniform particle size allows it to be used to "Grain" a stone which removes the previous image. In a similar process to sanding, coarser grit Carborundum is applied to the stone and worked with a Levigator, typically a round plate eccentric on a perpendicular shaft, then gradually finer and finer grit is applied until the stone is clean. This creates a grease sensitive surface.

Graphene production

Silicon carbide can be used in the production of graphene because of its chemical properties that promote the production of graphene on the surface of SiC nanostructures. When it comes to its production, silicon is used primarily as a substrate to grow the graphene. But there are actually several methods that can be used to grow the graphene on the silicon carbide. The confinement controlled sublimation (CCS) growth method consists of a SiC chip that is heated under vacuum with graphite. Then the vacuum is released very gradually to control the growth of graphene. This method yields the highest quality graphene layers. But other methods have been reported to yield the same product as well. Another way of growing graphene would be thermally decomposing SiC at a high temperature within a vacuum. But, this method turns out to yield graphene layers that contain smaller grains within the layers. So, there have been efforts to improve the quality and yield of graphene. One such method is to perform ''ex situ''

graphitization Graphitization is a process of transforming a carbonaceous material, such as coal or the carbon in certain forms of iron alloys, into graphite. Process The graphitization process involves a restructuring of the molecular structure of the carbon ...

of silicon terminated SiC in an atmosphere consisting of argon. This method has proved to yield layers of graphene with larger domain sizes than the layer that would be attainable via other methods. This new method can be very viable to make higher quality graphene for a multitude of technological applications. When it comes to understanding how or when to use these methods of graphene production, most of them mainly produce or grow this graphene on the SiC within a growth enabling environment. It is utilized most often at rather higher temperatures (such as 1,300 °C) because of SiC thermal properties. However, there have been certain procedures that have been performed and studied that could potentially yield methods that use lower temperatures to help manufacture graphene. More specifically this different approach to graphene growth has been observed to produce graphene within a temperature environment of around 750 °C. This method entails the combination of certain methods like chemical vapor deposition (CVD) and surface segregation. And when it comes to the substrate, the procedure would consist of coating a SiC substrate with thin films of a transition metal. And after the rapid heat treating of this substance, the carbon atoms would then become more abundant at the surface interface of the transition metal film which would then yield graphene. And this process was found to yield graphene layers that were more continuous throughout the substrate surface.

Quantum physics

Silicon carbide can host point defects in the crystal lattice, which are known as color centers. These defects can produce single photons on demand and thus serve as a platform for single-photon source. Such a device is a fundamental resource for many emerging applications of quantum information science. If one pumps a color center via an external optical source or electric current, the color center will be brought to the excited state and then relax with the emission of one photon. One well known point defect in silicon carbide is the divacancy which has a similar electronic structure as the nitrogen-vacancy center in diamond. In 4H-SiC, the divacancy has four different configurations which correspond to four zero-phonon lines (ZPL). These ZPL values are written using the notation V_Si-V_C and the unit eV: hh(1.095), kk(1.096), kh(1.119), and hk(1.150).

Fishing rod guides

Silicon carbide is used in the manufacturing of fishing guides because of its durability and wear resistance. Silicon Carbide rings are fit into a guide frame, typically made from stainless steel or titanium which keep the line from touching the rod blank. The rings provide a low friction surface which improves casting distance while providing adequate hardness that prevents abrasion from braided fishing line.

Pottery glazes

Silicon carbide is used as a raw ingredient in some glazes applied to ceramics. At high temperatures it can reduce metal oxides forming

and carbon dioxide. This can be used to make the glaze foam and crater due to the evolved carbon dioxide gas, or to reduce the colorant oxides and achieve colors such as copper reds otherwise only possible in a fuel powered reduction firing in an electric kiln.

References

External links

* * * * * {{Authority control Abrasives Carbides Ceramic materials Deoxidizers Diamond simulants Gemstones Group IV semiconductors Inorganic silicon compounds Refractory materials Semiconductors Superhard materials Synthetic minerals