Silicon carbide (SiC), is an extremely hard and dense ceramic with wide bandgap semiconductor properties such as excellent chemical resistance, low coefficient of thermal expansion and superior strength and rigidity.
SiC is increasingly being employed in power devices to increase the withstand voltages and decrease turn-on resistance compared with traditional silicon devices. SiC boasts 10 times greater breakdown electric field strength compared to silicon.
Physical Properties
Silicon is one of the most prevalent elements in nature; it can be found in computer chips, white beaches and various oddities such as menstrual cups and breast implants. Silica–composed of silica found in 25% of Earth’s crust–is made up of silicon; while technically considered neither metal nor nonmetal it does conduct electricity well and gets better with temperature increases.
Silicon carbide is an ideal material for applications requiring high temperatures, such as chemical production and paper manufacturing, energy technology and pipe system components, and pipe system components. It has been known to withstand temperatures as high as 1600degC without losing hardness or strength.
Silicon carbide (SiC), in its three forms amorphous, polycrystalline and single-crystal forms, offers various applications. Of the three solid forms available to us today, single crystal SiC offers superior physical properties than its counterparts and should therefore be preferred over them for most industrial uses.
SiC is an extremely durable material composed of carbon and silicon atoms tightly bound together into tetrahedra in a crystal lattice, giving rise to an extremely durable material with a high melting point, second only to boron carbide. SiC also boasts an exceptionally wide bandgap energy and extremely high breakdown electric field making it suitable for numerous electronic applications – its superior properties enable SiC transistors to achieve lower “on” resistance while still maintaining their breakdown voltage thresholds.
Electrical Properties
Silicon is the dominant semiconductor material, yet its limitations have become apparent in applications like power electronics for electric vehicles and instruments found aboard space rovers and probes sent out to explore our planet. Silicon carbide’s superior material properties – including wider bandgap energy, an exceptionally high breakdown electric field, higher thermal conductivity and electron mobility – have increasingly become evident.
Silicon carbide devices possess the ability to withstand much higher breakdown voltage than their silicon counterparts, enabling smaller transistors with increased breakdown voltage tolerance while still offering very low ON resistance per unit area.
Porous SiC is subject to various compositional and processing conditions when being produced, with porosity increasing resistance by decreasing cross-sectional area available for conduction as well as deflecting charge carriers away.
Sintered porous SiC is easily adjustable by altering its chemical composition, sintering temperature, porosity, pore size and morphology as well as its electrical characteristics. Pore diameter, morphology and shape determine how impurities distribute themselves across its conductivity phase and this impacts upon electrical properties like hole lifetime tp and diffusion length Lp of Porous SiC.
Thermal Properties
SiC boasts impressive physical, thermal and chemical properties. Its ability to withstand extremely high temperatures while resisting chemical shock makes it an excellent material choice for applications that face rigorous conditions.
Silicon carbide crystallizes in an intimate structure made up of tightly packed carbon atoms bonded covalently together through their shared electron pairs in two primary coordination tetrahedra; four silicon and four carbon atoms sharing their electron pairs through sp3 hybrid orbitals create two tetrahedra structures within which four silicon and four carbon atoms share electron pairs to give this hard and robust material its distinctive structural layout. This unique arrangement gives Silicon Carbide its remarkable hard and resilient nature.
Crystalline SiC crystals also exhibit excellent lattice mismatch tolerance and thermal conductivity, boasting both large lattice mismatch tolerance and outstanding thermal conductivity. Their thermal conductivity K at room temperature lies somewhere between that of pure diamond and copper, and increases with increasing doping levels N.
SiC also exhibits remarkable elastic properties, with its Youngs modulus measuring 131 GPa comparable to “hard” materials such as diamond (1 000 GPa), “hard” steels (200 GPa) and ceramics – but far outperforming soft materials like polyethylene and polypropylene.
Chemical Properties
Silicon is a brittle metallic element with similar appearance to iron; however, unlike iron it has a much lower melting point and can react with oxygen, phosphorus, nitrogen and many other elements when in its molten state. Silicon can also be doped heavily to produce either an n-type or p-type variety of the material.
Silicon carbide’s atomic structure resembles closely packed crystals. The material contains two primary coordination tetrahedra consisting of four silicon and four carbon atoms covalently bonded together and linked at their corners to form polytype structures – creating two primary coordination tetrahedra which form close-packed hexagonal networks known as polytypes.
Silicon carbide comes in various polytypes that feature hexagonal, cubic, rhombohedral or tetragonal crystal structures. Noncubic forms such as 4H-SiC and 6H-SiC belong to what’s referred to as the a-SiC family; cubical varieties include 10R-SiC, 12C-SiC, 14H-SiC and 15R-SiC polytypes.
Elemental silicon is insoluble in both water and alcohol, yet can dissolve at high concentrations in organic acids and alkalis. It acts as a strong reductant that forms compounds with many other elements and metals (including chromium, tungsten, and molybdenum) in its molten state. Furthermore, silicon acts as a weak oxidizer, producing toxic smoke when burned in air as it burns up while reacting with water to form sodium silicide, an explosively flammable compound when wet.
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