The Conductivity of Silicon Carbide

Okamoto et al. measured the conductivity of silicon carbide at various temperatures and found that small amounts of Si additive did not increase conductivity by two to three orders of magnitude, but exceeding 5 mol% caused conductivity levels to soar by up to three orders of magnitude.

Silicon carbide is a semiconductor material, capable of being altered into either an n-type or p-type state by doping with aluminium, boron, gallium, phosphorus or nitrogen ions.

電気伝導率

Silicon carbide is a semiconductor material, meaning that it lies somewhere between metals (which conduct electricity) and insulators (which resist current). At lower temperatures, silicon carbide behaves more like an insulator by resisting electrical energy flow; but at higher temperatures it becomes more like a conductor by allowing electrical current through it. Silicon carbide’s behavior depends on both temperature and impurities: aluminum, boron and gallium addition can produce an N-type semiconductor while nitrogen or phosphorus addition will create an N-type semiconductor effect; additionally controlled doping may produce superconductivity in this material.

SiC is an electrically semiconducting material with an initial resistance between 105 and 107 Ohm*cm in its pure state, though adding electrically conducting second phases may reduce this resistance sufficiently for heater applications; overall resistance depends upon morphology and processing conditions of the material itself.

Commercial SiC powder often features non-stoichiometric composition; it typically contains excess aluminium and silicon. While this poses no difficulties when it comes to sintering desired crystalline structures, its presence does make this task simpler in air due to the lower band gap of b-SiC. As N2 provides greater resistance against this transformation process as well as doping of SiC, which could minimize N-doping effects.

熱伝導率

Silicon Carbide (SiC) offers outstanding thermal conductivity properties that make it a key material in power electronics and optoelectronics1,2. Unfortunately, SiC devices’ high localized heat flux makes thermal management challenging resulting in device overheating that compromises performance and reliability, particularly for power devices that operate at temperatures exceeding ambient conditions. Thus a deeper understanding of SiC microstructure, phase composition and thermal conductivity is key for designing materials with even higher thermal conductivities.

As part of an investigation of the effect of phase composition, microstructure, and defect structure on SiC’s thermal conductivity, a submicron-size b-SiC powder was densified using liquid-phase spark plasma sintering (L-SPS) with various concentrations of Y2O3 and Yb2O3, to produce dense samples containing up to 20% graphene nanoplatelets (GNPs) through uniaxial pressing pressure during L-SPS process resulting in preferential alignment of GNPs perpendicularly to pressing axis and thus increased thermal conductivity along this direction; while parallel direction showed no improvement in thermal conductivity improvement.

Additionally, high-resolution scanning transmission electron microscopy (HR-STEM) was used to assess atomic-scale defect structures within these b-SiC samples, along with electron backscatter diffraction. No impact was noticed due to natural defects present; however Yb2O3 addition had a much greater effect on thermal conductivity, possibly suggesting that an impurity level had formed in response to excess Yb2O3 content in its lattice structure.

Chemical Conductivity

Silicon carbide (SiC) is an extraordinary chemical compound made up of equal parts silicon and carbon bonded together through strong covalent bonds similar to diamond, with Mohs hardness rating 9 on Mohs scale, making it extremely durable and resistant to extreme temperatures.

SiC is known for its wide band-gap semiconductor properties, enabling electrons to move freely throughout its material structure and thus allow it to conduct electricity when heated; at lower temperatures however, its structure acts more like an insulator, resisting electrical flow.

Silicon carbide’s electrical and thermal behavior can be altered through adding impurities. Doping aluminum, boron and gallium into it creates a p-type semiconductor; doping with nitrogen and phosphorus turns it into an n-type semiconductor; these changes may significantly enhance its electrical conductivity.

Due to its dense structure, single-crystalline SiC cannot fully benefit from its superior thermal conductivity in practical applications. Polycrystalline ceramics derived from commercially available powders often exhibit lower thermal conductivity as a result of random grain orientation, lattice imperfections and secondary phases with reduced conductivity at grain boundaries.

Before investing, it is crucial that the desired properties of a silicon carbide material can be met. Furthermore, understanding its performance over time may prove especially crucial in applications like heaters where its lifespan could be severely limited by wear-and-tear effects on its material can alter performance significantly.

Thermal Stability

Silicon carbide is an extremely robust hexagonal-structure chemical compound with wide band-gap semiconductor properties. The gap between electron release energy and its maximum energy valence band maximum energy is almost three times larger than in silicon; giving rise to its nickname as wide band-gap material and making it suitable for power electronics and high voltage applications like electric vehicle battery management systems.

Pure SiC is colorless, but industrial production combines it with phosphorus to form carborundum – a brown to black powder with rainbow-like luster, created from thin layers of passivation protecting crystals – which gives this material its name. At first, carborundum was most often seen used as detector diodes in shipboard radios; nowadays however, its primary use lies as hard insulators applications like cutting tools and brake pads.

At room temperature, n-type SiC exhibits an intrinsic conductivity of about 2 10-6 ohm-cm. However, its electrical conductivity can be increased through doping with nitrogen, phosphorus or beryllium to produce p-type material and through formation of boron acceptors on Si sites – increasing both electrical conductivity and electrical resistance.

Doping can compromise the thermal stability of n-type SiC due to accepting electrons and holes escaping from its lattice, creating hot spots in its material structure.

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