Silicon Carbide ( SiC ) black sharp-edged carbocorund - Various Grain Sizes Available

Silicon Carbide

Other Names: Silicon carbide, Carborundum, Silicon monocarbide, SiC
Chemical Formula: SiC
Molar Mass: 40.10 g/mol
CAS Number: 409-21-2
SMILES: [C-]#[Si+]
Appearance: Colorless to pale yellow crystals when pure; commercial material is commonly gray, green or black crystalline powder
Odor: Odorless

Silicon carbide (SiC) is an inorganic covalent solid composed of silicon and carbon in a 1:1 atomic ratio. Unlike discrete molecular compounds, bulk silicon carbide forms an extended three-dimensional crystal lattice characterized predominantly by strong Si–C bonds. This structure gives the material exceptional hardness, high thermal stability, chemical resistance and useful electronic properties. Silicon carbide exists in numerous crystalline modifications known as polytypes, which differ in the stacking sequence of Si–C layers. More than 200 polytypes have been identified, with cubic 3C-SiC and hexagonal 4H-SiC and 6H-SiC among the most extensively investigated. Differences in crystal structure produce significant variations in electronic and optical properties, making SiC important in materials science, semiconductor physics, ceramics and surface chemistry.

Chemical and physical properties

Silicon carbide is an exceptionally hard crystalline material. Its hardness is commonly reported at approximately 9–9.5 on the Mohs scale, placing it among the hardest technologically important materials. This property originates from the strong directional bonding within the Si–C crystal lattice.

The density of crystalline silicon carbide is approximately 3.21 g/cm³, although small variations occur between different polytypes and material grades. SiC does not exhibit a conventional low-temperature melting transition under atmospheric pressure. At very high temperatures it undergoes decomposition or sublimation, with significant decomposition occurring at temperatures above approximately 2700 °C.

Silicon carbide is essentially insoluble in water and is highly resistant to many chemical reagents at ambient temperature. Its chemical durability, oxidation behavior and corrosion resistance depend on temperature, surface condition, impurities and surrounding atmosphere. At elevated temperatures in oxidizing environments, a protective silica-rich surface layer can form and influence further oxidation kinetics.

SiC combines high thermal conductivity with a relatively low coefficient of thermal expansion. These properties contribute to excellent thermal-shock resistance and dimensional stability under changing temperatures. Thermal conductivity depends strongly on polytype, crystal quality, impurities, defects and temperature and can reach several hundred W·m⁻¹·K⁻¹ in high-quality single crystals.

Silicon carbide is a wide-band-gap semiconductor. The band gap depends on the polytype: cubic 3C-SiC has a band gap of approximately 2.36 eV, while 4H-SiC and 6H-SiC exhibit band gaps of approximately 3.26 eV and 3.0 eV, respectively. SiC also possesses a high critical electric field, high carrier saturation velocity and favorable thermal properties compared with conventional silicon.

The combination of mechanical hardness, high-temperature stability, thermal conductivity and wide-band-gap electronic behavior distinguishes silicon carbide from many conventional ceramic and semiconductor materials.

Applications

Silicon carbide is extensively used as an abrasive material because of its high hardness and resistance to mechanical wear. SiC particles are employed in grinding, polishing, lapping and surface-finishing processes involving metals, ceramics, glass and other hard materials. Controlled particle sizes are particularly important in precision polishing and materials preparation.

In advanced ceramics, silicon carbide is used to produce mechanically strong and thermally stable components. Dense and porous SiC ceramics are investigated for high-temperature structural components, mechanical seals, bearings, heat exchangers and wear-resistant parts. Different manufacturing approaches, including pressureless sintering, hot pressing and reaction bonding, are used to obtain SiC materials with tailored microstructures and properties.

Silicon carbide is an important semiconductor for high-power, high-voltage and high-temperature electronic devices. In particular, 4H-SiC is extensively investigated and employed for power semiconductor components because its wide band gap, high breakdown electric field and high thermal conductivity enable operation under conditions that are challenging for conventional silicon electronics.

SiC is also used as a substrate material for semiconductor and thin-film research. Single-crystalline SiC wafers provide thermally stable surfaces for epitaxial growth and fabrication of electronic structures. Surface preparation, oxidation, interface formation and defect control in SiC have consequently become major research areas in semiconductor materials science.

In nanomaterials research, silicon carbide is prepared in forms including nanoparticles, nanowires, nanotubes and nanostructured films. Such structures are investigated for electronic, optical, sensing, catalytic-support and composite-material applications. Their properties can differ significantly from those of bulk SiC because of increased surface area, nanoscale dimensions and modified defect structures.

Silicon carbide is additionally used as a reinforcing phase in ceramic- and metal-matrix composites. SiC particles, whiskers or fibers can improve hardness, stiffness, wear resistance and high-temperature mechanical performance of composite materials.

Scientific references

Cheung, R. Silicon Carbide Microelectromechanical Systems for Harsh Environments. Imperial College Press, 2006. Scientific reference covering the physical, mechanical, electronic and technological properties of silicon carbide.

Casady, J. B.; Johnson, R. W. Status of silicon carbide (SiC) as a wide-bandgap semiconductor for high-temperature applications: A review. Solid-State Electronics, 1996, 39(10), 1409–1422. DOI: 10.1016/0038-1101(96)00045-7.

Cooper, J. A.; Agarwal, A. SiC power-switching devices—the second electronics revolution? Proceedings of the IEEE, 2002, 90(6), 956–968. DOI: 10.1109/JPROC.2002.1021561.

Kimoto, T. Material science and device physics in SiC technology for high-voltage power devices. Japanese Journal of Applied Physics, 2015, 54, 040103. DOI: 10.7567/JJAP.54.040103.

Fissel, A. Artificially layered heteropolytypic structures based on SiC polytypes: molecular beam epitaxy, characterization and properties. Physics Reports, 2003, 379(3–4), 149–255. DOI: 10.1016/S0370-1573(02)00535-9.

Presser, V.; Nickel, K. G. Silica on silicon carbide. Critical Reviews in Solid State and Materials Sciences, 2008, 33(1), 1–99. DOI: 10.1080/10408430701718914.

Safety Information:

• Inhalation: Inhaling fine silicon carbide dust may cause respiratory irritation. Prolonged exposure can lead to lung disease. Use appropriate respiratory protection in dusty environments.

• Skin Contact: May cause mechanical irritation. Protective gloves are recommended when handling.

• Eye Contact: Dust particles can cause eye irritation. Safety goggles should be worn to prevent exposure.

• Ingestion: Not intended for ingestion. If ingested, seek medical attention.

Handling and Storage:

• Store in a cool, dry place in tightly sealed containers to prevent moisture absorption and contamination.

• Ensure adequate ventilation in areas where dust may be generated.

• Avoid creating dust; use dust collection systems where applicable.

*Note: The information provided is based on general data. Always refer to the Safety Data Sheet (SDS) provided by the supplier for detailed and accurate information.*