Silicon Carbide – Lightest, Hardest and Most Thermally Conductive Ceramic

Silicon carbide is one of the lightest, hardest, and thermally-conductive ceramic materials available today. It maintains its strength under high temperatures while being highly resistant to acids and lyes.

Natural moissanite is exceedingly rare; therefore most commercially available SiC is produced synthetically. It comes either in green or biscuit form for milling into complex shapes or sintered and reaction bonded for sintered bonding applications.

Thermal Conductivity (k)

Silicon carbide’s excellent thermal conductivity enables it to effectively manage the intense heat generated by power electronics components, while dissipating Joule-heating due to internal resistance and conduction losses. Furthermore, its low thermal expansion coefficient and hardness make it particularly suitable for optical applications like mirrors in large-scale astronomical telescopes.

Silicon carbide (SiC) is an phononic crystal that displays strong temperature dependence of its thermal conductivity (k). Pure monocrystals of SiC may reach room-temperature values exceeding 490 W m-1K-1; in polycrystalline silicon carbide ceramics it has much lower values due to lattice impurities and structural defects at grain boundaries, and also in LPSed SiC with Al-containing additives as this allows Al atoms to dissolve into SiC grains and form solid solutions or secondary phases with reduced conductivity.

Wafer-scale free-standing 3C-SiC bulk crystals reported in this study possess isotropic k values in excess of 500 W m-1K-1, more than 50% higher than commercially available 6H-SiC and AlN materials and ranking second among large crystal materials. Their high in-plane k values can be attributed to short phonon mean free paths measured using TDTR measurements; their non-monotonic temperature dependence further supports their strong doping.

Thermal Conductivity (T)

Silicon carbide (SiC) is an inorganic chemical compound composed of silicon and carbon. Naturally found as the rare mineral moissanite, SiC has been manufactured industrially since 1893 both as powder form and single crystal for use as an abrasive and ceramic plate applications for high pressure/temperature semiconductor furnace furnaces such as wafer tray supports/paddlers etc. Additionally its chemical purity, resistance to thermal attack and strength at higher temperatures have led to widespread usage in electrical devices like varistors (temperature variable resistors/varistors/varistors/etc).

SiC stands out among industrial ceramics such as alumina, zirconia and titanium dioxide due to its relatively high thermal conductivity. When measured at room temperature for pure single crystal SiC it approximates somewhere between diamond and copper as its thermal conductivity values and much greater than that of silicon.

SiC is often referred to as a phononic crystal due to its distinctive vibrational modes. With a low mean free path and short wavelength phonons, its thermal conductivity makes it one of the fastest heat transfer materials. However, its thermal conductivity can be decreased by impurities and structural defects within its material and has been demonstrated experimentally; this effect can be modelled using Callaway-Holland model which accounts for thermal resistance due to narrowing between hole openings.

Thermal Conductivity (T2)

Silicon carbide is one of the lightest, hardest, and thermally most conductive ceramic materials available today. Chemically inert to acids, alkalis and molten salts; highly corrosion resistant at extremely high temperatures; it boasts exceptional physical strength as well as low thermal conductivity and coefficient of expansion characteristics that make silicon carbide suitable for many applications at elevated temperatures.

SiC is the ideal material to be used in high-power power electronics, optoelectronics and quantum computing applications due to its simple crystal structure and exceptionally high specific heat rating; however, localized heat flux caused by these technologies can result in device temperature rise and performance degradation making thermal management an ongoing challenge.

As such, an extremely conductive thermal interface is key to the performance of devices made with SiC. Due to the fishbone-shaped atomic arrangement in 3C-SiC material, its extraordinary high phonon mean free path (MFP) facilitates superior thermal conductivity compared with traditional semiconductors.

CVD SiC’s high thermal conductivity is even more striking; produced through chemical vapor deposition and featuring an extremely pure face centered cubic polycrystalline structure, its thermal conductivity has been reported at being up to two times that of sintered or reaction bonded SiC; in fact, CVD SiC boasts one of the highest thermal conductivities among synthetically grown materials.

Thermal Conductivity (T3)

Silicon carbide is an extremely hard, chemical-resistant ceramic material with excellent thermal conductivity and thermal shock resistance properties, which makes it suitable for high temperature applications such as semiconductor manufacturing. Due to these qualities it has long been utilized in applications in metallurgy, refractories, ceramics and semiconductor industries as it boasts extreme hardness fatigue resistance as well as chemical inertness properties.

Moissanite can only be found naturally in minute quantities in certain types of meteorite and corundum deposits, yet is produced commercially in furnaces. The substance can be synthesized synthetically using various techniques – for instance by dissolving carbon into molten silica, melting clay (aluminium silicate), powdered coke and powdered coke mixture, dissolving carbon in liquid silica or melting mixture of clay (aluminium silicate) with powdered coke; also produced through electric furnace combustion of silicon carbon combination which gives off its natural color range from dark brown to black but which can also be dyed blue for sale as gemstone named moissanite.

3C-SiC exhibits a relatively high thermal conductivity of around 620 Wm-1 K-1, nearly ten times that of diamond. This can be attributed to its relatively low rate of diffuse surface scattering which limits phonon MFP as shown in Fig 4. Additionally, membrane and nanowire distributions measured here were plotted against their limiting dimensions to show they coincide with values obtained through bulk MFP cumulative functions41 and 42.