Breaking through Thermodynamic and Kinetic Barriers for Rapid Synthesis of High-Purity β-SiC Using Liquid Carbon and Silicon

High-purity SiC (>99.995%) is the crucial raw material for preparing SiC semiconductor devices and ceramics. Synthesis of high-purity SiC via the liquid-state reaction, Si(l) + C(l) = SiC(s), should be ideal but is considered an impossible approach. This is because it is very difficult to overcome the key thermodynamic barrier, the small value of liquid C, C(l), in the liquid Si, Si(l). Therefore, researchers have to use solid C, C(s), and adopt the well-known solid-state reactions, Si(l, s) + C(s) = SiC(s) at 1800–2150 °C (combustion synthesis) and 3C(s) + SiO 2 (l, s) → SiC(s) + 2CO(g) at 2200–2400 °C (Acheson process), to synthesize high-purity SiC, which presents multiple limitations and high requirements. In this study, this thermodynamic barrier was broken by enhancing the value of C(l) significantly with Ce as a C solubilizer. Thereafter, the synthesized solid SiC remained in the solution and became a key kinetic barrier influencing the mass transfer of liquid C. A top-lifting method was designed to separate it from the solution timely. This overcame the kinetic barrier while achieving semicontinuous production and a reusable reaction vessel, which is conducive to industrial application. Finally, rapid synthesis of high-purity SiC (99.9975%) with no Ce contamination was realized by even using low-purity (99.49–99.92%) raw materials at 1550 °C, which was 250–850 °C lower than that of the traditional solid-state reactions. Our new top-lifting solution method has advantages such as low-temperature and rapid synthesis, semicontinuous production, reusable crucible, low requirements for raw materials and reaction vessels, and easily achieved high purity.