Rapid synthesis of high-purity 3C-SiC in Si-Nd-C solution at 1600 °C via poly-SiC seed lifting method

High-purity SiC powders are the main source material for preparing the single-crystal SiC and advanced SiC ceramics. The current mainstream methods for synthesizing high-purity SiC have to choose solid-phase methods, which involve ultrahigh energy consumption and incomplete reactions due to the intrinsic properties of solid-state reactions. In this study, the rare earth metal, neodymium (Nd), served as a solubilizer of C in the Si-C solution to increase the solubility of C, thereby successfully synthesizing SiC polycrystals at 1600°C. Additionally, a poly-SiC seed lifting method was proposed to separate the synthesized SiC polycrystals from the Si-Nd-C solution to achieve the recycling of residual solution and the multiple uses of graphite crucible. Finally, a large poly-SiC ingot with a compactness of 71.93% was synthesized using a Si-30mol%Nd solvent, with a lifting speed of 2 mm/h at 1600°C for 7.5 hours. After the solvent inclusions in the poly-SiC ingot were removed through acid pickling, high-purity 3C-SiC powders (99.9978%) were prepared even though low-purity raw materials (99.32 to 99.94%) were employed. Compared with traditional solid-phase methods, the new liquid-phase method offers the advantages such as lower temperature, higher efficiency, lower energy consumption, and lower requirements for raw materials.