Modeling and Experimental Investigation of Thermal-Field Regulation in α-SiC Powder Synthesis Using Double-Induction-Coil Heating

High-purity SiC powder is an important feedstock for SiC crystal growth, but thermal-field regulation becomes difficult during large-batch synthesis. This study examined an α-SiC powder-synthesis furnace with upper and lower induction-coil groups through numerical simulations and 70 kg synthesis experiments. A representative two-dimensional axisymmetric model was used to compare eight cases with different coil-turn or numerical power allocations. Redistributing the coil turns changed E1, E2, volumetric Joule heat density, Q, and the resulting temperature and calculated gas-phase velocity-magnitude fields. From C01 to C04, the maximum calculated temperature decreased from 2501.10 to 2359.13 K, while ΔT decreased from 242.57 to 76.20 K. Increasing the upper-coil numerical power raised the temperature level while reducing ΔT to 152.41 K. Increasing the lower-coil numerical power also raised the temperature level, but increased ΔT to 292.26 K. Equal-total-power comparisons showed that axial power allocation affected Tmax and ΔT. XRD identified 6H-SiC as the detected crystalline phase in both analyzed middle-region specimens, although X-ray-amorphous carbon could not be excluded. The specimens also differed in macroscopic appearance, measured impurity concentrations, and local nitrogen concentration profiles. Because the experimental conditions were maintained nominally unchanged except for the upper-coil current, these specimen-level differences may be associated with altered internal thermal conditions. Such changes may affect local equilibrium, supersaturation, and species transport, providing a possible link to the observed material differences. The numerical results identify coil-turn allocation and axial power allocation as variables for regulating the calculated furnace fields.