Carbon Precursor-Dependent Si-C Interfacial Reactions and Phase Evolution in Silicon Carbide Synthesis.

Silicon carbide (SiC) synthesis from different carbon precursors was systematically investigated to clarify the interfacial reaction process and phase evolution over 1300-2250 °C. Flake graphite (FG), spherical graphite (SG), and petroleum coke (PC) were selected as representative carbon precursors. Multiscale characterizations, including XRD, Raman spectroscopy, SEM, TEM, and XPS, reveal that the Si-C reaction proceeds through distinct temperature-dependent stages. At lower temperatures, the reaction is mainly controlled by solid-state interfacial diffusion. With increasing temperature, liquid-phase surface infiltration becomes dominant, followed by recrystallization and the β→α phase transformation at elevated temperatures. Density functional theory (DFT) calculations suggest that intrinsic defects in PC may promote interfacial Si adsorption and orbital hybridization, which is consistent with its enhanced low-temperature reactivity. The synthesized 6H-SiC powders were further used as source materials for physical vapor transport (PVT) growth. High-quality 4H-SiC single crystals with low defect density were successfully obtained. By linking carbon-precursor surface structure, interfacial reaction behavior, phase evolution, and crystal-growth performance, this study provides guidance for the controllable preparation of high-quality SiC powders for SiC single-crystal growth.