Fig. 2 presents XRD patterns of products of the 1/8 mixture after 6 h at 1100 °C in a NaCl-based salt containing 0, 1.25, 2.5 or 5 wt% NaF. Almost no SiC was detected in the absence of NaF. However, when 1.25 wt% NaF was used in the salt, SiC peaks started to appear and Si peaks decreased concurrently. On further increasing the NaF content to 2.5 wt%, Si disappeared and only SiC along with unreacted carbon was present. In addition to the primary SiC peaks, two tiny shoulder peaks at 2θ ≈33.78° and 38.01° (marked as black stars) were seen, in particular, in the case of using 1.25 wt% NaF. They are believed to arise from the stacking faults commonly existing in β-SiC. 14 and 15 Further increasing the NaF content to 5 wt% did not result in any further phase changes, but the two small shoulder peaks almost disappeared. The XRD pattern in this case was almost identical to that when using 20 wt% NaF (Fig. 1), indicating that 2.5–5 wt% NaF in the binary salt was sufficient for the MSS process of SiC.