Low-Temperature Purification of Silicon by Dissolution and Solution Growth in Sodium Solvent

Condition of Si crystal formation by vaporizing Na from NaSi

“…1. The apparatus has been used for purification of Si, and details have been described elsewhere [10]. 2.0 g Si and a mixture of 0.6 g Na and 0.5 g Si were respectively charged in the lower and upper crucibles of the apparatus.…”

“…Furthermore, polycrystalline films, helical microtubes and granules of Si were crystallized from Na-Si melt by Na evaporation [7,9]. We proposed a low-temperature process of Si purification for solar cells at 1073-1173 K. It has been confirmed that Si was purified by dissolution and recrystallization [10].…”

Liquid-Phase Epitaxy

“…Recent work by Morito et al [473,474] demonstrated the crystallization of silicon from molten sodium and its utility for boron removal. Sodium melts have been used for GaN LPE (see section 17), but this is the first report [475] of its use for silicon crystallization.…”

Low-temperature synthesis of Si and Si-based compounds using Na

“…Phosphorus, which is difficult to remove by solidification segregation, was also reduced from 73 ppm in the raw Si powder to 3.4 ppm in the refined Si grains. 9) Boron was also efficiently removed by recrystallization of Si from a NaSi solution in a magnesium oxide crucible as shown in Table 1. 10)…”