Formation of Si grains from a NaSi melt prepared by reaction of SiO sub(2) and Na

A mixture of Na sub(2)SiO sub(3) and NaSi was found to be formed by reaction of SiO sub(2) and Na at 650 degree C as follows: 5Na+3SiO sub(2) arrow right 2Na sub(2)SiO sub(3)+NaSi. Single crystals of NaSi were grown by cooling the mixture of Na sub(2)SiO sub(3) and NaSi with an excess amount of Na from 850 degree C, and polycrystalline Si was obtained by vaporization of Na from the crystals. Coarse grains of Si were also crystallized by Na evaporation after the formation of Na sub(2)SiO sub(3) and Si-dissolved liquid Na at 830 degree C. The Si grains were collected by washing the product with water. The yield of the Si grains was 85% of the ideal amount expected from the reaction.