Formation of Si grains from a NaSi melt prepared by reaction of SiO2 and Na

A mixture of Na2SiO3 and NaSi was found to be formed by reaction of SiO2 and Na at 650 degrees C as follows: 5Na+3SiO(2) -> 2Na(2)SiO(3)+NaSi. Single crystals of NaSi were grown by cooling the mixture of Na2SiO3 and NaSi with an excess amount of Na from 850 degrees 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 Na2SiO3 and Si-dissolved liquid Na at 830 degrees 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. (C) 2013 Elsevier B.V. All rights reserved.