FLUX COMPOSITION USEFUL IN DIRECTIONAL SOLIDIFICATION FOR PURIFYING SILICON
The present invention provides for a flux composition, and the use thereof in a directional solidification for the purification of silicon.
1 . A composition comprising:
(a) silicon dioxide (SiO 2 );
(b) sodium carbonate (Na 2 CO 3 );
(c) optionally calcium oxide (CaO); and
(d) at least one of calcium fluoride (CaF 2 ) and calcium chloride (CaCl 2 ).
2 . The composition of claim 1 , wherein the silicon dioxide is present in about 35 wt. % to about 80 wt. % of the composition.
3 . The composition of claim 1 , wherein the sodium carbonate is present in about 40 wt. % to about 60 wt. % of the composition.
4 . The composition of claim 1 , wherein the sodium carbonate is present in about 40 wt. % to about 55 wt. % of the composition.
5 . The composition of claim 1 , wherein the calcium oxide is absent.
6 . The composition of claim 1 , wherein e calcium fluoride is present in about 0.50 wt. % to about 6.00 wt. % of the composition.
7 . The composition of claim 1 , wherein the calcium chloride is present in about 4.00 wt. % to about 6.00 wt. % of the composition.
8 . The composition of claim 1 wherein both the calcium fluoride and the calcium chloride are present in the composition.