Flux composition useful in directional solidification for purifying silicon

Abstract

The present invention provides for a flux composition, and the use thereof in a directional solidification for the purification of silicon.

We claim: 
     
         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.