Silica granules have good wettability to silicon melt

and could be used as seeds to grow fine and well-distributed columnar silicon grains for high-performance multi-crystalline silicon（MC-silicon）related with high conversion efficiency of the solar cells.Si3N4 was coated to the silica granules for improving the MC-silicon growth and ingot releasing effect.It is found that the Si3N4 coating on the silica granules is helpful for obtaining fine and uniformly distributed columnar grain to decrease the defect density and improve the quality of multi-crystalline silicon.In addition

the detachment of the silica granules from silicon ingot is realized easily to eliminate the stress from the bonding of multi-crystalline silicon with silica granules.