Polycrystalline silicon ingot casting mold, and the mold release material for a silicon nitride powder, the release layer for the silicon nitride powder containing slurry and casting the release material

Excellent adhesion to the mold at a low cost, solidified silicon ingot polycrystalline silicon ingot casting mold capable of the suppressing the occurrence of chipping or breakage at the time of release obtained in high yield with high silicon ingot quality, as well as the release agent for silicon nitride powder, the release layer for the silicon nitride powder containing slurry and casting the release material. Releasing agent for silicon nitride powder of the polycrystalline silicon ingot casting mold, characterized in that the proportion of single-Dispersed granular crystal primary particles is 95% or more in area ratio calculated from image analysis of SEM images of the powder it is.