Preparation and Characterization of Molten Multi-crystalline Silicon Ingot in Crucible Coated with Different Si₃N₄ Coatings

With α-Si₃N₄ and β-Si₃N₄ powders as raw materials, the α-Si₃N₄coating, β-Si₃N₄ coating and composite coating of α-Si₃N₄ and β-Si₃N₄, whose mass ratio was 1:1, were prepared on the inner-wall of crucible by the non-sintering process, respectively, and then the multi-crystalline silicon ingots were obtained in the coated crucible. The surface morphology of the coatings and silicon ingots were observed and the surface roughness, grain size and length of red zone for silicon ingot were measured. The results show that the surface of α-Si₃N₄ coating was rough and undulating unevenly, and the surface roughness and grain size of the corresponding silicon ingot was the largest and the red zone was the longest. The surface of β-Si₃N₄ coating was relatively smooth and undulating evenly; the surface roughness of the corresponding silicon ingot was the smallest, the grain size was relatively small and the red zone was the shortest. The surface roughness degree of composite coating was between those of the above two coatings; the grain size of the corresponding silicon ingot was the smallest and the length of red zone was between the above two silicon ingots.