Inhibiting Crystallization Of Fused Silica Ceramic At High Temperature With Addition Of Alpha-Si3n4

Fused silica (SiO2) ceramic crucibles with alpha-Si3N4 coating are commonly used for smelting photovoltaic silicon (Si). However, SiO2 ceramics will inevitably undergo crystallization and large volume change during the high temperature service, which will lead to crucible cracking and deteriorate the quality and yield of the Si ingot. In this work, alpha-Si3N4/SiO2 ceramics are fabricated by introducing alpha-Si3N4 into SiO2 ceramics to inhibit crystallization. The results show that the introduction of alpha-Si3N4 can effectively inhibit crystallization of SiO2 ceramics at temperature higher than 1450 degrees C. Only 5 wt% cristobalite form in SiO2 ceramic with 20 wt% alpha-Si3N4 (heated at 1550 degrees C for 30min). The crystallization activation energy of SiO2 ceramic containing 20 wt% alpha-Si3N4 increases by 2.27 times to 931.2kJ/mol compared with that of pure SiO2 ceramic (409.6kJ/mol). The inhibition crystallization effect and increased activation energy derive from the in-situ formation of O-Si-N chemical bond and physical isolation of SiO2 particles by alpha-Si3N4 powders.