Effect and Mechanism of Dephosphorization in Molten Silicon under Different Pressure Conditions

Industrial silicon was smelt in high temperature by tungsten wire mesh heating unit and the effects of different pressure conditions on dephosphorization by contrast tests of vacuum and low pressure were studied. The results show that when melting was done under the vacuum of 1×10-3-2×10-2 Pa, the content of phosphorus, which decreased quickly in early stage, decreased with melting time. The dephosphorization reaction was first-order kernel and the activation energy was 102 kJ·mol-1. The removal rate, which increased with the increase of the melting temperature, exceeded 80% at 2.7 ks. Under the low pressure of 2-6 Pa, the dephosphorization reaction could be expressed by first-order kernel, but the effect of temperature on the removal rate of phosphorus was not obvious and the removal rate contant affected by pressure was low comparing with vacuum condition. The control step of dephosphorization rate under different pressures was different.