Composition Change During Melting of PbO-PbBr_2-PbF_2-P_2O_5 System Glass

To study the composition change during melting of PbO-PbBr2-PbF2-P2O5 system glass, the quantitative chemical analysis was complied to measure the composition of the glass after melting. The results show that the loss of lead during melting is mainly ascribed to the volatilization of PbBr2. When a sample contains a high content of phosphorus and a low content of fluorine, the loss of bromine and phosphorus is remarkable, mainly in the form of PBr3. On the other hand, if a sample contains a high content of fluorine and a low content of bromine or a low content of phosphorus, bromine will not lose much while a large amount of phosphorus and fluorine are lost during melting, mainly in the form of PF5. The reaction between phosphorus and fluorine is much easier than that between phosphorus and bromine. The results of thermodynamic calculation are consistent with the above results and discussions. The content of oxygen is influenced by two factors. Volatilization of P2O5 decreases the content of oxygen, while the reaction between oxygen or water in air and halides in melts increases the content of oxygen.