Activities of P2O5 in Solid Solutions between Di-calcium Silicate and Tri-calcium Phosphate at 1573 K

The knowledge of P 2 O 5 activities in solid solutions between Ca 2 SiO 4 and Ca 3 P 2 O 8 is required for more effective dephosphorization. In the present study, firstly, the P 2 O 5 activities in these solid solutions coexisting with CaO or CaSiO 3 at 1 573 K were measured by equilibrating molten copper with oxide phases under a stream of Ar + H 2 + H 2 O gas mixtures. Subsequently, the sub-regular solution model was applied to Ca 2 SiO 4 –Ca 3 P 2 O 8 solid solutions. The P 2 O 5 activities calculated with the solution model agreed well with the present experimental results and the literature data. It was found that the P 2 O 5 activity in Ca 2 SiO 4 – Ca 3 P 2 O 8 solid solution coexisting with CaO was about 7 digits lower than that coexisting with CaSiO 3 .