Thermodynamic Properties of Phosphorus Oxide in the 2CaO•SiO2-3CaO•P2O5 Solid Solution Saturated with MgO

Molten iron was equilibrated with various compositions of the 2CaO center dot SiO2-3CaO center dot P2O5 solid solution saturated with MgO with the oxygen partial pressure of 5.22 x 10(-12) atm at 1823 K (1550 A degrees C) and 1.41 x 10(-11) atm at 1873 K (1600 A degrees C). From the concentration of P in molten iron at equilibrium, the activity of P2O5 relative to the hypothetical pure liquid P2O5 was determined. The saturating MgO phase at equilibrium was detected by X-ray diffraction for each sample, and thus, the activity of 3MgO center dot P2O5 was also estimated. The activity of P2O5 and 3MgO center dot P2O5 increased with the increase of 3CaO center dot P2O5 content in the solid solution. In addition, the activity of P2O5 in the 2CaO center dot SiO2-3CaO center dot P2O5 solid solution saturated with MgO was larger than that saturated with CaO. (C) The Minerals, Metals & Materials Society and ASM International 2016