Crystallography of the High-Temperature Ca₂SiO₄-Ca₃P₂O₈ Solid Solutions

The crystallography of the Ca₂SiO₄-Ca₃P₂O₈ solid solutions in the dephosphorization slag in current steelmaking process was determined in this study. Understanding the physical and chemical properties of these Ca₂SiO₄-Ca₃P₂O₈ solid solutions is a preliminary step towards understanding the role of the Ca₂SiO₄-Ca₃P₂O₈ solid solutions in the dephosphorization process. The range of Ca₃P₂O₈ in the Ca₂SiO₄-Ca₃P₂O₈ solid solutions synthesized for analysis varied from 10 to 90 mol pct, with an incremental increase of 10 mol pct per solid solution. In solid solutions with a Ca₃P₂O₈ content of up to 40 mol pct, the crystal structure at 1773 K was found to be hexagonal, while the solid solutions with a Ca₃P₂O₈ content over 70 mol pct had a trigonal structure. The silicocarnotite solid solutions observed when the Ca₃P₂O₈ content was 50 to 60 mol pct were likely formed by phase transformation during cooling. In the stable solid solution with a Ca₃P₂O₈ content of 50 to 60 mol pct at 1773 K before the occurrence of transformation, the crystal structure is trigonal since it is in the Ca₃P₂O₈-rich range. A linear increase in the lattice parameters c of the solid solutions in the range of (0, 40 mol pct) and (70 mol pct, 100 mol pct) was found with increasing Ca₃P₂O₈ content. The lattice parameter a, however, was almost independent of the Ca₃P₂O₈ content in the solid solutions.