Crystallography of the High-Temperature Ca 2 SiO 4 -Ca 3 P 2 O 8 Solid Solutions

The crystallography of the Ca 2 SiO 4 -Ca 3 P 2 O 8 solid solutions in the dephosphorization slag in current steelmaking process was determined in this study. Understanding the physical and chemical properties of these Ca 2 SiO 4 -Ca 3 P 2 O 8 solid solutions is a preliminary step towards understanding the role of the Ca 2 SiO 4 -Ca 3 P 2 O 8 solid solutions in the dephosphorization process. The range of Ca 3 P 2 O 8 in the Ca 2 SiO 4 -Ca 3 P 2 O 8 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 Ca 3 P 2 O 8 content of up to 40 mol pct, the crystal structure at 1773 K was found to be hexagonal, while the solid solutions with a Ca 3 P 2 O 8 content over 70 mol pct had a trigonal structure. The silicocarnotite solid solutions observed when the Ca 3 P 2 O 8 content was 50 to 60 mol pct were likely formed by phase transformation during cooling. In the stable solid solution with a Ca 3 P 2 O 8 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 Ca 3 P 2 O 8 -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 Ca 3 P 2 O 8 content. The lattice parameter a , however, was almost independent of the Ca 3 P 2 O 8 content in the solid solutions.