Quenching experiments were used to investigate the solid solution range, thermal stability, and selected phase relationships of silico-ferrite of calcium and aluminum (SFCA) within the FeA-CaO-Al2O3-SiO2 (FCAS) system. SFCA was found to be stable within a plane that connects the end members CF3 (CaO . 3Fe(2)O(3)), CA(3) (CaO . 3Al(2)O(3)), and C4S3 (4CaO . 3SiO(2)). Chemical substitution in the four component system follows the coupled substitution mechanism 2(Fe3+, Al3+) <----> (Ca2+, Fe2+) + Si4+ with the greatest range in chemical substitution occurring in the direction of the Al3+ <----> Fe3+ exchange (ranging from 0 wt pet Al2O3 to similar to31.5 wt pct Al2O3). The extent of Al3+ <----> Fe3+ substitution decreases with increasing temperature, and it was estimated that SFCA completely decomposes by similar to 1480 degreesC. Coupled substitution involving Ca2+ and Si4+ for 2M(3+) is not as extensive as the Al3+ <----> Fe3+ exchange, having a maximum range between 3 and 11 wt Pet C4S3 component. Additional phases encountered in the experimental program included hematite; magnetite; quench liquid; dicalcium silicate; Fe-bearing gehlenite; calcium alumino-ferrite solid solutions, C(A, F)(6) and C(A, F)(2), plus an unidentified phase, possibly representing a solid substitution between SFCA-1 and C(A, F)(3). Schematic phase diagrams have been constructed to show the relationship of SFCA with these surrounding phases.
