<p>The thermodynamic model of a silico-ferrites of calcium and aluminum solution, SFCA phase (Ca₂(Fe, Ca)₆^Oct(Fe, Al, Si)₆^TetO₂₀) was newly developed in the framework of the Compound Energy Formalism (CEF). Preferred substitution of Al atoms to tetrahedral sites in the SFCA solution was verified by X-ray absorption near edge structure (XANES) analysis. On considering crystallographic information in particular the short-range-ordering nature in the SFCA solution – the Ca₈(Fe³⁺)₂₀^Oct(CaSi⁶⁺, FeFe⁶⁺, FeAl⁶⁺)₃^Paired(CaSi⁶⁺)₁^Paired(Fe³⁺, Al³⁺)₂₀^TetO₈₀ structure was considered for modeling the SFCA solution. The optimized Gibbs energies of all end-members can successfully reproduce the experimental single phase region of the SFCA solution.</p>