[en] We investigate the high temperature thermodynamical chemistry behaviors of the spinel compounds concerning the radiation field formation. The characteristics of cation distribution in the spinel lattice was estimated by thermodynamic calculation. The non-stoichiometry and the change of free energy of single and mixed spinel compounds containing Fe²⁺, Ni²⁺, Co²⁺ and Zn²⁺ were calculated and evaluated. It appeared that the ferrites containing iron, nickel or cobalt had inverse spinel structures, while that containing zinc had a normal spinel structure. Each calculated value of the chemical compositions, x and y, in a binary or ternary mixed spinel system, A²⁺_xB²⁺_yFe³⁺_1-x-y(A²⁺_k-xB²⁺_1-k-yFe³⁺_1+x+y)O₂= (the k is initial mole fraction), in which A or B is Fe²⁺, Ni²⁺, Co²⁺ or Zn²⁺, was shown to be compound-dependent. The whole free energy changes of site transfer and formation appeared to be thermodynamically well mixed when k was 0.5 and when the temperature was higher. In addition, Nickel ferrite was synthesized by co-precipitation method and identified, and a chemical system for solution pH controlling and co-precipitate washing were selected