Abstract: The "Gibbs free energy method" was used to study the thermodynamics of preparation CoP by Fe₂P or FeP and Co. The Gibbs free energy of the reactions varied from-20.265 kJ·mol^-1 to-75.444 kJ·mol^-1, and from 13.149 kJ·mol^-1 to-54.889 kJ·mol^-1, respectively, when the temperature is in the range of 298 K to 1500 K. It is possible to prepare CoP in the calculated temperature range. The relationships were obtained of the Gibbs free energy and the equilibrium constant with temperature of preparation of CoP by Fe₂P and FeP added Co. They were ΔG_T=-0.0462T-6.1592, and ΔG_T=-0.0558T+31.5781, lgK^θ=0.3389+0.0024, lgK^θ=-1.5346+0.0028 of reaction of(1)and(2), respectively, under the same temperature range. The minimum temperature is -133 K and 566 K of the preparation reaction of CoP by FeP, Fe₂P and Co, respectively. It provides thermodynamic parameters for experimental study.

Key words: CoP, ferrophosphorus, preparation, thermodynamics