Statistico-Thermodynamical Studies on the Fundamental Reactions concerning Steel-Making. V : The Oxidation and Reduction Equilibrium of Mn-wustite (Fe, Mn) O with Gas Phase

It is known that Mn-wustite (Fe, Mn) O takes a from of solid solution over all compositions of Fe- and Mn-atoms, and its oxygen content varies with oxygen pressure in the thermal equilibrium and with temperature. So we examined the quantitative relation between the solid and gas phases in the above-mentioned system. Taking into consideration the previous papers in which wustite and magnetite solid solutions were discussed, a configurational model for the Mn-wustite was assumed as follows : (1) O^ and metal ions are arranged on the lattice of NaCl type, (2) in the negative ion lattice-sites O^ ions are perfectly packed, (3) in the positive ion sites Fe^, Mn^ and vacancies are randomly distributed, and (4) on some of Fe^ ions the electron-defects are trapped, producing Fe^ so that the total electrical charge of crystal is neutralized. Considering such a model, the partition function of Mn-wustite was formulated on the base of statistical thermodynamics, and the equilibrium relation between the solid composition and oxygen pressure in the gas phase was calculated. The calculated result was in agreement with the experimental values by Matoba and Gunji (1954) and our data obtained by repeated measurements of weight change using a spring balance