Abstract
The iron and oxygen atom-ratios of Fe-O melts are continuously variable by the change of oxygen pressure in gaseous phase. It is very reasonable that we suppose Fe-O melts are constructed by ionic components Fe++, Fe+++ and O−−, thanks to the knowledges on Fe-O solid-solution phases (ref. 5th and 9th Reports) and the electro-conductivity of melts. We assume the following configurational model for Fe-O molten system: (1) Oxygen ions O−− are arranged on the face-centered cubic lattice (nearly close-packed), because they are very large compared with iron ions. (2) Fe++ ions are distributed on the tetrahedral and octahedral interstitial lattice points of oxygen ion lattice. (3) If any tetrahedral lattice point is occupied by a iron ion, its nearest octahedral lattice points are vacant, and it is the same for the nearest neighbors of octahedral iron ions. (4) Positive holes are randomly distributed on Fe++ ions, and thus Fe+++ ions are formed. Using the above model the partition function of the Fe-O molten slag was formulated by the statistical thermodynamics, and the equilibrium relation between the slag composition and the pressure of oxygen in gas phase was calculated. This theoretical results are in good ageement with the measured values of Darken and Gurry (1946) in the wide range of pressure, 10−10 to 1 atm of O2, and temperature 1400° to 1600°.
