Phase Relations of the Fe₃O₄-ZnFe₂O₄-Fe₂O₃ System and Activities and Lattice Constants of the Fe₃O₄-ZnFe₂O₄ Spinel Solid Solutions

Fumdamental studies of zinc extraction by the iron-reduction distillation process (10th Report)

Abstract

Phase relations in the Fe₃O₄-ZnFe₂O₄-Fe₂O₃ system at 1, 100 K have been determined by the X-ray microanalysis and X-ray diffraction studies of the quenched samples. The results show that in the Fe₃0₄-ZnFe₂O₄ system magnetite (Fe₃0₄) and zinc ferrite (ZnFe₂O₄) form a complete series of solid solutions which is in equilibrium with the Fe₂O₃ that is practically pure.
The activities were measured by an e. m. f. method using the stabilized zirconia solid electrolytes. Both the activities of magnetite and zinc ferrite in the Fe₃O₄-ZnFe₂O₄ solid solutions coexisting with the Fe₂O₃ exhibit slightly positive deviations from Raoult's law at 1, 100 K. The activity coefficient at infinite dilution, γ⁰ZnFe2O4 at 1, 100 K was estimated at 2.2.
Lattice constants for the Fe₃O₄-ZnFe₂O₄ spinel solid solutions in equilibrium with the Fe₂O₃ obey Vegard's law. It was also found that the excess Gibbs energy of mixing in the Fe₃O₄-ZnFe₂O₄ solid solutions coexisting with the Fe₂0₃ at 1, 100 K showed small values. These two results are interrelated in the similar behavior, which suggest that activities are closely connected with crystal structures.