"A study was made of the ZnO-Fe₂O₃-Fe₃O₄ system at 1200ºC using oxygen pressures between 0.1 and 1x10⁻⁴ atmospheres. The results of this study were used to calculate the activities of ZnO, Fe₂O₄, and Fe₃O₄ in the spinel solid solution region of this ternary system. The activities of ZnFe₂O₄ and Fe₃O₄ across the pseudo-binary system were then calculated. The activities of the components in both the ternar and pseudo-binary systems exhibited large positive deviations from Raoult's Law, being more pronounced at the higher Fe₃O₄ content. The free energy, enthalpy, and entropy of mixing of the pseudo-binary system ZnFe₂O₄-Fe₃O₄ at 1200ºC were calculated from the activities of ZnFe₂O₄ and Fe₃O₄. The entropy of mixing was compared with the entropy of mixing calculated from two statistical models, one representing an ideal solution, and the other representing the mixing of a normal with an inverse spinel. The pseudo-binary entropy of mixing appeared to compare the best with the model of the mixing of a normal with an inverse spinel. This indicates that the cations of a normal and an inverse spinel tend to occupy the same positions in the spinel solid solution lattice that they would occupy in their respective pure components. This comparison also indicates that the cation distribution in the spinel solid solution is an important factor in determining the thermodynamic properties of the spinel solid solution"--Abstract, page ii.
O'Keefe, T. J. (Thomas J.)
James, William Joseph
Leighly, Hollis P., 1923-2004
Wolf, Robert V., 1929-1999
Materials Science and Engineering
M.S. in Metallurgical Engineering
University of Missouri at Rolla
vii, 63 pages
© 1966 Dennis George Dreyer, All rights reserved.
Thesis - Open Access
Spinel -- Thermal properties
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Dreyer, Dennis George, "The thermodynamics of the ZnO-Fe₂O₃-Fe₃O₄ system" (1966). Masters Theses. 5517.