Solid solution between spinels

By forming solid solutions between two ferrites, it is possible to tune the properties magnetically. An example is provided by the solid solution Zn,Ni1 xFe204, which is between the normal spinel ZnFe2C>4 and the inverse spinel NiFe2C>4. Reaction to form a solid solution with NiFe2C>4 ... 

Two different cations may be substituted into Fe304 for a variety of purposes. The experiments of Lotgering and Van Diepen for example, provided an interesting example of how judicious substitutions could be used to establish reaction (32) for B-site ions, and Mn substitutions into LiFc50g to suppress dielectric loss illustrates the use of a second-cation substitution to optimize a material for a specific application. In this final section on spinels, we choose to discuss the solid solution between Zn[Fc2]04 and Ge[Fe2]04, which would appear to offer the opportunity to study the evolution of the character of the B-site charge carriers with Fes -ion concentration. Ideally, the system would be Znil,GeJ" [Fe2i2xFe2t2x]04-... 

In this review, the relationships between structure, morphology, and surface reactivity of microcrystals of oxides and halides are assessed. The investigated systems we discuss include alkali halides, alkaline earth oxides, NiO, CoO, NiO-MgO, CoO-MgO solid solutions, ZnO, spinels, cuprous oxide, chromia, ferric oxide, alumina, lanthana, perovskites, anatase, rutile, and chromia/silica. A combination of high-resolution transmission electron microscopy with vibrational spectroscopy of adsorbed probes and of reaction intermediates and calorimetric methods was used to characterize the surface properties. A few examples of reactions catalyzed by oxides are also reported. 2001... 

The binary phase diagram for MgO-Al203 is simpler than that for the Ca0-Al203 system (Fig. 2). There is only one stable intermediate compound that of the spinel phase (Mg2A104) [60]. Spinel melts at 2,105°C, but there is a eutectic at 1,995°C and a limited solid solution between stoichiometric spinel and MgO (periclase), up to 6wt% MgO, can be dissolved into the spinel structure without exsolution. This limited solid solution is an important property that is utilized in manufacture of spinels for use in reducing conditions [70]. 

Harrison RJ, Putnis A (1995) Magnetic properties of the magnetite-spinel solid solution Saturation magnetization and cation distributions. Am Mineral 80 213-221 Harrison RJ, Putnis A (1997) The coupling between magnetic and cation ordering A macroscopic approach. Eur J Mineral 9 1115-1130... 

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