Spinel-type ferrite

In other work on spinels, Iwakura et al. [312, 313] observed that the overpotential at a fixed current density on spinel-type ferrite film electrodes... 

The formation ofthe spinel consists of two steps. Firstly, the hydroxide formed in co-precipitation occurs dehydration reaction to form oxides, then tire oxides was calcined to form copper ferrite with spinel structure. If the calcinations temperature is not high enough or tlie time is not long enough, the phase transformation could not be finished. Therefore, only the temperature exceeds 800°C, it is possible to form homogenous spinel type CuFe2O4 furthermore, the longer calcinations process is beneficial to the formation of pure spinel type ferrites. 

Watanabe, A., Yamamura, H., Moriyoshi, Y. Shirasaki, S. (1982). Crystal chemistry of the spinel-type ferrite series LijM FCgOn (M = Ti, Sn ", Ge, Si ). In Ferrites Proceedings of the Third International Conference. Eds. H. Watanabe, S. lida and M. Sugimoto. Center for Academic Publications, Tokyo, pp. 170-3. 

Rez] Rezlescun, N., Petrescu, V., Magnetoresistance of Spinel Type Ferrites , Rev. Roum. Phys., 13(4), 379-381 (1968) (Experimental, Magn. Prop., Electr. Prop., 9)... 

Pleonaste (syn. ceylonite, magnesioferrite) (ICSD 49551 and PDF 36-398) MgFe O M = 200.00 12.15 wt.% Mg 55.85 wt.% Fe 32.00 wt.% 0 Coordinence Mg(4), Fe(6) (Oxides and hydroxides) Cubic a = 836.6 pm Hl cF56 (Z=8) P.G. m3m S.G. Fd3m Spinel type (Ferrite series) Isotropic ip= 2.38 R = % 6-6.5 4650 Habit massive granular and also as well-formed fine sized crystals. Color brownish black, black. Diaphaneity opaque. Luster metallic. Streak dark red. Fracture uneven. Occurrence igneous volcanic rocks, Vesuvius and StromboU, Italy. 

Common Properties of Spinel Ferrites and M-Type Ferrites... 

The commercial sintered spinel and M-type ferrites have a porosity of 2—15 vol % and a grain size in the range of 1—10 ]lni. In addition, these materials usually contain up to about 1 wt % of a second phase, eg, CaO + Si02 on grain boundaries, originating from impurities or sinter aids. 

The sensitive dependence of the electrical and magnetic properties of spinel-type compounds on composition, temperature, and detailed cation arrangement has proved a powerful incentive for the extensive study of these compounds in connection with the solid-state electronics industry. Perhaps the best-known examples are the ferrites, including the extraordinary compound magnetite Fc304 (p. 1080) which has an inverse spinel structure (Fe )t[Fe Fe ]o04. 

The most extensively studied rate processes in this group are those which yield spinels [1] (ferrites, chromites, etc.), molybdates and tungstates, and complex iodides. These types are conveniently exemplified by the representative systems... 

The incorporation on a cation site of an impurity cation of higher charge than the host cation can stabilize a lower valence state of the host cation. The addition of titanium (as Ti02> to the spinel, zinc ferrite, leads to an B-type semi-conductor of this type of formula, Zn (Ti + Fe t28 Fe ) O. The defect centre may be described as an impurity cation of higher relative charge on a cation site plus a quasi-free electron bound on a neighbouring host cation. A necessary condition for the application of the prindple of controlled valency is that the impurity cation should be of much the same size as the host cation. 

Cobalt ferrite CoFejO, Spinel type, cubic H11, cF56 (Z = 8) Fd3m 0.53 520... 

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