Spinel ferrites formula

Most spinel ferrites used in device applications are not simple ternary oxides but rather contain proprietary mixtures of several different magnetic ions tailor made for specific applications. So-called (Mn, Zn) ferrites of general formula Zn+ c Fe+ i-x[Mn+ i cF ]04 and related (Ni, Zn) ferrites... 

Fig. 4.21. Saturation magnetisation (in Bohr magnetons per formula unit) of various spinel ferrites at low temperature, as a function of Zn substitution (Gorier, 1954 Guillaud Sage, 1951).

Normal spinel structure, where all Me2+ ions occupy A sites structural formula of such ferrites is Me2+[Fe2 O4 2-. This type of distribution takes place in zinc ferrites Zn2+[Fe2+Fe3+]04 2-. This type spinel ferrite are schematically illustrated in FigureS. 

The site preference of several transition-metal ions is discussed in References 4 and 24. The occupation of the sites is usually denoted by placing the cations on B-sites in stmcture formulas between brackets. There are three types of spinels normal spinels where the A-sites have all divalent cations and the B-sites all trivalent cations, eg, Zn-ferrite, [Fe ]04j inverse spinels where all the divalent cations are in B-sites and trivalent ions are distributed over A- and B-sites, eg, Ni-ferrite, Fe Fe ]04 and mixed spinels where both divalent and trivalent cations are distributed over both types of sites,... 

Nickel dioxide, 77 107 Nickel double salts, 77 113 Nickel electrodes, 3 430 72 216 Nickel electroplating solutions, 9 818t Nickel extraction, 70 791 Nickel ferrite brown spinel, formula and DCMA number, 7 348t Nickel fibers, 77 108 Nickel fluoride complexes, 77 111 Nickel fluoride tetrahydrate, 77 109-110 Nickel fluoroborate, 77 111 Nickel fluoroborate hexahydrate, 4 157t, 158, 159... 

Ni-Co ferrites with the general formula Nii cCoxFe204 were tested for the methylation of pyridine [110]. It was observed that the systems possessing x values >0.5 are selective for 3-picoline formation, whereas the ones with x values 0 and 0.2 give a mixture of 2- and 3-picolines. Pyridine conversion increased with the progressive substitution of Ni ions by Co ions. The cation distribution in the spinel lattice influences their acidic and basic properties, and these factors have been considered as helpful to evaluate the activity of the systems. 

Person 1 Calculate the net magnetic moment per unit cell for copper ferrite. Remember that there is more than one formula unit (CuFe204) per unit cell in the inverse spinel structure. 

The hexagonal ferrites have a structure related to the spinel structure but with hexagonal close-packed oxygen ions and a unit cell made up of two formulae of MN12O19, where M is divalent (Ba, Sr, or Pb) and N is trivalent (Al, Ga, Cr, or Fe),... 

Ferrite. Iron which, in pig iron or steel, has not combined with carbon to form cementite (FeaC). It exists in a, /9, y and 8 forms, which vary in magnetism and ahility to dissolve cementite. Name also applied to compd NaFe02 (called Na ferrite), to ferromagnetic oxides having a definite cryst structure (spinels) and the formula M++Fe ++04 of which the divalent metal may be Fe, Ni, Zn, or Mn. The magnetic props vary accdg to the divalent atom present, and ferrites are now tailored for their desired effect, as Ni-Al ferrite ... 

The name ferrite was originally given to a class of mixed oxides having an inverse spinel structure and the formula AFe204 where A is a divalent metal ion. The term has been extended to include other oxides, not necessarily containing iron, which have similar... 

The spinels are a class of double oxide of general formula AB204 industrially important members of this class include aluminates (e.g. MgAl204), ferrites (e.g. MgFe204) and chromites (e.g. MgCr204). 

Ferrites are spinels with a general formula AFe204. But, bulk Fe304 has an inverse spinel structure, where Fe3+ is located in the tetrahedral (T) sites and Fc2 and Fe3+ are located in the octahedral (O) sites. The inverse spinel structure consists of a FCC oxygen anionic framework (CCP), with the I c31 ions filling 1/8 of the tetrahedral A sites, and equal amounts of Fc2 and Fe3+ ions filling 1/2 of the octahedral B sites. 

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. 

Some rather complex crystals can be built on a cubic lattice. For example, the ferrites, which are magnetic and are used as memory cores in digital computers, have the formula MO Fe203, where M is a divalent metal ion like Mn, Ni, Fe, Co, etc. Their structure is related to that of the mineral spinel. The Bravais lattice of the ferrites is face-centered cubic, and the unit cell contains 8 molecules or a... 

Mixed metal oxides derived from Fe203 and of general formula M Fe 2C>4 or M Fe - 02 are commonly known as ferrites despite the absence of discrete oxoanions. They include compounds of commercial importance by virtue of their magnetic properties, e.g. electromagnetic devices for information storage for discussion of the magnetic properties of mixed metal oxides, see Chapter 27. Spinel and... 

---