Cation Arrangement in Spinels

Verwey, E. J. W.; Boer, Frank de; Santen, J. H. van

doi:10.1063/1.1746736

Cited by 164 publications

(43 citation statements)

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“…In the past much has been made of the fact that u was invariant in a particular spinel, and hence, on this premise electrostatic energy calculations, where u enters as an important parameter, were used to predict whether a spinel was normal or inverse (Verwey, de Boer & van Santen, 1948). While the general idea retains validity, Fig.…”

Section: Resultsmentioning

confidence: 99%

The temperature dependence of ordering in magnesium ferrite

Faller¹,

Birchenall²

1970

J Appl Cryst

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Cation ordering in magnesium and nickel ferrites was studied by X‐ray diffraction measurements carried out at the temperature of equilibration and also on quenched specimens. The order parameters on quenched specimens agreed with results previously reported by others but not with values measured at temperature. Previous results on quenched specimens had been described by a simple mass action relation with constant ordering energy. The new results on equilibrated specimens require a modified Bragg–Williams‐type relation in which the ordering energy varies with the degree of order. Both ferrites are inverted when in equilibrium at low temperature. Magnesium ferrite approaches a random distribution at high temperature with a Curie point at about 1070°C. Oxygen positional parameters were 0.243±0.001 for both ferrites at room temperature. The lattice parameter of nickel ferrite quenched from temperatures up to 1255°C was 8.3295±0.0001 Å. For magnesium ferrite the lattice parameter varied from 8.3775±0.0001 Å, when quenched from 784°C. to 8.3848, when quenched from 1271°C.

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Section: Resultsmentioning

confidence: 99%

The temperature dependence of ordering in magnesium ferrite

Faller¹,

Birchenall²

1970

J Appl Cryst

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“…The decrease of resistivity with increase of temperature indicates the semiconducting nature of ferrites. The conduction mechanism in ferrites was explained on the basis of Verwey and De Boer [26] mechanism, which involves the exchange of electrons between the ions of the same elements present in more than one valence state and randomly distributed over crystallographic equivalent lattice cites. The exchange of electrons between Fe 2+ ↔ Fe 3+ + e − is responsible for n-type charge carrier and the exchange of holes between Ni 3+ ↔ Ni 2+ + e + , Cu 2+ ↔ Cu 1+ + e + and Cd 2+ ↔ Cd 1+ + e + are responsible for p-type charge carriers in the ferrite phase.…”

Section: Ftir Studiesmentioning

confidence: 99%

Structural, electrical and magnetic properties of cadmium substituted nickel–copper ferrites

Belavi

Chavan

Naik

et al. 2012

Materials Chemistry and Physics

141

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“…Many types of cations can be inserted into the spinel crystal structure. A large variety of ionic radii and valence states can coexist in the spinel form and an element can present different oxidation states (and spin states) on the tetrahedral and/or octahedral sites [18,19]. Thus, the cation distribution in oxides of spinel structure is generally complex to identify as the valence and coordination polyhedra are depending on steric and energetic considerations that are also related to their environment [20].…”

Section: Introductionmentioning

confidence: 99%