The thermodynamics of cation distributions in simple spinels

Navrotsky, A.; Kleppa, O. J.

doi:10.1016/0022-1902(67)80008-3

Cited by 566 publications

(252 citation statements)

References 14 publications

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“…50 nm) with some large pores. These observations are in reasonable agreement with the XRD and specific surface area data and with earlier works [10][11][12].…”

Section: Powderssupporting

confidence: 93%

“…the Co 2+ ions are located in the tetrahedral sites of the cubic close-packing of O 2À ions whereas the Al 3+ ions occupy the octahedral sites. Moreover, a considerable solidsolution range exists on the Al 2 O 3 -rich side of the stoichiometric spinels [10,11]. The second aim is to investigate the microhardness and friction behavior of the Co-Al 2 O 3 composite layers and of the core of the specimens, made up of bulk CoAl 2 O 4 .…”

Section: Introductionmentioning

confidence: 99%

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Hardness and friction behavior of bulk CoAl2O4 and Co–Al2O3 composite layers formed during Spark Plasma Sintering of CoAl2O4 powders

Pavia

Billon

Weibel

et al. 2012

Ceramics International

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OATAO is an open access repository that collects the work of Toulouse researchers and makes it freely available over the web where possible. powders. The Co particles are precipitated because of a combination of high temperature and low O 2 partial pressure. The precipitation and densification processes hamper each other and thus the way the uniaxial pressure is applied during the sintering cycle is an important parameter to control the microstructure of composite layer and its thickness (about 100 mm) and obtain a dense sample (about 4 g/cm 3 ). The friction coefficient of the CoAl 2 O 3 composites against an Al 2 O 3 ball is lower than that found for an Al 2 O 3 specimen, which could reveal the lubricating role of submicrometer Co particles. However, increasing the load from 5 to 10 N load causes major changes in the friction contact, which are detrimental. Bulk CoAl 2 O 4 was found to have a Vickers microhardness about 15.5 GPa and an average friction coefficient lower than that of an Al 2 O 3 sample.

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“…50 nm) with some large pores. These observations are in reasonable agreement with the XRD and specific surface area data and with earlier works [10][11][12].…”

Section: Powderssupporting

confidence: 93%

Section: Introductionmentioning

confidence: 99%

Hardness and friction behavior of bulk CoAl2O4 and Co–Al2O3 composite layers formed during Spark Plasma Sintering of CoAl2O4 powders

Pavia

Billon

Weibel

et al. 2012

Ceramics International

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“…In case of cation disorder between the sub-lattices where degree of cation disorder is denoted by the parameter y, the tetrahedral sites consist of a binary alloy A 1−y B y and each of the octahedral sites has the composition A y/2 B 1−y/2 . The degree of cation disorder y at a finite temperature T can be calculated from the thermodynamic consideration of cation distributions by treating it as a simple chemical equilibrium 36 . Such modelling has been proved to agree reasonably well with the experiments in most of the cases 15,[37][38][39][40][41][42] .…”

Section: Details Of Calculationsmentioning

confidence: 99%

First-principles investigations into the thermodynamics of cation disorder and its impact on electronic structure and magnetic properties of spinel Co(Cr_1–xMn_x)₂O₄

Das

Ghosh

2016

J. Phys.: Condens. Matter

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Cation disorder over different crystallographic sites in spinel oxides is known to affect their properties. Recent experiments on Mn doped multiferroic CoCr2O4 indicate that a possible distribution of Mn atoms among tetrahedrally and octahedrally coordinated sites in the spinel lattice give rise to different variations in the structural parameters and saturation magnetisations in different concentration regimes of Mn atoms substituting the Cr. A composition dependent magnetic compensation behaviour points to the role conversions of the magnetic constituents. In this work, we have investigated the thermodynamics of cation disorder in Co (Cr1−xM nx) 2 O4 system and it's consequences on the structural, electronic and magnetic properties, using results from first-principles electronic structure calculations. We have computed the variations in the cation-disorder as a function of Mn concentration and the temperature and found that at the annealing temperature of the experiment many of the systems exhibit cation disorder. Our results support the interpretations of the experimental results regarding the qualitative variations in the sub-lattice occupancies and the associated magnetisation behaviour, with composition. We have analysed the variations in structural, magnetic and electronic properties of this system with variations in the compositions and the degree of cation disorder from the variations in their electronic structures and by using the ideas from crystal field theory. Our study provides a complete microscopic picture of the effects that are responsible for composition dependent behavioural differences of the properties of this system. This work lays down a general framework, based upon results from first-principles calculations, to understand and analyse the substitutional magnetic spinel oxides A (B1−xCx) 2 O4 in presence of cation disorder.

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“…The fundamental assumption, introduced by Schmalzried 14 and elaborated by Navrotsky and Kleppa, 15 is that the interchange of cations between two distinct sublattices can be viewed as a chemical equilibrium:…”

Section: Thermodynamic Modelmentioning

confidence: 99%

“…The enthalpy consists of two terms, one linear and one quadratic in the interchange parameter x, as was proposed by O'Neill and Navrotsky 16 as an expansion of the original model by Navrotsky and Kleppa. 15 Effects of volume and non-configurational entropy are neglected. The energy difference between different configurations with the same degree of cation interchange is not taken into account at this stage, so all SS configurations are for now assumed to be degenerate, and the same applies for the PP and SP configurations.…”

Section: Thermodynamic Modelmentioning

confidence: 99%

On the energetics of cation ordering in tungsten-bronze-type oxides

Olsen

Selbach

Grande

2015

Phys. Chem. Chem. Phys.

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Oxides with the tetragonal tungsten bronze (TTB) structure are well-known ferroelectrics that show a large flexibility both with respect to chemical composition and cation ordering. Two of the simplest compounds in this family are lead metaniobate (PbNb 2 O 6 or PN) and strontium barium niobate (Sr x Ba 1-x Nb 2 O 6 or SBN). While PN is a classical ferroelectric, SBN goes from ferroelectric to relaxor-like with increasing Sr content, with a polar direction different from that in PN. The partially occupied sublattices in both systems give the possibility for cation order-disorder phenomena, but it is not known if or how this influences the polarization and ferroelectricity. Here, we use density functional theory (DFT) calculations to investigate how cation and cation vacancy ordering influences the energetics of these compounds, by comparing both the energy differences and the barriers for transition between different cation configurations. We extend the thermodynamic model of O'Neill and Navrotsky, originally developed for cation interchange in spinels, to describe the order-disorder phenomenology in TTB oxides. The influence of order-disorder processes on the functional properties of PN and SBN is discussed.

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The thermodynamics of cation distributions in simple spinels

Cited by 566 publications

References 14 publications

Hardness and friction behavior of bulk CoAl2O4 and Co–Al2O3 composite layers formed during Spark Plasma Sintering of CoAl2O4 powders

Hardness and friction behavior of bulk CoAl2O4 and Co–Al2O3 composite layers formed during Spark Plasma Sintering of CoAl2O4 powders

First-principles investigations into the thermodynamics of cation disorder and its impact on electronic structure and magnetic properties of spinel Co(Cr_1–xMn_x)₂O₄

On the energetics of cation ordering in tungsten-bronze-type oxides

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The thermodynamics of cation distributions in simple spinels

Cited by 566 publications

References 14 publications

Hardness and friction behavior of bulk CoAl2O4 and Co–Al2O3 composite layers formed during Spark Plasma Sintering of CoAl2O4 powders

Hardness and friction behavior of bulk CoAl2O4 and Co–Al2O3 composite layers formed during Spark Plasma Sintering of CoAl2O4 powders

First-principles investigations into the thermodynamics of cation disorder and its impact on electronic structure and magnetic properties of spinel Co(Cr1–xMnx)2O4

On the energetics of cation ordering in tungsten-bronze-type oxides

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First-principles investigations into the thermodynamics of cation disorder and its impact on electronic structure and magnetic properties of spinel Co(Cr_1–xMn_x)₂O₄